237 lines
5.3 KiB
Go
237 lines
5.3 KiB
Go
// Package xxhash implements the 64-bit variant of xxHash (XXH64) as described
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// at http://cyan4973.github.io/xxHash/.
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package xxhash
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import (
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"encoding/binary"
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"errors"
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"math/bits"
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)
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const (
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prime1 uint64 = 11400714785074694791
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prime2 uint64 = 14029467366897019727
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prime3 uint64 = 1609587929392839161
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prime4 uint64 = 9650029242287828579
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prime5 uint64 = 2870177450012600261
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)
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// NOTE(caleb): I'm using both consts and vars of the primes. Using consts where
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// possible in the Go code is worth a small (but measurable) performance boost
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// by avoiding some MOVQs. Vars are needed for the asm and also are useful for
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// convenience in the Go code in a few places where we need to intentionally
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// avoid constant arithmetic (e.g., v1 := prime1 + prime2 fails because the
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// result overflows a uint64).
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var (
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prime1v = prime1
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prime2v = prime2
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prime3v = prime3
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prime4v = prime4
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prime5v = prime5
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)
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// Digest implements hash.Hash64.
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type Digest struct {
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v1 uint64
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v2 uint64
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v3 uint64
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v4 uint64
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total uint64
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mem [32]byte
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n int // how much of mem is used
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}
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// New creates a new Digest that computes the 64-bit xxHash algorithm.
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func New() *Digest {
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var d Digest
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d.Reset()
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return &d
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}
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// Reset clears the Digest's state so that it can be reused.
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func (d *Digest) Reset() {
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d.v1 = prime1v + prime2
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d.v2 = prime2
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d.v3 = 0
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d.v4 = -prime1v
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d.total = 0
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d.n = 0
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}
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// Size always returns 8 bytes.
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func (d *Digest) Size() int { return 8 }
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// BlockSize always returns 32 bytes.
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func (d *Digest) BlockSize() int { return 32 }
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// Write adds more data to d. It always returns len(b), nil.
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func (d *Digest) Write(b []byte) (n int, err error) {
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n = len(b)
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d.total += uint64(n)
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if d.n+n < 32 {
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// This new data doesn't even fill the current block.
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copy(d.mem[d.n:], b)
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d.n += n
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return
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}
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if d.n > 0 {
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// Finish off the partial block.
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copy(d.mem[d.n:], b)
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d.v1 = round(d.v1, u64(d.mem[0:8]))
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d.v2 = round(d.v2, u64(d.mem[8:16]))
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d.v3 = round(d.v3, u64(d.mem[16:24]))
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d.v4 = round(d.v4, u64(d.mem[24:32]))
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b = b[32-d.n:]
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d.n = 0
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}
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if len(b) >= 32 {
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// One or more full blocks left.
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nw := writeBlocks(d, b)
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b = b[nw:]
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}
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// Store any remaining partial block.
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copy(d.mem[:], b)
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d.n = len(b)
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return
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}
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// Sum appends the current hash to b and returns the resulting slice.
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func (d *Digest) Sum(b []byte) []byte {
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s := d.Sum64()
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return append(
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b,
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byte(s>>56),
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byte(s>>48),
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byte(s>>40),
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byte(s>>32),
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byte(s>>24),
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byte(s>>16),
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byte(s>>8),
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byte(s),
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)
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}
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// Sum64 returns the current hash.
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func (d *Digest) Sum64() uint64 {
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var h uint64
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if d.total >= 32 {
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v1, v2, v3, v4 := d.v1, d.v2, d.v3, d.v4
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h = rol1(v1) + rol7(v2) + rol12(v3) + rol18(v4)
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h = mergeRound(h, v1)
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h = mergeRound(h, v2)
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h = mergeRound(h, v3)
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h = mergeRound(h, v4)
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} else {
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h = d.v3 + prime5
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}
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h += d.total
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i, end := 0, d.n
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for ; i+8 <= end; i += 8 {
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k1 := round(0, u64(d.mem[i:i+8]))
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h ^= k1
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h = rol27(h)*prime1 + prime4
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}
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if i+4 <= end {
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h ^= uint64(u32(d.mem[i:i+4])) * prime1
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h = rol23(h)*prime2 + prime3
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i += 4
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}
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for i < end {
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h ^= uint64(d.mem[i]) * prime5
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h = rol11(h) * prime1
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i++
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}
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h ^= h >> 33
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h *= prime2
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h ^= h >> 29
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h *= prime3
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h ^= h >> 32
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return h
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}
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const (
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magic = "xxh\x06"
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marshaledSize = len(magic) + 8*5 + 32
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)
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// MarshalBinary implements the encoding.BinaryMarshaler interface.
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func (d *Digest) MarshalBinary() ([]byte, error) {
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b := make([]byte, 0, marshaledSize)
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b = append(b, magic...)
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b = appendUint64(b, d.v1)
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b = appendUint64(b, d.v2)
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b = appendUint64(b, d.v3)
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b = appendUint64(b, d.v4)
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b = appendUint64(b, d.total)
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b = append(b, d.mem[:d.n]...)
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b = b[:len(b)+len(d.mem)-d.n]
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return b, nil
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}
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// UnmarshalBinary implements the encoding.BinaryUnmarshaler interface.
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func (d *Digest) UnmarshalBinary(b []byte) error {
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if len(b) < len(magic) || string(b[:len(magic)]) != magic {
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return errors.New("xxhash: invalid hash state identifier")
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}
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if len(b) != marshaledSize {
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return errors.New("xxhash: invalid hash state size")
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}
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b = b[len(magic):]
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b, d.v1 = consumeUint64(b)
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b, d.v2 = consumeUint64(b)
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b, d.v3 = consumeUint64(b)
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b, d.v4 = consumeUint64(b)
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b, d.total = consumeUint64(b)
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copy(d.mem[:], b)
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b = b[len(d.mem):]
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d.n = int(d.total % uint64(len(d.mem)))
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return nil
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}
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func appendUint64(b []byte, x uint64) []byte {
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var a [8]byte
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binary.LittleEndian.PutUint64(a[:], x)
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return append(b, a[:]...)
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}
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func consumeUint64(b []byte) ([]byte, uint64) {
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x := u64(b)
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return b[8:], x
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}
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func u64(b []byte) uint64 { return binary.LittleEndian.Uint64(b) }
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func u32(b []byte) uint32 { return binary.LittleEndian.Uint32(b) }
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func round(acc, input uint64) uint64 {
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acc += input * prime2
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acc = rol31(acc)
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acc *= prime1
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return acc
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}
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func mergeRound(acc, val uint64) uint64 {
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val = round(0, val)
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acc ^= val
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acc = acc*prime1 + prime4
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return acc
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}
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func rol1(x uint64) uint64 { return bits.RotateLeft64(x, 1) }
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func rol7(x uint64) uint64 { return bits.RotateLeft64(x, 7) }
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func rol11(x uint64) uint64 { return bits.RotateLeft64(x, 11) }
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func rol12(x uint64) uint64 { return bits.RotateLeft64(x, 12) }
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func rol18(x uint64) uint64 { return bits.RotateLeft64(x, 18) }
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func rol23(x uint64) uint64 { return bits.RotateLeft64(x, 23) }
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func rol27(x uint64) uint64 { return bits.RotateLeft64(x, 27) }
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func rol31(x uint64) uint64 { return bits.RotateLeft64(x, 31) }
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