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package snowflake
import (
"fmt"
"strconv"
"sync"
"time"
"github.com/kyren223/eko/pkg/assert"
)
const (
// Epoch is set to the twitter snowflake epoch of Nov 04 2010 01:42:54 UTC in milliseconds
// TODO: change this to eko epoch when eko is production ready
Epoch int64 = 1288834974657
nodeBits = 10
stepBits = 12
NodeMax = 1<<nodeBits - 1
nodeMask = NodeMax << stepBits
stepMask = 1<<stepBits - 1
timeShift = nodeBits + stepBits
nodeShift = stepBits
)
type ID int64
func (id ID) String() string {
return strconv.FormatInt(int64(id), 10)
}
func (id ID) Time() (msSinceEpoch int64) {
return (int64(id) >> timeShift) + Epoch
}
func (id ID) Node() int64 {
return int64(id) & nodeMask >> nodeShift
}
func (id ID) Step() int64 {
return int64(id) & stepMask
}
type Node struct {
mu sync.Mutex
epoch time.Time
time int64
node int64
step int64
}
func (n *Node) String() string {
return fmt.Sprintf("Node%v(epoch: %v, step: %v, time: %v)", n.node, n.epoch, n.step, n.time)
}
// Creates a new node for generating unique IDs.
// To gurantee uniqueness, the given node ID must be unique.
func NewNode(node int64) *Node {
assert.Assert(nodeBits+stepBits == 22, "node and step bits must add up to 22")
assert.Assert(0 <= node && node <= NodeMax, "node must be within 0 and NodeMax", "node", node)
// Credit to https://github.com/bwmarrin/snowflake
currentTime := time.Now()
// add time.Duration to curTime to make sure we use the monotonic clock if available
epoch := currentTime.Add(time.Unix(Epoch/1000, (Epoch%1000)*1000000).Sub(currentTime))
return &Node{
node: node,
epoch: epoch,
}
}
// Generates a unique snowflake ID.
func (n *Node) Generate() ID {
n.mu.Lock()
defer n.mu.Unlock()
now := time.Since(n.epoch).Milliseconds()
if now == n.time {
n.step = (n.step + 1) & stepMask
for n.step == 0 && now <= n.time {
now = time.Since(n.epoch).Milliseconds()
}
} else {
n.step = 0
}
n.time = now
return ID((now << timeShift) | (n.node << nodeShift) | (n.step))
}
// Json marshling to avoid inprecision of json number (float64)
func (id ID) MarshalJSON() ([]byte, error) {
buffer := make([]byte, 0, 22) // 2 quotes, 19 digits, 1 sign
buffer = append(buffer, '"')
buffer = strconv.AppendInt(buffer, int64(id), 10)
buffer = append(buffer, '"')
return buffer, nil
}
func (id *ID) UnmarshalJSON(data []byte) error {
if len(data) < 3 || data[0] != '"' || data[len(data)-1] != '"' {
return fmt.Errorf("invalid snowflake ID %q", string(data))
}
num, err := strconv.ParseInt(string(data[1:len(data)-1]), 10, 64)
if err != nil {
return err
}
*id = ID(num)
return nil
}
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