hash32.go

Documentation: runtime

     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
     9  // +build 386 arm mips mipsle
    10  
    11  package runtime
    12  
    13  import "unsafe"
    14  
    15  func memhash32Fallback(p unsafe.Pointer, seed uintptr) uintptr {
    16  	a, b := mix32(uint32(seed), uint32(4^hashkey[0]))
    17  	t := readUnaligned32(p)
    18  	a ^= t
    19  	b ^= t
    20  	a, b = mix32(a, b)
    21  	a, b = mix32(a, b)
    22  	return uintptr(a ^ b)
    23  }
    24  
    25  func memhash64Fallback(p unsafe.Pointer, seed uintptr) uintptr {
    26  	a, b := mix32(uint32(seed), uint32(8^hashkey[0]))
    27  	a ^= readUnaligned32(p)
    28  	b ^= readUnaligned32(add(p, 4))
    29  	a, b = mix32(a, b)
    30  	a, b = mix32(a, b)
    31  	return uintptr(a ^ b)
    32  }
    33  
    34  func memhashFallback(p unsafe.Pointer, seed, s uintptr) uintptr {
    35  
    36  	a, b := mix32(uint32(seed), uint32(s^hashkey[0]))
    37  	if s == 0 {
    38  		return uintptr(a ^ b)
    39  	}
    40  	for ; s > 8; s -= 8 {
    41  		a ^= readUnaligned32(p)
    42  		b ^= readUnaligned32(add(p, 4))
    43  		a, b = mix32(a, b)
    44  		p = add(p, 8)
    45  	}
    46  	if s >= 4 {
    47  		a ^= readUnaligned32(p)
    48  		b ^= readUnaligned32(add(p, s-4))
    49  	} else {
    50  		t := uint32(*(*byte)(p))
    51  		t |= uint32(*(*byte)(add(p, s>>1))) << 8
    52  		t |= uint32(*(*byte)(add(p, s-1))) << 16
    53  		b ^= t
    54  	}
    55  	a, b = mix32(a, b)
    56  	a, b = mix32(a, b)
    57  	return uintptr(a ^ b)
    58  }
    59  
    60  func mix32(a, b uint32) (uint32, uint32) {
    61  	c := uint64(a^uint32(hashkey[1])) * uint64(b^uint32(hashkey[2]))
    62  	return uint32(c), uint32(c >> 32)
    63  }
    64
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