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|
package uuid
import (
"crypto/rand"
"encoding/binary"
"encoding/hex"
"errors"
"flag"
"fmt"
"io"
"os"
"strings"
"time"
)
type versionFlag byte
const (
versionFlag_v4 versionFlag = 0b01000000
versionFlag_v7 versionFlag = 0b01110000
)
type actionType byte
const(
actionType_generate actionType = iota
actionType_parse
)
const (
variant0b10 = 0b10000000
ByteCount = 16
dashCount = 4
encodedLength = (ByteCount * 2) + dashCount
)
var (
dashIndexes = []int{ 8, 13, 18, 23 }
randomReader = rand.Reader
ErrBadLength = errors.New(
"uuid: str isn't of the correct length",
)
ErrBadDashCount = errors.New("uuid: Bad count of dashes in string")
ErrBadDashPosition = errors.New("uuid: Bad char in string")
DefaultVersion = 4
Nil = UUID{ 0, 0, 0, 0, 0, 0, 0, 0, }
Max = UUID{ 255, 255, 255, 255, 255, 255, 255, 255, }
)
type UUID [ByteCount]byte
type argsT struct{
allArgs []string
subArgs []string
action actionType
version uint8
}
func NewV4From(r io.Reader) (UUID, error) {
var uuid UUID
_, err := io.ReadFull(r, uuid[:])
if err != nil {
return UUID{}, err
}
uuid[6] = (uuid[6] & 0b00001111) | byte(versionFlag_v4)
uuid[8] = (uuid[8] & 0b00111111) | variant0b10
return uuid, nil
}
func NewV4() UUID {
uuid, err := NewV4From(randomReader)
if err != nil {
panic(err)
}
return uuid
}
func NewV7From(r io.Reader, nowNanoFn func() uint64) (UUID, error) {
var uuid UUID
now := uint64(nowNanoFn())
binary.BigEndian.PutUint64(uuid[:8], now)
_, err := io.ReadFull(r, uuid[8:])
if err != nil {
return UUID{}, err
}
uuid[6] = (uuid[6] & 0b00001111) | byte(versionFlag_v7)
uuid[8] = (uuid[8] & 0b00111111) | variant0b10
return uuid, nil
}
func nowNano() uint64 {
return uint64(time.Now().UnixNano())
}
func NewV7() UUID {
uuid, err := NewV7From(randomReader, nowNano)
if err != nil {
panic(err)
}
return uuid
}
func New() UUID {
if DefaultVersion == 4 {
return NewV4()
} else {
return NewV7()
}
}
func (uuid UUID) String() string {
dst := [encodedLength]byte {
0, 0, 0, 0,
0, 0, 0, 0,
'-',
0, 0, 0, 0,
'-',
0, 0, 0, 0,
'-',
0, 0, 0, 0,
'-',
0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0,
}
hex.Encode(dst[ 0:8], uuid[0:4])
hex.Encode(dst[ 9:13], uuid[4:6])
hex.Encode(dst[14:18], uuid[6:8])
hex.Encode(dst[19:23], uuid[8:10])
hex.Encode(dst[24:36], uuid[10:])
return string(dst[:])
}
func FromString(str string) (UUID, error) {
if len(str) != encodedLength {
return UUID{}, ErrBadLength
}
if strings.Count(str, "-") != dashCount {
return UUID{}, ErrBadDashCount
}
for _, idx := range dashIndexes {
if str[idx] != '-' {
return UUID{}, ErrBadDashPosition
}
}
hexstr := strings.Join(strings.Split(str, "-"), "")
data, err := hex.DecodeString(hexstr)
if err != nil {
return UUID{}, err
}
return [ByteCount]byte(data), nil
}
func usage(argv0 string, w io.Writer) {
fmt.Fprintf(
w,
("Usage:\n" +
" %s [-v (4|7)]\n" +
" %s STRING\n"),
argv0,
argv0,
)
}
func actionForSubargs(subArgs []string) actionType {
if len(subArgs) == 0 {
return actionType_generate
} else {
return actionType_parse
}
}
func getopt(allArgs []string, w io.Writer) (argsT, int) {
argv0 := allArgs[0]
argv := allArgs[1:]
fs := flag.NewFlagSet("", flag.ContinueOnError)
fs.Usage = func() {}
fs.SetOutput(w)
versionNumber := fs.Uint(
"v",
4,
"which UUID version to generate",
)
if fs.Parse(argv) != nil {
usage(argv0, w)
return argsT{}, 2
}
subArgs := fs.Args()
actionType := actionForSubargs(subArgs)
var version uint8
if *versionNumber == 4 || *versionNumber == 7 {
version = uint8(*versionNumber)
} else {
fmt.Fprintf(w, "Bad value for VERSION: %s.\n", *versionNumber)
usage(argv0, w)
return argsT{}, 2
}
return argsT{
allArgs: allArgs,
subArgs: subArgs,
action: actionType,
version: version,
}, 0
}
func run(args argsT, _ io.Reader, stdout io.Writer, stderr io.Writer) int {
switch args.action {
case actionType_generate:
if args.version == 4 {
fmt.Fprintf(stdout, "%v\n", NewV4().String())
} else if args.version == 7 {
fmt.Fprintf(stdout, "%v\n", NewV7().String())
}
return 0
case actionType_parse:
_, err := FromString(strings.TrimSpace(args.subArgs[0]))
if err != nil {
fmt.Fprintln(stderr, err)
return 3
} else {
return 0
}
}
return 126
}
func Main() {
args, rc := getopt(os.Args, os.Stderr)
if rc != 0 {
os.Exit(rc)
}
os.Exit(run(args, os.Stdin, os.Stdout, os.Stderr))
}
|
