281 lines
6.2 KiB
Go
281 lines
6.2 KiB
Go
// Package snowflake provides a very simple Twitter snowflake generator and parser.
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package snowflake
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import (
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"encoding/base64"
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"encoding/binary"
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"errors"
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"fmt"
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"strconv"
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"sync"
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"time"
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)
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const (
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spareBits = 22
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nodeBits = 10
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stepBits = spareBits - nodeBits
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nodeMax = -1 ^ (-1 << nodeBits)
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nodeMask = nodeMax << stepBits
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stepMask int64 = -1 ^ (-1 << stepBits)
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timeShift uint8 = nodeBits + stepBits
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nodeShift uint8 = stepBits
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)
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const encodeBase32Map = "ybndrfg8ejkmcpqxot1uwisza345h769"
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var decodeBase32Map [256]byte
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const encodeBase58Map = "123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ"
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var decodeBase58Map [256]byte
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// A JSONSyntaxError is returned from UnmarshalJSON if an invalid ID is provided.
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type JSONSyntaxError struct{ original []byte }
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func (j JSONSyntaxError) Error() string {
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return fmt.Sprintf("invalid snowflake ID %q", string(j.original))
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}
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// Create a map for decoding Base58. This speeds up the process tremendously.
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func init() {
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for i := 0; i < len(encodeBase58Map); i++ {
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decodeBase58Map[i] = 0xFF
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}
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for i := 0; i < len(encodeBase58Map); i++ {
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decodeBase58Map[encodeBase58Map[i]] = byte(i)
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}
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for i := 0; i < len(encodeBase32Map); i++ {
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decodeBase32Map[i] = 0xFF
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}
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for i := 0; i < len(encodeBase32Map); i++ {
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decodeBase32Map[encodeBase32Map[i]] = byte(i)
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}
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}
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// ErrInvalidBase58 is returned by ParseBase58 when given an invalid []byte
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var ErrInvalidBase58 = errors.New("invalid base58")
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// ErrInvalidBase32 is returned by ParseBase32 when given an invalid []byte
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var ErrInvalidBase32 = errors.New("invalid base32")
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// Epoch is set to the twitter snowflake epoch of 2006-03-21:20:50:14 GMT
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// You may customize this to set a different epoch for your application.
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var Epoch int64 = 1288834974657
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// A Node struct holds the basic information needed for a snowflake generator
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// node
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type Node struct {
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mu sync.Mutex
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time int64
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node int64
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step int64
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}
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// An ID is a custom type used for a snowflake ID. This is used so we can
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// attach methods onto the ID.
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type ID int64
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// NewNode returns a new snowflake node that can be used to generate snowflake
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// IDs
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func NewNode(node int64) (*Node, error) {
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if node < 0 || node > nodeMax {
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return nil, errors.New("Node number must be between 0 and 1023")
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}
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return &Node{
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time: 0,
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node: node,
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step: 0,
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}, nil
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}
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// Generate creates and returns a unique snowflake ID
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func (n *Node) Generate() ID {
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n.mu.Lock()
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now := time.Now().UnixNano() / 1000000
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if n.time == now {
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n.step = (n.step + 1) & stepMask
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if n.step == 0 {
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for now <= n.time {
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now = time.Now().UnixNano() / 1000000
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}
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}
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} else {
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n.step = 0
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}
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n.time = now
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r := ID((now-Epoch)<<timeShift |
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(n.node << nodeShift) |
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(n.step),
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)
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n.mu.Unlock()
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return r
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}
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// Int64 returns an int64 of the snowflake ID
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func (f ID) Int64() int64 {
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return int64(f)
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}
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// String returns a string of the snowflake ID
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func (f ID) String() string {
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return strconv.FormatInt(int64(f), 10)
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}
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// Base2 returns a string base2 of the snowflake ID
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func (f ID) Base2() string {
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return strconv.FormatInt(int64(f), 2)
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}
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// Base36 returns a base36 string of the snowflake ID
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func (f ID) Base36() string {
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return strconv.FormatInt(int64(f), 36)
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}
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// Base32 uses the z-base-32 character set but encodes and decodes similar
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// to base58, allowing it to create an even smaller result string.
