445 lines
13 KiB
Rust
445 lines
13 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.
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#![allow(deprecated)]
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use marker::PhantomData;
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use ptr;
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use cmp;
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use mem;
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/// An implementation of SipHash 1-3.
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///
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/// This is currently the default hashing function used by standard library
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/// (eg. `collections::HashMap` uses it by default).
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///
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/// See: <https://131002.net/siphash>
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#[unstable(feature = "sip_hash_13", issue = "34767")]
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#[rustc_deprecated(since = "1.13.0",
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reason = "use `std::collections::hash_map::DefaultHasher` instead")]
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#[derive(Debug, Clone, Default)]
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pub struct SipHasher13 {
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hasher: Hasher<Sip13Rounds>,
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}
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/// An implementation of SipHash 2-4.
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///
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/// See: <https://131002.net/siphash/>
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#[unstable(feature = "sip_hash_13", issue = "34767")]
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#[rustc_deprecated(since = "1.13.0",
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reason = "use `std::collections::hash_map::DefaultHasher` instead")]
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#[derive(Debug, Clone, Default)]
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pub struct SipHasher24 {
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hasher: Hasher<Sip24Rounds>,
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}
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/// An implementation of SipHash 2-4.
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///
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/// See: <https://131002.net/siphash/>
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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 as
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/// [`rand::os::OsRng`](https://doc.rust-lang.org/rand/rand/os/struct.OsRng.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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#[rustc_deprecated(since = "1.13.0",
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reason = "use `std::collections::hash_map::DefaultHasher` instead")]
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#[derive(Debug, Clone, Default)]
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pub struct SipHasher(SipHasher24);
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#[derive(Debug)]
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struct Hasher<S: Sip> {
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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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state: State, // hash State
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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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_marker: PhantomData<S>,
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}
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#[derive(Debug, Clone, Copy)]
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#[repr(C)]
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struct State {
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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,
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v2: u64,
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v1: u64,
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v3: u64,
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}
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macro_rules! compress {
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($state:expr) => ({
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compress!($state.v0, $state.v1, $state.v2, $state.v3)
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});
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($v0:expr, $v1:expr, $v2:expr, $v3:expr) =>
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({
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$v0 = $v0.wrapping_add($v1); $v1 = $v1.rotate_left(13); $v1 ^= $v0;
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$v0 = $v0.rotate_left(32);
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$v2 = $v2.wrapping_add($v3); $v3 = $v3.rotate_left(16); $v3 ^= $v2;
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$v0 = $v0.wrapping_add($v3); $v3 = $v3.rotate_left(21); $v3 ^= $v0;
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$v2 = $v2.wrapping_add($v1); $v1 = $v1.rotate_left(17); $v1 ^= $v2;
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$v2 = $v2.rotate_left(32);
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});
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}
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/// Load an integer of the desired type from a byte stream, in LE order. Uses
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/// `copy_nonoverlapping` to let the compiler generate the most efficient way
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/// to load it from a possibly unaligned address.
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///
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/// Unsafe because: unchecked indexing at i..i+size_of(int_ty)
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macro_rules! load_int_le {
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($buf:expr, $i:expr, $int_ty:ident) =>
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({
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debug_assert!($i + mem::size_of::<$int_ty>() <= $buf.len());
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let mut data = 0 as $int_ty;
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ptr::copy_nonoverlapping($buf.get_unchecked($i),
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&mut data as *mut _ as *mut u8,
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mem::size_of::<$int_ty>());
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data.to_le()
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});
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}
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/// Load an u64 using up to 7 bytes of a byte slice.
