openethereum/util/nibblevec/src/lib.rs
Hawstein ade37be25b separate trie from util and make its dependencies into libs:
* bytes
* hashdb
* memorydb
* nibbleslice
* nibblevec
2017-09-15 11:03:53 +08:00

149 lines
3.3 KiB
Rust

// Copyright 2015-2017 Parity Technologies (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/>.
//! An owning, nibble-oriented byte vector.
extern crate nibbleslice;
extern crate elastic_array;
use nibbleslice::NibbleSlice;
use elastic_array::ElasticArray36;
/// Owning, nibble-oriented byte vector. Counterpart to `NibbleSlice`.
#[derive(Clone, PartialEq, Eq, Debug)]
pub struct NibbleVec {
inner: ElasticArray36<u8>,
len: usize,
}
impl Default for NibbleVec {
fn default() -> Self {
NibbleVec::new()
}
}
impl NibbleVec {
/// Make a new `NibbleVec`
pub fn new() -> Self {
NibbleVec {
inner: ElasticArray36::new(),
len: 0
}
}
/// Length of the `NibbleVec`
pub fn len(&self) -> usize { self.len }
/// Retrurns true if `NibbleVec` has zero length
pub fn is_empty(&self) -> bool { self.len == 0 }
/// Try to get the nibble at the given offset.
pub fn at(&self, idx: usize) -> u8 {
if idx % 2 == 0 {
self.inner[idx / 2] >> 4
} else {
self.inner[idx / 2] & 0x0F
}
}
/// Push a nibble onto the `NibbleVec`. Ignores the high 4 bits.
pub fn push(&mut self, nibble: u8) {
let nibble = nibble & 0x0F;
if self.len % 2 == 0 {
self.inner.push(nibble << 4);
} else {
*self.inner.last_mut().expect("len != 0 since len % 2 != 0; inner has a last element; qed") |= nibble;
}
self.len += 1;
}
/// Try to pop a nibble off the `NibbleVec`. Fails if len == 0.
pub fn pop(&mut self) -> Option<u8> {
if self.is_empty() {
return None;
}
let byte = self.inner.pop().expect("len != 0; inner has last elem; qed");
let nibble = if self.len % 2 == 0 {
self.inner.push(byte & 0xF0);
byte & 0x0F
} else {
byte >> 4
};
self.len -= 1;
Some(nibble)
}
/// Try to treat this `NibbleVec` as a `NibbleSlice`. Works only if len is even.
pub fn as_nibbleslice(&self) -> Option<NibbleSlice> {
if self.len % 2 == 0 {
Some(NibbleSlice::new(self.inner()))
} else {
None
}
}
/// Get the underlying byte slice.
pub fn inner(&self) -> &[u8] {
&self.inner[..]
}
}
impl<'a> From<NibbleSlice<'a>> for NibbleVec {
fn from(s: NibbleSlice<'a>) -> Self {
let mut v = NibbleVec::new();
for i in 0..s.len() {
v.push(s.at(i));
}
v
}
}
#[cfg(test)]
mod tests {
use super::NibbleVec;
#[test]
fn push_pop() {
let mut v = NibbleVec::new();
for i in 0..16 {
v.push(i);
assert_eq!(v.len() - 1, i as usize);
assert_eq!(v.at(i as usize), i);
}
for i in (0..16).rev() {
assert_eq!(v.pop(), Some(i));
assert_eq!(v.len(), i as usize);
}
}
#[test]
fn nibbleslice_conv() {
let mut v = NibbleVec::new();
for i in 0..10 {
v.push(i);
}
let v2: NibbleVec = v.as_nibbleslice().unwrap().into();
assert_eq!(v, v2);
}
}