openethereum/ethcore/src/state/mod.rs

// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.

// Parity Ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity Ethereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity Ethereum.  If not, see <http://www.gnu.org/licenses/>.

//! A mutable state representation suitable to execute transactions.
//! Generic over a `Backend`. Deals with `Account`s.
//! Unconfirmed sub-states are managed with `checkpoint`s which may be canonicalized
//! or rolled back.

use hash::{KECCAK_EMPTY, KECCAK_NULL_RLP};
use std::{
    cell::{RefCell, RefMut},
    collections::{hash_map::Entry, BTreeMap, BTreeSet, HashMap, HashSet},
    fmt,
    sync::Arc,
};

use error::Error;
use executed::{Executed, ExecutionError};
use executive::{Executive, TransactOptions};
use factory::{Factories, VmFactory};
use machine::EthereumMachine as Machine;
use pod_account::*;
use pod_state::{self, PodState};
use state_db::StateDB;
use trace::{self, FlatTrace, VMTrace};
use types::{
    basic_account::BasicAccount,
    receipt::{Receipt, TransactionOutcome},
    state_diff::StateDiff,
    transaction::SignedTransaction,
};
use vm::EnvInfo;

use bytes::Bytes;
use ethereum_types::{Address, H256, U256};
use hash_db::{AsHashDB, HashDB};
use keccak_hasher::KeccakHasher;
use kvdb::DBValue;

use ethtrie::{Result as TrieResult, TrieDB};
use trie::{Recorder, Trie, TrieError};

mod account;
mod substate;

pub mod backend;

pub use self::{account::Account, backend::Backend, substate::Substate};

/// Used to return information about an `State::apply` operation.
pub struct ApplyOutcome<T, V> {
    /// The receipt for the applied transaction.
    pub receipt: Receipt,
    /// The output of the applied transaction.
    pub output: Bytes,
    /// The trace for the applied transaction, empty if tracing was not produced.
    pub trace: Vec<T>,
    /// The VM trace for the applied transaction, None if tracing was not produced.
    pub vm_trace: Option<V>,
}

/// Result type for the execution ("application") of a transaction.
pub type ApplyResult<T, V> = Result<ApplyOutcome<T, V>, Error>;

/// Return type of proof validity check.
#[derive(Debug, Clone)]
pub enum ProvedExecution {
    /// Proof wasn't enough to complete execution.
    BadProof,
    /// The transaction failed, but not due to a bad proof.
    Failed(ExecutionError),
    /// The transaction successfully completed with the given proof.
    Complete(Box<Executed>),
}

#[derive(Eq, PartialEq, Clone, Copy, Debug)]
/// Account modification state. Used to check if the account was
/// Modified in between commits and overall.
enum AccountState {
    /// Account was loaded from disk and never modified in this state object.
    CleanFresh,
    /// Account was loaded from the global cache and never modified.
    CleanCached,
    /// Account has been modified and is not committed to the trie yet.
    /// This is set if any of the account data is changed, including
    /// storage and code.
    Dirty,
    /// Account was modified and committed to the trie.
    Committed,
}

#[derive(Debug)]
/// In-memory copy of the account data. Holds the optional account
/// and the modification status.
/// Account entry can contain existing (`Some`) or non-existing
/// account (`None`)
struct AccountEntry {
    /// Account entry. `None` if account known to be non-existant.
    account: Option<Account>,
    /// Unmodified account balance.
    old_balance: Option<U256>,
    /// Entry state.
    state: AccountState,
}

// Account cache item. Contains account data and
// modification state
impl AccountEntry {
    fn is_dirty(&self) -> bool {
        self.state == AccountState::Dirty
    }

    fn exists_and_is_null(&self) -> bool {
        self.account.as_ref().map_or(false, |a| a.is_null())
    }

    /// Clone dirty data into new `AccountEntry`. This includes
    /// basic account data and modified storage keys.
    /// Returns None if clean.
    fn clone_if_dirty(&self) -> Option<AccountEntry> {
        match self.is_dirty() {
            true => Some(self.clone_dirty()),
            false => None,
        }
    }

    /// Clone dirty data into new `AccountEntry`. This includes
    /// basic account data and modified storage keys.
    fn clone_dirty(&self) -> AccountEntry {
        AccountEntry {
            old_balance: self.old_balance,
            account: self.account.as_ref().map(Account::clone_dirty),
            state: self.state,
        }
    }

    // Create a new account entry and mark it as dirty.
    fn new_dirty(account: Option<Account>) -> AccountEntry {
        AccountEntry {
            old_balance: account.as_ref().map(|a| a.balance().clone()),
            account: account,
            state: AccountState::Dirty,
        }
    }

    // Create a new account entry and mark it as clean.
    fn new_clean(account: Option<Account>) -> AccountEntry {
        AccountEntry {
            old_balance: account.as_ref().map(|a| a.balance().clone()),
            account: account,
            state: AccountState::CleanFresh,
        }
    }

    // Create a new account entry and mark it as clean and cached.
    fn new_clean_cached(account: Option<Account>) -> AccountEntry {
        AccountEntry {
            old_balance: account.as_ref().map(|a| a.balance().clone()),
            account: account,
            state: AccountState::CleanCached,
        }
    }

    // Replace data with another entry but preserve storage cache.
    fn overwrite_with(&mut self, other: AccountEntry) {
        self.state = other.state;
        match other.account {
            Some(acc) => {
                if let Some(ref mut ours) = self.account {
                    ours.overwrite_with(acc);
                } else {
                    self.account = Some(acc);
                }
            }
            None => self.account = None,
        }
    }
}

/// Check the given proof of execution.
/// `Err(ExecutionError::Internal)` indicates failure, everything else indicates
/// a successful proof (as the transaction itself may be poorly chosen).
pub fn check_proof(
    proof: &[DBValue],
    root: H256,
    transaction: &SignedTransaction,
    machine: &Machine,
    env_info: &EnvInfo,
) -> ProvedExecution {
    let backend = self::backend::ProofCheck::new(proof);
    let mut factories = Factories::default();
    factories.accountdb = ::account_db::Factory::Plain;

    let res = State::from_existing(
        backend,
        root,
        machine.account_start_nonce(env_info.number),
        factories,
    );

    let mut state = match res {
        Ok(state) => state,
        Err(_) => return ProvedExecution::BadProof,
    };

    let options = TransactOptions::with_no_tracing().save_output_from_contract();
    match state.execute(env_info, machine, transaction, options, true) {
        Ok(executed) => ProvedExecution::Complete(Box::new(executed)),
        Err(ExecutionError::Internal(_)) => ProvedExecution::BadProof,
        Err(e) => ProvedExecution::Failed(e),
    }
}

/// Prove a `virtual` transaction on the given state.
/// Returns `None` when the transacion could not be proved,
/// and a proof otherwise.
pub fn prove_transaction_virtual<H: AsHashDB<KeccakHasher, DBValue> + Send + Sync>(
    db: H,
    root: H256,
    transaction: &SignedTransaction,
    machine: &Machine,
    env_info: &EnvInfo,
    factories: Factories,
) -> Option<(Bytes, Vec<DBValue>)> {
    use self::backend::Proving;

    let backend = Proving::new(db);
    let res = State::from_existing(
        backend,
        root,
        machine.account_start_nonce(env_info.number),
        factories,
    );

    let mut state = match res {
        Ok(state) => state,
        Err(_) => return None,
    };

    let options = TransactOptions::with_no_tracing()
        .dont_check_nonce()
        .save_output_from_contract();
    match state.execute(env_info, machine, transaction, options, true) {
        Err(ExecutionError::Internal(_)) => None,
        Err(e) => {
            trace!(target: "state", "Proved call failed: {}", e);
            Some((Vec::new(), state.drop().1.extract_proof()))
        }
        Ok(res) => Some((res.output, state.drop().1.extract_proof())),
    }
}

/// Representation of the entire state of all accounts in the system.
///
/// `State` can work together with `StateDB` to share account cache.
///
/// Local cache contains changes made locally and changes accumulated
/// locally from previous commits. Global cache reflects the database
/// state and never contains any changes.
///
/// Cache items contains account data, or the flag that account does not exist
/// and modification state (see `AccountState`)
///
/// Account data can be in the following cache states:
/// * In global but not local - something that was queried from the database,
/// but never modified
/// * In local but not global - something that was just added (e.g. new account)
/// * In both with the same value - something that was changed to a new value,
/// but changed back to a previous block in the same block (same State instance)
/// * In both with different values - something that was overwritten with a
/// new value.
///
/// All read-only state queries check local cache/modifications first,
/// then global state cache. If data is not found in any of the caches
/// it is loaded from the DB to the local cache.
///
/// **** IMPORTANT *************************************************************
/// All the modifications to the account data must set the `Dirty` state in the
/// `AccountEntry`. This is done in `require` and `require_or_from`. So just
/// use that.
/// ****************************************************************************
///
/// Upon destruction all the local cache data propagated into the global cache.
/// Propagated items might be rejected if current state is non-canonical.
///
/// State checkpointing.
///
/// A new checkpoint can be created with `checkpoint()`. checkpoints can be
/// created in a hierarchy.
/// When a checkpoint is active all changes are applied directly into
/// `cache` and the original value is copied into an active checkpoint.
/// Reverting a checkpoint with `revert_to_checkpoint` involves copying
/// original values from the latest checkpoint back into `cache`. The code
/// takes care not to overwrite cached storage while doing that.
/// checkpoint can be discarded with `discard_checkpoint`. All of the orignal
/// backed-up values are moved into a parent checkpoint (if any).
///
pub struct State<B> {
    db: B,
    root: H256,
    cache: RefCell<HashMap<Address, AccountEntry>>,
    // The original account is preserved in
    checkpoints: RefCell<Vec<HashMap<Address, Option<AccountEntry>>>>,
    account_start_nonce: U256,
    factories: Factories,
}

#[derive(Copy, Clone)]
enum RequireCache {
    None,
    CodeSize,
    Code,
}

/// Mode of dealing with null accounts.
#[derive(PartialEq)]
pub enum CleanupMode<'a> {
    /// Create accounts which would be null.
    ForceCreate,
    /// Don't delete null accounts upon touching, but also don't create them.
    NoEmpty,
    /// Mark all touched accounts.
    TrackTouched(&'a mut HashSet<Address>),
}

/// Provides subset of `State` methods to query state information
pub trait StateInfo {
    /// Get the nonce of account `a`.
    fn nonce(&self, a: &Address) -> TrieResult<U256>;

    /// Get the balance of account `a`.
    fn balance(&self, a: &Address) -> TrieResult<U256>;

    /// Mutate storage of account `address` so that it is `value` for `key`.
    fn storage_at(&self, address: &Address, key: &H256) -> TrieResult<H256>;

    /// Get accounts' code.
    fn code(&self, a: &Address) -> TrieResult<Option<Arc<Bytes>>>;
}

impl<B: Backend> StateInfo for State<B> {
    fn nonce(&self, a: &Address) -> TrieResult<U256> {
        State::nonce(self, a)
    }
    fn balance(&self, a: &Address) -> TrieResult<U256> {
        State::balance(self, a)
    }
    fn storage_at(&self, address: &Address, key: &H256) -> TrieResult<H256> {
        State::storage_at(self, address, key)
    }
    fn code(&self, address: &Address) -> TrieResult<Option<Arc<Bytes>>> {
        State::code(self, address)
    }
}

const SEC_TRIE_DB_UNWRAP_STR: &'static str = "A state can only be created with valid root. Creating a SecTrieDB with a valid root will not fail. \
			 Therefore creating a SecTrieDB with this state's root will not fail.";

impl<B: Backend> State<B> {
    /// Creates new state with empty state root
    /// Used for tests.
    pub fn new(mut db: B, account_start_nonce: U256, factories: Factories) -> State<B> {
        let mut root = H256::new();
        {
            // init trie and reset root to null
            let _ = factories.trie.create(db.as_hash_db_mut(), &mut root);
        }

