/
key.go
90 lines (77 loc) · 2.53 KB
/
key.go
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// Copyright 2021 hardcore-os Project Authors
//
// Licensed under the Apache License, Version 2.0 (the "License")
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package utils
import (
"bytes"
"encoding/binary"
"math"
"time"
"unsafe"
)
type stringStruct struct {
str unsafe.Pointer
len int
}
//go:noescape
//go:linkname memhash runtime.memhash
func memhash(p unsafe.Pointer, h, s uintptr) uintptr
// ParseKey parses the actual key from the key bytes.
func ParseKey(key []byte) []byte {
if len(key) < 8 {
return key
}
return key[:len(key)-8]
}
// ParseTs parses the timestamp from the key bytes.
func ParseTs(key []byte) uint64 {
if len(key) <= 8 {
return 0
}
return math.MaxUint64 - binary.BigEndian.Uint64(key[len(key)-8:])
}
// SameKey checks for key equality ignoring the version timestamp suffix.
func SameKey(src, dst []byte) bool {
if len(src) != len(dst) {
return false
}
return bytes.Equal(ParseKey(src), ParseKey(dst))
}
// KeyWithTs generates a new key by appending ts to key.
func KeyWithTs(key []byte, ts uint64) []byte {
out := make([]byte, len(key)+8)
copy(out, key)
binary.BigEndian.PutUint64(out[len(key):], math.MaxUint64-ts)
return out
}
// MemHash is the hash function used by go map, it utilizes available hardware instructions(behaves
// as aeshash if aes instruction is available).
// NOTE: The hash seed changes for every process. So, this cannot be used as a persistent hash.
func MemHash(data []byte) uint64 {
ss := (*stringStruct)(unsafe.Pointer(&data))
return uint64(memhash(ss.str, 0, uintptr(ss.len)))
}
// MemHashString is the hash function used by go map, it utilizes available hardware instructions
// (behaves as aeshash if aes instruction is available).
// NOTE: The hash seed changes for every process. So, this cannot be used as a persistent hash.
func MemHashString(str string) uint64 {
ss := (*stringStruct)(unsafe.Pointer(&str))
return uint64(memhash(ss.str, 0, uintptr(ss.len)))
}
// SafeCopy does append(a[:0], src...).
func SafeCopy(a, src []byte) []byte {
return append(a[:0], src...)
}
func NewCurVersion() uint64 {
return uint64(time.Now().UnixNano() / 1e9)
}