| //! An implementation of SipHash. |
| |
| // ignore-tidy-undocumented-unsafe |
| |
| #![allow(deprecated)] // the types in this module are deprecated |
| |
| use crate::cmp; |
| use crate::marker::PhantomData; |
| use crate::mem; |
| use crate::ptr; |
| |
| /// An implementation of SipHash 1-3. |
| /// |
| /// This is currently the default hashing function used by standard library |
| /// (e.g., `collections::HashMap` uses it by default). |
| /// |
| /// See: <https://131002.net/siphash> |
| #[unstable(feature = "hashmap_internals", issue = "0")] |
| #[rustc_deprecated( |
| since = "1.13.0", |
| reason = "use `std::collections::hash_map::DefaultHasher` instead" |
| )] |
| #[derive(Debug, Clone, Default)] |
| #[doc(hidden)] |
| pub struct SipHasher13 { |
| hasher: Hasher<Sip13Rounds>, |
| } |
| |
| /// An implementation of SipHash 2-4. |
| /// |
| /// See: <https://131002.net/siphash/> |
| #[unstable(feature = "hashmap_internals", issue = "0")] |
| #[rustc_deprecated( |
| since = "1.13.0", |
| reason = "use `std::collections::hash_map::DefaultHasher` instead" |
| )] |
| #[derive(Debug, Clone, Default)] |
| struct SipHasher24 { |
| hasher: Hasher<Sip24Rounds>, |
| } |
| |
| /// An implementation of SipHash 2-4. |
| /// |
| /// See: <https://131002.net/siphash/> |
| /// |
| /// SipHash is a general-purpose hashing function: it runs at a good |
| /// speed (competitive with Spooky and City) and permits strong _keyed_ |
| /// hashing. This lets you key your hashtables from a strong RNG, such as |
| /// [`rand::os::OsRng`](https://doc.rust-lang.org/rand/rand/os/struct.OsRng.html). |
| /// |
| /// Although the SipHash algorithm is considered to be generally strong, |
| /// it is not intended for cryptographic purposes. As such, all |
| /// cryptographic uses of this implementation are _strongly discouraged_. |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_deprecated( |
| since = "1.13.0", |
| reason = "use `std::collections::hash_map::DefaultHasher` instead" |
| )] |
| #[derive(Debug, Clone, Default)] |
| pub struct SipHasher(SipHasher24); |
| |
| #[derive(Debug)] |
| struct Hasher<S: Sip> { |
| k0: u64, |
| k1: u64, |
| length: usize, // how many bytes we've processed |
| state: State, // hash State |
| tail: u64, // unprocessed bytes le |
| ntail: usize, // how many bytes in tail are valid |
| _marker: PhantomData<S>, |
| } |
| |
| #[derive(Debug, Clone, Copy)] |
| #[repr(C)] |
| struct State { |
| // v0, v2 and v1, v3 show up in pairs in the algorithm, |
| // and simd implementations of SipHash will use vectors |
| // of v02 and v13. By placing them in this order in the struct, |
| // the compiler can pick up on just a few simd optimizations by itself. |
| v0: u64, |
| v2: u64, |
| v1: u64, |
| v3: u64, |
| } |
| |
| macro_rules! compress { |
| ($state:expr) => {{ compress!($state.v0, $state.v1, $state.v2, $state.v3) }}; |
| ($v0:expr, $v1:expr, $v2:expr, $v3:expr) => {{ |
| $v0 = $v0.wrapping_add($v1); |
| $v1 = $v1.rotate_left(13); |
| $v1 ^= $v0; |
| $v0 = $v0.rotate_left(32); |
| $v2 = $v2.wrapping_add($v3); |
| $v3 = $v3.rotate_left(16); |
| $v3 ^= $v2; |
| $v0 = $v0.wrapping_add($v3); |
| $v3 = $v3.rotate_left(21); |
| $v3 ^= $v0; |
| $v2 = $v2.wrapping_add($v1); |
| $v1 = $v1.rotate_left(17); |
| $v1 ^= $v2; |
| $v2 = $v2.rotate_left(32); |
| }}; |
| } |
| |
| /// Loads an integer of the desired type from a byte stream, in LE order. Uses |
| /// `copy_nonoverlapping` to let the compiler generate the most efficient way |
| /// to load it from a possibly unaligned address. |
| /// |
| /// Unsafe because: unchecked indexing at i..i+size_of(int_ty) |
| macro_rules! load_int_le { |
| ($buf:expr, $i:expr, $int_ty:ident) => {{ |
| debug_assert!($i + mem::size_of::<$int_ty>() <= $buf.len()); |
| let mut data = 0 as $int_ty; |