        State {
            db: db,
            root: root,
            cache: RefCell::new(HashMap::new()),
            checkpoints: RefCell::new(Vec::new()),
            account_start_nonce: account_start_nonce,
            factories: factories,
        }
    }

    /// Creates new state with existing state root
    pub fn from_existing(
        db: B,
        root: H256,
        account_start_nonce: U256,
        factories: Factories,
    ) -> TrieResult<State<B>> {
        if !db.as_hash_db().contains(&root) {
            return Err(Box::new(TrieError::InvalidStateRoot(root)));
        }

        let state = State {
            db: db,
            root: root,
            cache: RefCell::new(HashMap::new()),
            checkpoints: RefCell::new(Vec::new()),
            account_start_nonce: account_start_nonce,
            factories: factories,
        };

        Ok(state)
    }

    /// Get a VM factory that can execute on this state.
    pub fn vm_factory(&self) -> VmFactory {
        self.factories.vm.clone()
    }

    /// Create a recoverable checkpoint of this state. Return the checkpoint index.
    pub fn checkpoint(&mut self) -> usize {
        let checkpoints = self.checkpoints.get_mut();
        let index = checkpoints.len();
        checkpoints.push(HashMap::new());
        index
    }

    /// Merge last checkpoint with previous.
    pub fn discard_checkpoint(&mut self) {
        // merge with previous checkpoint
        let last = self.checkpoints.get_mut().pop();
        if let Some(mut checkpoint) = last {
            if let Some(ref mut prev) = self.checkpoints.get_mut().last_mut() {
                if prev.is_empty() {
                    **prev = checkpoint;
                } else {
                    for (k, v) in checkpoint.drain() {
                        prev.entry(k).or_insert(v);
                    }
                }
            }
        }
    }

    /// Revert to the last checkpoint and discard it.
    pub fn revert_to_checkpoint(&mut self) {
        if let Some(mut checkpoint) = self.checkpoints.get_mut().pop() {
            for (k, v) in checkpoint.drain() {
                match v {
                    Some(v) => {
                        match self.cache.get_mut().entry(k) {
                            Entry::Occupied(mut e) => {
                                // Merge checkpointed changes back into the main account
                                // storage preserving the cache.
                                e.get_mut().overwrite_with(v);
                            }
                            Entry::Vacant(e) => {
                                e.insert(v);
                            }
                        }
                    }
                    None => {
                        if let Entry::Occupied(e) = self.cache.get_mut().entry(k) {
                            if e.get().is_dirty() {
                                e.remove();
                            }
                        }
                    }
                }
            }
        }
    }

    fn insert_cache(&self, address: &Address, account: AccountEntry) {
        // Dirty account which is not in the cache means this is a new account.
        // It goes directly into the checkpoint as there's nothing to rever to.
        //
        // In all other cases account is read as clean first, and after that made
        // dirty in and added to the checkpoint with `note_cache`.
        let is_dirty = account.is_dirty();
        let old_value = self.cache.borrow_mut().insert(*address, account);
        if is_dirty {
            if let Some(ref mut checkpoint) = self.checkpoints.borrow_mut().last_mut() {
                checkpoint.entry(*address).or_insert(old_value);
            }
        }
    }

    fn note_cache(&self, address: &Address) {
        if let Some(ref mut checkpoint) = self.checkpoints.borrow_mut().last_mut() {
            checkpoint.entry(*address).or_insert_with(|| {
                self.cache
                    .borrow()
                    .get(address)
                    .map(AccountEntry::clone_dirty)
            });
        }
    }

    /// Destroy the current object and return root and database.
    pub fn drop(mut self) -> (H256, B) {
        self.propagate_to_global_cache();
        (self.root, self.db)
    }

    /// Destroy the current object and return single account data.
    pub fn into_account(
        self,
        account: &Address,
    ) -> TrieResult<(Option<Arc<Bytes>>, HashMap<H256, H256>)> {
        // TODO: deconstruct without cloning.
        let account = self.require(account, true)?;
        Ok((account.code().clone(), account.storage_changes().clone()))
    }

    /// Return reference to root
    pub fn root(&self) -> &H256 {
        &self.root
    }

    /// Create a new contract at address `contract`. If there is already an account at the address
    /// it will have its code reset, ready for `init_code()`.
    pub fn new_contract(
        &mut self,
        contract: &Address,
        balance: U256,
        nonce_offset: U256,
    ) -> TrieResult<()> {
        let original_storage_root = self.original_storage_root(contract)?;
        let (nonce, overflow) = self.account_start_nonce.overflowing_add(nonce_offset);
        if overflow {
            return Err(Box::new(TrieError::DecoderError(
                H256::from(contract),
                rlp::DecoderError::Custom("Nonce overflow".into()),
            )));
        }
        self.insert_cache(
            contract,
            AccountEntry::new_dirty(Some(Account::new_contract(
                balance,
                nonce,
                original_storage_root,
            ))),
        );
        Ok(())
    }

    /// Remove an existing account.
    pub fn kill_account(&mut self, account: &Address) {
        self.insert_cache(account, AccountEntry::new_dirty(None));
    }

    /// Determine whether an account exists.
    pub fn exists(&self, a: &Address) -> TrieResult<bool> {
        // Bloom filter does not contain empty accounts, so it is important here to
        // check if account exists in the database directly before EIP-161 is in effect.
        self.ensure_cached(a, RequireCache::None, false, |a| a.is_some())
    }

    /// Determine whether an account exists and if not empty.
    pub fn exists_and_not_null(&self, a: &Address) -> TrieResult<bool> {
        self.ensure_cached(a, RequireCache::None, false, |a| {
            a.map_or(false, |a| !a.is_null())
        })
    }

    /// Determine whether an account exists and has code or non-zero nonce.
    pub fn exists_and_has_code_or_nonce(&self, a: &Address) -> TrieResult<bool> {
        self.ensure_cached(a, RequireCache::CodeSize, false, |a| {
            a.map_or(false, |a| {
                a.code_hash() != KECCAK_EMPTY || *a.nonce() != self.account_start_nonce
            })
        })
    }

    /// Get the balance of account `a`.
    pub fn balance(&self, a: &Address) -> TrieResult<U256> {
        self.ensure_cached(a, RequireCache::None, true, |a| {
            a.as_ref()
                .map_or(U256::zero(), |account| *account.balance())
        })
    }

    /// Get the nonce of account `a`.
    pub fn nonce(&self, a: &Address) -> TrieResult<U256> {
        self.ensure_cached(a, RequireCache::None, true, |a| {
            a.as_ref()
                .map_or(self.account_start_nonce, |account| *account.nonce())
        })
    }

    /// Whether the base storage root of an account remains unchanged.
    pub fn is_base_storage_root_unchanged(&self, a: &Address) -> TrieResult<bool> {
        Ok(self
            .ensure_cached(a, RequireCache::None, true, |a| {
                a.as_ref()
                    .map(|account| account.is_base_storage_root_unchanged())
            })?
            .unwrap_or(true))
    }

    /// Get the storage root of account `a`.
    pub fn storage_root(&self, a: &Address) -> TrieResult<Option<H256>> {
        self.ensure_cached(a, RequireCache::None, true, |a| {
            a.as_ref().and_then(|account| account.storage_root())
        })
    }

    /// Get the original storage root since last commit of account `a`.
    pub fn original_storage_root(&self, a: &Address) -> TrieResult<H256> {
        Ok(self
            .ensure_cached(a, RequireCache::None, true, |a| {
                a.as_ref().map(|account| account.original_storage_root())
            })?
            .unwrap_or(KECCAK_NULL_RLP))
    }

    /// Get the value of storage at a specific checkpoint.
    pub fn checkpoint_storage_at(
        &self,
        start_checkpoint_index: usize,
        address: &Address,
        key: &H256,
    ) -> TrieResult<Option<H256>> {
        #[must_use]
        enum ReturnKind {
            /// Use original storage at value at this address.
            OriginalAt,
            /// The checkpoint storage value is the same as the checkpoint storage value at the next checkpoint.
            SameAsNext,
        }

        let kind = {
            let checkpoints = self.checkpoints.borrow();

            if start_checkpoint_index >= checkpoints.len() {
                // The checkpoint was not found. Return None.
                return Ok(None);
            }

            let mut kind = None;

            for checkpoint in checkpoints.iter().skip(start_checkpoint_index) {
                match checkpoint.get(address) {
                    // The account exists at this checkpoint.
                    Some(Some(AccountEntry {
                        account: Some(ref account),
                        ..
                    })) => {
                        if let Some(value) = account.cached_storage_at(key) {
                            return Ok(Some(value));
                        } else {
                            // This account has checkpoint entry, but the key is not in the entry's cache. We can use
                            // original_storage_at if current account's original storage root is the same as checkpoint
                            // account's original storage root. Otherwise, the account must be a newly created contract.
                            if account.base_storage_root() == self.original_storage_root(address)? {
                                kind = Some(ReturnKind::OriginalAt);
                                break;
                            } else {
                                // If account base storage root is different from the original storage root since last
                                // commit, then it can only be created from a new contract, where the base storage root
                                // would always be empty. Note that this branch is actually never called, because
                                // `cached_storage_at` handled this case.
                                warn!(target: "state", "Trying to get an account's cached storage value, but base storage root does not equal to original storage root! Assuming the value is empty.");
                                return Ok(Some(H256::new()));
                            }
                        }
                    }
                    // The account didn't exist at that point. Return empty value.
                    Some(Some(AccountEntry { account: None, .. })) => return Ok(Some(H256::new())),
                    // The value was not cached at that checkpoint, meaning it was not modified at all.
                    Some(None) => {
                        kind = Some(ReturnKind::OriginalAt);
                        break;
                    }
                    // This key does not have a checkpoint entry.
                    None => {
                        kind = Some(ReturnKind::SameAsNext);
                    }
                }
            }

            kind.expect("start_checkpoint_index is checked to be below checkpoints_len; for loop above must have been executed at least once; it will either early return, or set the kind value to Some; qed")
        };

        match kind {
            ReturnKind::SameAsNext => {
                // If we reached here, all previous SameAsNext failed to early return. It means that the value we want
                // to fetch is the same as current.
                Ok(Some(self.storage_at(address, key)?))
            }
            ReturnKind::OriginalAt => Ok(Some(self.original_storage_at(address, key)?)),
        }
    }

    fn storage_at_inner<FCachedStorageAt, FStorageAt>(
        &self,
        address: &Address,
        key: &H256,
        f_cached_at: FCachedStorageAt,
        f_at: FStorageAt,
    ) -> TrieResult<H256>
    where
        FCachedStorageAt: Fn(&Account, &H256) -> Option<H256>,
        FStorageAt: Fn(&Account, &dyn HashDB<KeccakHasher, DBValue>, &H256) -> TrieResult<H256>,
    {
        // Storage key search and update works like this:
        // 1. If there's an entry for the account in the local cache check for the key and return it if found.
        // 2. If there's an entry for the account in the global cache check for the key or load it into that account.
        // 3. If account is missing in the global cache load it into the local cache and cache the key there.

