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Refactor triedb constructors to error on invalid state root (#1230)

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* add TrieError, refactor Trie DB creation

* remove Result type alias due to glob import conflicts

* fix fallout in state.rs

* add debug, display impl for TrieError

* fix fallout in account.rs

* ethcore::Error::TrieError variant

* fix remaining fallout in ethcore crate

* added From<TrieError> impl for Error, removed map_err calls

* fix test breakages

* fix doc tests

* update docs

[ci skip]
This commit is contained in:
Robert Habermeier 2016-06-07 20:44:09 +02:00 committed by Gav Wood
parent fdc22db3f4
commit 13968aaa38
13 changed files with 146 additions and 92 deletions
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12
ethcore/src/account.rs
View File

@ -116,7 +116,12 @@ impl Account {
/// Get (and cache) the contents of the trie's storage at `key`.
pub fn storage_at(&self, db: &AccountDB, key: &H256) -> H256 {
self.storage_overlay.borrow_mut().entry(key.clone()).or_insert_with(||{
(Filth::Clean, H256::from(SecTrieDB::new(db, &self.storage_root).get(key.bytes()).map_or(U256::zero(), |v| -> U256 {decode(v)})))
let db = SecTrieDB::new(db, &self.storage_root)
.expect("Account storage_root initially set to zero (valid) and only altered by SecTrieDBMut. \
SecTrieDBMut would not set it to an invalid state root. Therefore the root is valid and DB creation \
using it will not fail.");
(Filth::Clean, H256::from(db.get(key.bytes()).map_or(U256::zero(), |v| -> U256 {decode(v)})))
}).1.clone()
}
@ -204,7 +209,10 @@ impl Account {
/// Commit the `storage_overlay` to the backing DB and update `storage_root`.
pub fn commit_storage(&mut self, db: &mut AccountDBMut) {
let mut t = SecTrieDBMut::from_existing(db, &mut self.storage_root);
let mut t = SecTrieDBMut::from_existing(db, &mut self.storage_root)
.expect("Account storage_root initially set to zero (valid) and only altered by SecTrieDBMut. \
SecTrieDBMut would not set it to an invalid state root. Therefore the root is valid and DB creation \
using it will not fail.");
for (k, &mut (ref mut f, ref mut v)) in self.storage_overlay.borrow_mut().iter_mut() {
if f == &Filth::Dirty {
// cast key and value to trait type,

2
ethcore/src/basic_authority.rs
View File

@ -278,7 +278,7 @@ mod tests {
spec.ensure_db_good(db.as_hashdb_mut());
let last_hashes = vec![genesis_header.hash()];
let vm_factory = Default::default();
let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, addr.clone(), 3141562.into(), vec![]);
let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, addr.clone(), 3141562.into(), vec![]).unwrap();
let b = b.close_and_lock();
let seal = engine.generate_seal(b.block(), Some(&tap)).unwrap();

