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