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///
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/// Unsafe because: unchecked indexing at start..start+len
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#[inline]
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unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 {
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debug_assert!(len < 8);
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let mut i = 0; // current byte index (from LSB) in the output u64
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let mut out = 0;
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if i + 3 < len {
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out = load_int_le!(buf, start + i, u32) as u64;
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i += 4;
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}
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if i + 1 < len {
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out |= (load_int_le!(buf, start + i, u16) as u64) << (i * 8);
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i += 2
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}
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if i < len {
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out |= (*buf.get_unchecked(start + i) as u64) << (i * 8);
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i += 1;
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}
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debug_assert_eq!(i, len);
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out
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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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#[rustc_deprecated(since = "1.13.0",
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reason = "use `std::collections::hash_map::DefaultHasher` instead")]
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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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#[rustc_deprecated(since = "1.13.0",
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reason = "use `std::collections::hash_map::DefaultHasher` instead")]
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pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher {
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SipHasher(SipHasher24::new_with_keys(key0, key1))
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}
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}
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impl SipHasher13 {
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/// Creates a new `SipHasher13` with the two initial keys set to 0.
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#[inline]
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#[unstable(feature = "sip_hash_13", issue = "34767")]
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#[rustc_deprecated(since = "1.13.0",
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reason = "use `std::collections::hash_map::DefaultHasher` instead")]
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pub fn new() -> SipHasher13 {
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SipHasher13::new_with_keys(0, 0)
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}
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/// Creates a `SipHasher13` that is keyed off the provided keys.
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#[inline]
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#[unstable(feature = "sip_hash_13", issue = "34767")]
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#[rustc_deprecated(since = "1.13.0",
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reason = "use `std::collections::hash_map::DefaultHasher` instead")]
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pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher13 {
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SipHasher13 {
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hasher: Hasher::new_with_keys(key0, key1)
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}
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}
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}
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impl SipHasher24 {
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/// Creates a new `SipHasher24` with the two initial keys set to 0.
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#[inline]
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#[unstable(feature = "sip_hash_13", issue = "34767")]
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#[rustc_deprecated(since = "1.13.0",
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reason = "use `std::collections::hash_map::DefaultHasher` instead")]
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pub fn new() -> SipHasher24 {
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SipHasher24::new_with_keys(0, 0)
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}
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/// Creates a `SipHasher24` that is keyed off the provided keys.
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#[inline]
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#[unstable(feature = "sip_hash_13", issue = "34767")]
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#[rustc_deprecated(since = "1.13.0",
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reason = "use `std::collections::hash_map::DefaultHasher` instead")]
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pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher24 {
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SipHasher24 {
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hasher: Hasher::new_with_keys(key0, key1)
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}
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}
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}
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impl<S: Sip> Hasher<S> {
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#[inline]
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fn new_with_keys(key0: u64, key1: u64) -> Hasher<S> {
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let mut state = Hasher {
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k0: key0,
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k1: key1,
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length: 0,
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state: State {
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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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},
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tail: 0,
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ntail: 0,
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_marker: PhantomData,
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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.state.v0 = self.k0 ^ 0x736f6d6570736575;
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self.state.v1 = self.k1 ^ 0x646f72616e646f6d;
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self.state.v2 = self.k0 ^ 0x6c7967656e657261;
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self.state.v3 = self.k1 ^ 0x7465646279746573;
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self.ntail = 0;
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}
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// Specialized write function that is only valid for buffers with len <= 8.
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// It's used to force inlining of write_u8 and write_usize, those would normally be inlined
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// except for composite types (that includes slices and str hashing because of delimiter).
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// Without this extra push the compiler is very reluctant to inline delimiter writes,
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// degrading performance substantially for the most common use cases.
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#[inline]
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fn short_write(&mut self, msg: &[u8]) {
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debug_assert!(msg.len() <= 8);
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let length = msg.len();
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self.length += length;
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let needed = 8 - self.ntail;
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let fill = cmp::min(length, needed);
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if fill == 8 {
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self.tail = unsafe { load_int_le!(msg, 0, u64) };
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} else {
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self.tail |= unsafe { u8to64_le(msg, 0, fill) } << (8 * self.ntail);
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if length < needed {
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self.ntail += length;
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return;
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}
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}
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self.state.v3 ^= self.tail;
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S::c_rounds(&mut self.state);
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self.state.v0 ^= self.tail;
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// Buffered tail is now flushed, process new input.