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// NOTE: There are many different base32 implementations so becareful when
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// doing any interoperation interop with other packages.
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func (f ID) Base32() string {
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if f < 32 {
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return string(encodeBase32Map[f])
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}
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b := make([]byte, 0, 12)
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for f >= 32 {
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b = append(b, encodeBase32Map[f%32])
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f /= 32
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}
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b = append(b, encodeBase32Map[f])
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for x, y := 0, len(b)-1; x < y; x, y = x+1, y-1 {
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b[x], b[y] = b[y], b[x]
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}
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return string(b)
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}
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// ParseBase32 parses a base32 []byte into a snowflake ID
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// NOTE: There are many different base32 implementations so becareful when
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// doing any interoperation interop with other packages.
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func ParseBase32(b []byte) (ID, error) {
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var id int64
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for i := range b {
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if decodeBase32Map[b[i]] == 0xFF {
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return -1, ErrInvalidBase32
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}
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id = id*32 + int64(decodeBase32Map[b[i]])
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}
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return ID(id), nil
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}
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// Base58 returns a base58 string of the snowflake ID
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func (f ID) Base58() string {
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if f < 58 {
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return string(encodeBase58Map[f])
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}
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b := make([]byte, 0, 11)
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for f >= 58 {
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b = append(b, encodeBase58Map[f%58])
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f /= 58
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}
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b = append(b, encodeBase58Map[f])
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for x, y := 0, len(b)-1; x < y; x, y = x+1, y-1 {
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b[x], b[y] = b[y], b[x]
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}
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return string(b)
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}
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// ParseBase58 parses a base58 []byte into a snowflake ID
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func ParseBase58(b []byte) (ID, error) {
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var id int64
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for i := range b {
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if decodeBase58Map[b[i]] == 0xFF {
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return -1, ErrInvalidBase58
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}
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id = id*58 + int64(decodeBase58Map[b[i]])
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}
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return ID(id), nil
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}
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// Base64 returns a base64 string of the snowflake ID
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func (f ID) Base64() string {
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return base64.StdEncoding.EncodeToString(f.Bytes())
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}
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// Bytes returns a byte slice of the snowflake ID
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func (f ID) Bytes() []byte {
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return []byte(f.String())
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}
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// IntBytes returns an array of bytes of the snowflake ID, encoded as a
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// big endian integer.
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func (f ID) IntBytes() [8]byte {
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var b [8]byte
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binary.BigEndian.PutUint64(b[:], uint64(f))
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return b
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}
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// Time returns an int64 unix timestamp of the snowflake ID time
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func (f ID) Time() int64 {
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return (int64(f) >> 22) + Epoch
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}
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// Node returns an int64 of the snowflake ID node number
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func (f ID) Node() int64 {
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return int64(f) & nodeMask >> nodeShift
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}
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// Step returns an int64 of the snowflake step (or sequence) number
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func (f ID) Step() int64 {
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return int64(f) & stepMask
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}
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// MarshalJSON returns a json byte array string of the snowflake ID.
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func (f ID) MarshalJSON() ([]byte, error) {
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buff := make([]byte, 0, 22)
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buff = append(buff, '"')
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buff = strconv.AppendInt(buff, int64(f), 10)
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buff = append(buff, '"')
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return buff, nil
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}
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// UnmarshalJSON converts a json byte array of a snowflake ID into an ID type.
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func (f *ID) UnmarshalJSON(b []byte) error {
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if len(b) < 3 || b[0] != '"' || b[len(b)-1] != '"' {
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return JSONSyntaxError{b}
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}
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i, err := strconv.ParseInt(string(b[1:len(b)-1]), 10, 64)
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if err != nil {
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return err
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}
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*f = ID(i)
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return nil
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}
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