        {
            // check local cache first without updating
            let local_cache = self.cache.borrow_mut();
            let mut local_account = None;
            if let Some(maybe_acc) = local_cache.get(address) {
                match maybe_acc.account {
                    Some(ref account) => {
                        if let Some(value) = f_cached_at(account, key) {
                            return Ok(value);
                        } else {
                            local_account = Some(maybe_acc);
                        }
                    }
                    _ => return Ok(H256::new()),
                }
            }
            // check the global cache and and cache storage key there if found,
            let trie_res = self.db.get_cached(address, |acc| match acc {
                None => Ok(H256::new()),
                Some(a) => {
                    let account_db = self
                        .factories
                        .accountdb
                        .readonly(self.db.as_hash_db(), a.address_hash(address));
                    f_at(a, account_db.as_hash_db(), key)
                }
            });

            if let Some(res) = trie_res {
                return res;
            }

            // otherwise cache the account localy and cache storage key there.
            if let Some(ref mut acc) = local_account {
                if let Some(ref account) = acc.account {
                    let account_db = self
                        .factories
                        .accountdb
                        .readonly(self.db.as_hash_db(), account.address_hash(address));
                    return f_at(account, account_db.as_hash_db(), key);
                } else {
                    return Ok(H256::new());
                }
            }
        }

        // check if the account could exist before any requests to trie
        if self.db.is_known_null(address) {
            return Ok(H256::zero());
        }

        // account is not found in the global cache, get from the DB and insert into local
        let db = &self.db.as_hash_db();
        let db = self
            .factories
            .trie
            .readonly(db, &self.root)
            .expect(SEC_TRIE_DB_UNWRAP_STR);
        let from_rlp = |b: &[u8]| Account::from_rlp(b).expect("decoding db value failed");
        let maybe_acc = db.get_with(address, from_rlp)?;
        let r = maybe_acc.as_ref().map_or(Ok(H256::new()), |a| {
            let account_db = self
                .factories
                .accountdb
                .readonly(self.db.as_hash_db(), a.address_hash(address));
            f_at(a, account_db.as_hash_db(), key)
        });
        self.insert_cache(address, AccountEntry::new_clean(maybe_acc));
        r
    }

    /// Mutate storage of account `address` so that it is `value` for `key`.
    pub fn storage_at(&self, address: &Address, key: &H256) -> TrieResult<H256> {
        self.storage_at_inner(
            address,
            key,
            |account, key| account.cached_storage_at(key),
            |account, db, key| account.storage_at(db, key),
        )
    }

    /// Get the value of storage after last state commitment.
    pub fn original_storage_at(&self, address: &Address, key: &H256) -> TrieResult<H256> {
        self.storage_at_inner(
            address,
            key,
            |account, key| account.cached_original_storage_at(key),
            |account, db, key| account.original_storage_at(db, key),
        )
    }

    /// Get accounts' code.
    pub fn code(&self, a: &Address) -> TrieResult<Option<Arc<Bytes>>> {
        self.ensure_cached(a, RequireCache::Code, true, |a| {
            a.as_ref().map_or(None, |a| a.code().clone())
        })
    }

    /// Get an account's code hash.
    pub fn code_hash(&self, a: &Address) -> TrieResult<Option<H256>> {
        self.ensure_cached(a, RequireCache::None, true, |a| {
            a.as_ref().map(|a| a.code_hash())
        })
    }

    /// Get accounts' code size.
    pub fn code_size(&self, a: &Address) -> TrieResult<Option<usize>> {
        self.ensure_cached(a, RequireCache::CodeSize, true, |a| {
            a.as_ref().and_then(|a| a.code_size())
        })
    }

    /// Add `incr` to the balance of account `a`.
    pub fn add_balance(
        &mut self,
        a: &Address,
        incr: &U256,
        cleanup_mode: CleanupMode,
    ) -> TrieResult<()> {
        trace!(target: "state", "add_balance({}, {}): {}", a, incr, self.balance(a)?);
        let is_value_transfer = !incr.is_zero();
        if is_value_transfer || (cleanup_mode == CleanupMode::ForceCreate && !self.exists(a)?) {
            self.require(a, false)?.add_balance(incr);
        } else if let CleanupMode::TrackTouched(set) = cleanup_mode {
            if self.exists(a)? {
                set.insert(*a);
                self.touch(a)?;
            }
        }
        Ok(())
    }

    /// Subtract `decr` from the balance of account `a`.
    pub fn sub_balance(
        &mut self,
        a: &Address,
        decr: &U256,
        cleanup_mode: &mut CleanupMode,
    ) -> TrieResult<()> {
        trace!(target: "state", "sub_balance({}, {}): {}", a, decr, self.balance(a)?);
        if !decr.is_zero() || !self.exists(a)? {
            self.require(a, false)?.sub_balance(decr);
        }
        if let CleanupMode::TrackTouched(ref mut set) = *cleanup_mode {
            set.insert(*a);
        }
        Ok(())
    }

    /// Subtracts `by` from the balance of `from` and adds it to that of `to`.
    pub fn transfer_balance(
        &mut self,
        from: &Address,
        to: &Address,
        by: &U256,
        mut cleanup_mode: CleanupMode,
    ) -> TrieResult<()> {
        self.sub_balance(from, by, &mut cleanup_mode)?;
        self.add_balance(to, by, cleanup_mode)?;
        Ok(())
    }

    /// Increment the nonce of account `a` by 1.
    pub fn inc_nonce(&mut self, a: &Address) -> TrieResult<()> {
        self.require(a, false).map(|mut x| x.inc_nonce())
    }

    /// Mutate storage of account `a` so that it is `value` for `key`.
    pub fn set_storage(&mut self, a: &Address, key: H256, value: H256) -> TrieResult<()> {
        trace!(target: "state", "set_storage({}:{:x} to {:x})", a, key, value);
        if self.storage_at(a, &key)? != value {
            self.require(a, false)?.set_storage(key, value)
        }

        Ok(())
    }

    /// Initialise the code of account `a` so that it is `code`.
    /// NOTE: Account should have been created with `new_contract`.
    pub fn init_code(&mut self, a: &Address, code: Bytes) -> TrieResult<()> {
        self.require_or_from(
            a,
            true,
            || Account::new_contract(0.into(), self.account_start_nonce, KECCAK_NULL_RLP),
            |_| {},
        )?
        .init_code(code);
        Ok(())
    }

    /// Reset the code of account `a` so that it is `code`.
    pub fn reset_code(&mut self, a: &Address, code: Bytes) -> TrieResult<()> {
        self.require_or_from(
            a,
            true,
            || Account::new_contract(0.into(), self.account_start_nonce, KECCAK_NULL_RLP),
            |_| {},
        )?
        .reset_code(code);
        Ok(())
    }

    /// Execute a given transaction, producing a receipt and an optional trace.
    /// This will change the state accordingly.
    pub fn apply(
        &mut self,
        env_info: &EnvInfo,
        machine: &Machine,
        t: &SignedTransaction,
        tracing: bool,
    ) -> ApplyResult<FlatTrace, VMTrace> {
        if tracing {
            let options = TransactOptions::with_tracing();
            self.apply_with_tracing(env_info, machine, t, options.tracer, options.vm_tracer)
        } else {
            let options = TransactOptions::with_no_tracing();
            self.apply_with_tracing(env_info, machine, t, options.tracer, options.vm_tracer)
        }
    }

    /// Execute a given transaction with given tracer and VM tracer producing a receipt and an optional trace.
    /// This will change the state accordingly.
    pub fn apply_with_tracing<V, T>(
        &mut self,
        env_info: &EnvInfo,
        machine: &Machine,
        t: &SignedTransaction,
        tracer: T,
        vm_tracer: V,
    ) -> ApplyResult<T::Output, V::Output>
    where
        T: trace::Tracer,
        V: trace::VMTracer,
    {
        let options = TransactOptions::new(tracer, vm_tracer);
        let e = self.execute(env_info, machine, t, options, false)?;
        let params = machine.params();

        let eip658 = env_info.number >= params.eip658_transition;
        let no_intermediate_commits = eip658
            || (env_info.number >= params.eip98_transition
                && env_info.number >= params.validate_receipts_transition);

        let outcome = if no_intermediate_commits {
            if eip658 {
                TransactionOutcome::StatusCode(if e.exception.is_some() { 0 } else { 1 })
            } else {
                TransactionOutcome::Unknown
            }
        } else {
            self.commit()?;
            TransactionOutcome::StateRoot(self.root().clone())
        };

        let output = e.output;
        let receipt = Receipt::new(outcome, e.cumulative_gas_used, e.logs);
        trace!(target: "state", "Transaction receipt: {:?}", receipt);

        Ok(ApplyOutcome {
            receipt,
            output,
            trace: e.trace,
            vm_trace: e.vm_trace,
        })
    }

    // Execute a given transaction without committing changes.
    //
    // `virt` signals that we are executing outside of a block set and restrictions like
    // gas limits and gas costs should be lifted.
    fn execute<T, V>(
        &mut self,
        env_info: &EnvInfo,
        machine: &Machine,
        t: &SignedTransaction,
        options: TransactOptions<T, V>,
        virt: bool,
    ) -> Result<Executed<T::Output, V::Output>, ExecutionError>
    where
        T: trace::Tracer,
        V: trace::VMTracer,
    {
        let schedule = machine.schedule(env_info.number);
        let mut e = Executive::new(self, env_info, machine, &schedule);

        match virt {
            true => e.transact_virtual(t, options),
            false => e.transact(t, options),
        }
    }

    fn touch(&mut self, a: &Address) -> TrieResult<()> {
        self.require(a, false)?;
        Ok(())
    }

    /// Commits our cached account changes into the trie.
    pub fn commit(&mut self) -> Result<(), Error> {
        assert!(self.checkpoints.borrow().is_empty());
        // first, commit the sub trees.
        let mut accounts = self.cache.borrow_mut();
        for (address, ref mut a) in accounts.iter_mut().filter(|&(_, ref a)| a.is_dirty()) {
            if let Some(ref mut account) = a.account {
                let addr_hash = account.address_hash(address);
                {
                    let mut account_db = self
                        .factories
                        .accountdb
                        .create(self.db.as_hash_db_mut(), addr_hash);
                    account.commit_storage(&self.factories.trie, account_db.as_hash_db_mut())?;
                    account.commit_code(account_db.as_hash_db_mut());
                }
                if !account.is_empty() {
                    self.db.note_non_null_account(address);
                }
            }
        }

        {
            let mut trie = self
                .factories
                .trie
                .from_existing(self.db.as_hash_db_mut(), &mut self.root)?;
            for (address, ref mut a) in accounts.iter_mut().filter(|&(_, ref a)| a.is_dirty()) {
                a.state = AccountState::Committed;
                match a.account {
                    Some(ref mut account) => {
                        trie.insert(address, &account.rlp())?;
                    }
                    None => {
                        trie.remove(address)?;
                    }
                };
            }
        }

        Ok(())
    }

    /// Propagate local cache into shared canonical state cache.
    fn propagate_to_global_cache(&mut self) {
        let mut addresses = self.cache.borrow_mut();
        trace!("Committing cache {:?} entries", addresses.len());
        for (address, a) in addresses.drain().filter(|&(_, ref a)| {
            a.state == AccountState::Committed || a.state == AccountState::CleanFresh
        }) {
            self.db
                .add_to_account_cache(address, a.account, a.state == AccountState::Committed);
        }
    }

    /// Clear state cache
    pub fn clear(&mut self) {
        assert!(self.checkpoints.borrow().is_empty());
        self.cache.borrow_mut().clear();
    }

    /// Remove any touched empty or dust accounts.
    pub fn kill_garbage(
        &mut self,
        touched: &HashSet<Address>,
        remove_empty_touched: bool,
        min_balance: &Option<U256>,
        kill_contracts: bool,
    ) -> TrieResult<()> {
        let to_kill: HashSet<_> = {
            self.cache.borrow().iter().filter_map(|(address, ref entry)|
			if touched.contains(address) && // Check all touched accounts
				((remove_empty_touched && entry.exists_and_is_null()) // Remove all empty touched accounts.
				|| min_balance.map_or(false, |ref balance| entry.account.as_ref().map_or(false, |account|
					(account.is_basic() || kill_contracts) // Remove all basic and optionally contract accounts where balance has been decreased.
					&& account.balance() < balance && entry.old_balance.as_ref().map_or(false, |b| account.balance() < b)))) {

