libgo/go/runtime/hash32.go

   1 // Copyright 2014 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // Hashing algorithm inspired by
   6 // wyhash: https://github.com/wangyi-fudan/wyhash/blob/ceb019b530e2c1c14d70b79bfa2bc49de7d95bc1/Modern%20Non-Cryptographic%20Hash%20Function%20and%20Pseudorandom%20Number%20Generator.pdf
   7
   8 //go:build 386 || arm || mips || mipsle || amd64p32 || armbe || m68k || mips64p32 || mips64p32le || nios2 || ppc || riscv || s390 || sh || shbe || sparc
   9 // +build 386 arm mips mipsle amd64p32 armbe m68k mips64p32 mips64p32le nios2 ppc riscv s390 sh shbe sparc
  10
  11 package runtime
  12
  13 import "unsafe"
  14
  15 // For gccgo, use go:linkname to export compiler-called functions.
  16 //
  17 //go:linkname memhash
  18
  19 func memhash32(p unsafe.Pointer, seed uintptr) uintptr {
  20         a, b := mix32(uint32(seed), uint32(4^hashkey[0]))
  21         t := readUnaligned32(p)
  22         a ^= t
  23         b ^= t
  24         a, b = mix32(a, b)
  25         a, b = mix32(a, b)
  26         return uintptr(a ^ b)
  27 }
  28
  29 func memhash64(p unsafe.Pointer, seed uintptr) uintptr {
  30         a, b := mix32(uint32(seed), uint32(8^hashkey[0]))
  31         a ^= readUnaligned32(p)
  32         b ^= readUnaligned32(add(p, 4))
  33         a, b = mix32(a, b)
  34         a, b = mix32(a, b)
  35         return uintptr(a ^ b)
  36 }
  37
  38 func memhash(p unsafe.Pointer, seed, s uintptr) uintptr {
  39         if GOARCH == "386" && GOOS != "nacl" && useAeshash {
  40                 return aeshash(p, seed, s)
  41         }
  42         a, b := mix32(uint32(seed), uint32(s^hashkey[0]))
  43         if s == 0 {
  44                 return uintptr(a ^ b)
  45         }
  46         for ; s > 8; s -= 8 {
  47                 a ^= readUnaligned32(p)
  48                 b ^= readUnaligned32(add(p, 4))
  49                 a, b = mix32(a, b)
  50                 p = add(p, 8)
  51         }
  52         if s >= 4 {
  53                 a ^= readUnaligned32(p)
  54                 b ^= readUnaligned32(add(p, s-4))
  55         } else {
  56                 t := uint32(*(*byte)(p))
  57                 t |= uint32(*(*byte)(add(p, s>>1))) << 8
  58                 t |= uint32(*(*byte)(add(p, s-1))) << 16
  59                 b ^= t
  60         }
  61         a, b = mix32(a, b)
  62         a, b = mix32(a, b)
  63         return uintptr(a ^ b)
  64 }
  65
  66 func mix32(a, b uint32) (uint32, uint32) {
  67         c := uint64(a^uint32(hashkey[1])) * uint64(b^uint32(hashkey[2]))
  68         return uint32(c), uint32(c >> 32)
  69 }