1 files changed, 401 insertions, 0 deletions
diff --git a/library/core/src/hash/sip.rs b/library/core/src/hash/sip.rs
new file mode 100644
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+++ b/library/core/src/hash/sip.rs
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+//! An implementation of SipHash.
+
+#![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 = "none")]
+#[deprecated(since = "1.13.0", note = "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 = "none")]
+#[deprecated(since = "1.13.0", note = "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 hash tables from a strong RNG, such as
+/// [`rand::os::OsRng`](https://docs.rs/rand/latest/rand/rngs/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")]
+#[deprecated(since = "1.13.0", note = "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 = $v2.rotate_left(32);
+    }};
+}
+
+/// Loads an integer of the desired type from a byte stream, in LE order. Uses
+/// `copy_nonoverlapping` to let the compiler generate the most efficient way
+/// to load it from a possibly unaligned address.
+///
+/// Safety: this performs unchecked indexing of `$buf` at
+/// `$i..$i+size_of::<$int_ty>()`, so that must be in-bounds.
+macro_rules! load_int_le {
+    ($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(
+            $buf.as_ptr().add($i),
+            &mut data as *mut _ as *mut u8,
+            mem::size_of::<$int_ty>(),
+        );
+        data.to_le()
+    }};
+}
+
+/// Loads a u64 using up to 7 bytes of a byte slice. It looks clumsy but the
+/// `copy_nonoverlapping` calls that occur (via `load_int_le!`) all have fixed
+/// sizes and avoid calling `memcpy`, which is good for speed.
+///
+/// Safety: this performs unchecked indexing of `buf` at `start..start+len`, so
+/// that must be in-bounds.
+#[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 {
+        // SAFETY: `i` cannot be greater than `len`, and the caller must guarantee
+        // that the index start..start+len is in bounds.
+        out = unsafe { load_int_le!(buf, start + i, u32) } as u64;
+        i += 4;
+    }
+    if i + 1 < len {
+        // SAFETY: same as above.
+        out |= (unsafe { load_int_le!(buf, start + i, u16) } as u64) << (i * 8);
+        i += 2
+    }
+    if i < len {
+        // SAFETY: same as above.
+        out |= (unsafe { *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")]
+    #[deprecated(
+        since = "1.13.0",
+        note = "use `std::collections::hash_map::DefaultHasher` instead"
+    )]
+    #[must_use]
+    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")]
+    #[deprecated(
+        since = "1.13.0",
+        note = "use `std::collections::hash_map::DefaultHasher` instead"
+    )]
+    #[must_use]
+    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 = "none")]
+    #[deprecated(
+        since = "1.13.0",
+        note = "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 = "none")]
+    #[deprecated(
+        since = "1.13.0",
+        note = "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;
+    }
+}
+
+#[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 write_str(&mut self, s: &str) {
+        self.0.hasher.write_str(s);
+    }
+
+    #[inline]
+    fn finish(&self) -> u64 {
+        self.0.hasher.finish()
+    }
+}
+
+#[unstable(feature = "hashmap_internals", issue = "none")]
+impl super::Hasher for SipHasher13 {
+    #[inline]
+    fn write(&mut self, msg: &[u8]) {
+        self.hasher.write(msg)
+    }
+
+    #[inline]
+    fn write_str(&mut self, s: &str) {
+        self.hasher.write_str(s);
+    }
+
+    #[inline]
+    fn finish(&self) -> u64 {
+        self.hasher.finish()
+    }
+}
+
+impl<S: Sip> super::Hasher for Hasher<S> {
+    // Note: no integer hashing methods (`write_u*`, `write_i*`) are defined
+    // for this type. We could add them, copy the `short_write` implementation
+    // in librustc_data_structures/sip128.rs, and add `write_u*`/`write_i*`
+    // methods to `SipHasher`, `SipHasher13`, and `DefaultHasher`. This would
+    // greatly speed up integer hashing by those hashers, at the cost of
+    // slightly slowing down compile speeds on some benchmarks. See #69152 for
+    // details.
+    #[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;
+            // SAFETY: `cmp::min(length, needed)` is guaranteed to not be over `length`
+            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; // len % 8
+
+        let mut i = needed;
+        while i < len - left {
+            // SAFETY: because `len - left` is the biggest multiple of 8 under
+            // `len`, and because `i` starts at `needed` where `len` is `length - needed`,
+            // `i + 8` is guaranteed to be less than or equal to `length`.
+            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;
+        }
+
+        // SAFETY: `i` is now `needed + len.div_euclid(8) * 8`,
+        // so `i + left` = `needed + len` = `length`, which is by
+        // definition equal to `msg.len()`.
+        self.tail = unsafe { u8to64_le(msg, i, left) };
+        self.ntail = left;
+    }
+
+    #[inline]
+    fn write_str(&mut self, s: &str) {
+        // This hasher works byte-wise, and `0xFF` cannot show up in a `str`,
+        // so just hashing the one extra byte is enough to be prefix-free.
+        self.write(s.as_bytes());
+        self.write_u8(0xFF);
+    }
+
+    #[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);
+    }
+}