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uuid.go
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uuid.go
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// Copyright 2015 The Cockroach 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. See the AUTHORS file
// for names of contributors.
//
// Author: Spencer Kimball (spencer.kimball@gmail.com)
//
// Based on code from http://code.google.com/p/go-uuid/uuid
package uuid
import (
"crypto/rand"
"fmt"
"io"
)
const (
// UUIDSize is the size in bytes of a UUID.
UUIDSize = 16
)
// UUID is a 16 byte UUID.
type UUID []byte
// NewUUID4 returns a new UUID (Version 4) using 16 random bytes or panics.
//
// The uniqueness depends on the strength of crypto/rand. Version 4
// UUIDs have 122 random bits.
func NewUUID4() UUID {
uuid := make([]byte, UUIDSize)
if _, err := io.ReadFull(rand.Reader, uuid); err != nil {
panic(err) // rand should never fail
}
// UUID (Version 4) compliance.
uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4
uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10
return uuid
}
// String formats as hex xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx,
// or "" if u is invalid.
func (u UUID) String() string {
if len(u) != UUIDSize {
return ""
}
b := []byte(u)
return fmt.Sprintf("%08x-%04x-%04x-%04x-%012x", b[:4], b[4:6], b[6:8], b[8:10], b[10:])
}
// Short formats the UUID using only the first four bytes for brevity.
func (u UUID) Short() string {
if len(u) != UUIDSize {
return ""
}
b := []byte(u)
return fmt.Sprintf("%08x", b[:4])
}