				Some(address.clone())
			} else { None }).collect()
        };
        for address in to_kill {
            self.kill_account(&address);
        }
        Ok(())
    }

    /// Populate the state from `accounts`.
    /// Used for tests.
    pub fn populate_from(&mut self, accounts: PodState) {
        assert!(self.checkpoints.borrow().is_empty());
        for (add, acc) in accounts.drain().into_iter() {
            self.cache
                .borrow_mut()
                .insert(add, AccountEntry::new_dirty(Some(Account::from_pod(acc))));
        }
    }

    /// Populate a PodAccount map from this state.
    fn to_pod_cache(&self) -> PodState {
        assert!(self.checkpoints.borrow().is_empty());
        PodState::from(
            self.cache
                .borrow()
                .iter()
                .fold(BTreeMap::new(), |mut m, (add, opt)| {
                    if let Some(ref acc) = opt.account {
                        m.insert(*add, PodAccount::from_account(acc));
                    }
                    m
                }),
        )
    }

    #[cfg(feature = "to-pod-full")]
    /// Populate a PodAccount map from this state.
    /// Warning this is not for real time use.
    /// Use of this method requires FatDB mode to be able
    /// to iterate on accounts.
    pub fn to_pod_full(&self) -> Result<PodState, Error> {
        assert!(self.checkpoints.borrow().is_empty());
        assert!(self.factories.trie.is_fat());

        let mut result = BTreeMap::new();

        let db = &self.db.as_hash_db();
        let trie = self.factories.trie.readonly(db, &self.root)?;

        // put trie in cache
        for item in trie.iter()? {
            if let Ok((addr, _dbval)) = item {
                let address = Address::from_slice(&addr);
                let _ = self.require(&address, true);
            }
        }

        // Resolve missing part
        for (add, opt) in self.cache.borrow().iter() {
            if let Some(ref acc) = opt.account {
                let pod_account = self.account_to_pod_account(acc, add)?;
                result.insert(add.clone(), pod_account);
            }
        }

        Ok(PodState::from(result))
    }

    /// Create a PodAccount from an account.
    /// Differs from existing method by including all storage
    /// values of the account to the PodAccount.
    /// This function is only intended for use in small tests or with fresh accounts.
    /// It requires FatDB.
    #[cfg(feature = "to-pod-full")]
    fn account_to_pod_account(
        &self,
        account: &Account,
        address: &Address,
    ) -> Result<PodAccount, Error> {
        let mut pod_storage = BTreeMap::new();
        let addr_hash = account.address_hash(address);
        let accountdb = self
            .factories
            .accountdb
            .readonly(self.db.as_hash_db(), addr_hash);
        let root = account.base_storage_root();

        let accountdb = &accountdb.as_hash_db();
        let trie = self.factories.trie.readonly(accountdb, &root)?;
        for o_kv in trie.iter()? {
            if let Ok((key, val)) = o_kv {
                pod_storage.insert(
                    key[..].into(),
                    rlp::decode::<U256>(&val[..])
                        .expect("Decoded from trie which was encoded from the same type; qed")
                        .into(),
                );
            }
        }

        let mut pod_account = PodAccount::from_account(&account);
        // cached one first
        pod_storage.append(&mut pod_account.storage);
        pod_account.storage = pod_storage;
        Ok(pod_account)
    }

    /// Populate a PodAccount map from this state, with another state as the account and storage query.
    fn to_pod_diff<X: Backend>(&mut self, query: &State<X>) -> TrieResult<PodState> {
        assert!(self.checkpoints.borrow().is_empty());

        // Merge PodAccount::to_pod for cache of self and `query`.
        let all_addresses = self
            .cache
            .borrow()
            .keys()
            .cloned()
            .chain(query.cache.borrow().keys().cloned())
            .collect::<BTreeSet<_>>();

        Ok(PodState::from(all_addresses.into_iter().fold(
            Ok(BTreeMap::new()),
            |m: TrieResult<_>, address| {
                let mut m = m?;

                let account = self.ensure_cached(&address, RequireCache::Code, true, |acc| {
                    acc.map(|acc| {
                        // Merge all modified storage keys.
                        let all_keys = {
                            let self_keys = acc
                                .storage_changes()
                                .keys()
                                .cloned()
                                .collect::<BTreeSet<_>>();

                            if let Some(ref query_storage) =
                                query.cache.borrow().get(&address).and_then(|opt| {
                                    Some(
                                        opt.account
                                            .as_ref()?
                                            .storage_changes()
                                            .keys()
                                            .cloned()
                                            .collect::<BTreeSet<_>>(),
                                    )
                                })
                            {
                                self_keys.union(&query_storage).cloned().collect::<Vec<_>>()
                            } else {
                                self_keys.into_iter().collect::<Vec<_>>()
                            }
                        };

                        // Storage must be fetched after ensure_cached to avoid borrow problem.
                        (
                            *acc.balance(),
                            *acc.nonce(),
                            all_keys,
                            acc.code().map(|x| x.to_vec()),
                        )
                    })
                })?;

                if let Some((balance, nonce, storage_keys, code)) = account {
                    let storage = storage_keys.into_iter().fold(
                        Ok(BTreeMap::new()),
                        |s: TrieResult<_>, key| {
                            let mut s = s?;

                            s.insert(key, self.storage_at(&address, &key)?);
                            Ok(s)
                        },
                    )?;

                    m.insert(
                        address,
                        PodAccount {
                            balance,
                            nonce,
                            storage,
                            code,
                        },
                    );
                }

                Ok(m)
            },
        )?))
    }

    /// Returns a `StateDiff` describing the difference from `orig` to `self`.
    /// Consumes self.
    pub fn diff_from<X: Backend>(&self, mut orig: State<X>) -> TrieResult<StateDiff> {
        let pod_state_post = self.to_pod_cache();
        let pod_state_pre = orig.to_pod_diff(self)?;
        Ok(pod_state::diff_pod(&pod_state_pre, &pod_state_post))
    }

    /// Load required account data from the databases. Returns whether the cache succeeds.
    #[must_use]
    fn update_account_cache(
        require: RequireCache,
        account: &mut Account,
        state_db: &B,
        db: &dyn HashDB<KeccakHasher, DBValue>,
    ) -> bool {
        if let RequireCache::None = require {
            return true;
        }

        if account.is_cached() {
            return true;
        }

        // if there's already code in the global cache, always cache it localy
        let hash = account.code_hash();
        match state_db.get_cached_code(&hash) {
            Some(code) => {
                account.cache_given_code(code);
                true
            }
            None => match require {
                RequireCache::None => true,
                RequireCache::Code => {
                    if let Some(code) = account.cache_code(db) {
                        // propagate code loaded from the database to
                        // the global code cache.
                        state_db.cache_code(hash, code);
                        true
                    } else {
                        false
                    }
                }
                RequireCache::CodeSize => account.cache_code_size(db),
            },
        }
    }

    /// Check caches for required data
    /// First searches for account in the local, then the shared cache.
    /// Populates local cache if nothing found.
    fn ensure_cached<F, U>(
        &self,
        a: &Address,
        require: RequireCache,
        check_null: bool,
        f: F,
    ) -> TrieResult<U>
    where
        F: Fn(Option<&Account>) -> U,
    {
        // check local cache first
        if let Some(ref mut maybe_acc) = self.cache.borrow_mut().get_mut(a) {
            if let Some(ref mut account) = maybe_acc.account {
                let accountdb = self
                    .factories
                    .accountdb
                    .readonly(self.db.as_hash_db(), account.address_hash(a));
                if Self::update_account_cache(require, account, &self.db, accountdb.as_hash_db()) {
                    return Ok(f(Some(account)));
                } else {
                    return Err(Box::new(TrieError::IncompleteDatabase(H256::from(a))));
                }
            }
            return Ok(f(None));
        }
        // check global cache
        let result = self.db.get_cached(a, |mut acc| {
            if let Some(ref mut account) = acc {
                let accountdb = self
                    .factories
                    .accountdb
                    .readonly(self.db.as_hash_db(), account.address_hash(a));
                if !Self::update_account_cache(require, account, &self.db, accountdb.as_hash_db()) {
                    return Err(Box::new(TrieError::IncompleteDatabase(H256::from(a))));
                }
            }
            Ok(f(acc.map(|a| &*a)))
        });
        match result {
            Some(r) => Ok(r?),
            None => {
                // first check if it is not in database for sure
                if check_null && self.db.is_known_null(a) {
                    return Ok(f(None));
                }

                // not found in the global cache, get from the DB and insert into local
                let db = &self.db.as_hash_db();
                let db = self.factories.trie.readonly(db, &self.root)?;
                let from_rlp = |b: &[u8]| Account::from_rlp(b).expect("decoding db value failed");
                let mut maybe_acc = db.get_with(a, from_rlp)?;
                if let Some(ref mut account) = maybe_acc.as_mut() {
                    let accountdb = self
                        .factories
                        .accountdb
                        .readonly(self.db.as_hash_db(), account.address_hash(a));
                    if !Self::update_account_cache(
                        require,
                        account,
                        &self.db,
                        accountdb.as_hash_db(),
                    ) {
                        return Err(Box::new(TrieError::IncompleteDatabase(H256::from(a))));
                    }
                }
                let r = f(maybe_acc.as_ref());
                self.insert_cache(a, AccountEntry::new_clean(maybe_acc));
                Ok(r)
            }
        }
    }

    /// Pull account `a` in our cache from the trie DB. `require_code` requires that the code be cached, too.
    fn require<'a>(&'a self, a: &Address, require_code: bool) -> TrieResult<RefMut<'a, Account>> {
        self.require_or_from(
            a,
            require_code,
            || Account::new_basic(0u8.into(), self.account_start_nonce),
            |_| {},
        )
    }

    /// Pull account `a` in our cache from the trie DB. `require_code` requires that the code be cached, too.
    /// If it doesn't exist, make account equal the evaluation of `default`.
    fn require_or_from<'a, F, G>(
        &'a self,
        a: &Address,
        require_code: bool,
        default: F,
        not_default: G,
    ) -> TrieResult<RefMut<'a, Account>>
    where
        F: FnOnce() -> Account,
        G: FnOnce(&mut Account),
    {
        let contains_key = self.cache.borrow().contains_key(a);
        if !contains_key {
            match self.db.get_cached_account(a) {
                Some(acc) => self.insert_cache(a, AccountEntry::new_clean_cached(acc)),
                None => {
                    let maybe_acc = if !self.db.is_known_null(a) {
                        let db = &self.db.as_hash_db();
                        let db = self.factories.trie.readonly(db, &self.root)?;
                        let from_rlp =
                            |b: &[u8]| Account::from_rlp(b).expect("decoding db value failed");
                        AccountEntry::new_clean(db.get_with(a, from_rlp)?)
                    } else {
                        AccountEntry::new_clean(None)
                    };
                    self.insert_cache(a, maybe_acc);
                }
            }
        }
        self.note_cache(a);

        // at this point the entry is guaranteed to be in the cache.
        let mut account = RefMut::map(self.cache.borrow_mut(), |c| {
            let entry = c
                .get_mut(a)
                .expect("entry known to exist in the cache; qed");

            match &mut entry.account {
                &mut Some(ref mut acc) => not_default(acc),
                slot => *slot = Some(default()),
            }

            // set the dirty flag after changing account data.
            entry.state = AccountState::Dirty;
            entry
                .account
                .as_mut()
                .expect("Required account must always exist; qed")
        });

        if require_code {
            let addr_hash = account.address_hash(a);
            let accountdb = self
                .factories
                .accountdb
                .readonly(self.db.as_hash_db(), addr_hash);

            if !Self::update_account_cache(
                RequireCache::Code,
                &mut account,
                &self.db,
                accountdb.as_hash_db(),
            ) {
                return Err(Box::new(TrieError::IncompleteDatabase(H256::from(a))));
            }
        }