28
ethcore/src/block.rs
View File

@ -228,9 +228,20 @@ pub struct SealedBlock {
impl<'x> OpenBlock<'x> {
#[cfg_attr(feature="dev", allow(too_many_arguments))]
/// Create a new `OpenBlock` ready for transaction pushing.
pub fn new(engine: &'x Engine, vm_factory: &'x EvmFactory, tracing: bool, db: Box<JournalDB>, parent: &Header, last_hashes: LastHashes, author: Address, gas_floor_target: U256, extra_data: Bytes) -> Self {
pub fn new(
engine: &'x Engine,
vm_factory: &'x EvmFactory,
tracing: bool,
db: Box<JournalDB>,
parent: &Header,
last_hashes: LastHashes,
author: Address,
gas_floor_target: U256,
extra_data: Bytes
) -> Result<Self, Error> {
let state = try!(State::from_existing(db, parent.state_root().clone(), engine.account_start_nonce()));
let mut r = OpenBlock {
block: ExecutedBlock::new(State::from_existing(db, parent.state_root().clone(), engine.account_start_nonce()), tracing),
block: ExecutedBlock::new(state, tracing),
engine: engine,
vm_factory: vm_factory,
last_hashes: last_hashes,
@ -245,7 +256,7 @@ impl<'x> OpenBlock<'x> {
engine.populate_from_parent(&mut r.block.base.header, parent, gas_floor_target);
engine.on_new_block(&mut r.block);
r
Ok(r)
}
/// Alter the author for the block.
@ -464,12 +475,12 @@ impl IsBlock for SealedBlock {
pub fn enact(header: &Header, transactions: &[SignedTransaction], uncles: &[Header], engine: &Engine, tracing: bool, db: Box<JournalDB>, parent: &Header, last_hashes: LastHashes, vm_factory: &EvmFactory) -> Result<LockedBlock, Error> {
{
if ::log::max_log_level() >= ::log::LogLevel::Trace {
let s = State::from_existing(db.boxed_clone(), parent.state_root().clone(), engine.account_start_nonce());
let s = try!(State::from_existing(db.boxed_clone(), parent.state_root().clone(), engine.account_start_nonce()));
trace!("enact(): root={}, author={}, author_balance={}\n", s.root(), header.author(), s.balance(&header.author()));
}
}
let mut b = OpenBlock::new(engine, vm_factory, tracing, db, parent, last_hashes, header.author().clone(), 3141562.into(), header.extra_data().clone());
let mut b = try!(OpenBlock::new(engine, vm_factory, tracing, db, parent, last_hashes, header.author().clone(), 3141562.into(), header.extra_data().clone()));
b.set_difficulty(*header.difficulty());
b.set_gas_limit(*header.gas_limit());
b.set_timestamp(header.timestamp());
@ -514,7 +525,7 @@ mod tests {
spec.ensure_db_good(db.as_hashdb_mut());
let last_hashes = vec![genesis_header.hash()];
let vm_factory = Default::default();
let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, Address::zero(), 3141562.into(), vec![]);
let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, Address::zero(), 3141562.into(), vec![]).unwrap();
let b = b.close_and_lock();
let _ = b.seal(engine.deref(), vec![]);
}
@ -530,7 +541,8 @@ mod tests {
let mut db = db_result.take();
spec.ensure_db_good(db.as_hashdb_mut());
let vm_factory = Default::default();
let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, vec![genesis_header.hash()], Address::zero(), 3141562.into(), vec![]).close_and_lock().seal(engine.deref(), vec![]).unwrap();
let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, vec![genesis_header.hash()], Address::zero(), 3141562.into(), vec![]).unwrap()
.close_and_lock().seal(engine.deref(), vec![]).unwrap();
let orig_bytes = b.rlp_bytes();
let orig_db = b.drain();
@ -557,7 +569,7 @@ mod tests {
let mut db = db_result.take();
spec.ensure_db_good(db.as_hashdb_mut());
let vm_factory = Default::default();
let mut open_block = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, vec![genesis_header.hash()], Address::zero(), 3141562.into(), vec![]);
let mut open_block = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, vec![genesis_header.hash()], Address::zero(), 3141562.into(), vec![]).unwrap();
let mut uncle1_header = Header::new();
uncle1_header.extra_data = b"uncle1".to_vec();
let mut uncle2_header = Header::new();

11
ethcore/src/client/client.rs
View File

@ -386,18 +386,14 @@ impl<V> Client<V> where V: Verifier {
let root = HeaderView::new(&header).state_root();
// TODO [rob]: refactor State::from_existing so we avoid doing redundant lookups.
if !db.contains(&root) {
return None;
}
Some(State::from_existing(db, root, self.engine.account_start_nonce()))
State::from_existing(db, root, self.engine.account_start_nonce()).ok()
})
}
/// Get a copy of the best block's state.
pub fn state(&self) -> State {
State::from_existing(self.state_db.lock().unwrap().boxed_clone(), HeaderView::new(&self.best_block_header()).state_root(), self.engine.account_start_nonce())
.expect("State root of best block header always valid.")
}
/// Get info on the cache.
@ -776,7 +772,8 @@ impl<V> MiningBlockChainClient for Client<V> where V: Verifier {
author,
gas_floor_target,
extra_data,
);
).expect("OpenBlock::new only fails if parent state root invalid. State root of best block's header is never invalid. \
Therefore creating an OpenBlock with the best block's header will not fail.");
// Add uncles
self.chain

