openethereum/util/src/trie/standardmap.rs
2016-02-27 15:49:44 +01:00

121 lines
4.0 KiB
Rust

// Copyright 2015, 2016 Ethcore (UK) Ltd.
// This file is part of Parity.
// Parity is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Parity is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Parity. If not, see <http://www.gnu.org/licenses/>.
//! Key-value datastore with a modified Merkle tree.
extern crate rand;
use bytes::*;
use sha3::*;
use hash::*;
use rlp::encode;
/// Alphabet to use when creating words for insertion into tries.
pub enum Alphabet {
/// All values are allowed in each bytes of the key.
All,
/// Only a 6 values ('a' - 'f') are chosen to compose the key.
Low,
/// Quite a few values (around 32) are chosen to compose the key.
Mid,
/// A set of bytes given is used to compose the key.
Custom(Bytes),
}
/// Means of determining the value.
pub enum ValueMode {
/// Same as the key.
Mirror,
/// Randomly (50:50) 1 or 32 byte randomly string.
Random,
/// RLP-encoded index.
Index,
}
/// Standard test map for profiling tries.
pub struct StandardMap {
/// The alphabet to use for keys.
pub alphabet: Alphabet,
/// Minimum size of key.
pub min_key: usize,
/// Delta size of key.
pub journal_key: usize,
/// Mode of value generation.
pub value_mode: ValueMode,
/// Number of keys.
pub count: usize,
}
impl StandardMap {
/// Get a bunch of random bytes, at least `min_count` bytes, at most `min_count` + `journal_count` bytes.
/// `seed` is mutated pseudoramdonly and used.
fn random_bytes(min_count: usize, journal_count: usize, seed: &mut H256) -> Vec<u8> {
assert!(min_count + journal_count <= 32);
*seed = seed.sha3();
let r = min_count + (seed.bytes()[31] as usize % (journal_count + 1));
seed.bytes()[0..r].to_vec()
}
/// Get a random value. Equal chance of being 1 byte as of 32. `seed` is mutated pseudoramdonly and used.
fn random_value(seed: &mut H256) -> Bytes {
*seed = seed.sha3();
match seed.bytes()[0] % 2 {
1 => vec![seed.bytes()[31];1],
_ => seed.bytes().to_vec(),
}
}
/// Get a random word of, at least `min_count` bytes, at most `min_count` + `journal_count` bytes.
/// Each byte is an item from `alphabet`. `seed` is mutated pseudoramdonly and used.
fn random_word(alphabet: &[u8], min_count: usize, journal_count: usize, seed: &mut H256) -> Vec<u8> {
assert!(min_count + journal_count <= 32);
*seed = seed.sha3();
let r = min_count + (seed.bytes()[31] as usize % (journal_count + 1));
let mut ret: Vec<u8> = Vec::with_capacity(r);
for i in 0..r {
ret.push(alphabet[seed.bytes()[i] as usize % alphabet.len()]);
}
ret
}
/// Create the standard map (set of keys and values) for the object's fields.
pub fn make(&self) -> Vec<(Bytes, Bytes)> {
self.make_with(&mut H256::new())
}
/// Create the standard map (set of keys and values) for the object's fields, using the given seed.
pub fn make_with(&self, seed: &mut H256) -> Vec<(Bytes, Bytes)> {
let low = b"abcdef";
let mid = b"@QWERTYUIOPASDFGHJKLZXCVBNM[/]^_";
let mut d: Vec<(Bytes, Bytes)> = Vec::new();
for index in 0..self.count {
let k = match self.alphabet {
Alphabet::All => Self::random_bytes(self.min_key, self.journal_key, seed),
Alphabet::Low => Self::random_word(low, self.min_key, self.journal_key, seed),
Alphabet::Mid => Self::random_word(mid, self.min_key, self.journal_key, seed),
Alphabet::Custom(ref a) => Self::random_word(&a, self.min_key, self.journal_key, seed),
};
let v = match self.value_mode {
ValueMode::Mirror => k.clone(),
ValueMode::Random => Self::random_value(seed),
ValueMode::Index => encode(&index).to_vec(),
};
d.push((k, v))
}
d
}
}