296 lines
9.0 KiB
Rust
296 lines
9.0 KiB
Rust
//! Disk-backed HashDB implementation.
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use error::*;
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use hash::*;
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use bytes::*;
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use rlp::*;
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use hashdb::*;
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use memorydb::*;
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use std::ops::*;
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use std::sync::*;
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use std::env;
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use rocksdb::{DB, Writable};
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#[derive(Clone)]
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/// Implementation of the HashDB trait for a disk-backed database with a memory overlay.
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///
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/// The operations `insert()` and `kill()` take place on the memory overlay; batches of
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/// such operations may be flushed to the disk-backed DB with `commit()` or discarded with
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/// `revert()`.
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///
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/// `lookup()` and `exists()` maintain normal behaviour - all `insert()` and `kill()`
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/// queries have an immediate effect in terms of these functions.
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pub struct OverlayDB {
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overlay: MemoryDB,
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backing: Arc<DB>,
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}
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impl OverlayDB {
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/// Create a new instance of OverlayDB given a `backing` database.
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pub fn new(backing: DB) -> OverlayDB {
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OverlayDB{ overlay: MemoryDB::new(), backing: Arc::new(backing) }
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}
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/// Create a new instance of OverlayDB with an anonymous temporary database.
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pub fn new_temp() -> OverlayDB {
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let mut dir = env::temp_dir();
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dir.push(H32::random().hex());
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Self::new(DB::open_default(dir.to_str().unwrap()).unwrap())
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}
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/// Commit all memory operations to the backing database.
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///
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/// Returns either an error or the number of items changed in the backing database.
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///
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/// Will return an error if the number of `kill()`s ever exceeds the number of
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/// `insert()`s for any key. This will leave the database in an undeterminate
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/// state. Don't ever let it happen.
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///
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/// # Example
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/// ```
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/// extern crate ethcore_util;
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/// use ethcore_util::hashdb::*;
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/// use ethcore_util::overlaydb::*;
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/// fn main() {
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/// let mut m = OverlayDB::new_temp();
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/// let key = m.insert(b"foo"); // insert item.
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/// assert!(m.exists(&key)); // key exists (in memory).
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/// assert_eq!(m.commit().unwrap(), 1); // 1 item changed.
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/// assert!(m.exists(&key)); // key still exists (in backing).
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/// m.kill(&key); // delete item.
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/// assert!(!m.exists(&key)); // key "doesn't exist" (though still does in backing).
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/// m.kill(&key); // oh dear... more kills than inserts for the key...
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/// //m.commit().unwrap(); // this commit/unwrap would cause a panic.
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/// m.revert(); // revert both kills.
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/// assert!(m.exists(&key)); // key now still exists.
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/// }
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/// ```
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pub fn commit(&mut self) -> Result<u32, EthcoreError> {
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let mut ret = 0u32;
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for i in self.overlay.drain().into_iter() {
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let (key, (value, rc)) = i;
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if rc != 0 {
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match self.payload(&key) {
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Some(x) => {
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let (back_value, back_rc) = x;
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let total_rc: i32 = back_rc as i32 + rc;
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if total_rc < 0 {
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return Err(From::from(BaseDataError::NegativelyReferencedHash));
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}
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self.put_payload(&key, (back_value, total_rc as u32));
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}
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None => {
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if rc < 0 {
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return Err(From::from(BaseDataError::NegativelyReferencedHash));
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}
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self.put_payload(&key, (value, rc as u32));
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}
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};
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ret += 1;
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}
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}
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Ok(ret)
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}
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/// Revert all operations on this object (i.e. `insert()`s and `kill()`s) since the
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/// last `commit()`.
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///
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/// # Example
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/// ```
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/// extern crate ethcore_util;
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/// use ethcore_util::hashdb::*;
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/// use ethcore_util::overlaydb::*;
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/// fn main() {
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/// let mut m = OverlayDB::new_temp();
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/// let foo = m.insert(b"foo"); // insert foo.
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/// m.commit().unwrap(); // commit - new operations begin here...
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/// let bar = m.insert(b"bar"); // insert bar.
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/// m.kill(&foo); // kill foo.
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/// assert!(!m.exists(&foo)); // foo is gone.
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/// assert!(m.exists(&bar)); // bar is here.
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/// m.revert(); // revert the last two operations.
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/// assert!(m.exists(&foo)); // foo is here.
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/// assert!(!m.exists(&bar)); // bar is gone.
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/// }
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/// ```
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pub fn revert(&mut self) { self.overlay.clear(); }
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/// Get the refs and value of the given key.
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fn payload(&self, key: &H256) -> Option<(Bytes, u32)> {
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self.backing.get(&key.bytes())
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.expect("Low-level database error. Some issue with your hard disk?")
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.map(|d| {
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let r = Rlp::new(d.deref());
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(Bytes::decode(&r.at(1)), u32::decode(&r.at(0)))
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})
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}
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/// Get the refs and value of the given key.
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fn put_payload(&self, key: &H256, payload: (Bytes, u32)) {
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let mut s = RlpStream::new_list(2);
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s.append(&payload.1);
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s.append(&payload.0);
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self.backing.put(&key.bytes(), &s.out()).expect("Low-level database error. Some issue with your hard disk?");
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}
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}
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impl HashDB for OverlayDB {
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fn lookup(&self, key: &H256) -> Option<&[u8]> {
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// return ok if positive; if negative, check backing - might be enough references there to make
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// it positive again.
