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// Copyright 2014 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.
// Hashing algorithm inspired by
// wyhash: https://github.com/wangyi-fudan/wyhash
//go:build amd64 || arm64 || loong64 || mips64 || mips64le || ppc64 || ppc64le || riscv64 || s390x || wasm
package runtime
import (
"runtime/internal/math"
"unsafe"
)
const (
m1 = 0xa0761d6478bd642f
m2 = 0xe7037ed1a0b428db
m3 = 0x8ebc6af09c88c6e3
m4 = 0x589965cc75374cc3
m5 = 0x1d8e4e27c47d124f
)
func memhashFallback(p unsafe.Pointer, seed, s uintptr) uintptr {
var a, b uintptr
seed ^= hashkey[0] ^ m1
switch {
case s == 0:
return seed
case s < 4:
a = uintptr(*(*byte)(p))
a |= uintptr(*(*byte)(add(p, s>>1))) << 8
a |= uintptr(*(*byte)(add(p, s-1))) << 16
case s == 4:
a = r4(p)
b = a
case s < 8:
a = r4(p)
b = r4(add(p, s-4))
case s == 8:
a = r8(p)
b = a
case s <= 16:
a = r8(p)
b = r8(add(p, s-8))
default:
l := s
if l > 48 {
seed1 := seed
seed2 := seed
for ; l > 48; l -= 48 {
seed = mix(r8(p)^m2, r8(add(p, 8))^seed)
seed1 = mix(r8(add(p, 16))^m3, r8(add(p, 24))^seed1)
seed2 = mix(r8(add(p, 32))^m4, r8(add(p, 40))^seed2)
p = add(p, 48)
}
seed ^= seed1 ^ seed2
}
for ; l > 16; l -= 16 {
seed = mix(r8(p)^m2, r8(add(p, 8))^seed)
p = add(p, 16)
}
a = r8(add(p, l-16))
b = r8(add(p, l-8))
}
return mix(m5^s, mix(a^m2, b^seed))
}
func memhash32Fallback(p unsafe.Pointer, seed uintptr) uintptr {
a := r4(p)
return mix(m5^4, mix(a^m2, a^seed^hashkey[0]^m1))
}
func memhash64Fallback(p unsafe.Pointer, seed uintptr) uintptr {
a := r8(p)
return mix(m5^8, mix(a^m2, a^seed^hashkey[0]^m1))
}
func mix(a, b uintptr) uintptr {
hi, lo := math.Mul64(uint64(a), uint64(b))
return uintptr(hi ^ lo)
}
func r4(p unsafe.Pointer) uintptr {
return uintptr(readUnaligned32(p))
}
func r8(p unsafe.Pointer) uintptr {
return uintptr(readUnaligned64(p))
}
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