source: code/trunk/vendor/github.com/google/uuid/uuid.go@ 822

// Copyright 2018 Google Inc.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package uuid

import (
        "bytes"
        "crypto/rand"
        "encoding/hex"
        "errors"
        "fmt"
        "io"
        "strings"
        "sync"
)

// A UUID is a 128 bit (16 byte) Universal Unique IDentifier as defined in RFC
// 4122.
type UUID [16]byte

// A Version represents a UUID's version.
type Version byte

// A Variant represents a UUID's variant.
type Variant byte

// Constants returned by Variant.
const (
        Invalid   = Variant(iota) // Invalid UUID
        RFC4122                   // The variant specified in RFC4122
        Reserved                  // Reserved, NCS backward compatibility.
        Microsoft                 // Reserved, Microsoft Corporation backward compatibility.
        Future                    // Reserved for future definition.
)

const randPoolSize = 16 * 16

var (
        rander      = rand.Reader // random function
        poolEnabled = false
        poolMu      sync.Mutex
        poolPos     = randPoolSize     // protected with poolMu
        pool        [randPoolSize]byte // protected with poolMu
)

type invalidLengthError struct{ len int }

func (err invalidLengthError) Error() string {
        return fmt.Sprintf("invalid UUID length: %d", err.len)
}

// IsInvalidLengthError is matcher function for custom error invalidLengthError
func IsInvalidLengthError(err error) bool {
        _, ok := err.(invalidLengthError)
        return ok
}

// Parse decodes s into a UUID or returns an error.  Both the standard UUID
// forms of xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx and
// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx are decoded as well as the
// Microsoft encoding {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} and the raw hex
// encoding: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.
func Parse(s string) (UUID, error) {
        var uuid UUID
        switch len(s) {
        // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
        case 36:

        // urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
        case 36 + 9:
                if strings.ToLower(s[:9]) != "urn:uuid:" {
                        return uuid, fmt.Errorf("invalid urn prefix: %q", s[:9])
                }
                s = s[9:]

        // {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
        case 36 + 2:
                s = s[1:]

        // xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
        case 32:
                var ok bool
                for i := range uuid {
                        uuid[i], ok = xtob(s[i*2], s[i*2+1])
                        if !ok {
                                return uuid, errors.New("invalid UUID format")
                        }
                }
                return uuid, nil
        default:
                return uuid, invalidLengthError{len(s)}
        }
        // s is now at least 36 bytes long
        // it must be of the form  xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
        if s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-' {
                return uuid, errors.New("invalid UUID format")
        }
        for i, x := range [16]int{
                0, 2, 4, 6,
                9, 11,
                14, 16,
                19, 21,
                24, 26, 28, 30, 32, 34} {
                v, ok := xtob(s[x], s[x+1])
                if !ok {
                        return uuid, errors.New("invalid UUID format")
                }
                uuid[i] = v
        }
        return uuid, nil
}

// ParseBytes is like Parse, except it parses a byte slice instead of a string.
func ParseBytes(b []byte) (UUID, error) {
        var uuid UUID
        switch len(b) {
        case 36: // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
        case 36 + 9: // urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
                if !bytes.Equal(bytes.ToLower(b[:9]), []byte("urn:uuid:")) {
                        return uuid, fmt.Errorf("invalid urn prefix: %q", b[:9])
                }
                b = b[9:]
        case 36 + 2: // {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
                b = b[1:]
        case 32: // xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
                var ok bool
                for i := 0; i < 32; i += 2 {
                        uuid[i/2], ok = xtob(b[i], b[i+1])
                        if !ok {
                                return uuid, errors.New("invalid UUID format")
                        }
                }
                return uuid, nil
        default:
                return uuid, invalidLengthError{len(b)}
        }
        // s is now at least 36 bytes long
        // it must be of the form  xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
        if b[8] != '-' || b[13] != '-' || b[18] != '-' || b[23] != '-' {
                return uuid, errors.New("invalid UUID format")
        }
        for i, x := range [16]int{
                0, 2, 4, 6,
                9, 11,
                14, 16,
                19, 21,
                24, 26, 28, 30, 32, 34} {
                v, ok := xtob(b[x], b[x+1])
                if !ok {
                        return uuid, errors.New("invalid UUID format")
                }
                uuid[i] = v
        }
        return uuid, nil
}

