mirror of https://go.googlesource.com/go
89 lines
1.9 KiB
Go
89 lines
1.9 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Hashing algorithm inspired by
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// wyhash: https://github.com/wangyi-fudan/wyhash
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//go:build amd64 || arm64 || loong64 || mips64 || mips64le || ppc64 || ppc64le || riscv64 || s390x || wasm
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package runtime
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import (
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"runtime/internal/math"
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"unsafe"
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)
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const (
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m5 = 0x1d8e4e27c47d124f
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)
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func memhashFallback(p unsafe.Pointer, seed, s uintptr) uintptr {
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var a, b uintptr
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seed ^= hashkey[0]
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switch {
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case s == 0:
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return seed
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case s < 4:
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a = uintptr(*(*byte)(p))
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a |= uintptr(*(*byte)(add(p, s>>1))) << 8
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a |= uintptr(*(*byte)(add(p, s-1))) << 16
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case s == 4:
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a = r4(p)
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b = a
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case s < 8:
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a = r4(p)
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b = r4(add(p, s-4))
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case s == 8:
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a = r8(p)
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b = a
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case s <= 16:
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a = r8(p)
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b = r8(add(p, s-8))
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default:
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l := s
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if l > 48 {
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seed1 := seed
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seed2 := seed
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for ; l > 48; l -= 48 {
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seed = mix(r8(p)^hashkey[1], r8(add(p, 8))^seed)
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seed1 = mix(r8(add(p, 16))^hashkey[2], r8(add(p, 24))^seed1)
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seed2 = mix(r8(add(p, 32))^hashkey[3], r8(add(p, 40))^seed2)
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p = add(p, 48)
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}
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seed ^= seed1 ^ seed2
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}
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for ; l > 16; l -= 16 {
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seed = mix(r8(p)^hashkey[1], r8(add(p, 8))^seed)
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p = add(p, 16)
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}
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a = r8(add(p, l-16))
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b = r8(add(p, l-8))
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}
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return mix(m5^s, mix(a^hashkey[1], b^seed))
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}
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func memhash32Fallback(p unsafe.Pointer, seed uintptr) uintptr {
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a := r4(p)
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return mix(m5^4, mix(a^hashkey[1], a^seed^hashkey[0]))
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}
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func memhash64Fallback(p unsafe.Pointer, seed uintptr) uintptr {
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a := r8(p)
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return mix(m5^8, mix(a^hashkey[1], a^seed^hashkey[0]))
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}
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func mix(a, b uintptr) uintptr {
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hi, lo := math.Mul64(uint64(a), uint64(b))
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return uintptr(hi ^ lo)
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}
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func r4(p unsafe.Pointer) uintptr {
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return uintptr(readUnaligned32(p))
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}
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func r8(p unsafe.Pointer) uintptr {
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return uintptr(readUnaligned64(p))
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}
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