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let k = self.overlay.raw(key);
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match k {
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Some(&(ref d, rc)) if rc > 0 => Some(d),
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_ => {
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let memrc = k.map(|&(_, rc)| rc).unwrap_or(0);
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match self.payload(key) {
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Some(x) => {
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let (d, rc) = x;
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if rc as i32 + memrc > 0 {
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Some(&self.overlay.denote(key, d).0)
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}
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else {
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None
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}
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}
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// Replace above match arm with this once https://github.com/rust-lang/rust/issues/15287 is done.
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//Some((d, rc)) if rc + memrc > 0 => Some(d),
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_ => None,
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}
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}
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}
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}
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fn exists(&self, key: &H256) -> bool {
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// return ok if positive; if negative, check backing - might be enough references there to make
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// it positive again.
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let k = self.overlay.raw(key);
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match k {
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Some(&(_, rc)) if rc > 0 => true,
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_ => {
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let memrc = k.map(|&(_, rc)| rc).unwrap_or(0);
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match self.payload(key) {
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Some(x) => {
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let (_, rc) = x;
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if rc as i32 + memrc > 0 {
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true
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}
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else {
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false
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}
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}
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// Replace above match arm with this once https://github.com/rust-lang/rust/issues/15287 is done.
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//Some((d, rc)) if rc + memrc > 0 => true,
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_ => false,
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}
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}
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}
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}
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fn insert(&mut self, value: &[u8]) -> H256 { self.overlay.insert(value) }
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fn emplace(&mut self, key: H256, value: Bytes) { self.overlay.emplace(key, value); }
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fn kill(&mut self, key: &H256) { self.overlay.kill(key); }
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}
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#[test]
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fn overlaydb_overlay_insert_and_kill() {
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let mut trie = OverlayDB::new_temp();
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let h = trie.insert(b"hello world");
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assert_eq!(trie.lookup(&h).unwrap(), b"hello world");
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trie.kill(&h);
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assert_eq!(trie.lookup(&h), None);
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}
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#[test]
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fn overlaydb_backing_insert_revert() {
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let mut trie = OverlayDB::new_temp();
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let h = trie.insert(b"hello world");
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assert_eq!(trie.lookup(&h).unwrap(), b"hello world");
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trie.commit().unwrap();
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assert_eq!(trie.lookup(&h).unwrap(), b"hello world");
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trie.revert();
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assert_eq!(trie.lookup(&h).unwrap(), b"hello world");
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}
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#[test]
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fn overlaydb_backing_kill() {
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let mut trie = OverlayDB::new_temp();
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let h = trie.insert(b"hello world");
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trie.commit().unwrap();
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trie.kill(&h);
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assert_eq!(trie.lookup(&h), None);
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trie.commit().unwrap();
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assert_eq!(trie.lookup(&h), None);
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trie.revert();
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assert_eq!(trie.lookup(&h), None);
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}
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#[test]
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fn overlaydb_backing_kill_revert() {
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let mut trie = OverlayDB::new_temp();
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let h = trie.insert(b"hello world");
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trie.commit().unwrap();
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trie.kill(&h);
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assert_eq!(trie.lookup(&h), None);
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trie.revert();
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assert_eq!(trie.lookup(&h).unwrap(), b"hello world");
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}
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#[test]
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fn overlaydb_negative() {
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let mut trie = OverlayDB::new_temp();
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let h = trie.insert(b"hello world");
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trie.commit().unwrap();
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trie.kill(&h);
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trie.kill(&h); //bad - sends us into negative refs.
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assert_eq!(trie.lookup(&h), None);
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assert!(trie.commit().is_err());
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}
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#[test]
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fn overlaydb_complex() {
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let mut trie = OverlayDB::new_temp();
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let hfoo = trie.insert(b"foo");
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assert_eq!(trie.lookup(&hfoo).unwrap(), b"foo");
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let hbar = trie.insert(b"bar");
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assert_eq!(trie.lookup(&hbar).unwrap(), b"bar");
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trie.commit().unwrap();
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assert_eq!(trie.lookup(&hfoo).unwrap(), b"foo");
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assert_eq!(trie.lookup(&hbar).unwrap(), b"bar");
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trie.insert(b"foo"); // two refs
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assert_eq!(trie.lookup(&hfoo).unwrap(), b"foo");
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trie.commit().unwrap();
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assert_eq!(trie.lookup(&hfoo).unwrap(), b"foo");
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assert_eq!(trie.lookup(&hbar).unwrap(), b"bar");
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trie.kill(&hbar); // zero refs - delete
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assert_eq!(trie.lookup(&hbar), None);
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trie.kill(&hfoo); // one ref - keep
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assert_eq!(trie.lookup(&hfoo).unwrap(), b"foo");
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trie.commit().unwrap();
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assert_eq!(trie.lookup(&hfoo).unwrap(), b"foo");
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trie.kill(&hfoo); // zero ref - would delete, but...
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assert_eq!(trie.lookup(&hfoo), None);
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trie.insert(b"foo"); // one ref - keep after all.
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assert_eq!(trie.lookup(&hfoo).unwrap(), b"foo");
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trie.commit().unwrap();
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assert_eq!(trie.lookup(&hfoo).unwrap(), b"foo");
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trie.kill(&hfoo); // zero ref - delete
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assert_eq!(trie.lookup(&hfoo), None);
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trie.commit().unwrap(); //
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assert_eq!(trie.lookup(&hfoo), None);
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}
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#[test]
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fn playpen() {
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use std::fs;
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{
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let db: DB = DB::open_default("/tmp/test").unwrap();
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db.put(b"test", b"test2").unwrap();
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match db.get(b"test") {
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Ok(Some(value)) => println!("Got value {:?}", value.deref()),
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Ok(None) => println!("No value for that key"),
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Err(..) => println!("Gah"),
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}
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db.delete(b"test").unwrap();
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}
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fs::remove_dir_all("/tmp/test").unwrap();
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}
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