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hash.go
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hash.go
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// Copyright (C) 2017 Google Inc.
//
// 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 id
import (
"crypto/sha1"
"fmt"
"hash"
"io"
"os"
"sync"
"sync/atomic"
"time"
)
var sha1Pool = sync.Pool{New: func() interface{} { return sha1.New() }}
// Hash creates a new ID by calling f and hashing all data written to w.
func Hash(f func(w io.Writer) error) (ID, error) {
h := sha1Pool.Get().(hash.Hash)
defer sha1Pool.Put(h)
h.Reset()
err := f(h)
id := ID{}
copy(id[:], h.Sum(nil))
return id, err
}
// OfBytes calculates the ID for the supplied data using the Hash function.
func OfBytes(data ...[]byte) ID {
id, _ := Hash(func(w io.Writer) error {
for _, d := range data {
w.Write(d)
}
return nil
})
return id
}
// OfString calculates the ID for the supplied strings using the Hash function.
func OfString(strings ...string) ID {
id, _ := Hash(func(w io.Writer) error {
for _, s := range strings {
io.WriteString(w, s)
}
return nil
})
return id
}
// uniqueNumber is used to generate a unique number per call to the Unique function.
// Needed in case Unique is called faster than the resolution of time.Now
var uniqueNumber uint32
// Unique returns a unique identifier by hashing the current time and machine hostname.
func Unique() ID {
id, _ := Hash(func(w io.Writer) error {
name, _ := os.Hostname()
num := atomic.AddUint32(&uniqueNumber, 1)
fmt.Fprint(w, "%s:%v:%v", name, time.Now(), num)
return nil
})
return id
}