        Ok(account)
    }

    /// Replace account code and storage. Creates account if it does not exist.
    pub fn patch_account(
        &self,
        a: &Address,
        code: Arc<Bytes>,
        storage: HashMap<H256, H256>,
    ) -> TrieResult<()> {
        Ok(self
            .require(a, false)?
            .reset_code_and_storage(code, storage))
    }
}

// State proof implementations; useful for light client protocols.
impl<B: Backend> State<B> {
    /// Prove an account's existence or nonexistence in the state trie.
    /// Returns a merkle proof of the account's trie node omitted or an encountered trie error.
    /// If the account doesn't exist in the trie, prove that and return defaults.
    /// Requires a secure trie to be used for accurate results.
    /// `account_key` == keccak(address)
    pub fn prove_account(&self, account_key: H256) -> TrieResult<(Vec<Bytes>, BasicAccount)> {
        let mut recorder = Recorder::new();
        let db = &self.db.as_hash_db();
        let trie = TrieDB::new(db, &self.root)?;
        let maybe_account: Option<BasicAccount> = {
            let panicky_decoder = |bytes: &[u8]| {
                ::rlp::decode(bytes).unwrap_or_else(|_| {
                    panic!(
                        "prove_account, could not query trie for account key={}",
                        &account_key
                    )
                })
            };
            let query = (&mut recorder, panicky_decoder);
            trie.get_with(&account_key, query)?
        };
        let account = maybe_account.unwrap_or_else(|| BasicAccount {
            balance: 0.into(),
            nonce: self.account_start_nonce,
            code_hash: KECCAK_EMPTY,
            storage_root: KECCAK_NULL_RLP,
        });

        Ok((
            recorder.drain().into_iter().map(|r| r.data).collect(),
            account,
        ))
    }

    /// Prove an account's storage key's existence or nonexistence in the state.
    /// Returns a merkle proof of the account's storage trie.
    /// Requires a secure trie to be used for correctness.
    /// `account_key` == keccak(address)
    /// `storage_key` == keccak(key)
    pub fn prove_storage(
        &self,
        account_key: H256,
        storage_key: H256,
    ) -> TrieResult<(Vec<Bytes>, H256)> {
        // TODO: probably could look into cache somehow but it's keyed by
        // address, not keccak(address).
        let db = &self.db.as_hash_db();
        let trie = TrieDB::new(db, &self.root)?;
        let from_rlp = |b: &[u8]| Account::from_rlp(b).expect("decoding db value failed");
        let acc = match trie.get_with(&account_key, from_rlp)? {
            Some(acc) => acc,
            None => return Ok((Vec::new(), H256::new())),
        };

        let account_db = self
            .factories
            .accountdb
            .readonly(self.db.as_hash_db(), account_key);
        acc.prove_storage(account_db.as_hash_db(), storage_key)
    }
}

impl<B: Backend> fmt::Debug for State<B> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{:?}", self.cache.borrow())
    }
}

impl State<StateDB> {
    /// Get a reference to the underlying state DB.
    pub fn db(&self) -> &StateDB {
        &self.db
    }
}

// TODO: cloning for `State` shouldn't be possible in general; Remove this and use
// checkpoints where possible.
impl Clone for State<StateDB> {
    fn clone(&self) -> State<StateDB> {
        let cache = {
            let mut cache: HashMap<Address, AccountEntry> = HashMap::new();
            for (key, val) in self.cache.borrow().iter() {
                if let Some(entry) = val.clone_if_dirty() {
                    cache.insert(key.clone(), entry);
                }
            }
            cache
        };

        State {
            db: self.db.boxed_clone(),
            root: self.root.clone(),
            cache: RefCell::new(cache),
            checkpoints: RefCell::new(Vec::new()),
            account_start_nonce: self.account_start_nonce.clone(),
            factories: self.factories.clone(),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use ethereum_types::{Address, H256, U256};
    use ethkey::Secret;
    use evm::CallType;
    use hash::{keccak, KECCAK_NULL_RLP};
    use machine::EthereumMachine;
    use rustc_hex::FromHex;
    use spec::*;
    use std::{str::FromStr, sync::Arc};
    use test_helpers::{get_temp_state, get_temp_state_db};
    use trace::{trace, FlatTrace, TraceError};
    use types::transaction::*;
    use vm::EnvInfo;

    fn secret() -> Secret {
        keccak("").into()
    }

    fn make_frontier_machine(max_depth: usize) -> EthereumMachine {
        let mut machine = ::ethereum::new_frontier_test_machine();
        machine.set_schedule_creation_rules(Box::new(move |s, _| s.max_depth = max_depth));
        machine
    }

    #[test]
    fn should_apply_create_transaction() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = make_frontier_machine(5);

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Create,
            value: 100.into(),
            data: FromHex::from_hex("601080600c6000396000f3006000355415600957005b60203560003555")
                .unwrap(),
        }
        .sign(&secret(), None);

        state
            .add_balance(&t.sender(), &(100.into()), CleanupMode::NoEmpty)
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();
        let expected_trace = vec![FlatTrace {
            trace_address: Default::default(),
            subtraces: 0,
            action: trace::Action::Create(trace::Create {
                from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                value: 100.into(),
                gas: 77412.into(),
                init: vec![
                    96, 16, 128, 96, 12, 96, 0, 57, 96, 0, 243, 0, 96, 0, 53, 84, 21, 96, 9, 87, 0,
                    91, 96, 32, 53, 96, 0, 53, 85,
                ],
            }),
            result: trace::Res::Create(trace::CreateResult {
                gas_used: U256::from(3224),
                address: Address::from_str("8988167e088c87cd314df6d3c2b83da5acb93ace").unwrap(),
                code: vec![96, 0, 53, 84, 21, 96, 9, 87, 0, 91, 96, 32, 53, 96, 0, 53],
            }),
        }];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_work_when_cloned() {
        let _ = env_logger::try_init();

        let a = Address::zero();

        let mut state = {
            let mut state = get_temp_state();
            assert_eq!(state.exists(&a).unwrap(), false);
            state.inc_nonce(&a).unwrap();
            state.commit().unwrap();
            state.clone()
        };

        state.inc_nonce(&a).unwrap();
        state.commit().unwrap();
    }

    #[test]
    fn should_trace_failed_create_transaction() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = make_frontier_machine(5);

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Create,
            value: 100.into(),
            data: FromHex::from_hex("5b600056").unwrap(),
        }
        .sign(&secret(), None);

        state
            .add_balance(&t.sender(), &(100.into()), CleanupMode::NoEmpty)
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();
        let expected_trace = vec![FlatTrace {
            trace_address: Default::default(),
            action: trace::Action::Create(trace::Create {
                from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                value: 100.into(),
                gas: 78792.into(),
                init: vec![91, 96, 0, 86],
            }),
            result: trace::Res::FailedCreate(TraceError::OutOfGas),
            subtraces: 0,
        }];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_trace_call_transaction() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = make_frontier_machine(5);

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 100.into(),
            data: vec![],
        }
        .sign(&secret(), None);

        state
            .init_code(&0xa.into(), FromHex::from_hex("6000").unwrap())
            .unwrap();
        state
            .add_balance(&t.sender(), &(100.into()), CleanupMode::NoEmpty)
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();
        let expected_trace = vec![FlatTrace {
            trace_address: Default::default(),
            action: trace::Action::Call(trace::Call {
                from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                to: 0xa.into(),
                value: 100.into(),
                gas: 79000.into(),
                input: vec![],
                call_type: CallType::Call,
            }),
            result: trace::Res::Call(trace::CallResult {
                gas_used: U256::from(3),
                output: vec![],
            }),
            subtraces: 0,
        }];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_trace_basic_call_transaction() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = make_frontier_machine(5);

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 100.into(),
            data: vec![],
        }
        .sign(&secret(), None);

        state
            .add_balance(&t.sender(), &(100.into()), CleanupMode::NoEmpty)
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();
        let expected_trace = vec![FlatTrace {
            trace_address: Default::default(),
            action: trace::Action::Call(trace::Call {
                from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                to: 0xa.into(),
                value: 100.into(),
                gas: 79000.into(),
                input: vec![],
                call_type: CallType::Call,
            }),
            result: trace::Res::Call(trace::CallResult {
                gas_used: U256::from(0),
                output: vec![],
            }),
            subtraces: 0,
        }];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_trace_call_transaction_to_builtin() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = Spec::new_test_machine();

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0x1.into()),
            value: 0.into(),
            data: vec![],
        }
        .sign(&secret(), None);

        let result = state.apply(&info, &machine, &t, true).unwrap();

        let expected_trace = vec![FlatTrace {
            trace_address: Default::default(),
            action: trace::Action::Call(trace::Call {
                from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                to: "0000000000000000000000000000000000000001".into(),
                value: 0.into(),
                gas: 79_000.into(),
                input: vec![],
                call_type: CallType::Call,
            }),
            result: trace::Res::Call(trace::CallResult {
                gas_used: U256::from(3000),
                output: vec![],
            }),
            subtraces: 0,
        }];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_not_trace_subcall_transaction_to_builtin() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = Spec::new_test_machine();

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 0.into(),
            data: vec![],
        }
        .sign(&secret(), None);

        state
            .init_code(
                &0xa.into(),
                FromHex::from_hex("600060006000600060006001610be0f1").unwrap(),
            )
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();

        let expected_trace = vec![FlatTrace {
            trace_address: Default::default(),
            action: trace::Action::Call(trace::Call {
                from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                to: 0xa.into(),
                value: 0.into(),
                gas: 79000.into(),
                input: vec![],
                call_type: CallType::Call,
            }),
            result: trace::Res::Call(trace::CallResult {
                gas_used: U256::from(3_721), // in post-eip150
                output: vec![],
            }),
            subtraces: 0,
        }];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_trace_callcode_properly() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = Spec::new_test_machine();

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 0.into(),
            data: vec![],
        }
        .sign(&secret(), None);

        state
            .init_code(
                &0xa.into(),
                FromHex::from_hex("60006000600060006000600b611000f2").unwrap(),
            )
            .unwrap();
        state
            .init_code(&0xb.into(), FromHex::from_hex("6000").unwrap())
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();

        let expected_trace = vec![
            FlatTrace {
                trace_address: Default::default(),
                subtraces: 1,
                action: trace::Action::Call(trace::Call {
                    from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                    to: 0xa.into(),
                    value: 0.into(),
                    gas: 79000.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: 724.into(), // in post-eip150
                    output: vec![],
                }),
            },
            FlatTrace {
                trace_address: vec![0].into_iter().collect(),
                subtraces: 0,
                action: trace::Action::Call(trace::Call {
                    from: 0xa.into(),
                    to: 0xb.into(),
                    value: 0.into(),
                    gas: 4096.into(),
                    input: vec![],
                    call_type: CallType::CallCode,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: 3.into(),
                    output: vec![],
                }),
            },
        ];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_trace_delegatecall_properly() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        info.number = 0x789b0;
        let machine = Spec::new_test_machine();

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 0.into(),
            data: vec![],
        }
        .sign(&secret(), None);

        state
            .init_code(
                &0xa.into(),
                FromHex::from_hex("6000600060006000600b618000f4").unwrap(),
            )
            .unwrap();
        state
            .init_code(
                &0xb.into(),
                FromHex::from_hex("60056000526001601ff3").unwrap(),
            )
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();

        let expected_trace = vec![
            FlatTrace {
                trace_address: Default::default(),
                subtraces: 1,
                action: trace::Action::Call(trace::Call {
                    from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                    to: 0xa.into(),
                    value: 0.into(),
                    gas: 79000.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: U256::from(736), // in post-eip150
                    output: vec![],
                }),
            },
            FlatTrace {
                trace_address: vec![0].into_iter().collect(),
                subtraces: 0,
                action: trace::Action::Call(trace::Call {
                    from: 0xa.into(),
                    to: 0xb.into(),
                    value: 0.into(),
                    gas: 32768.into(),
                    input: vec![],
                    call_type: CallType::DelegateCall,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: 18.into(),
                    output: vec![5],
                }),
            },
        ];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_trace_failed_call_transaction() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = make_frontier_machine(5);

