forked from gitea/gitea
47 lines
1.4 KiB
Go
47 lines
1.4 KiB
Go
|
// +build !appengine
|
||
|
|
|
||
|
|
// This file encapsulates usage of unsafe.
|
||
|
|
// xxhash_safe.go contains the safe implementations.
|
||
|
|
|
||
|
|
package xxhash
|
||
|
|
|
||
|
|
import (
|
||
|
|
"reflect"
|
||
|
|
"unsafe"
|
||
|
|
)
|
||
|
|
|
||
|
|
// Notes:
|
||
|
|
//
|
||
|
|
// See https://groups.google.com/d/msg/golang-nuts/dcjzJy-bSpw/tcZYBzQqAQAJ
|
||
|
|
// for some discussion about these unsafe conversions.
|
||
|
|
//
|
||
|
|
// In the future it's possible that compiler optimizations will make these
|
||
|
|
// unsafe operations unnecessary: https://golang.org/issue/2205.
|
||
|
|
//
|
||
|
|
// Both of these wrapper functions still incur function call overhead since they
|
||
|
|
// will not be inlined. We could write Go/asm copies of Sum64 and Digest.Write
|
||
|
|
// for strings to squeeze out a bit more speed. Mid-stack inlining should
|
||
|
|
// eventually fix this.
|
||
|
|
|
||
|
|
// Sum64String computes the 64-bit xxHash digest of s.
|
||
|
|
// It may be faster than Sum64([]byte(s)) by avoiding a copy.
|
||
|
|
func Sum64String(s string) uint64 {
|
||
|
|
var b []byte
|
||
|
|
bh := (*reflect.SliceHeader)(unsafe.Pointer(&b))
|
||
|
|
bh.Data = (*reflect.StringHeader)(unsafe.Pointer(&s)).Data
|
||
|
|
bh.Len = len(s)
|
||
|
|
bh.Cap = len(s)
|
||
|
|
return Sum64(b)
|
||
|
|
}
|
||
|
|
|
||
|
|
// WriteString adds more data to d. It always returns len(s), nil.
|
||
|
|
// It may be faster than Write([]byte(s)) by avoiding a copy.
|
||
|
|
func (d *Digest) WriteString(s string) (n int, err error) {
|
||
|
|
var b []byte
|
||
|
|
bh := (*reflect.SliceHeader)(unsafe.Pointer(&b))
|
||
|
|
bh.Data = (*reflect.StringHeader)(unsafe.Pointer(&s)).Data
|
||
|
|
bh.Len = len(s)
|
||
|
|
bh.Cap = len(s)
|
||
|
|
return d.Write(b)
|
||
|
|
}
|