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use std::hash::Hasher;
use std::marker::PhantomData;
use std::mem;
use blake2b::Blake2bHasher;
use rustc_serialize::leb128;
fn write_unsigned_leb128_to_buf(buf: &mut [u8; 16], value: u64) -> usize {
leb128::write_unsigned_leb128_to(value as u128, |i, v| buf[i] = v)
}
fn write_signed_leb128_to_buf(buf: &mut [u8; 16], value: i64) -> usize {
leb128::write_signed_leb128_to(value as i128, |i, v| buf[i] = v)
}
#[derive(Debug)]
pub struct StableHasher<W> {
state: Blake2bHasher,
bytes_hashed: u64,
width: PhantomData<W>,
}
pub trait StableHasherResult: Sized {
fn finish(hasher: StableHasher<Self>) -> Self;
}
impl<W: StableHasherResult> StableHasher<W> {
pub fn new() -> Self {
StableHasher {
state: Blake2bHasher::new(mem::size_of::<W>(), &[]),
bytes_hashed: 0,
width: PhantomData,
}
}
pub fn finish(self) -> W {
W::finish(self)
}
}
impl StableHasherResult for [u8; 20] {
fn finish(mut hasher: StableHasher<Self>) -> Self {
let mut result: [u8; 20] = [0; 20];
result.copy_from_slice(hasher.state.finalize());
result
}
}
impl StableHasherResult for u64 {
fn finish(mut hasher: StableHasher<Self>) -> Self {
hasher.state.finalize();
hasher.state.finish()
}
}
impl<W> StableHasher<W> {
#[inline]
pub fn finalize(&mut self) -> &[u8] {
self.state.finalize()
}
#[inline]
pub fn bytes_hashed(&self) -> u64 {
self.bytes_hashed
}
#[inline]
fn write_uleb128(&mut self, value: u64) {
let mut buf = [0; 16];
let len = write_unsigned_leb128_to_buf(&mut buf, value);
self.state.write(&buf[..len]);
self.bytes_hashed += len as u64;
}
#[inline]
fn write_ileb128(&mut self, value: i64) {
let mut buf = [0; 16];
let len = write_signed_leb128_to_buf(&mut buf, value);
self.state.write(&buf[..len]);
self.bytes_hashed += len as u64;
}
}
impl<W> Hasher for StableHasher<W> {
fn finish(&self) -> u64 {
panic!("use StableHasher::finish instead");
}
#[inline]
fn write(&mut self, bytes: &[u8]) {
self.state.write(bytes);
self.bytes_hashed += bytes.len() as u64;
}
#[inline]
fn write_u8(&mut self, i: u8) {
self.state.write_u8(i);
self.bytes_hashed += 1;
}
#[inline]
fn write_u16(&mut self, i: u16) {
self.write_uleb128(i as u64);
}
#[inline]
fn write_u32(&mut self, i: u32) {
self.write_uleb128(i as u64);
}
#[inline]
fn write_u64(&mut self, i: u64) {
self.write_uleb128(i);
}
#[inline]
fn write_usize(&mut self, i: usize) {
self.write_uleb128(i as u64);
}
#[inline]
fn write_i8(&mut self, i: i8) {
self.state.write_i8(i);
self.bytes_hashed += 1;
}
#[inline]
fn write_i16(&mut self, i: i16) {
self.write_ileb128(i as i64);
}
#[inline]
fn write_i32(&mut self, i: i32) {
self.write_ileb128(i as i64);
}
#[inline]
fn write_i64(&mut self, i: i64) {
self.write_ileb128(i);
}
#[inline]
fn write_isize(&mut self, i: isize) {
self.write_ileb128(i as i64);
}
}