Trait ethcore_util::hashdb::HashDB
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[src]
pub trait HashDB: AsHashDB + Send + Sync { fn keys(&self) -> HashMap<H256, i32>; fn get(&self, key: &H256) -> Option<DBValue>; fn contains(&self, key: &H256) -> bool; fn insert(&mut self, value: &[u8]) -> H256; fn emplace(&mut self, key: H256, value: DBValue); fn remove(&mut self, key: &H256); }
Trait modelling datastore keyed by a 32-byte Keccak hash.
Required Methods
fn keys(&self) -> HashMap<H256, i32>
Get the keys in the database together with number of underlying references.
fn get(&self, key: &H256) -> Option<DBValue>
Look up a given hash into the bytes that hash to it, returning None if the hash is not known.
Examples
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.get(&hash).unwrap(), hello_bytes); }
fn contains(&self, key: &H256) -> bool
Check for the existance of a hash-key.
Examples
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.contains(&hello_bytes.sha3())); let key = m.insert(hello_bytes); assert!(m.contains(&key)); m.remove(&key); assert!(!m.contains(&key)); }
fn insert(&mut self, value: &[u8]) -> H256
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 remove()
s must be performed before the data
is considered dead.
Examples
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.contains(&key)); }
fn emplace(&mut self, key: H256, value: DBValue)
Like insert()
, except you provide the key and the data is all moved.
fn remove(&mut self, key: &H256)
Remove a datum previously inserted. Insertions can be "owed" such that the same number of insert()
s may
happen without the data being eventually being inserted into the DB.
Examples
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.remove(key); // OK - we now owe an insertion. assert!(!m.contains(key)); m.insert(d); // OK - now it's "empty" again. assert!(!m.contains(key)); m.insert(d); // OK - now we've assert_eq!(m.get(key).unwrap(), d); }