forked from dolab/gogo
/
utils.go
153 lines (136 loc) · 4.51 KB
/
utils.go
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package gogo
import (
"crypto/md5"
"crypto/rand"
"encoding/binary"
"encoding/hex"
"fmt"
"io"
"os"
"sync/atomic"
"time"
)
// NOTE: copied from http://bazaar.launchpad.net/+branch/mgo/v2/view/head:/bson/bson.go#L161
var (
// machineId stores machine id generated once and used in subsequent calls
// to NewObjectId function.
machineId = func() []byte {
var sum [3]byte
id := sum[:]
hostname, err1 := os.Hostname()
if err1 != nil {
_, err2 := io.ReadFull(rand.Reader, id)
if err2 != nil {
panic(fmt.Errorf("cannot get hostname: %v; %v", err1, err2))
}
return id
}
hw := md5.New()
hw.Write([]byte(hostname))
copy(id, hw.Sum(nil))
return id
}()
// objectIdCounter is atomically incremented when generating a new ObjectId
// using NewObjectId() function. It's used as a counter part of an id.
objectIdCounter uint32 = 0
)
// ObjectId is a unique ID identifying a BSON value. It must be exactly 12 bytes
// long. MongoDB objects by default have such a property set in their "_id"
// property.
//
// http://www.mongodb.org/display/DOCS/Object+IDs
type ObjectId string
// IsObjectIdHex returns whether s is a valid hex representation of
// an ObjectId. See the ObjectIdHex function.
func IsObjectIdHex(s string) bool {
if len(s) != 24 {
return false
}
_, err := hex.DecodeString(s)
return err == nil
}
// ObjectIdHex returns an ObjectId from the provided hex representation.
// Calling this function with an invalid hex representation will
// cause a runtime panic. See the IsObjectIdHex function.
func ObjectIdHex(s string) ObjectId {
d, err := hex.DecodeString(s)
if err != nil || len(d) != 12 {
panic(fmt.Sprintf("Invalid input to ObjectIdHex: %q", s))
}
return ObjectId(d)
}
// NewObjectId returns a new unique ObjectId.
func NewObjectId() ObjectId {
var b [12]byte
// Timestamp, 4 bytes, big endian
binary.BigEndian.PutUint32(b[:], uint32(time.Now().Unix()))
// Machine, first 3 bytes of md5(hostname)
b[4] = machineId[0]
b[5] = machineId[1]
b[6] = machineId[2]
// Pid, 2 bytes, specs don't specify endianness, but we use big endian.
pid := os.Getpid()
b[7] = byte(pid >> 8)
b[8] = byte(pid)
// Increment, 3 bytes, big endian
i := atomic.AddUint32(&objectIdCounter, 1)
b[9] = byte(i >> 16)
b[10] = byte(i >> 8)
b[11] = byte(i)
return ObjectId(b[:])
}
// NewObjectIdWithTime returns a dummy ObjectId with the timestamp part filled
// with the provided number of seconds from epoch UTC, and all other parts
// filled with zeroes. It's not safe to insert a document with an id generated
// by this method, it is useful only for queries to find documents with ids
// generated before or after the specified timestamp.
func NewObjectIdWithTime(t time.Time) ObjectId {
var b [12]byte
binary.BigEndian.PutUint32(b[:4], uint32(t.Unix()))
return ObjectId(string(b[:]))
}
// String returns a hex string representation of the id.
// Example: ObjectIdHex("4d88e15b60f486e428412dc9").
func (id ObjectId) String() string {
return fmt.Sprintf(`ObjectIdHex("%x")`, string(id))
}
// Hex returns a hex representation of the ObjectId.
func (id ObjectId) Hex() string {
return hex.EncodeToString([]byte(id))
}
// Valid returns true if id is valid. A valid id must contain exactly 12 bytes.
func (id ObjectId) Valid() bool {
return len(id) == 12
}
// byteSlice returns byte slice of id from start to end.
// Calling this function with an invalid id will cause a runtime panic.
func (id ObjectId) byteSlice(start, end int) []byte {
if len(id) != 12 {
panic(fmt.Sprintf("Invalid ObjectId: %q", string(id)))
}
return []byte(string(id)[start:end])
}
// Time returns the timestamp part of the id.
// It's a runtime error to call this method with an invalid id.
func (id ObjectId) Time() time.Time {
// First 4 bytes of ObjectId is 32-bit big-endian seconds from epoch.
secs := int64(binary.BigEndian.Uint32(id.byteSlice(0, 4)))
return time.Unix(secs, 0)
}
// Machine returns the 3-byte machine id part of the id.
// It's a runtime error to call this method with an invalid id.
func (id ObjectId) Machine() []byte {
return id.byteSlice(4, 7)
}
// Pid returns the process id part of the id.
// It's a runtime error to call this method with an invalid id.
func (id ObjectId) Pid() uint16 {
return binary.BigEndian.Uint16(id.byteSlice(7, 9))
}
// Counter returns the incrementing value part of the id.
// It's a runtime error to call this method with an invalid id.
func (id ObjectId) Counter() int32 {
b := id.byteSlice(9, 12)
// Counter is stored as big-endian 3-byte value
return int32(uint32(b[0])<<16 | uint32(b[1])<<8 | uint32(b[2]))
}