1 //! An implementation of SipHash.
3 // ignore-tidy-undocumented-unsafe
5 #![allow(deprecated)] // the types in this module are deprecated
8 use crate::marker::PhantomData;
12 /// An implementation of SipHash 1-3.
14 /// This is currently the default hashing function used by standard library
15 /// (e.g., `collections::HashMap` uses it by default).
17 /// See: <https://131002.net/siphash>
18 #[unstable(feature = "hashmap_internals", issue = "none")]
21 reason = "use `std::collections::hash_map::DefaultHasher` instead"
23 #[derive(Debug, Clone, Default)]
25 pub struct SipHasher13 {
26 hasher: Hasher<Sip13Rounds>,
29 /// An implementation of SipHash 2-4.
31 /// See: <https://131002.net/siphash/>
32 #[unstable(feature = "hashmap_internals", issue = "none")]
35 reason = "use `std::collections::hash_map::DefaultHasher` instead"
37 #[derive(Debug, Clone, Default)]
39 hasher: Hasher<Sip24Rounds>,
42 /// An implementation of SipHash 2-4.
44 /// See: <https://131002.net/siphash/>
46 /// SipHash is a general-purpose hashing function: it runs at a good
47 /// speed (competitive with Spooky and City) and permits strong _keyed_
48 /// hashing. This lets you key your hashtables from a strong RNG, such as
49 /// [`rand::os::OsRng`](https://doc.rust-lang.org/rand/rand/os/struct.OsRng.html).
51 /// Although the SipHash algorithm is considered to be generally strong,
52 /// it is not intended for cryptographic purposes. As such, all
53 /// cryptographic uses of this implementation are _strongly discouraged_.
54 #[stable(feature = "rust1", since = "1.0.0")]
57 reason = "use `std::collections::hash_map::DefaultHasher` instead"
59 #[derive(Debug, Clone, Default)]
60 pub struct SipHasher(SipHasher24);
63 struct Hasher<S: Sip> {
66 length: usize, // how many bytes we've processed
67 state: State, // hash State
68 tail: u64, // unprocessed bytes le
69 ntail: usize, // how many bytes in tail are valid
70 _marker: PhantomData<S>,
73 #[derive(Debug, Clone, Copy)]
76 // v0, v2 and v1, v3 show up in pairs in the algorithm,
77 // and simd implementations of SipHash will use vectors
78 // of v02 and v13. By placing them in this order in the struct,
79 // the compiler can pick up on just a few simd optimizations by itself.
86 macro_rules! compress {
87 ($state:expr) => {{ compress!($state.v0, $state.v1, $state.v2, $state.v3) }};
88 ($v0:expr, $v1:expr, $v2:expr, $v3:expr) => {{
89 $v0 = $v0.wrapping_add($v1);
90 $v1 = $v1.rotate_left(13);
92 $v0 = $v0.rotate_left(32);
93 $v2 = $v2.wrapping_add($v3);
94 $v3 = $v3.rotate_left(16);
96 $v0 = $v0.wrapping_add($v3);
97 $v3 = $v3.rotate_left(21);
99 $v2 = $v2.wrapping_add($v1);
100 $v1 = $v1.rotate_left(17);
102 $v2 = $v2.rotate_left(32);
106 /// Loads an integer of the desired type from a byte stream, in LE order. Uses
107 /// `copy_nonoverlapping` to let the compiler generate the most efficient way
108 /// to load it from a possibly unaligned address.
110 /// Unsafe because: unchecked indexing at i..i+size_of(int_ty)
111 macro_rules! load_int_le {
112 ($buf:expr, $i:expr, $int_ty:ident) => {{
113 debug_assert!($i + mem::size_of::<$int_ty>() <= $buf.len());
114 let mut data = 0 as $int_ty;
115 ptr::copy_nonoverlapping(
116 $buf.get_unchecked($i),
117 &mut data as *mut _ as *mut u8,
118 mem::size_of::<$int_ty>(),
124 /// Loads a u64 using up to 7 bytes of a byte slice. It looks clumsy but the
125 /// `copy_nonoverlapping` calls that occur (via `load_int_le!`) all have fixed
126 /// sizes and avoid calling `memcpy`, which is good for speed.
128 /// Unsafe because: unchecked indexing at start..start+len
130 unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 {
131 debug_assert!(len < 8);
132 let mut i = 0; // current byte index (from LSB) in the output u64
135 out = load_int_le!(buf, start + i, u32) as u64;
139 out |= (load_int_le!(buf, start + i, u16) as u64) << (i * 8);
143 out |= (*buf.get_unchecked(start + i) as u64) << (i * 8);
146 debug_assert_eq!(i, len);
151 /// Creates a new `SipHasher` with the two initial keys set to 0.