9
ethcore/src/error.rs
View File

@ -224,6 +224,8 @@ pub enum Error {
PowHashInvalid,
/// The value of the nonce or mishash is invalid.
PowInvalid,
/// Error concerning TrieDBs
TrieError(TrieError),
}
impl fmt::Display for Error {
@ -239,6 +241,7 @@ impl fmt::Display for Error {
f.write_fmt(format_args!("Unknown engine name ({})", name)),
Error::PowHashInvalid => f.write_str("Invalid or out of date PoW hash."),
Error::PowInvalid => f.write_str("Invalid nonce or mishash"),
Error::TrieError(ref err) => f.write_fmt(format_args!("{}", err)),
}
}
}
@ -300,6 +303,12 @@ impl From<IoError> for Error {
}
}
impl From<TrieError> for Error {
fn from(err: TrieError) -> Error {
Error::TrieError(err)
}
}
// TODO: uncomment below once https://github.com/rust-lang/rust/issues/27336 sorted.
/*#![feature(concat_idents)]
macro_rules! assimilate {

4
ethcore/src/ethereum/ethash.rs
View File

@ -308,7 +308,7 @@ mod tests {
spec.ensure_db_good(db.as_hashdb_mut());
let last_hashes = vec![genesis_header.hash()];
let vm_factory = Default::default();
let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, Address::zero(), 3141562.into(), vec![]);
let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, Address::zero(), 3141562.into(), vec![]).unwrap();
let b = b.close();
assert_eq!(b.state().balance(&Address::zero()), U256::from_str("4563918244f40000").unwrap());
}
@ -323,7 +323,7 @@ mod tests {
spec.ensure_db_good(db.as_hashdb_mut());
let last_hashes = vec![genesis_header.hash()];
let vm_factory = Default::default();
let mut b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, Address::zero(), 3141562.into(), vec![]);
let mut b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, Address::zero(), 3141562.into(), vec![]).unwrap();
let mut uncle = Header::new();
let uncle_author = address_from_hex("ef2d6d194084c2de36e0dabfce45d046b37d1106");
uncle.author = uncle_author.clone();

2
ethcore/src/ethereum/mod.rs
View File

@ -62,7 +62,7 @@ mod tests {
let mut db_result = get_temp_journal_db();
let mut db = db_result.take();
spec.ensure_db_good(db.as_hashdb_mut());
let s = State::from_existing(db, genesis_header.state_root.clone(), engine.account_start_nonce());
let s = State::from_existing(db, genesis_header.state_root.clone(), engine.account_start_nonce()).unwrap();
assert_eq!(s.balance(&address_from_hex("0000000000000000000000000000000000000001")), U256::from(1u64));
assert_eq!(s.balance(&address_from_hex("0000000000000000000000000000000000000002")), U256::from(1u64));
assert_eq!(s.balance(&address_from_hex("0000000000000000000000000000000000000003")), U256::from(1u64));

