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56 lines
1.5 KiB
Go

package main
import (
"encoding/binary"
"fmt"
"sync/atomic"
"time"
)
// NewObjectId returns a new unique ObjectId.
// This function causes a runtime error if it fails to get the hostname
// of the current machine.
func NewId() Id {
b := make([]byte, 12)
// Timestamp, 4 bytes, big endian
binary.BigEndian.PutUint32(b, uint32(time.Now().Unix()))
b[4] = global.machineId[0]
b[5] = global.machineId[1]
b[6] = global.machineId[2]
// Pid, 2 bytes, specs don't specify endianness, but we use big endian.
b[7] = byte(global.pid >> 8)
b[8] = byte(global.pid)
// Increment, 3 bytes, big endian
i := atomic.AddUint32(&global.idCounter, 1)
b[9] = byte(i >> 16)
b[10] = byte(i >> 8)
b[11] = byte(i)
return Id(b)
}
// Id is used for tagging each incoming http request for logging
// purposes. The actual implementation is just the ObjectId implementation
// found in launchpad.net/mgo/bson. This will most likely change and evolve
// into its own format.
type Id string
func (id Id) String() string {
return fmt.Sprintf("%x", string(id))
}
// Time returns the timestamp part of the id.
// It's a runtime error to call this method with an invalid id.
func (id Id) Time() time.Time {
secs := int64(binary.BigEndian.Uint32(id.byteSlice(0, 4)))
return time.Unix(secs, 0)
}
// byteSlice returns byte slice of id from start to end.
// Calling this function with an invalid id will cause a runtime panic.
func (id Id) byteSlice(start, end int) []byte {
if len(id) != 12 {
panic(fmt.Sprintf("Invalid Id: %q", string(id)))
}
return []byte(string(id)[start:end])
}