153 #[stable(feature = "rust1", since = "1.0.0")]
156 reason = "use `std::collections::hash_map::DefaultHasher` instead"
158 pub fn new() -> SipHasher {
159 SipHasher::new_with_keys(0, 0)
162 /// Creates a `SipHasher` that is keyed off the provided keys.
164 #[stable(feature = "rust1", since = "1.0.0")]
167 reason = "use `std::collections::hash_map::DefaultHasher` instead"
169 pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher {
170 SipHasher(SipHasher24 { hasher: Hasher::new_with_keys(key0, key1) })
175 /// Creates a new `SipHasher13` with the two initial keys set to 0.
177 #[unstable(feature = "hashmap_internals", issue = "none")]
180 reason = "use `std::collections::hash_map::DefaultHasher` instead"
182 pub fn new() -> SipHasher13 {
183 SipHasher13::new_with_keys(0, 0)
186 /// Creates a `SipHasher13` that is keyed off the provided keys.
188 #[unstable(feature = "hashmap_internals", issue = "none")]
191 reason = "use `std::collections::hash_map::DefaultHasher` instead"
193 pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher13 {
194 SipHasher13 { hasher: Hasher::new_with_keys(key0, key1) }
198 impl<S: Sip> Hasher<S> {
200 fn new_with_keys(key0: u64, key1: u64) -> Hasher<S> {
201 let mut state = Hasher {
205 state: State { v0: 0, v1: 0, v2: 0, v3: 0 },
208 _marker: PhantomData,
215 fn reset(&mut self) {
217 self.state.v0 = self.k0 ^ 0x736f6d6570736575;
218 self.state.v1 = self.k1 ^ 0x646f72616e646f6d;
219 self.state.v2 = self.k0 ^ 0x6c7967656e657261;
220 self.state.v3 = self.k1 ^ 0x7465646279746573;
225 #[stable(feature = "rust1", since = "1.0.0")]
226 impl super::Hasher for SipHasher {
228 fn write(&mut self, msg: &[u8]) {
229 self.0.hasher.write(msg)
233 fn finish(&self) -> u64 {
234 self.0.hasher.finish()
238 #[unstable(feature = "hashmap_internals", issue = "none")]
239 impl super::Hasher for SipHasher13 {
241 fn write(&mut self, msg: &[u8]) {
242 self.hasher.write(msg)
246 fn finish(&self) -> u64 {
251 impl<S: Sip> super::Hasher for Hasher<S> {
252 // Note: no integer hashing methods (`write_u*`, `write_i*`) are defined
253 // for this type. We could add them, copy the `short_write` implementation
254 // in librustc_data_structures/sip128.rs, and add `write_u*`/`write_i*`
255 // methods to `SipHasher`, `SipHasher13`, and `DefaultHasher`. This would
256 // greatly speed up integer hashing by those hashers, at the cost of
257 // slightly slowing down compile speeds on some benchmarks. See #69152 for
260 fn write(&mut self, msg: &[u8]) {
261 let length = msg.len();
262 self.length += length;
267 needed = 8 - self.ntail;
268 self.tail |= unsafe { u8to64_le(msg, 0, cmp::min(length, needed)) } << (8 * self.ntail);
270 self.ntail += length;
273 self.state.v3 ^= self.tail;
274 S::c_rounds(&mut self.state);
275 self.state.v0 ^= self.tail;
280 // Buffered tail is now flushed, process new input.
281 let len = length - needed;
282 let left = len & 0x7;
285 while i < len - left {
286 let mi = unsafe { load_int_le!(msg, i, u64) };
289 S::c_rounds(&mut self.state);
295 self.tail = unsafe { u8to64_le(msg, i, left) };
300 fn finish(&self) -> u64 {
301 let mut state = self.state;
303 let b: u64 = ((self.length as u64 & 0xff) << 56) | self.tail;
306 S::c_rounds(&mut state);
310 S::d_rounds(&mut state);
312 state.v0 ^ state.v1 ^ state.v2 ^ state.v3
316 impl<S: Sip> Clone for Hasher<S> {
318 fn clone(&self) -> Hasher<S> {
326 _marker: self._marker,
331 impl<S: Sip> Default for Hasher<S> {
332 /// Creates a `Hasher<S>` with the two initial keys set to 0.
334 fn default() -> Hasher<S> {
335 Hasher::new_with_keys(0, 0)
341 fn c_rounds(_: &mut State);
342 fn d_rounds(_: &mut State);
345 #[derive(Debug, Clone, Default)]
348 impl Sip for Sip13Rounds {
350 fn c_rounds(state: &mut State) {
355 fn d_rounds(state: &mut State) {
362 #[derive(Debug, Clone, Default)]
365 impl Sip for Sip24Rounds {
367 fn c_rounds(state: &mut State) {
373 fn d_rounds(state: &mut State) {