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self.ntail = length - needed;
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self.tail = unsafe { u8to64_le(msg, needed, self.ntail) };
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl super::Hasher for SipHasher {
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#[inline]
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fn write(&mut self, msg: &[u8]) {
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self.0.write(msg)
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}
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#[inline]
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fn finish(&self) -> u64 {
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self.0.finish()
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}
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}
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#[unstable(feature = "sip_hash_13", issue = "34767")]
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impl super::Hasher for SipHasher13 {
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#[inline]
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fn write(&mut self, msg: &[u8]) {
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self.hasher.write(msg)
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}
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#[inline]
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fn finish(&self) -> u64 {
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self.hasher.finish()
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}
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}
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#[unstable(feature = "sip_hash_13", issue = "34767")]
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impl super::Hasher for SipHasher24 {
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#[inline]
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fn write(&mut self, msg: &[u8]) {
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self.hasher.write(msg)
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}
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#[inline]
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fn finish(&self) -> u64 {
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self.hasher.finish()
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}
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}
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impl<S: Sip> super::Hasher for Hasher<S> {
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// see short_write comment for explanation
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#[inline]
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fn write_usize(&mut self, i: usize) {
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let bytes = unsafe {
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::slice::from_raw_parts(&i as *const usize as *const u8, mem::size_of::<usize>())
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};
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self.short_write(bytes);
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}
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// see short_write comment for explanation
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#[inline]
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fn write_u8(&mut self, i: u8) {
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self.short_write(&[i]);
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}
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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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self.tail |= unsafe { u8to64_le(msg, 0, cmp::min(length, needed)) } << 8 * self.ntail;
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if length < needed {
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self.ntail += length;
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return
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} else {
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self.state.v3 ^= self.tail;
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S::c_rounds(&mut self.state);
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self.state.v0 ^= self.tail;
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self.ntail = 0;
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}
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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_int_le!(msg, i, u64) };
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self.state.v3 ^= mi;
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S::c_rounds(&mut self.state);
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self.state.v0 ^= mi;
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i += 8;
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}
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self.tail = unsafe { 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 state = self.state;
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let b: u64 = ((self.length as u64 & 0xff) << 56) | self.tail;
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state.v3 ^= b;
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S::c_rounds(&mut state);
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state.v0 ^= b;
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state.v2 ^= 0xff;
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S::d_rounds(&mut state);
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state.v0 ^ state.v1 ^ state.v2 ^ state.v3
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}
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}
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impl<S: Sip> Clone for Hasher<S> {
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#[inline]
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fn clone(&self) -> Hasher<S> {
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Hasher {
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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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state: self.state,
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tail: self.tail,
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ntail: self.ntail,
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_marker: self._marker,
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}
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}
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}
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impl<S: Sip> Default for Hasher<S> {
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/// Creates a `Hasher<S>` with the two initial keys set to 0.
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#[inline]
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fn default() -> Hasher<S> {
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Hasher::new_with_keys(0, 0)
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}
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}
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#[doc(hidden)]
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trait Sip {
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fn c_rounds(_: &mut State);
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fn d_rounds(_: &mut State);
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}
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#[derive(Debug, Clone, Default)]
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struct Sip13Rounds;
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impl Sip for Sip13Rounds {
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#[inline]
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fn c_rounds(state: &mut State) {
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compress!(state);
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}
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#[inline]
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fn d_rounds(state: &mut State) {
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compress!(state);
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compress!(state);
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compress!(state);
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}
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}
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#[derive(Debug, Clone, Default)]
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struct Sip24Rounds;
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impl Sip for Sip24Rounds {
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#[inline]
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fn c_rounds(state: &mut State) {
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compress!(state);
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compress!(state);
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}
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#[inline]
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fn d_rounds(state: &mut State) {
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compress!(state);
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compress!(state);
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compress!(state);
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compress!(state);
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}
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}
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