github.com/cloudwego/dynamicgo@v0.2.6-0.20240519101509-707f41b6b834/internal/caching/hashing.go (about)

     1  /*
     2   * Copyright 2023 CloudWeGo Authors.
     3   *
     4   * Licensed under the Apache License, Version 2.0 (the "License");
     5   * you may not use this file except in compliance with the License.
     6   * You may obtain a copy of the License at
     7   *
     8   *     http://www.apache.org/licenses/LICENSE-2.0
     9   *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  
    17  package caching
    18  
    19  import (
    20  	"unsafe"
    21  
    22  	"github.com/cloudwego/dynamicgo/internal/rt"
    23  )
    24  
    25  var (
    26  	V_strhash    = rt.UnpackEface(strhash)
    27  	S_strhash    = *(*uintptr)(V_strhash.Value)
    28  	byteTypeSize = unsafe.Sizeof(byte(0))
    29  )
    30  
    31  //go:noescape
    32  //go:linkname strhash runtime.strhash
    33  func strhash(_ unsafe.Pointer, _ uintptr) uintptr
    34  
    35  func StrHash(s string) uint64 {
    36  	if v := strhash(unsafe.Pointer(&s), 0); v == 0 {
    37  		return 1
    38  	} else {
    39  		return uint64(v)
    40  	}
    41  }
    42  
    43  func DJBHash32(k string) uint32 {
    44  	var hash uint32 = 5381
    45  	var ks = *(*unsafe.Pointer)(unsafe.Pointer(&k))
    46  	for i := 0; i < len(k); i++ {
    47  		c := *(*byte)(rt.IndexPtr(ks, byteTypeSize, i))
    48  		hash = ((hash << 5) + hash + uint32(c))
    49  	}
    50  	return hash
    51  }
    52  
    53  func DJBHash64(k string) uint64 {
    54  	var hash uint64 = 5381
    55  	var ks = *(*unsafe.Pointer)(unsafe.Pointer(&k))
    56  	for i := 0; i < len(k); i++ {
    57  		c := *(*byte)(rt.IndexPtr(ks, byteTypeSize, i))
    58  		hash = ((hash << 5) + hash + uint64(c))
    59  	}
    60  	return hash
    61  }