37
ethcore/src/state.rs
View File

@ -44,6 +44,9 @@ pub struct State {
account_start_nonce: U256,
}
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 State {
/// Creates new state with empty state root
#[cfg(test)]
@ -64,18 +67,17 @@ impl State {
}
/// Creates new state with existing state root
pub fn from_existing(db: Box<JournalDB>, root: H256, account_start_nonce: U256) -> State {
{
// trie should panic! if root does not exist
let _ = SecTrieDB::new(db.as_hashdb(), &root);
}
State {
pub fn from_existing(db: Box<JournalDB>, root: H256, account_start_nonce: U256) -> Result<State, TrieError> {
if !db.as_hashdb().contains(&root) {
Err(TrieError::InvalidStateRoot)
} else {
Ok(State {
db: db,
root: root,
cache: RefCell::new(HashMap::new()),
snapshots: RefCell::new(Vec::new()),
account_start_nonce: account_start_nonce,
})
}
}
@ -154,7 +156,8 @@ impl State {
/// Determine whether an account exists.
pub fn exists(&self, a: &Address) -> bool {
self.cache.borrow().get(&a).unwrap_or(&None).is_some() || SecTrieDB::new(self.db.as_hashdb(), &self.root).contains(&a)
let db = SecTrieDB::new(self.db.as_hashdb(), &self.root).expect(SEC_TRIE_DB_UNWRAP_STR);
self.cache.borrow().get(&a).unwrap_or(&None).is_some() || db.contains(&a)
}
/// Get the balance of account `a`.
@ -245,7 +248,7 @@ impl State {
}
{
let mut trie = SecTrieDBMut::from_existing(db, root);
let mut trie = SecTrieDBMut::from_existing(db, root).unwrap();
for (address, ref a) in accounts.iter() {
match **a {
Some(ref account) => trie.insert(address, &account.rlp()),
@ -308,7 +311,8 @@ impl State {
fn get<'a>(&'a self, a: &Address, require_code: bool) -> &'a Option<Account> {
let have_key = self.cache.borrow().contains_key(a);
if !have_key {
self.insert_cache(a, SecTrieDB::new(self.db.as_hashdb(), &self.root).get(&a).map(Account::from_rlp))
let db = SecTrieDB::new(self.db.as_hashdb(), &self.root).expect(SEC_TRIE_DB_UNWRAP_STR);
self.insert_cache(a, db.get(&a).map(Account::from_rlp))
}
if require_code {
if let Some(ref mut account) = self.cache.borrow_mut().get_mut(a).unwrap().as_mut() {
@ -328,7 +332,8 @@ impl State {
fn require_or_from<'a, F: FnOnce() -> Account, G: FnOnce(&mut Account)>(&self, a: &Address, require_code: bool, default: F, not_default: G) -> &'a mut Account {
let have_key = self.cache.borrow().contains_key(a);
if !have_key {
self.insert_cache(a, SecTrieDB::new(self.db.as_hashdb(), &self.root).get(&a).map(Account::from_rlp))
let db = SecTrieDB::new(self.db.as_hashdb(), &self.root).expect(SEC_TRIE_DB_UNWRAP_STR);
self.insert_cache(a, db.get(&a).map(Account::from_rlp))
} else {
self.note_cache(a);
}
@ -1145,7 +1150,7 @@ fn code_from_database() {
state.drop()
};
let state = State::from_existing(db, root, U256::from(0u8));
let state = State::from_existing(db, root, U256::from(0u8)).unwrap();
assert_eq!(state.code(&a), Some([1u8, 2, 3].to_vec()));
}
@ -1160,7 +1165,7 @@ fn storage_at_from_database() {
state.drop()
};
let s = State::from_existing(db, root, U256::from(0u8));
let s = State::from_existing(db, root, U256::from(0u8)).unwrap();
assert_eq!(s.storage_at(&a, &H256::from(&U256::from(01u64))), H256::from(&U256::from(69u64)));
}
@ -1177,7 +1182,7 @@ fn get_from_database() {
state.drop()
};
let state = State::from_existing(db, root, U256::from(0u8));
let state = State::from_existing(db, root, U256::from(0u8)).unwrap();
assert_eq!(state.balance(&a), U256::from(69u64));
assert_eq!(state.nonce(&a), U256::from(1u64));
}
@ -1210,7 +1215,7 @@ fn remove_from_database() {
};
let (root, db) = {
let mut state = State::from_existing(db, root, U256::from(0u8));
let mut state = State::from_existing(db, root, U256::from(0u8)).unwrap();
assert_eq!(state.exists(&a), true);
assert_eq!(state.nonce(&a), U256::from(1u64));
state.kill_account(&a);
@ -1220,7 +1225,7 @@ fn remove_from_database() {
state.drop()
};
let state = State::from_existing(db, root, U256::from(0u8));
let state = State::from_existing(db, root, U256::from(0u8)).unwrap();
assert_eq!(state.exists(&a), false);
assert_eq!(state.nonce(&a), U256::from(0u64));
}