| ptr::copy_nonoverlapping( |
| $buf.get_unchecked($i), |
| &mut data as *mut _ as *mut u8, |
| mem::size_of::<$int_ty>(), |
| ); |
| data.to_le() |
| }}; |
| } |
| |
| /// Loads an u64 using up to 7 bytes of a byte slice. |
| /// |
| /// Unsafe because: unchecked indexing at start..start+len |
| #[inline] |
| unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 { |
| debug_assert!(len < 8); |
| let mut i = 0; // current byte index (from LSB) in the output u64 |
| let mut out = 0; |
| if i + 3 < len { |
| out = load_int_le!(buf, start + i, u32) as u64; |
| i += 4; |
| } |
| if i + 1 < len { |
| out |= (load_int_le!(buf, start + i, u16) as u64) << (i * 8); |
| i += 2 |
| } |
| if i < len { |
| out |= (*buf.get_unchecked(start + i) as u64) << (i * 8); |
| i += 1; |
| } |
| debug_assert_eq!(i, len); |
| out |
| } |
| |
| impl SipHasher { |
| /// Creates a new `SipHasher` with the two initial keys set to 0. |
| #[inline] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_deprecated( |
| since = "1.13.0", |
| reason = "use `std::collections::hash_map::DefaultHasher` instead" |
| )] |
| pub fn new() -> SipHasher { |
| SipHasher::new_with_keys(0, 0) |
| } |
| |
| /// Creates a `SipHasher` that is keyed off the provided keys. |
| #[inline] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_deprecated( |
| since = "1.13.0", |
| reason = "use `std::collections::hash_map::DefaultHasher` instead" |
| )] |
| pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher { |
| SipHasher(SipHasher24 { hasher: Hasher::new_with_keys(key0, key1) }) |
| } |
| } |
| |
| impl SipHasher13 { |
| /// Creates a new `SipHasher13` with the two initial keys set to 0. |
| #[inline] |
| #[unstable(feature = "hashmap_internals", issue = "0")] |
| #[rustc_deprecated( |
| since = "1.13.0", |
| reason = "use `std::collections::hash_map::DefaultHasher` instead" |
| )] |
| pub fn new() -> SipHasher13 { |
| SipHasher13::new_with_keys(0, 0) |
| } |
| |
| /// Creates a `SipHasher13` that is keyed off the provided keys. |
| #[inline] |
| #[unstable(feature = "hashmap_internals", issue = "0")] |
| #[rustc_deprecated( |
| since = "1.13.0", |
| reason = "use `std::collections::hash_map::DefaultHasher` instead" |
| )] |
| pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher13 { |
| SipHasher13 { hasher: Hasher::new_with_keys(key0, key1) } |
| } |
| } |
| |
| impl<S: Sip> Hasher<S> { |
| #[inline] |
| fn new_with_keys(key0: u64, key1: u64) -> Hasher<S> { |
| let mut state = Hasher { |
| k0: key0, |
| k1: key1, |
| length: 0, |
| state: State { v0: 0, v1: 0, v2: 0, v3: 0 }, |
| tail: 0, |
| ntail: 0, |
| _marker: PhantomData, |
| }; |
| state.reset(); |
| state |
| } |
| |
| #[inline] |
| fn reset(&mut self) { |
| self.length = 0; |
| self.state.v0 = self.k0 ^ 0x736f6d6570736575; |
| self.state.v1 = self.k1 ^ 0x646f72616e646f6d; |
| self.state.v2 = self.k0 ^ 0x6c7967656e657261; |
| self.state.v3 = self.k1 ^ 0x7465646279746573; |
| self.ntail = 0; |
| } |
| |
| // Specialized write function that is only valid for buffers with len <= 8. |
| // It's used to force inlining of write_u8 and write_usize, those would normally be inlined |
| // except for composite types (that includes slices and str hashing because of delimiter). |
| // Without this extra push the compiler is very reluctant to inline delimiter writes, |
| // degrading performance substantially for the most common use cases. |
| #[inline] |
| fn short_write(&mut self, msg: &[u8]) { |
| debug_assert!(msg.len() <= 8); |
| let length = msg.len(); |
| self.length += length; |
| |
| let needed = 8 - self.ntail; |
| let fill = cmp::min(length, needed); |
| if fill == 8 { |
| self.tail = unsafe { load_int_le!(msg, 0, u64) }; |
| } else { |
| self.tail |= unsafe { u8to64_le(msg, 0, fill) } << (8 * self.ntail); |
