129 lines
3.0 KiB
Rust
129 lines
3.0 KiB
Rust
//! Reference-counted memory-based HashDB implementation.
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use hash::*;
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use bytes::*;
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use sha3::*;
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use hashdb::*;
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use std::collections::HashMap;
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#[derive(Debug,Clone)]
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/// Reference-counted memory-based HashDB implementation.
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///
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/// Use `new()` to create a new database. Insert items with `insert()`, remove items
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/// with `kill()`, check for existance with `exists()` and lookup a hash to derive
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/// the data with `lookup()`. Clear with `clear()` and purge the portions of the data
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/// that have no references with `purge()`.
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///
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/// # Example
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/// ```rust
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/// extern crate ethcore_util;
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/// use ethcore_util::hashdb::*;
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/// use ethcore_util::memorydb::*;
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/// fn main() {
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/// let mut m = MemoryDB::new();
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/// let d = "Hello world!".as_bytes();
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///
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/// let k = m.insert(d);
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/// assert!(m.exists(&k));
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/// assert_eq!(m.lookup(&k).unwrap(), &d);
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///
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/// m.insert(d);
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/// assert!(m.exists(&k));
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///
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/// m.kill(&k);
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/// assert!(m.exists(&k));
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///
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/// m.kill(&k);
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/// assert!(!m.exists(&k));
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///
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/// m.insert(d);
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/// assert!(m.exists(&k));
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/// assert_eq!(m.lookup(&k).unwrap(), &d);
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///
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/// m.kill(&k);
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/// assert!(!m.exists(&k));
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/// }
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/// ```
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pub struct MemoryDB {
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data: HashMap<H256, (Bytes, i32)>,
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}
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impl MemoryDB {
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/// Create a new instance of the memory DB.
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pub fn new() -> MemoryDB {
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MemoryDB {
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data: HashMap::new()
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}
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}
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/// Clear all data from the database.
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///
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/// # Examples
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/// ```rust
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/// extern crate ethcore_util;
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/// use ethcore_util::hashdb::*;
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/// use ethcore_util::memorydb::*;
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/// fn main() {
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/// let mut m = MemoryDB::new();
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/// let hello_bytes = "Hello world!".as_bytes();
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/// let hash = m.insert(hello_bytes);
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/// assert!(m.exists(&hash));
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/// m.clear();
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/// assert!(!m.exists(&hash));
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/// }
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/// ```
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pub fn clear(&mut self) {
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self.data.clear();
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}
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/// Purge all zero-referenced data from the database.
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pub fn purge(&mut self) {
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let empties: Vec<_> = self.data.iter()
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.filter(|&(_, &(_, rc))| rc == 0)
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.map(|(k, _)| k.clone())
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.collect();
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for empty in empties { self.data.remove(&empty); }
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}
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}
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impl HashDB for MemoryDB {
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fn lookup(&self, key: &H256) -> Option<&Bytes> {
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match self.data.get(key) {
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Some(&(ref d, rc)) if rc > 0 => Some(d),
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_ => None
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}
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}
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fn exists(&self, key: &H256) -> bool {
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match self.data.get(key) {
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Some(&(_, x)) if x > 0 => true,
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_ => false
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}
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}
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fn insert(&mut self, value: &[u8]) -> H256 {
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let key = value.sha3();
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if match self.data.get_mut(&key) {
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Some(&mut (ref mut old_value, ref mut rc @ 0)) => {
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*old_value = From::from(value.bytes());
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*rc = 1;
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false
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},
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Some(&mut (_, ref mut x)) => { *x += 1; false } ,
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None => true,
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}{ // ... None falls through into...
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self.data.insert(key.clone(), (From::from(value.bytes()), 1));
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}
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key
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}
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fn kill(&mut self, key: &H256) {
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if match self.data.get_mut(key) {
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Some(&mut (_, ref mut x)) => { *x -= 1; false }
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None => true
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}{ // ... None falls through into...
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self.data.insert(key.clone(), (Bytes::new(), -1));
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}
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}
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}
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