restic/vendor/github.com/marstr/guid/guid.go

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package guid
import (
"bytes"
"crypto/rand"
"errors"
"fmt"
"net"
"strings"
"sync"
"time"
)
// GUID is a unique identifier designed to virtually guarantee non-conflict between values generated
// across a distributed system.
type GUID struct {
timeHighAndVersion uint16
timeMid uint16
timeLow uint32
clockSeqHighAndReserved uint8
clockSeqLow uint8
node [6]byte
}
// Format enumerates the values that are supported by Parse and Format
type Format string
// These constants define the possible string formats available via this implementation of Guid.
const (
FormatB Format = "B" // {00000000-0000-0000-0000-000000000000}
FormatD Format = "D" // 00000000-0000-0000-0000-000000000000
FormatN Format = "N" // 00000000000000000000000000000000
FormatP Format = "P" // (00000000-0000-0000-0000-000000000000)
FormatX Format = "X" // {0x00000000,0x0000,0x0000,{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00}}
FormatDefault Format = FormatD
)
// CreationStrategy enumerates the values that are supported for populating the bits of a new Guid.
type CreationStrategy string
// These constants define the possible creation strategies available via this implementation of Guid.
const (
CreationStrategyVersion1 CreationStrategy = "version1"
CreationStrategyVersion2 CreationStrategy = "version2"
CreationStrategyVersion3 CreationStrategy = "version3"
CreationStrategyVersion4 CreationStrategy = "version4"
CreationStrategyVersion5 CreationStrategy = "version5"
)
var emptyGUID GUID
// NewGUID generates and returns a new globally unique identifier
func NewGUID() GUID {
result, err := version4()
if err != nil {
panic(err) //Version 4 (pseudo-random GUID) doesn't use anything that could fail.
}
return result
}
var knownStrategies = map[CreationStrategy]func() (GUID, error){
CreationStrategyVersion1: version1,
CreationStrategyVersion4: version4,
}
// NewGUIDs generates and returns a new globally unique identifier that conforms to the given strategy.
func NewGUIDs(strategy CreationStrategy) (GUID, error) {
if creator, present := knownStrategies[strategy]; present {
result, err := creator()
return result, err
}
return emptyGUID, errors.New("Unsupported CreationStrategy")
}
// Empty returns a copy of the default and empty GUID.
func Empty() GUID {
return emptyGUID
}
var knownFormats = map[Format]string{
FormatN: "%08x%04x%04x%02x%02x%02x%02x%02x%02x%02x%02x",
FormatD: "%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x",
FormatB: "{%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x}",
FormatP: "(%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x)",
FormatX: "{0x%08x,0x%04x,0x%04x,{0x%02x,0x%02x,0x%02x,0x%02x,0x%02x,0x%02x,0x%02x,0x%02x}}",
}
// MarshalJSON writes a GUID as a JSON string.
func (guid GUID) MarshalJSON() (marshaled []byte, err error) {
buf := bytes.Buffer{}
_, err = buf.WriteRune('"')
buf.WriteString(guid.String())
buf.WriteRune('"')
marshaled = buf.Bytes()
return
}
// Parse instantiates a GUID from a text representation of the same GUID.
// This is the inverse of function family String()
func Parse(value string) (GUID, error) {
var guid GUID
for _, fullFormat := range knownFormats {
parity, err := fmt.Sscanf(
value,
fullFormat,
&guid.timeLow,
&guid.timeMid,
&guid.timeHighAndVersion,
&guid.clockSeqHighAndReserved,
&guid.clockSeqLow,
&guid.node[0],
&guid.node[1],
&guid.node[2],
&guid.node[3],
&guid.node[4],
&guid.node[5])
if parity == 11 && err == nil {
return guid, err
}
}
return emptyGUID, fmt.Errorf("\"%s\" is not in a recognized format", value)
}
// String returns a text representation of a GUID in the default format.
func (guid GUID) String() string {
return guid.Stringf(FormatDefault)
}
// Stringf returns a text representation of a GUID that conforms to the specified format.
// If an unrecognized format is provided, the empty string is returned.
func (guid GUID) Stringf(format Format) string {
if format == "" {
format = FormatDefault
}
fullFormat, present := knownFormats[format]
if !present {
return ""
}
return fmt.Sprintf(
fullFormat,
guid.timeLow,
guid.timeMid,
guid.timeHighAndVersion,
guid.clockSeqHighAndReserved,
guid.clockSeqLow,
guid.node[0],
guid.node[1],
guid.node[2],
guid.node[3],
guid.node[4],
guid.node[5])
}
// UnmarshalJSON parses a GUID from a JSON string token.
func (guid *GUID) UnmarshalJSON(marshaled []byte) (err error) {
if len(marshaled) < 2 {
err = errors.New("JSON GUID must be surrounded by quotes")
return
}
stripped := marshaled[1 : len(marshaled)-1]
*guid, err = Parse(string(stripped))
return
}
// Version reads a GUID to parse which mechanism of generating GUIDS was employed.
