238 lines
6.7 KiB
Rust
238 lines
6.7 KiB
Rust
// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! An implementation of SipHash 2-4.
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use prelude::v1::*;
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use ptr;
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use super::Hasher;
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/// An implementation of SipHash 2-4.
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///
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/// See: http://131002.net/siphash/
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///
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/// This is the default hashing function used by standard library (eg.
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/// `collections::HashMap` uses it by default).
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///
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/// SipHash is a general-purpose hashing function: it runs at a good
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/// speed (competitive with Spooky and City) and permits strong _keyed_
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/// hashing. This lets you key your hashtables from a strong RNG, such
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/// as [`rand::Rng`](https://doc.rust-lang.org/rand/rand/trait.Rng.html).
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///
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/// Although the SipHash algorithm is considered to be generally strong,
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/// it is not intended for cryptographic purposes. As such, all
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/// cryptographic uses of this implementation are _strongly discouraged_.
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct SipHasher {
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k0: u64,
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k1: u64,
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length: usize, // how many bytes we've processed
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// v0, v2 and v1, v3 show up in pairs in the algorithm,
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// and simd implementations of SipHash will use vectors
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// of v02 and v13. By placing them in this order in the struct,
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// the compiler can pick up on just a few simd optimizations by itself.
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v0: u64, // hash state
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v2: u64,
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v1: u64,
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v3: u64,
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tail: u64, // unprocessed bytes le
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ntail: usize, // how many bytes in tail are valid
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}
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// sadly, these macro definitions can't appear later,
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// because they're needed in the following defs;
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// this design could be improved.
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macro_rules! u8to64_le {
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($buf:expr, $i:expr) =>
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($buf[0+$i] as u64 |
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($buf[1+$i] as u64) << 8 |
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($buf[2+$i] as u64) << 16 |
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($buf[3+$i] as u64) << 24 |
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($buf[4+$i] as u64) << 32 |
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($buf[5+$i] as u64) << 40 |
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($buf[6+$i] as u64) << 48 |
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($buf[7+$i] as u64) << 56);
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($buf:expr, $i:expr, $len:expr) =>
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({
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let mut t = 0;
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let mut out = 0;
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while t < $len {
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out |= ($buf[t+$i] as u64) << t*8;
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t += 1;
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}
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out
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});
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}
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/// Load a full u64 word from a byte stream, in LE order. Use
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/// `copy_nonoverlapping` to let the compiler generate the most efficient way
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/// to load u64 from a possibly unaligned address.
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///
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/// Unsafe because: unchecked indexing at i..i+8
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#[inline]
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unsafe fn load_u64_le(buf: &[u8], i: usize) -> u64 {
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debug_assert!(i + 8 <= buf.len());
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let mut data = 0u64;
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ptr::copy_nonoverlapping(buf.get_unchecked(i), &mut data as *mut _ as *mut u8, 8);
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data.to_le()
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}
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macro_rules! rotl {
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($x:expr, $b:expr) =>
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(($x << $b) | ($x >> (64_i32.wrapping_sub($b))))
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}
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macro_rules! compress {
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($v0:expr, $v1:expr, $v2:expr, $v3:expr) =>
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({
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$v0 = $v0.wrapping_add($v1); $v1 = rotl!($v1, 13); $v1 ^= $v0;
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$v0 = rotl!($v0, 32);
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$v2 = $v2.wrapping_add($v3); $v3 = rotl!($v3, 16); $v3 ^= $v2;
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$v0 = $v0.wrapping_add($v3); $v3 = rotl!($v3, 21); $v3 ^= $v0;
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$v2 = $v2.wrapping_add($v1); $v1 = rotl!($v1, 17); $v1 ^= $v2;
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$v2 = rotl!($v2, 32);
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})
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}
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impl SipHasher {
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/// Creates a new `SipHasher` with the two initial keys set to 0.
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn new() -> SipHasher {
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SipHasher::new_with_keys(0, 0)
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}
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/// Creates a `SipHasher` that is keyed off the provided keys.
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher {
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let mut state = SipHasher {
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k0: key0,
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k1: key1,
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length: 0,
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v0: 0,
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v1: 0,
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v2: 0,
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v3: 0,
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tail: 0,
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ntail: 0,
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};
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state.reset();
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state
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}
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#[inline]
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fn reset(&mut self) {
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self.length = 0;
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self.v0 = self.k0 ^ 0x736f6d6570736575;
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self.v1 = self.k1 ^ 0x646f72616e646f6d;
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self.v2 = self.k0 ^ 0x6c7967656e657261;
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self.v3 = self.k1 ^ 0x7465646279746573;
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self.ntail = 0;
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl Hasher for SipHasher {
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#[inline]
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fn write(&mut self, msg: &[u8]) {
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let length = msg.len();
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self.length += length;
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let mut needed = 0;
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if self.ntail != 0 {
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needed = 8 - self.ntail;
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if length < needed {
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self.tail |= u8to64_le!(msg, 0, length) << 8 * self.ntail;
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self.ntail += length;
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return
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}
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let m = self.tail | u8to64_le!(msg, 0, needed) << 8 * self.ntail;
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self.v3 ^= m;
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compress!(self.v0, self.v1, self.v2, self.v3);
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compress!(self.v0, self.v1, self.v2, self.v3);
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self.v0 ^= m;
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self.ntail = 0;
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}
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// Buffered tail is now flushed, process new input.
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let len = length - needed;
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let left = len & 0x7;
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let mut i = needed;
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while i < len - left {
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let mi = unsafe { load_u64_le(msg, i) };
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self.v3 ^= mi;
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compress!(self.v0, self.v1, self.v2, self.v3);
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compress!(self.v0, self.v1, self.v2, self.v3);
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self.v0 ^= mi;
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i += 8;
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}
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self.tail = u8to64_le!(msg, i, left);
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self.ntail = left;
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}
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#[inline]
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fn finish(&self) -> u64 {
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let mut v0 = self.v0;
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let mut v1 = self.v1;
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let mut v2 = self.v2;
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let mut v3 = self.v3;
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let b: u64 = ((self.length as u64 & 0xff) << 56) | self.tail;
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v3 ^= b;
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compress!(v0, v1, v2, v3);
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compress!(v0, v1, v2, v3);
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v0 ^= b;
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v2 ^= 0xff;
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compress!(v0, v1, v2, v3);
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compress!(v0, v1, v2, v3);
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compress!(v0, v1, v2, v3);
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compress!(v0, v1, v2, v3);
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v0 ^ v1 ^ v2 ^ v3
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl Clone for SipHasher {
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#[inline]
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fn clone(&self) -> SipHasher {
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SipHasher {
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k0: self.k0,
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k1: self.k1,
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length: self.length,
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v0: self.v0,
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v1: self.v1,
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v2: self.v2,
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v3: self.v3,
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tail: self.tail,
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ntail: self.ntail,
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}
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl Default for SipHasher {
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fn default() -> SipHasher {
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SipHasher::new()
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}
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}
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