Memory DB.

This commit is contained in:
Gav Wood 2015-11-28 00:14:40 +01:00
parent 6477b2ad69
commit 2db779a63b
5 changed files with 188 additions and 7 deletions

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@ -10,6 +10,8 @@ use std::fmt;
use std::error::Error as StdError; use std::error::Error as StdError;
use uint::{U128, U256}; use uint::{U128, U256};
pub type Bytes = Vec<u8>;
pub trait BytesConvertable { pub trait BytesConvertable {
fn bytes(&self) -> &[u8]; fn bytes(&self) -> &[u8];
} }

9
src/hashdb.rs Normal file
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@ -0,0 +1,9 @@
use hash::*;
use bytes::Bytes;
pub trait HashDB {
fn lookup(&self, key: &H256) -> Option<&Bytes>;
fn exists(&self, key: &H256) -> bool;
fn insert(&mut self, value: &[u8]) -> H256;
fn kill(&mut self, key: &H256);
}

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@ -6,8 +6,6 @@ extern crate tiny_keccak;
#[macro_use] #[macro_use]
extern crate log; extern crate log;
pub use std::str::FromStr;
pub mod error; pub mod error;
pub mod hash; pub mod hash;
pub mod uint; pub mod uint;
@ -16,11 +14,15 @@ pub mod rlp;
pub mod vector; pub mod vector;
pub mod db; pub mod db;
pub mod sha3; pub mod sha3;
pub mod hashdb;
pub mod memorydb;
//pub mod network; //pub mod network;
pub type Bytes = Vec<u8>; pub use std::str::FromStr;
pub use hash::*;
pub use sha3::*;
pub use bytes::*;
pub use hashdb::*;
pub use memorydb::*;
#[test]
fn it_works() {
}

168
src/memorydb.rs Normal file
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@ -0,0 +1,168 @@
//! Reference-counted memory-based HashDB implementation.
//!
//! # Example
//! ```rust
//! extern crate ethcore_util;
//! use ethcore_util::hashdb::*;
//! use ethcore_util::memorydb::*;
//! fn main() {
//! let mut m = MemoryDB::new();
//! let d = "Hello world!".as_bytes();
//!
//! let k = m.insert(d);
//! assert!(m.exists(&k));
//! assert_eq!(m.lookup(&k).unwrap(), &d);
//!
//! m.insert(d);
//! assert!(m.exists(&k));
//!
//! m.kill(&k);
//! assert!(m.exists(&k));
//!
//! m.kill(&k);
//! assert!(!m.exists(&k));
//!
//! m.insert(d);
//! assert!(m.exists(&k));
//! assert_eq!(m.lookup(&k).unwrap(), &d);
//!
//! m.kill(&k);
//! assert!(!m.exists(&k));
//! }
//! ```
use hash::*;
use bytes::*;
use sha3::*;
use hashdb::*;
use std::collections::HashMap;
#[derive(Debug,Clone)]
pub struct MemoryDB {
data: HashMap<H256, (Bytes, i32)>,
}
impl MemoryDB {
pub fn new() -> MemoryDB {
MemoryDB {
data: HashMap::new()
}
}
pub fn clear(&mut self) {
self.data.clear();
}
pub fn purge(&mut self) {
let empties: Vec<_> = self.data.iter().filter(|&(_, &(_, rc))| rc <= 0).map(|(k, _)| k.clone()).collect();
for empty in empties { self.data.remove(&empty); }
}
}
impl HashDB for MemoryDB {
/// Do a hash dereference and look up a given hash into the bytes that make it up,
/// returning None if nothing is found (or if the only entries have 0 or fewer
/// references).
///
/// # Examples
/// ```rust
/// extern crate ethcore_util;
/// use ethcore_util::hashdb::*;
/// use ethcore_util::memorydb::*;
/// fn main() {
/// let mut m = MemoryDB::new();
/// let hello_bytes = "Hello world!".as_bytes();
/// let hash = m.insert(hello_bytes);
/// assert_eq!(m.lookup(&hash).unwrap(), &hello_bytes);
/// }
/// ```
fn lookup(&self, key: &H256) -> Option<&Bytes> {
match self.data.get(key) {
Some(&(ref d, rc)) if rc > 0 => Some(d),
_ => None
}
}
/// Check for the existance of a hash-key.
///
/// # Examples
/// ```rust
/// extern crate ethcore_util;
/// use ethcore_util::hashdb::*;
/// use ethcore_util::memorydb::*;
/// use ethcore_util::sha3::*;
/// fn main() {
/// let mut m = MemoryDB::new();
/// let hello_bytes = "Hello world!".as_bytes();
/// assert!(!m.exists(&hello_bytes.sha3()));
/// let key = m.insert(hello_bytes);
/// assert!(m.exists(&key));
/// m.kill(&key);
/// assert!(!m.exists(&key));
/// }
/// ```
fn exists(&self, key: &H256) -> bool {
match self.data.get(key) {
Some(&(_, x)) if x > 0 => true,
_ => false
}
}
/// Insert a datum item into the DB and return the datum's hash for a later lookup. Insertions
/// are counted and the equivalent number of `kill()`s must be performed before the data
/// is considered dead.
///
/// # Examples
/// ```rust
/// extern crate ethcore_util;
/// use ethcore_util::hashdb::*;
/// use ethcore_util::memorydb::*;
/// use ethcore_util::hash::*;
/// fn main() {
/// let mut m = MemoryDB::new();
/// let key = m.insert("Hello world!".as_bytes());
/// assert!(m.exists(&key));
/// }
/// ```
fn insert(&mut self, value: &[u8]) -> H256 {
let key = value.sha3();
if match self.data.get_mut(&key) {
Some(&mut (ref mut old_value, ref mut rc @ 0)) => { *old_value = From::from(value.bytes()); *rc = 1; false },
Some(&mut (_, ref mut x)) => { *x += 1; false } ,
None => true,
}{ // ... None falls through into...
self.data.insert(key, (From::from(value.bytes()), 1));
}
key
}
/// Remove a datum previously inserted. Insertions can be "owed" such that the same number of inserts may
/// happen without the data being eventually being inserted into the DB.
///
/// # Examples
/// ```rust
/// extern crate ethcore_util;
/// use ethcore_util::hashdb::*;
/// use ethcore_util::memorydb::*;
/// use ethcore_util::sha3::*;
/// fn main() {
/// let mut m = MemoryDB::new();
/// let d = "Hello world!".as_bytes();
/// let key = &d.sha3();
/// m.kill(key); // OK - we now owe an insertion.
/// assert!(!m.exists(key));
/// m.insert(d); // OK - now it's "empty" again.
/// assert!(!m.exists(key));
/// m.insert(d); // OK - now we've
/// assert_eq!(m.lookup(key).unwrap(), &d);
/// }
/// ```
fn kill(&mut self, key: &H256) {
if match self.data.get_mut(key) {
Some(&mut (_, ref mut x)) => { *x -= 1; false }
None => true
}{ // ... None falls through into...
self.data.insert(*key, (Bytes::new(), -1));
}
}
}

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@ -3,7 +3,7 @@ use tiny_keccak::keccak_256;
use bytes::BytesConvertable; use bytes::BytesConvertable;
use hash::H256; use hash::H256;
trait Hashable { pub trait Hashable {
fn sha3(&self) -> H256; fn sha3(&self) -> H256;
} }