github.com/songzhibin97/gkit@v1.2.13/internal/wyhash/wyhash.go (about)

     1  // Package wyhash implements https://github.com/wangyi-fudan/wyhash
     2  package wyhash
     3  
     4  import (
     5  	"github.com/songzhibin97/gkit/internal/hack"
     6  	"math/bits"
     7  	"unsafe"
     8  
     9  	"github.com/songzhibin97/gkit/internal/runtimex"
    10  )
    11  
    12  const (
    13  	DefaultSeed = 0xa0761d6478bd642f // s0
    14  	s1          = 0xe7037ed1a0b428db
    15  	s2          = 0x8ebc6af09c88c6e3
    16  	s3          = 0x589965cc75374cc3
    17  	s4          = 0x1d8e4e27c47d124f
    18  )
    19  
    20  func _wymix(a, b uint64) uint64 {
    21  	hi, lo := bits.Mul64(a, b)
    22  	return hi ^ lo
    23  }
    24  
    25  //go:nosplit
    26  func add(p unsafe.Pointer, x uintptr) unsafe.Pointer {
    27  	return unsafe.Pointer(uintptr(p) + x)
    28  }
    29  
    30  func Sum64(data []byte) uint64 {
    31  	return Sum64WithSeed(data, DefaultSeed)
    32  }
    33  
    34  func Sum64String(data string) uint64 {
    35  	return Sum64StringWithSeed(data, DefaultSeed)
    36  }
    37  
    38  func Sum64WithSeed(data []byte, seed uint64) uint64 {
    39  	return Sum64StringWithSeed(hack.BytesToString(data), seed)
    40  }
    41  
    42  func Sum64StringWithSeed(data string, seed uint64) uint64 {
    43  	var (
    44  		a, b uint64
    45  	)
    46  
    47  	length := len(data)
    48  	i := uintptr(len(data))
    49  	paddr := *(*unsafe.Pointer)(unsafe.Pointer(&data))
    50  
    51  	if i > 64 {
    52  		var see1 = seed
    53  		for i > 64 {
    54  			seed = _wymix(runtimex.ReadUnaligned64(paddr)^s1, runtimex.ReadUnaligned64(add(paddr, 8))^seed) ^ _wymix(runtimex.ReadUnaligned64(add(paddr, 16))^s2, runtimex.ReadUnaligned64(add(paddr, 24))^seed)
    55  			see1 = _wymix(runtimex.ReadUnaligned64(add(paddr, 32))^s3, runtimex.ReadUnaligned64(add(paddr, 40))^see1) ^ _wymix(runtimex.ReadUnaligned64(add(paddr, 48))^s4, runtimex.ReadUnaligned64(add(paddr, 56))^see1)
    56  			paddr = add(paddr, 64)
    57  			i -= 64
    58  		}
    59  		seed ^= see1
    60  	}
    61  
    62  	for i > 16 {
    63  		seed = _wymix(runtimex.ReadUnaligned64(paddr)^s1, runtimex.ReadUnaligned64(add(paddr, 8))^seed)
    64  		paddr = add(paddr, 16)
    65  		i -= 16
    66  	}
    67  
    68  	// i <= 16
    69  	switch {
    70  	case i == 0:
    71  		return _wymix(s1, _wymix(s1, seed))
    72  	case i < 4:
    73  		a = uint64(*(*byte)(paddr))<<16 | uint64(*(*byte)(add(paddr, uintptr(i>>1))))<<8 | uint64(*(*byte)(add(paddr, uintptr(i-1))))
    74  		// b = 0
    75  		return _wymix(s1^uint64(length), _wymix(a^s1, seed))
    76  	case i == 4:
    77  		a = runtimex.ReadUnaligned32(paddr)
    78  		// b = 0
    79  		return _wymix(s1^uint64(length), _wymix(a^s1, seed))
    80  	case i < 8:
    81  		a = runtimex.ReadUnaligned32(paddr)
    82  		b = runtimex.ReadUnaligned32(add(paddr, i-4))
    83  		return _wymix(s1^uint64(length), _wymix(a^s1, b^seed))
    84  	case i == 8:
    85  		a = runtimex.ReadUnaligned64(paddr)
    86  		// b = 0
    87  		return _wymix(s1^uint64(length), _wymix(a^s1, seed))
    88  	default: // 8 < i <= 16
    89  		a = runtimex.ReadUnaligned64(paddr)
    90  		b = runtimex.ReadUnaligned64(add(paddr, i-8))
    91  		return _wymix(s1^uint64(length), _wymix(a^s1, b^seed))
    92  	}
    93  }