| if length < needed { |
| self.ntail += length; |
| return; |
| } |
| } |
| self.state.v3 ^= self.tail; |
| S::c_rounds(&mut self.state); |
| self.state.v0 ^= self.tail; |
| |
| // Buffered tail is now flushed, process new input. |
| self.ntail = length - needed; |
| self.tail = unsafe { u8to64_le(msg, needed, self.ntail) }; |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl super::Hasher for SipHasher { |
| #[inline] |
| fn write(&mut self, msg: &[u8]) { |
| self.0.hasher.write(msg) |
| } |
| |
| #[inline] |
| fn finish(&self) -> u64 { |
| self.0.hasher.finish() |
| } |
| } |
| |
| #[unstable(feature = "hashmap_internals", issue = "0")] |
| impl super::Hasher for SipHasher13 { |
| #[inline] |
| fn write(&mut self, msg: &[u8]) { |
| self.hasher.write(msg) |
| } |
| |
| #[inline] |
| fn finish(&self) -> u64 { |
| self.hasher.finish() |
| } |
| } |
| |
| impl<S: Sip> super::Hasher for Hasher<S> { |
| // see short_write comment for explanation |
| #[inline] |
| fn write_usize(&mut self, i: usize) { |
| let bytes = unsafe { |
| crate::slice::from_raw_parts(&i as *const usize as *const u8, mem::size_of::<usize>()) |
| }; |
| self.short_write(bytes); |
| } |
| |
| // see short_write comment for explanation |
| #[inline] |
| fn write_u8(&mut self, i: u8) { |
| self.short_write(&[i]); |
| } |
| |
| #[inline] |
| fn write(&mut self, msg: &[u8]) { |
| let length = msg.len(); |
| self.length += length; |
| |
| let mut needed = 0; |
| |
| if self.ntail != 0 { |
| needed = 8 - self.ntail; |
| self.tail |= unsafe { u8to64_le(msg, 0, cmp::min(length, needed)) } << 8 * self.ntail; |
| if length < needed { |
| self.ntail += length; |
| return; |
| } else { |
| self.state.v3 ^= self.tail; |
| S::c_rounds(&mut self.state); |
| self.state.v0 ^= self.tail; |
| self.ntail = 0; |
| } |
| } |
| |
| // Buffered tail is now flushed, process new input. |
| let len = length - needed; |
| let left = len & 0x7; |
| |
| let mut i = needed; |
| while i < len - left { |
| let mi = unsafe { load_int_le!(msg, i, u64) }; |
| |
| self.state.v3 ^= mi; |
| S::c_rounds(&mut self.state); |
| self.state.v0 ^= mi; |
| |
| i += 8; |
| } |
| |
| self.tail = unsafe { u8to64_le(msg, i, left) }; |
| self.ntail = left; |
| } |
| |
| #[inline] |
| fn finish(&self) -> u64 { |
| let mut state = self.state; |
| |
| let b: u64 = ((self.length as u64 & 0xff) << 56) | self.tail; |
| |
| state.v3 ^= b; |
| S::c_rounds(&mut state); |
| state.v0 ^= b; |
| |
| state.v2 ^= 0xff; |
| S::d_rounds(&mut state); |
| |
| state.v0 ^ state.v1 ^ state.v2 ^ state.v3 |
| } |
| } |
| |
| impl<S: Sip> Clone for Hasher<S> { |
| #[inline] |
| fn clone(&self) -> Hasher<S> { |
| Hasher { |
| k0: self.k0, |
| k1: self.k1, |
| length: self.length, |
| state: self.state, |
| tail: self.tail, |
| ntail: self.ntail, |
| _marker: self._marker, |
| } |
| } |
| } |
| |
| impl<S: Sip> Default for Hasher<S> { |
| /// Creates a `Hasher<S>` with the two initial keys set to 0. |
| #[inline] |
| fn default() -> Hasher<S> { |
| Hasher::new_with_keys(0, 0) |
| } |
| } |
| |
| #[doc(hidden)] |
| trait Sip { |
| fn c_rounds(_: &mut State); |
| fn d_rounds(_: &mut State); |
| } |
| |
| #[derive(Debug, Clone, Default)] |
| struct Sip13Rounds; |
| |
| impl Sip for Sip13Rounds { |
| #[inline] |
| fn c_rounds(state: &mut State) { |
| compress!(state); |
| } |
| |
| #[inline] |
| fn d_rounds(state: &mut State) { |
| compress!(state); |
| compress!(state); |
| compress!(state); |
| } |
| } |
| |
| #[derive(Debug, Clone, Default)] |
| struct Sip24Rounds; |
| |
| impl Sip for Sip24Rounds { |
| #[inline] |
| fn c_rounds(state: &mut State) { |
| compress!(state); |
| compress!(state); |
| } |
| |
| #[inline] |
| fn d_rounds(state: &mut State) { |
| compress!(state); |
| compress!(state); |
| compress!(state); |
| compress!(state); |
| } |
| } |