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// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build purego
package maphash
import (
"crypto/rand"
"math/bits"
)
func rthash(buf []byte, seed uint64) uint64 {
if len(buf) == 0 {
return seed
}
return wyhash(buf, seed, uint64(len(buf)))
}
func rthashString(s string, state uint64) uint64 {
return rthash([]byte(s), state)
}
func randUint64() uint64 {
buf := make([]byte, 8)
_, _ = rand.Read(buf)
return leUint64(buf)
}
// This is a port of wyhash implementation in runtime/hash64.go,
// without using unsafe for purego.
const (
m1 = 0xa0761d6478bd642f
m2 = 0xe7037ed1a0b428db
m3 = 0x8ebc6af09c88c6e3
m4 = 0x589965cc75374cc3
m5 = 0x1d8e4e27c47d124f
)
func wyhash(key []byte, seed, len uint64) uint64 {
p := key
i := len
var a, b uint64
seed ^= m1
if i > 16 {
if i > 48 {
seed1 := seed
seed2 := seed
for ; i > 48; i -= 48 {
seed = mix(r8(p)^m2, r8(p[8:])^seed)
seed1 = mix(r8(p[16:])^m3, r8(p[24:])^seed1)
seed2 = mix(r8(p[32:])^m4, r8(p[40:])^seed2)
p = p[48:]
}
seed ^= seed1 ^ seed2
}
for ; i > 16; i -= 16 {
seed = mix(r8(p)^m2, r8(p[8:])^seed)
p = p[16:]
}
}
switch {
case i == 0:
return seed
case i < 4:
a = r3(p, i)
default:
n := (i >> 3) << 2
a = r4(p)<<32 | r4(p[n:])
b = r4(p[i-4:])<<32 | r4(p[i-4-n:])
}
return mix(m5^len, mix(a^m2, b^seed))
}
func r3(p []byte, k uint64) uint64 {
return (uint64(p[0]) << 16) | (uint64(p[k>>1]) << 8) | uint64(p[k-1])
}
func r4(p []byte) uint64 {
return uint64(leUint32(p))
}
func r8(p []byte) uint64 {
return leUint64(p)
}
func mix(a, b uint64) uint64 {
hi, lo := bits.Mul64(a, b)
return hi ^ lo
}
func leUint32(b []byte) uint32 {
_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
}
func leUint64(b []byte) uint64 {
_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
}
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