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 100.into(),
            data: vec![],
        }
        .sign(&secret(), None);

        state
            .init_code(&0xa.into(), FromHex::from_hex("5b600056").unwrap())
            .unwrap();
        state
            .add_balance(&t.sender(), &(100.into()), CleanupMode::NoEmpty)
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();
        let expected_trace = vec![FlatTrace {
            trace_address: Default::default(),
            action: trace::Action::Call(trace::Call {
                from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                to: 0xa.into(),
                value: 100.into(),
                gas: 79000.into(),
                input: vec![],
                call_type: CallType::Call,
            }),
            result: trace::Res::FailedCall(TraceError::OutOfGas),
            subtraces: 0,
        }];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_trace_call_with_subcall_transaction() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = make_frontier_machine(5);

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 100.into(),
            data: vec![],
        }
        .sign(&secret(), None);

        state
            .init_code(
                &0xa.into(),
                FromHex::from_hex("60006000600060006000600b602b5a03f1").unwrap(),
            )
            .unwrap();
        state
            .init_code(&0xb.into(), FromHex::from_hex("6000").unwrap())
            .unwrap();
        state
            .add_balance(&t.sender(), &(100.into()), CleanupMode::NoEmpty)
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();

        let expected_trace = vec![
            FlatTrace {
                trace_address: Default::default(),
                subtraces: 1,
                action: trace::Action::Call(trace::Call {
                    from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                    to: 0xa.into(),
                    value: 100.into(),
                    gas: 79000.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: U256::from(69),
                    output: vec![],
                }),
            },
            FlatTrace {
                trace_address: vec![0].into_iter().collect(),
                subtraces: 0,
                action: trace::Action::Call(trace::Call {
                    from: 0xa.into(),
                    to: 0xb.into(),
                    value: 0.into(),
                    gas: 78934.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: U256::from(3),
                    output: vec![],
                }),
            },
        ];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_trace_call_with_basic_subcall_transaction() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = make_frontier_machine(5);

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 100.into(),
            data: vec![],
        }
        .sign(&secret(), None);

        state
            .init_code(
                &0xa.into(),
                FromHex::from_hex("60006000600060006045600b6000f1").unwrap(),
            )
            .unwrap();
        state
            .add_balance(&t.sender(), &(100.into()), CleanupMode::NoEmpty)
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();
        let expected_trace = vec![
            FlatTrace {
                trace_address: Default::default(),
                subtraces: 1,
                action: trace::Action::Call(trace::Call {
                    from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                    to: 0xa.into(),
                    value: 100.into(),
                    gas: 79000.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: U256::from(31761),
                    output: vec![],
                }),
            },
            FlatTrace {
                trace_address: vec![0].into_iter().collect(),
                subtraces: 0,
                action: trace::Action::Call(trace::Call {
                    from: 0xa.into(),
                    to: 0xb.into(),
                    value: 69.into(),
                    gas: 2300.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::Call(trace::CallResult::default()),
            },
        ];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_not_trace_call_with_invalid_basic_subcall_transaction() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = make_frontier_machine(5);

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 100.into(),
            data: vec![],
        }
        .sign(&secret(), None);

        state
            .init_code(
                &0xa.into(),
                FromHex::from_hex("600060006000600060ff600b6000f1").unwrap(),
            )
            .unwrap(); // not enough funds.
        state
            .add_balance(&t.sender(), &(100.into()), CleanupMode::NoEmpty)
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();
        let expected_trace = vec![FlatTrace {
            trace_address: Default::default(),
            subtraces: 0,
            action: trace::Action::Call(trace::Call {
                from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                to: 0xa.into(),
                value: 100.into(),
                gas: 79000.into(),
                input: vec![],
                call_type: CallType::Call,
            }),
            result: trace::Res::Call(trace::CallResult {
                gas_used: U256::from(31761),
                output: vec![],
            }),
        }];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_trace_failed_subcall_transaction() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = make_frontier_machine(5);

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 100.into(),
            data: vec![], //600480600b6000396000f35b600056
        }
        .sign(&secret(), None);

        state
            .init_code(
                &0xa.into(),
                FromHex::from_hex("60006000600060006000600b602b5a03f1").unwrap(),
            )
            .unwrap();
        state
            .init_code(&0xb.into(), FromHex::from_hex("5b600056").unwrap())
            .unwrap();
        state
            .add_balance(&t.sender(), &(100.into()), CleanupMode::NoEmpty)
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();
        let expected_trace = vec![
            FlatTrace {
                trace_address: Default::default(),
                subtraces: 1,
                action: trace::Action::Call(trace::Call {
                    from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                    to: 0xa.into(),
                    value: 100.into(),
                    gas: 79000.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: U256::from(79_000),
                    output: vec![],
                }),
            },
            FlatTrace {
                trace_address: vec![0].into_iter().collect(),
                subtraces: 0,
                action: trace::Action::Call(trace::Call {
                    from: 0xa.into(),
                    to: 0xb.into(),
                    value: 0.into(),
                    gas: 78934.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::FailedCall(TraceError::OutOfGas),
            },
        ];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_trace_call_with_subcall_with_subcall_transaction() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = make_frontier_machine(5);

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 100.into(),
            data: vec![],
        }
        .sign(&secret(), None);

        state
            .init_code(
                &0xa.into(),
                FromHex::from_hex("60006000600060006000600b602b5a03f1").unwrap(),
            )
            .unwrap();
        state
            .init_code(
                &0xb.into(),
                FromHex::from_hex("60006000600060006000600c602b5a03f1").unwrap(),
            )
            .unwrap();
        state
            .init_code(&0xc.into(), FromHex::from_hex("6000").unwrap())
            .unwrap();
        state
            .add_balance(&t.sender(), &(100.into()), CleanupMode::NoEmpty)
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();
        let expected_trace = vec![
            FlatTrace {
                trace_address: Default::default(),
                subtraces: 1,
                action: trace::Action::Call(trace::Call {
                    from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                    to: 0xa.into(),
                    value: 100.into(),
                    gas: 79000.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: U256::from(135),
                    output: vec![],
                }),
            },
            FlatTrace {
                trace_address: vec![0].into_iter().collect(),
                subtraces: 1,
                action: trace::Action::Call(trace::Call {
                    from: 0xa.into(),
                    to: 0xb.into(),
                    value: 0.into(),
                    gas: 78934.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: U256::from(69),
                    output: vec![],
                }),
            },
            FlatTrace {
                trace_address: vec![0, 0].into_iter().collect(),
                subtraces: 0,
                action: trace::Action::Call(trace::Call {
                    from: 0xb.into(),
                    to: 0xc.into(),
                    value: 0.into(),
                    gas: 78868.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: U256::from(3),
                    output: vec![],
                }),
            },
        ];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_trace_failed_subcall_with_subcall_transaction() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = make_frontier_machine(5);

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 100.into(),
            data: vec![], //600480600b6000396000f35b600056
        }
        .sign(&secret(), None);

        state
            .init_code(
                &0xa.into(),
                FromHex::from_hex("60006000600060006000600b602b5a03f1").unwrap(),
            )
            .unwrap();
        state
            .init_code(
                &0xb.into(),
                FromHex::from_hex("60006000600060006000600c602b5a03f1505b601256").unwrap(),
            )
            .unwrap();
        state
            .init_code(&0xc.into(), FromHex::from_hex("6000").unwrap())
            .unwrap();
        state
            .add_balance(&t.sender(), &(100.into()), CleanupMode::NoEmpty)
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();

        let expected_trace = vec![
            FlatTrace {
                trace_address: Default::default(),
                subtraces: 1,
                action: trace::Action::Call(trace::Call {
                    from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                    to: 0xa.into(),
                    value: 100.into(),
                    gas: 79000.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: U256::from(79_000),
                    output: vec![],
                }),
            },
            FlatTrace {
                trace_address: vec![0].into_iter().collect(),
                subtraces: 1,
                action: trace::Action::Call(trace::Call {
                    from: 0xa.into(),
                    to: 0xb.into(),
                    value: 0.into(),
                    gas: 78934.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::FailedCall(TraceError::OutOfGas),
            },
            FlatTrace {
                trace_address: vec![0, 0].into_iter().collect(),
                subtraces: 0,
                action: trace::Action::Call(trace::Call {
                    from: 0xb.into(),
                    to: 0xc.into(),
                    value: 0.into(),
                    gas: 78868.into(),
                    call_type: CallType::Call,
                    input: vec![],
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: U256::from(3),
                    output: vec![],
                }),
            },
        ];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn should_trace_suicide() {
        let _ = env_logger::try_init();

        let mut state = get_temp_state();

        let mut info = EnvInfo::default();
        info.gas_limit = 1_000_000.into();
        let machine = make_frontier_machine(5);

        let t = Transaction {
            nonce: 0.into(),
            gas_price: 0.into(),
            gas: 100_000.into(),
            action: Action::Call(0xa.into()),
            value: 100.into(),
            data: vec![],
        }
        .sign(&secret(), None);

        state
            .init_code(
                &0xa.into(),
                FromHex::from_hex("73000000000000000000000000000000000000000bff").unwrap(),
            )
            .unwrap();
        state
            .add_balance(&0xa.into(), &50.into(), CleanupMode::NoEmpty)
            .unwrap();
        state
            .add_balance(&t.sender(), &100.into(), CleanupMode::NoEmpty)
            .unwrap();
        let result = state.apply(&info, &machine, &t, true).unwrap();
        let expected_trace = vec![
            FlatTrace {
                trace_address: Default::default(),
                subtraces: 1,
                action: trace::Action::Call(trace::Call {
                    from: "9cce34f7ab185c7aba1b7c8140d620b4bda941d6".into(),
                    to: 0xa.into(),
                    value: 100.into(),
                    gas: 79000.into(),
                    input: vec![],
                    call_type: CallType::Call,
                }),
                result: trace::Res::Call(trace::CallResult {
                    gas_used: 3.into(),
                    output: vec![],
                }),
            },
            FlatTrace {
                trace_address: vec![0].into_iter().collect(),
                subtraces: 0,
                action: trace::Action::Suicide(trace::Suicide {
                    address: 0xa.into(),
                    refund_address: 0xb.into(),
                    balance: 150.into(),
                }),
                result: trace::Res::None,
            },
        ];

        assert_eq!(result.trace, expected_trace);
    }

    #[test]
    fn code_from_database() {
        let a = Address::zero();
        let (root, db) = {
            let mut state = get_temp_state();
            state
                .require_or_from(
                    &a,
                    false,
                    || Account::new_contract(42.into(), 0.into(), KECCAK_NULL_RLP),
                    |_| {},
                )
                .unwrap();
            state.init_code(&a, vec![1, 2, 3]).unwrap();
            assert_eq!(state.code(&a).unwrap(), Some(Arc::new(vec![1u8, 2, 3])));
            state.commit().unwrap();
            assert_eq!(state.code(&a).unwrap(), Some(Arc::new(vec![1u8, 2, 3])));
            state.drop()
        };

        let state = State::from_existing(db, root, U256::from(0u8), Default::default()).unwrap();
        assert_eq!(state.code(&a).unwrap(), Some(Arc::new(vec![1u8, 2, 3])));
    }

    #[test]
    fn storage_at_from_database() {
        let a = Address::zero();
        let (root, db) = {
            let mut state = get_temp_state();
            state
                .set_storage(
                    &a,
                    H256::from(&U256::from(1u64)),
                    H256::from(&U256::from(69u64)),
                )
                .unwrap();
            state.commit().unwrap();
            state.drop()
        };

        let s = State::from_existing(db, root, U256::from(0u8), Default::default()).unwrap();
        assert_eq!(
            s.storage_at(&a, &H256::from(&U256::from(1u64))).unwrap(),
            H256::from(&U256::from(69u64))
        );
    }

