github.com/fufuok/utils@v1.0.10/xhash/hasher_xsync.go (about)

     1  //go:build go1.18
     2  // +build go1.18
     3  
     4  package xhash
     5  
     6  /*
     7  From https://github.com/puzpuzpuz/xsync
     8  
     9  MIT License
    10  
    11  Copyright (c) 2021 Andrey Pechkurov
    12  
    13  Permission is hereby granted, free of charge, to any person obtaining a copy
    14  of this software and associated documentation files (the "Software"), to deal
    15  in the Software without restriction, including without limitation the rights
    16  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    17  copies of the Software, and to permit persons to whom the Software is
    18  furnished to do so, subject to the following conditions:
    19  
    20  The above copyright notice and this permission notice shall be included in all
    21  copies or substantial portions of the Software.
    22  
    23  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    24  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    25  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    26  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    27  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    28  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
    29  SOFTWARE.
    30  */
    31  
    32  import (
    33  	"reflect"
    34  	"unsafe"
    35  )
    36  
    37  // MakeHasher creates a fast hash function for the given comparable type.
    38  // The only limitation is that the type should not contain interfaces inside
    39  // based on runtime.typehash.
    40  func MakeHasher[T comparable]() func(T) uint64 {
    41  	var zero T
    42  	seed := MakeSeed()
    43  	if reflect.TypeOf(&zero).Elem().Kind() == reflect.Interface {
    44  		return func(value T) uint64 {
    45  			iValue := any(value)
    46  			i := (*iface)(unsafe.Pointer(&iValue))
    47  			return runtimeTypehash64(i.typ, i.word, seed)
    48  		}
    49  	}
    50  	var iZero any = zero
    51  	i := (*iface)(unsafe.Pointer(&iZero))
    52  	return func(value T) uint64 {
    53  		return runtimeTypehash64(i.typ, unsafe.Pointer(&value), seed)
    54  	}
    55  }
    56  
    57  // MakeSeed creates a random seed.
    58  func MakeSeed() uint64 {
    59  	var s1 uint32
    60  	for {
    61  		s1 = runtimeFastrand()
    62  		// We use seed 0 to indicate an uninitialized seed/hash,
    63  		// so keep trying until we get a non-zero seed.
    64  		if s1 != 0 {
    65  			break
    66  		}
    67  	}
    68  	s2 := runtimeFastrand()
    69  	return uint64(s1)<<32 | uint64(s2)
    70  }
    71  
    72  // how interface is represented in memory
    73  type iface struct {
    74  	typ  uintptr
    75  	word unsafe.Pointer
    76  }
    77  
    78  // same as runtimeTypehash, but always returns a uint64
    79  // see: maphash.rthash function for details
    80  func runtimeTypehash64(t uintptr, p unsafe.Pointer, seed uint64) uint64 {
    81  	if unsafe.Sizeof(uintptr(0)) == 8 {
    82  		return uint64(runtimeTypehash(t, p, uintptr(seed)))
    83  	}
    84  
    85  	lo := runtimeTypehash(t, p, uintptr(seed))
    86  	hi := runtimeTypehash(t, p, uintptr(seed>>32))
    87  	return uint64(hi)<<32 | uint64(lo)
    88  }
    89  
    90  //go:noescape
    91  //go:linkname runtimeTypehash runtime.typehash
    92  func runtimeTypehash(t uintptr, p unsafe.Pointer, h uintptr) uintptr
    93  
    94  //go:noescape
    95  //go:linkname runtimeFastrand runtime.fastrand
    96  func runtimeFastrand() uint32