27
util/src/trie/mod.rs
View File

@ -16,6 +16,8 @@
//! Trie interface and implementation.
use std::fmt;
/// Export the trietraits module.
pub mod trietraits;
/// Export the standardmap module.
@ -33,9 +35,22 @@ pub mod sectriedb;
/// Export the sectriedbmut module.
pub mod sectriedbmut;
pub use self::trietraits::*;
pub use self::standardmap::*;
pub use self::triedbmut::*;
pub use self::triedb::*;
pub use self::sectriedbmut::*;
pub use self::sectriedb::*;
pub use self::trietraits::{Trie, TrieMut};
pub use self::standardmap::{Alphabet, StandardMap, ValueMode};
pub use self::triedbmut::TrieDBMut;
pub use self::triedb::TrieDB;
pub use self::sectriedbmut::SecTrieDBMut;
pub use self::sectriedb::SecTrieDB;
/// Trie Errors
#[derive(Debug)]
pub enum TrieError {
/// Attempted to create a trie with a state root not in the DB.
InvalidStateRoot,
}
impl fmt::Display for TrieError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "Trie Error: Invalid state root.")
}
}

20
util/src/trie/sectriedb.rs
View File

@ -16,9 +16,10 @@
use hash::*;
use sha3::*;
use hashdb::*;
use super::triedb::*;
use super::trietraits::*;
use hashdb::HashDB;
use super::triedb::TrieDB;
use super::trietraits::Trie;
use super::TrieError;
/// A `Trie` implementation which hashes keys and uses a generic `HashDB` backing database.
///
@ -29,10 +30,12 @@ pub struct SecTrieDB<'db> {
impl<'db> SecTrieDB<'db> {
/// Create a new trie with the backing database `db` and empty `root`
///
/// Initialise to the state entailed by the genesis block.
/// This guarantees the trie is built correctly.
pub fn new(db: &'db HashDB, root: &'db H256) -> Self {
SecTrieDB { raw: TrieDB::new(db, root) }
/// Returns an error if root does not exist.
pub fn new(db: &'db HashDB, root: &'db H256) -> Result<Self, TrieError> {
Ok(SecTrieDB { raw: try!(TrieDB::new(db, root)) })
}
/// Get a reference to the underlying raw `TrieDB` struct.
@ -60,8 +63,9 @@ impl<'db> Trie for SecTrieDB<'db> {
#[test]
fn trie_to_sectrie() {
use memorydb::*;
use super::triedbmut::*;
use memorydb::MemoryDB;
use super::triedbmut::TrieDBMut;
use super::trietraits::TrieMut;
let mut memdb = MemoryDB::new();
let mut root = H256::new();
@ -69,6 +73,6 @@ fn trie_to_sectrie() {
let mut t = TrieDBMut::new(&mut memdb, &mut root);
t.insert(&(&[0x01u8, 0x23]).sha3(), &[0x01u8, 0x23]);
}
let t = SecTrieDB::new(&memdb, &root);
let t = SecTrieDB::new(&memdb, &root).unwrap();
assert_eq!(t.get(&[0x01u8, 0x23]).unwrap(), &[0x01u8, 0x23]);
}

18
util/src/trie/sectriedbmut.rs
View File

@ -16,9 +16,10 @@
use hash::*;
use sha3::*;
use hashdb::*;
use super::triedbmut::*;
use super::trietraits::*;
use hashdb::HashDB;
use super::triedbmut::TrieDBMut;
use super::trietraits::{Trie, TrieMut};
use super::TrieError;
/// A mutable `Trie` implementation which hashes keys and uses a generic `HashDB` backing database.
///
@ -35,10 +36,11 @@ impl<'db> SecTrieDBMut<'db> {
SecTrieDBMut { raw: TrieDBMut::new(db, root) }
}
/// Create a new trie with the backing database `db` and `root`
/// Panics, if `root` does not exist
pub fn from_existing(db: &'db mut HashDB, root: &'db mut H256) -> Self {
SecTrieDBMut { raw: TrieDBMut::from_existing(db, root) }
/// Create a new trie with the backing database `db` and `root`.
///
/// Returns an error if root does not exist.
pub fn from_existing(db: &'db mut HashDB, root: &'db mut H256) -> Result<Self, TrieError> {
Ok(SecTrieDBMut { raw: try!(TrieDBMut::from_existing(db, root)) })
}
/// Get the backing database.
@ -81,6 +83,6 @@ fn sectrie_to_trie() {
let mut t = SecTrieDBMut::new(&mut memdb, &mut root);
t.insert(&[0x01u8, 0x23], &[0x01u8, 0x23]);
}
let t = TrieDB::new(&memdb, &root);
let t = TrieDB::new(&memdb, &root).unwrap();
assert_eq!(t.get(&(&[0x01u8, 0x23]).sha3()).unwrap(), &[0x01u8, 0x23]);
}