    #[test]
    fn get_from_database() {
        let a = Address::zero();
        let (root, db) = {
            let mut state = get_temp_state();
            state.inc_nonce(&a).unwrap();
            state
                .add_balance(&a, &U256::from(69u64), CleanupMode::NoEmpty)
                .unwrap();
            state.commit().unwrap();
            assert_eq!(state.balance(&a).unwrap(), U256::from(69u64));
            state.drop()
        };

        let state = State::from_existing(db, root, U256::from(0u8), Default::default()).unwrap();
        assert_eq!(state.balance(&a).unwrap(), U256::from(69u64));
        assert_eq!(state.nonce(&a).unwrap(), U256::from(1u64));
    }

    #[test]
    fn remove() {
        let a = Address::zero();
        let mut state = get_temp_state();
        assert_eq!(state.exists(&a).unwrap(), false);
        assert_eq!(state.exists_and_not_null(&a).unwrap(), false);
        state.inc_nonce(&a).unwrap();
        assert_eq!(state.exists(&a).unwrap(), true);
        assert_eq!(state.exists_and_not_null(&a).unwrap(), true);
        assert_eq!(state.nonce(&a).unwrap(), U256::from(1u64));
        state.kill_account(&a);
        assert_eq!(state.exists(&a).unwrap(), false);
        assert_eq!(state.exists_and_not_null(&a).unwrap(), false);
        assert_eq!(state.nonce(&a).unwrap(), U256::from(0u64));
    }

    #[test]
    fn empty_account_is_not_created() {
        let a = Address::zero();
        let db = get_temp_state_db();
        let (root, db) = {
            let mut state = State::new(db, U256::from(0), Default::default());
            state
                .add_balance(&a, &U256::default(), CleanupMode::NoEmpty)
                .unwrap(); // create an empty account
            state.commit().unwrap();
            state.drop()
        };
        let state = State::from_existing(db, root, U256::from(0u8), Default::default()).unwrap();
        assert!(!state.exists(&a).unwrap());
        assert!(!state.exists_and_not_null(&a).unwrap());
    }

    #[test]
    fn empty_account_exists_when_creation_forced() {
        let a = Address::zero();
        let db = get_temp_state_db();
        let (root, db) = {
            let mut state = State::new(db, U256::from(0), Default::default());
            state
                .add_balance(&a, &U256::default(), CleanupMode::ForceCreate)
                .unwrap(); // create an empty account
            state.commit().unwrap();
            state.drop()
        };
        let state = State::from_existing(db, root, U256::from(0u8), Default::default()).unwrap();
        assert!(state.exists(&a).unwrap());
        assert!(!state.exists_and_not_null(&a).unwrap());
    }

    #[test]
    fn remove_from_database() {
        let a = Address::zero();
        let (root, db) = {
            let mut state = get_temp_state();
            state.inc_nonce(&a).unwrap();
            state.commit().unwrap();
            assert_eq!(state.exists(&a).unwrap(), true);
            assert_eq!(state.nonce(&a).unwrap(), U256::from(1u64));
            state.drop()
        };

        let (root, db) = {
            let mut state =
                State::from_existing(db, root, U256::from(0u8), Default::default()).unwrap();
            assert_eq!(state.exists(&a).unwrap(), true);
            assert_eq!(state.nonce(&a).unwrap(), U256::from(1u64));
            state.kill_account(&a);
            state.commit().unwrap();
            assert_eq!(state.exists(&a).unwrap(), false);
            assert_eq!(state.nonce(&a).unwrap(), U256::from(0u64));
            state.drop()
        };

        let state = State::from_existing(db, root, U256::from(0u8), Default::default()).unwrap();
        assert_eq!(state.exists(&a).unwrap(), false);
        assert_eq!(state.nonce(&a).unwrap(), U256::from(0u64));
    }

    #[test]
    fn alter_balance() {
        let mut state = get_temp_state();
        let a = Address::zero();
        let b = 1u64.into();
        state
            .add_balance(&a, &U256::from(69u64), CleanupMode::NoEmpty)
            .unwrap();
        assert_eq!(state.balance(&a).unwrap(), U256::from(69u64));
        state.commit().unwrap();
        assert_eq!(state.balance(&a).unwrap(), U256::from(69u64));
        state
            .sub_balance(&a, &U256::from(42u64), &mut CleanupMode::NoEmpty)
            .unwrap();
        assert_eq!(state.balance(&a).unwrap(), U256::from(27u64));
        state.commit().unwrap();
        assert_eq!(state.balance(&a).unwrap(), U256::from(27u64));
        state
            .transfer_balance(&a, &b, &U256::from(18u64), CleanupMode::NoEmpty)
            .unwrap();
        assert_eq!(state.balance(&a).unwrap(), U256::from(9u64));
        assert_eq!(state.balance(&b).unwrap(), U256::from(18u64));
        state.commit().unwrap();
        assert_eq!(state.balance(&a).unwrap(), U256::from(9u64));
        assert_eq!(state.balance(&b).unwrap(), U256::from(18u64));
    }

    #[test]
    fn alter_nonce() {
        let mut state = get_temp_state();
        let a = Address::zero();
        state.inc_nonce(&a).unwrap();
        assert_eq!(state.nonce(&a).unwrap(), U256::from(1u64));
        state.inc_nonce(&a).unwrap();
        assert_eq!(state.nonce(&a).unwrap(), U256::from(2u64));
        state.commit().unwrap();
        assert_eq!(state.nonce(&a).unwrap(), U256::from(2u64));
        state.inc_nonce(&a).unwrap();
        assert_eq!(state.nonce(&a).unwrap(), U256::from(3u64));
        state.commit().unwrap();
        assert_eq!(state.nonce(&a).unwrap(), U256::from(3u64));
    }

    #[test]
    fn balance_nonce() {
        let mut state = get_temp_state();
        let a = Address::zero();
        assert_eq!(state.balance(&a).unwrap(), U256::from(0u64));
        assert_eq!(state.nonce(&a).unwrap(), U256::from(0u64));
        state.commit().unwrap();
        assert_eq!(state.balance(&a).unwrap(), U256::from(0u64));
        assert_eq!(state.nonce(&a).unwrap(), U256::from(0u64));
    }

    #[test]
    fn ensure_cached() {
        let mut state = get_temp_state();
        let a = Address::zero();
        state.require(&a, false).unwrap();
        state.commit().unwrap();
        assert_eq!(
            *state.root(),
            "0ce23f3c809de377b008a4a3ee94a0834aac8bec1f86e28ffe4fdb5a15b0c785".into()
        );
    }

    #[test]
    fn checkpoint_basic() {
        let mut state = get_temp_state();
        let a = Address::zero();
        state.checkpoint();
        state
            .add_balance(&a, &U256::from(69u64), CleanupMode::NoEmpty)
            .unwrap();
        assert_eq!(state.balance(&a).unwrap(), U256::from(69u64));
        state.discard_checkpoint();
        assert_eq!(state.balance(&a).unwrap(), U256::from(69u64));
        state.checkpoint();
        state
            .add_balance(&a, &U256::from(1u64), CleanupMode::NoEmpty)
            .unwrap();
        assert_eq!(state.balance(&a).unwrap(), U256::from(70u64));
        state.revert_to_checkpoint();
        assert_eq!(state.balance(&a).unwrap(), U256::from(69u64));
    }

    #[test]
    fn checkpoint_nested() {
        let mut state = get_temp_state();
        let a = Address::zero();
        state.checkpoint();
        state.checkpoint();
        state
            .add_balance(&a, &U256::from(69u64), CleanupMode::NoEmpty)
            .unwrap();
        assert_eq!(state.balance(&a).unwrap(), U256::from(69u64));
        state.discard_checkpoint();
        assert_eq!(state.balance(&a).unwrap(), U256::from(69u64));
        state.revert_to_checkpoint();
        assert_eq!(state.balance(&a).unwrap(), U256::from(0));
    }

    #[test]
    fn checkpoint_revert_to_get_storage_at() {
        let mut state = get_temp_state();
        let a = Address::zero();
        let k = H256::from(U256::from(0));

        let c0 = state.checkpoint();
        let c1 = state.checkpoint();
        state.set_storage(&a, k, H256::from(U256::from(1))).unwrap();

        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(state.storage_at(&a, &k).unwrap(), H256::from(U256::from(1)));

        state.revert_to_checkpoint(); // Revert to c1.
        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(state.storage_at(&a, &k).unwrap(), H256::from(U256::from(0)));
    }

    #[test]
    fn checkpoint_from_empty_get_storage_at() {
        let mut state = get_temp_state();
        let a = Address::zero();
        let k = H256::from(U256::from(0));
        let k2 = H256::from(U256::from(1));

        assert_eq!(state.storage_at(&a, &k).unwrap(), H256::from(U256::from(0)));
        state.clear();

        let c0 = state.checkpoint();
        state.new_contract(&a, U256::zero(), U256::zero()).unwrap();
        let c1 = state.checkpoint();
        state.set_storage(&a, k, H256::from(U256::from(1))).unwrap();
        let c2 = state.checkpoint();
        let c3 = state.checkpoint();
        state
            .set_storage(&a, k2, H256::from(U256::from(3)))
            .unwrap();
        state.set_storage(&a, k, H256::from(U256::from(3))).unwrap();
        let c4 = state.checkpoint();
        state.set_storage(&a, k, H256::from(U256::from(4))).unwrap();
        let c5 = state.checkpoint();

        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c2, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c3, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c4, &a, &k).unwrap(),
            Some(H256::from(U256::from(3)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c5, &a, &k).unwrap(),
            Some(H256::from(U256::from(4)))
        );

        state.discard_checkpoint(); // Commit/discard c5.
        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c2, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c3, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c4, &a, &k).unwrap(),
            Some(H256::from(U256::from(3)))
        );

        state.revert_to_checkpoint(); // Revert to c4.
        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c2, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c3, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );

        state.discard_checkpoint(); // Commit/discard c3.
        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c2, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );

        state.revert_to_checkpoint(); // Revert to c2.
        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );

        state.discard_checkpoint(); // Commit/discard c1.
        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
    }

    #[test]
    fn checkpoint_get_storage_at() {
        let mut state = get_temp_state();
        let a = Address::zero();
        let k = H256::from(U256::from(0));
        let k2 = H256::from(U256::from(1));

        state
            .set_storage(&a, k, H256::from(U256::from(0xffff)))
            .unwrap();
        state.commit().unwrap();
        state.clear();

        assert_eq!(
            state.storage_at(&a, &k).unwrap(),
            H256::from(U256::from(0xffff))
        );
        state.clear();

        let cm1 = state.checkpoint();
        let c0 = state.checkpoint();
        state.new_contract(&a, U256::zero(), U256::zero()).unwrap();
        let c1 = state.checkpoint();
        state.set_storage(&a, k, H256::from(U256::from(1))).unwrap();
        let c2 = state.checkpoint();
        let c3 = state.checkpoint();
        state
            .set_storage(&a, k2, H256::from(U256::from(3)))
            .unwrap();
        state.set_storage(&a, k, H256::from(U256::from(3))).unwrap();
        let c4 = state.checkpoint();
        state.set_storage(&a, k, H256::from(U256::from(4))).unwrap();
        let c5 = state.checkpoint();

        assert_eq!(
            state.checkpoint_storage_at(cm1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0xffff)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0xffff)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c2, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c3, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c4, &a, &k).unwrap(),
            Some(H256::from(U256::from(3)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c5, &a, &k).unwrap(),
            Some(H256::from(U256::from(4)))
        );

        state.discard_checkpoint(); // Commit/discard c5.
        assert_eq!(
            state.checkpoint_storage_at(cm1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0xffff)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0xffff)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c2, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c3, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c4, &a, &k).unwrap(),
            Some(H256::from(U256::from(3)))
        );

        state.revert_to_checkpoint(); // Revert to c4.
        assert_eq!(
            state.checkpoint_storage_at(cm1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0xffff)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0xffff)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c2, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c3, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );

        state.discard_checkpoint(); // Commit/discard c3.
        assert_eq!(
            state.checkpoint_storage_at(cm1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0xffff)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0xffff)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c2, &a, &k).unwrap(),
            Some(H256::from(U256::from(1)))
        );

        state.revert_to_checkpoint(); // Revert to c2.
        assert_eq!(
            state.checkpoint_storage_at(cm1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0xffff)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0xffff)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0)))
        );

        state.discard_checkpoint(); // Commit/discard c1.
        assert_eq!(
            state.checkpoint_storage_at(cm1, &a, &k).unwrap(),
            Some(H256::from(U256::from(0xffff)))
        );
        assert_eq!(
            state.checkpoint_storage_at(c0, &a, &k).unwrap(),
            Some(H256::from(U256::from(0xffff)))
        );
    }