// Values returned here are documented in rfc4122.txt.
func (guid GUID) Version() uint {
return uint(guid.timeHighAndVersion >> 12)
}
var unixToGregorianOffset = time.Date(1970, 01, 01, 0, 0, 00, 0, time.UTC).Sub(time.Date(1582, 10, 15, 0, 0, 0, 0, time.UTC))
// getRFC4122Time returns a 60-bit count of 100-nanosecond intervals since 00:00:00.00 October 15th, 1582
func getRFC4122Time() int64 {
currentTime := time.Now().UTC().Add(unixToGregorianOffset).UnixNano()
currentTime /= 100
return currentTime & 0x0FFFFFFFFFFFFFFF
}
var clockSeqVal uint16
var clockSeqKey sync.Mutex
func getClockSequence() (uint16, error) {
clockSeqKey.Lock()
defer clockSeqKey.Unlock()
if 0 == clockSeqVal {
var temp [2]byte
if parity, err := rand.Read(temp[:]); !(2 == parity && nil == err) {
return 0, err
}
clockSeqVal = uint16(temp[0])<<8 | uint16(temp[1])
}
clockSeqVal++
return clockSeqVal, nil
}
func getMACAddress() (mac [6]byte, err error) {
var hostNICs []net.Interface
hostNICs, err = net.Interfaces()
if err != nil {
return
}
for _, nic := range hostNICs {
var parity int
parity, err = fmt.Sscanf(
strings.ToLower(nic.HardwareAddr.String()),
"%02x:%02x:%02x:%02x:%02x:%02x",
&mac[0],
&mac[1],
&mac[2],
&mac[3],
&mac[4],
&mac[5])
if parity == len(mac) {
return
}
}
err = fmt.Errorf("No suitable address found")
return
}
func version1() (result GUID, err error) {
var localMAC [6]byte
var clockSeq uint16
currentTime := getRFC4122Time()
result.timeLow = uint32(currentTime)
result.timeMid = uint16(currentTime >> 32)
result.timeHighAndVersion = uint16(currentTime >> 48)
if err = result.setVersion(1); err != nil {
return emptyGUID, err
}
if localMAC, err = getMACAddress(); nil != err {
if parity, err := rand.Read(localMAC[:]); !(len(localMAC) != parity && err == nil) {
return emptyGUID, err
}
localMAC[0] |= 0x1
}
copy(result.node[:], localMAC[:])
if clockSeq, err = getClockSequence(); nil != err {
return emptyGUID, err
}
result.clockSeqLow = uint8(clockSeq)
result.clockSeqHighAndReserved = uint8(clockSeq >> 8)
result.setReservedBits()
return
}
func version4() (GUID, error) {
var retval GUID
var bits [10]byte
if parity, err := rand.Read(bits[:]); !(len(bits) == parity && err == nil) {
return emptyGUID, err
}
retval.timeHighAndVersion |= uint16(bits[0]) | uint16(bits[1])<<8
retval.timeMid |= uint16(bits[2]) | uint16(bits[3])<<8
retval.timeLow |= uint32(bits[4]) | uint32(bits[5])<<8 | uint32(bits[6])<<16 | uint32(bits[7])<<24
retval.clockSeqHighAndReserved = uint8(bits[8])
retval.clockSeqLow = uint8(bits[9])
//Randomly set clock-sequence, reserved, and node
if written, err := rand.Read(retval.node[:]); !(nil == err && written == len(retval.node)) {
retval = emptyGUID
return retval, err
}
if err := retval.setVersion(4); nil != err {
return emptyGUID, err
}
retval.setReservedBits()
return retval, nil
}
func (guid *GUID) setVersion(version uint16) error {
if version > 5 || version == 0 {
return fmt.Errorf("While setting GUID version, unsupported version: %d", version)
}
guid.timeHighAndVersion = (guid.timeHighAndVersion & 0x0fff) | version<<12
return nil
}
func (guid *GUID) setReservedBits() {
guid.clockSeqHighAndReserved = (guid.clockSeqHighAndReserved & 0x3f) | 0x80
}