adding ttl field to volume super block

go/storage/volume_super_block.go

@@ -2,6 +2,7 @@ package storage
 
 import (
 	"code.google.com/p/weed-fs/go/glog"
+	"code.google.com/p/weed-fs/go/util"
 	"fmt"
 	"os"
 )
@@ -10,9 +11,16 @@ const (
 	SuperBlockSize = 8
 )
 
+/*
+* Super block currently has 8 bytes allocated for each volume.
+* Byte 0: version, 1 or 2
+* Byte 1: Replica Placement strategy, 000, 001, 002, 010, etc
+* Byte 2 and byte 3: Time to live in minutes
+ */
 type SuperBlock struct {
 	version          Version
 	ReplicaPlacement *ReplicaPlacement
+	Ttl              uint16
 }
 
 func (s *SuperBlock) Version() Version {
@@ -22,6 +30,7 @@ func (s *SuperBlock) Bytes() []byte {
 	header := make([]byte, SuperBlockSize)
 	header[0] = byte(s.version)
 	header[1] = s.ReplicaPlacement.Byte()
+	util.Uint16toBytes(header[2:4], s.Ttl)
 	return header
 }
 
@@ -61,5 +70,6 @@ func ParseSuperBlock(header []byte) (superBlock SuperBlock, err error) {
 	if superBlock.ReplicaPlacement, err = NewReplicaPlacementFromByte(header[1]); err != nil {
 		err = fmt.Errorf("cannot read replica type: %s", err.Error())
 	}
+	superBlock.Ttl = util.BytesToUint16(header[2:4])
 	return
 }

go/storage/volume_super_block_test.go

@@ -0,0 +1,22 @@
+package storage
+
+import (
+	"testing"
+)
+
+func TestSuperBlockReadWrite(t *testing.T) {
+	rp, _ := NewReplicaPlacementFromByte(byte(001))
+	s := &SuperBlock{
+		version:          CurrentVersion,
+		ReplicaPlacement: rp,
+		Ttl:              uint16(35),
+	}
+
+	bytes := s.Bytes()
+
+	if !(bytes[2] == 0 && bytes[3] == 35) {
+	  println("byte[2]:", bytes[2], "byte[3]:", bytes[3])
+		t.Fail()
+	}
+
+}

go/util/bytes.go

@@ -1,5 +1,7 @@
 package util
 
+// big endian
+
 func BytesToUint64(b []byte) (v uint64) {
 	length := uint(len(b))
 	for i := uint(0); i < length-1; i++ {
@@ -18,6 +20,12 @@ func BytesToUint32(b []byte) (v uint32) {
 	v += uint32(b[length-1])
 	return
 }
+func BytesToUint16(b []byte) (v uint16) {
+	v += uint16(b[0])
+	v <<= 8
+	v += uint16(b[1])
+	return
+}
 func Uint64toBytes(b []byte, v uint64) {
 	for i := uint(0); i < 8; i++ {
 		b[7-i] = byte(v >> (i * 8))
@@ -28,6 +36,10 @@ func Uint32toBytes(b []byte, v uint32) {
 		b[3-i] = byte(v >> (i * 8))
 	}
 }
+func Uint16toBytes(b []byte, v uint16) {
+	b[0] = byte(v >> 8)
+	b[1] = byte(v)
+}
 func Uint8toBytes(b []byte, v uint8) {
 	b[0] = byte(v)
 }

go/util/constants.go

@@ -3,5 +3,5 @@ package util
 import ()
 
 const (
-	VERSION = "0.63 beta"
+	VERSION = "0.63"
 )