    #[test]
    fn kill_account_with_checkpoints() {
        let mut state = get_temp_state();
        let a = Address::zero();
        let k = H256::from(U256::from(0));
        state.checkpoint();
        state.set_storage(&a, k, H256::from(U256::from(1))).unwrap();
        state.checkpoint();
        state.kill_account(&a);

        assert_eq!(state.storage_at(&a, &k).unwrap(), H256::from(U256::from(0)));
        state.revert_to_checkpoint();
        assert_eq!(state.storage_at(&a, &k).unwrap(), H256::from(U256::from(1)));
    }

    #[test]
    fn create_contract_fail() {
        let mut state = get_temp_state();
        let orig_root = state.root().clone();
        let a: Address = 1000.into();

        state.checkpoint(); // c1
        state.new_contract(&a, U256::zero(), U256::zero()).unwrap();
        state
            .add_balance(&a, &U256::from(1), CleanupMode::ForceCreate)
            .unwrap();
        state.checkpoint(); // c2
        state
            .add_balance(&a, &U256::from(1), CleanupMode::ForceCreate)
            .unwrap();
        state.discard_checkpoint(); // discard c2
        state.revert_to_checkpoint(); // revert to c1
        assert_eq!(state.exists(&a).unwrap(), false);

        state.commit().unwrap();
        assert_eq!(orig_root, state.root().clone());
    }

    #[test]
    fn create_contract_fail_previous_storage() {
        let mut state = get_temp_state();
        let a: Address = 1000.into();
        let k = H256::from(U256::from(0));

        state
            .set_storage(&a, k, H256::from(U256::from(0xffff)))
            .unwrap();
        state.commit().unwrap();
        state.clear();

        let orig_root = state.root().clone();
        assert_eq!(
            state.storage_at(&a, &k).unwrap(),
            H256::from(U256::from(0xffff))
        );
        state.clear();

        state.checkpoint(); // c1
        state.new_contract(&a, U256::zero(), U256::zero()).unwrap();
        state.checkpoint(); // c2
        state.set_storage(&a, k, H256::from(U256::from(2))).unwrap();
        state.revert_to_checkpoint(); // revert to c2
        assert_eq!(state.storage_at(&a, &k).unwrap(), H256::from(U256::from(0)));
        state.revert_to_checkpoint(); // revert to c1
        assert_eq!(
            state.storage_at(&a, &k).unwrap(),
            H256::from(U256::from(0xffff))
        );

        state.commit().unwrap();
        assert_eq!(orig_root, state.root().clone());
    }

    #[test]
    fn create_empty() {
        let mut state = get_temp_state();
        state.commit().unwrap();
        assert_eq!(
            *state.root(),
            "56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421".into()
        );
    }

    #[test]
    fn should_not_panic_on_state_diff_with_storage() {
        let mut state = get_temp_state();

        let a: Address = 0xa.into();
        state.init_code(&a, b"abcdefg".to_vec()).unwrap();
        state
            .add_balance(&a, &256.into(), CleanupMode::NoEmpty)
            .unwrap();
        state.set_storage(&a, 0xb.into(), 0xc.into()).unwrap();

        let mut new_state = state.clone();
        new_state.set_storage(&a, 0xb.into(), 0xd.into()).unwrap();

        new_state.diff_from(state).unwrap();
    }

    #[test]
    fn should_kill_garbage() {
        let a = 10.into();
        let b = 20.into();
        let c = 30.into();
        let d = 40.into();
        let e = 50.into();
        let x = 0.into();
        let db = get_temp_state_db();
        let (root, db) = {
            let mut state = State::new(db, U256::from(0), Default::default());
            state
                .add_balance(&a, &U256::default(), CleanupMode::ForceCreate)
                .unwrap(); // create an empty account
            state
                .add_balance(&b, &100.into(), CleanupMode::ForceCreate)
                .unwrap(); // create a dust account
            state
                .add_balance(&c, &101.into(), CleanupMode::ForceCreate)
                .unwrap(); // create a normal account
            state
                .add_balance(&d, &99.into(), CleanupMode::ForceCreate)
                .unwrap(); // create another dust account
            state.new_contract(&e, 100.into(), 1.into()).unwrap(); // create a contract account
            state.init_code(&e, vec![0x00]).unwrap();
            state.commit().unwrap();
            state.drop()
        };

        let mut state =
            State::from_existing(db, root, U256::from(0u8), Default::default()).unwrap();
        let mut touched = HashSet::new();
        state
            .add_balance(
                &a,
                &U256::default(),
                CleanupMode::TrackTouched(&mut touched),
            )
            .unwrap(); // touch an account
        state
            .transfer_balance(&b, &x, &1.into(), CleanupMode::TrackTouched(&mut touched))
            .unwrap(); // touch an account decreasing its balance
        state
            .transfer_balance(&c, &x, &1.into(), CleanupMode::TrackTouched(&mut touched))
            .unwrap(); // touch an account decreasing its balance
        state
            .transfer_balance(&e, &x, &1.into(), CleanupMode::TrackTouched(&mut touched))
            .unwrap(); // touch an account decreasing its balance
        state.kill_garbage(&touched, true, &None, false).unwrap();
        assert!(!state.exists(&a).unwrap());
        assert!(state.exists(&b).unwrap());
        state
            .kill_garbage(&touched, true, &Some(100.into()), false)
            .unwrap();
        assert!(!state.exists(&b).unwrap());
        assert!(state.exists(&c).unwrap());
        assert!(state.exists(&d).unwrap());
        assert!(state.exists(&e).unwrap());
        state
            .kill_garbage(&touched, true, &Some(100.into()), true)
            .unwrap();
        assert!(state.exists(&c).unwrap());
        assert!(state.exists(&d).unwrap());
        assert!(!state.exists(&e).unwrap());
    }

    #[test]
    fn should_trace_diff_suicided_accounts() {
        use pod_account;

        let a = 10.into();
        let db = get_temp_state_db();
        let (root, db) = {
            let mut state = State::new(db, U256::from(0), Default::default());
            state
                .add_balance(&a, &100.into(), CleanupMode::ForceCreate)
                .unwrap();
            state.commit().unwrap();
            state.drop()
        };

        let mut state =
            State::from_existing(db, root, U256::from(0u8), Default::default()).unwrap();
        let original = state.clone();
        state.kill_account(&a);

        let diff = state.diff_from(original).unwrap();
        let diff_map = diff.get();
        assert_eq!(diff_map.len(), 1);
        assert!(diff_map.get(&a).is_some());
        assert_eq!(
            diff_map.get(&a),
            pod_account::diff_pod(
                Some(&PodAccount {
                    balance: U256::from(100),
                    nonce: U256::zero(),
                    code: Some(Default::default()),
                    storage: Default::default()
                }),
                None
            )
            .as_ref()
        );
    }

    #[test]
    fn should_trace_diff_unmodified_storage() {
        use pod_account;

        let a = 10.into();
        let db = get_temp_state_db();

        let (root, db) = {
            let mut state = State::new(db, U256::from(0), Default::default());
            state
                .set_storage(
                    &a,
                    H256::from(&U256::from(1u64)),
                    H256::from(&U256::from(20u64)),
                )
                .unwrap();
            state.commit().unwrap();
            state.drop()
        };

        let mut state =
            State::from_existing(db, root, U256::from(0u8), Default::default()).unwrap();
        let original = state.clone();
        state
            .set_storage(
                &a,
                H256::from(&U256::from(1u64)),
                H256::from(&U256::from(100u64)),
            )
            .unwrap();

        let diff = state.diff_from(original).unwrap();
        let diff_map = diff.get();
        assert_eq!(diff_map.len(), 1);
        assert!(diff_map.get(&a).is_some());
        assert_eq!(
            diff_map.get(&a),
            pod_account::diff_pod(
                Some(&PodAccount {
                    balance: U256::zero(),
                    nonce: U256::zero(),
                    code: Some(Default::default()),
                    storage: vec![(
                        H256::from(&U256::from(1u64)),
                        H256::from(&U256::from(20u64))
                    )]
                    .into_iter()
                    .collect(),
                }),
                Some(&PodAccount {
                    balance: U256::zero(),
                    nonce: U256::zero(),
                    code: Some(Default::default()),
                    storage: vec![(
                        H256::from(&U256::from(1u64)),
                        H256::from(&U256::from(100u64))
                    )]
                    .into_iter()
                    .collect(),
                })
            )
            .as_ref()
        );
    }

    #[cfg(feature = "to-pod-full")]
    #[test]
    fn should_get_full_pod_storage_values() {
        use trie::{TrieFactory, TrieSpec};

        let a = 10.into();
        let db = get_temp_state_db();

        let factories = Factories {
            vm: Default::default(),
            trie: TrieFactory::new(TrieSpec::Fat),
            accountdb: Default::default(),
        };

        let get_pod_state_val = |pod_state: &PodState, ak, k| {
            pod_state
                .get()
                .get(ak)
                .unwrap()
                .storage
                .get(&k)
                .unwrap()
                .clone()
        };

        let storage_address = H256::from(&U256::from(1u64));

        let (root, db) = {
            let mut state = State::new(db, U256::from(0), factories.clone());
            state
                .set_storage(&a, storage_address.clone(), H256::from(&U256::from(20u64)))
                .unwrap();
            let dump = state.to_pod_full().unwrap();
            assert_eq!(
                get_pod_state_val(&dump, &a, storage_address.clone()),
                H256::from(&U256::from(20u64))
            );
            state.commit().unwrap();
            let dump = state.to_pod_full().unwrap();
            assert_eq!(
                get_pod_state_val(&dump, &a, storage_address.clone()),
                H256::from(&U256::from(20u64))
            );
            state.drop()
        };

        let mut state = State::from_existing(db, root, U256::from(0u8), factories).unwrap();
        let dump = state.to_pod_full().unwrap();
        assert_eq!(
            get_pod_state_val(&dump, &a, storage_address.clone()),
            H256::from(&U256::from(20u64))
        );
        state
            .set_storage(&a, storage_address.clone(), H256::from(&U256::from(21u64)))
            .unwrap();
        let dump = state.to_pod_full().unwrap();
        assert_eq!(
            get_pod_state_val(&dump, &a, storage_address.clone()),
            H256::from(&U256::from(21u64))
        );
        state.commit().unwrap();
        state
            .set_storage(&a, storage_address.clone(), H256::from(&U256::from(0u64)))
            .unwrap();
        let dump = state.to_pod_full().unwrap();
        assert_eq!(
            get_pod_state_val(&dump, &a, storage_address.clone()),
            H256::from(&U256::from(0u64))
        );
    }
}