// MustParse is like Parse but panics if the string cannot be parsed.
// It simplifies safe initialization of global variables holding compiled UUIDs.
func MustParse(s string) UUID {
        uuid, err := Parse(s)
        if err != nil {
                panic(`uuid: Parse(` + s + `): ` + err.Error())
        }
        return uuid
}

// FromBytes creates a new UUID from a byte slice. Returns an error if the slice
// does not have a length of 16. The bytes are copied from the slice.
func FromBytes(b []byte) (uuid UUID, err error) {
        err = uuid.UnmarshalBinary(b)
        return uuid, err
}

// Must returns uuid if err is nil and panics otherwise.
func Must(uuid UUID, err error) UUID {
        if err != nil {
                panic(err)
        }
        return uuid
}

// String returns the string form of uuid, xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
// , or "" if uuid is invalid.
func (uuid UUID) String() string {
        var buf [36]byte
        encodeHex(buf[:], uuid)
        return string(buf[:])
}

// URN returns the RFC 2141 URN form of uuid,
// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx,  or "" if uuid is invalid.
func (uuid UUID) URN() string {
        var buf [36 + 9]byte
        copy(buf[:], "urn:uuid:")
        encodeHex(buf[9:], uuid)
        return string(buf[:])
}

func encodeHex(dst []byte, uuid UUID) {
        hex.Encode(dst, uuid[:4])
        dst[8] = '-'
        hex.Encode(dst[9:13], uuid[4:6])
        dst[13] = '-'
        hex.Encode(dst[14:18], uuid[6:8])
        dst[18] = '-'
        hex.Encode(dst[19:23], uuid[8:10])
        dst[23] = '-'
        hex.Encode(dst[24:], uuid[10:])
}

// Variant returns the variant encoded in uuid.
func (uuid UUID) Variant() Variant {
        switch {
        case (uuid[8] & 0xc0) == 0x80:
                return RFC4122
        case (uuid[8] & 0xe0) == 0xc0:
                return Microsoft
        case (uuid[8] & 0xe0) == 0xe0:
                return Future
        default:
                return Reserved
        }
}

// Version returns the version of uuid.
func (uuid UUID) Version() Version {
        return Version(uuid[6] >> 4)
}

func (v Version) String() string {
        if v > 15 {
                return fmt.Sprintf("BAD_VERSION_%d", v)
        }
        return fmt.Sprintf("VERSION_%d", v)
}

func (v Variant) String() string {
        switch v {
        case RFC4122:
                return "RFC4122"
        case Reserved:
                return "Reserved"
        case Microsoft:
                return "Microsoft"
        case Future:
                return "Future"
        case Invalid:
                return "Invalid"
        }
        return fmt.Sprintf("BadVariant%d", int(v))
}

// SetRand sets the random number generator to r, which implements io.Reader.
// If r.Read returns an error when the package requests random data then
// a panic will be issued.
//
// Calling SetRand with nil sets the random number generator to the default
// generator.
func SetRand(r io.Reader) {
        if r == nil {
                rander = rand.Reader
                return
        }
        rander = r
}

// EnableRandPool enables internal randomness pool used for Random
// (Version 4) UUID generation. The pool contains random bytes read from
// the random number generator on demand in batches. Enabling the pool
// may improve the UUID generation throughput significantly.
//
// Since the pool is stored on the Go heap, this feature may be a bad fit
// for security sensitive applications.
//
// Both EnableRandPool and DisableRandPool are not thread-safe and should
// only be called when there is no possibility that New or any other
// UUID Version 4 generation function will be called concurrently.
func EnableRandPool() {
        poolEnabled = true
}

// DisableRandPool disables the randomness pool if it was previously
// enabled with EnableRandPool.
//
// Both EnableRandPool and DisableRandPool are not thread-safe and should
// only be called when there is no possibility that New or any other
// UUID Version 4 generation function will be called concurrently.
func DisableRandPool() {
        poolEnabled = false
        defer poolMu.Unlock()
        poolMu.Lock()
        poolPos = randPoolSize
}