package mcrypto import ( "bytes" "crypto/rand" "encoding/binary" "encoding/hex" "encoding/json" "errors" "fmt" "time" "github.com/mediocregopher/mediocre-go-lib/mlog" ) var errMalformedUUID = errors.New("malformed UUID string") // UUID is a universally unique identifier which embeds within it a timestamp. // // Only Unmarshal methods should be called on the zero UUID value. // // Comparing the equality of two UUID's should always be done using the Equal // method, or by comparing their string forms. // // The string form of UUIDs (returned by String or MarshalText) are // lexigraphically order-able by their embedded timestamp. type UUID struct { // the UUID type is actually just an opaque wrapper. For the most part // UUID's don't ever need the information in them (like their timestamp) // unpacked, so it's more efficient to just keep the string and unpack // on-the-fly str string } // NewUUID populates and returns a new UUID instance which embeds the given time func NewUUID(t time.Time) UUID { b := make([]byte, 16) binary.BigEndian.PutUint64(b[:8], uint64(t.UnixNano())) if _, err := rand.Read(b[8:]); err != nil { panic(err) } return UUID{ str: uuidV0 + hex.EncodeToString(b), } } func (u UUID) String() string { return u.str } // Equal returns whether or not the two UUID's are the same value func (u UUID) Equal(u2 UUID) bool { return u.str == u2.str } // Time unpacks and returns the timestamp embedded in the UUID func (u UUID) Time() time.Time { b, err := hex.DecodeString(u.str[2:]) if err != nil { // once a UUID has been created it should always be valid panic(fmt.Sprintf("malformed UUID: %q", u.str)) } unixNano := int64(binary.BigEndian.Uint64(b[:8])) return time.Unix(0, unixNano).Local() } // KV implements the method for the mlog.KVer interface func (u UUID) KV() mlog.KV { return mlog.KV{"uuid": u.String()} } // MarshalText implements the method for the encoding.TextMarshaler interface func (u UUID) MarshalText() ([]byte, error) { return []byte(u.String()), nil } // UnmarshalText implements the method for the encoding.TextUnmarshaler // interface func (u *UUID) UnmarshalText(b []byte) error { if !bytes.HasPrefix(b, []byte(uuidV0)) || len(b) != len(uuidV0)+32 { return mlog.ErrWithKV(errMalformedUUID, mlog.KV{"uuidStr": string(b)}) } u.str = string(b) return nil } // MarshalJSON implements the method for the json.Marshaler interface func (u UUID) MarshalJSON() ([]byte, error) { return json.Marshal(u.String()) } // UnmarshalJSON implements the method for the json.Unmarshaler interface func (u *UUID) UnmarshalJSON(b []byte) error { var s string if err := json.Unmarshal(b, &s); err != nil { return err } return u.UnmarshalText([]byte(s)) }