24
util/src/trie/triedb.rs
View File

@ -18,8 +18,9 @@ use common::*;
use hashdb::*;
use nibbleslice::*;
use rlp::*;
use super::trietraits::*;
use super::node::*;
use super::trietraits::Trie;
use super::node::Node;
use super::TrieError;
/// A `Trie` implementation using a generic `HashDB` backing database.
///
@ -41,7 +42,7 @@ use super::node::*;
/// let mut memdb = MemoryDB::new();
/// let mut root = H256::new();
/// TrieDBMut::new(&mut memdb, &mut root).insert(b"foo", b"bar");
/// let t = TrieDB::new(&memdb, &root);
/// let t = TrieDB::new(&memdb, &root).unwrap();
/// assert!(t.contains(b"foo"));
/// assert_eq!(t.get(b"foo").unwrap(), b"bar");
/// assert!(t.db_items_remaining().is_empty());
@ -57,16 +58,16 @@ pub struct TrieDB<'db> {
#[cfg_attr(feature="dev", allow(wrong_self_convention))]
impl<'db> TrieDB<'db> {
/// Create a new trie with the backing database `db` and `root`
/// Panics, if `root` does not exist
pub fn new(db: &'db HashDB, root: &'db H256) -> Self {
/// Returns an error if `root` does not exist
pub fn new(db: &'db HashDB, root: &'db H256) -> Result<Self, TrieError> {
if !db.contains(root) {
flushln!("TrieDB::new({}): Trie root not found!", root);
panic!("Trie root not found!");
}
TrieDB {
Err(TrieError::InvalidStateRoot)
} else {
Ok(TrieDB {
db: db,
root: root,
hash_count: 0
})
}
}
@ -356,6 +357,7 @@ impl<'db> fmt::Debug for TrieDB<'db> {
#[test]
fn iterator() {
use super::trietraits::TrieMut;
use memorydb::*;
use super::triedbmut::*;
@ -369,6 +371,6 @@ fn iterator() {
t.insert(&x, &x);
}
}
assert_eq!(d.iter().map(|i|i.to_vec()).collect::<Vec<_>>(), TrieDB::new(&memdb, &root).iter().map(|x|x.0).collect::<Vec<_>>());
assert_eq!(d, TrieDB::new(&memdb, &root).iter().map(|x|x.1).collect::<Vec<_>>());
assert_eq!(d.iter().map(|i|i.to_vec()).collect::<Vec<_>>(), TrieDB::new(&memdb, &root).unwrap().iter().map(|x|x.0).collect::<Vec<_>>());
assert_eq!(d, TrieDB::new(&memdb, &root).unwrap().iter().map(|x|x.1).collect::<Vec<_>>());
}

20
util/src/trie/triedbmut.rs
View File

@ -18,9 +18,10 @@ use common::*;
use hashdb::*;
use nibbleslice::*;
use rlp::*;
use super::node::*;
use super::journal::*;
use super::trietraits::*;
use super::node::Node;
use super::journal::Journal;
use super::trietraits::{Trie, TrieMut};
use super::TrieError;
/// A `Trie` implementation using a generic `HashDB` backing database.
///
@ -84,17 +85,16 @@ impl<'db> TrieDBMut<'db> {
}
/// Create a new trie with the backing database `db` and `root`.
/// Panics, if `root` does not exist.
// TODO: return Result<Self, TrieError>
pub fn from_existing(db: &'db mut HashDB, root: &'db mut H256) -> Self {
/// Returns an error if `root` does not exist.
pub fn from_existing(db: &'db mut HashDB, root: &'db mut H256) -> Result<Self, TrieError> {
if !db.exists(root) {
flushln!("Trie root not found {}", root);
panic!("Trie root not found!");
}
TrieDBMut {
Err(TrieError::InvalidStateRoot)
} else {
Ok(TrieDBMut {
db: db,
root: root,
hash_count: 0
})
}
}