seaweedfs/weed-fs/src/pkg/storage/volume.go

package storage

import (
	"os"
	"path"
	"strconv"
	"log"
)

type Volume struct {
	Id       uint32
	dir      string
	dataFile *os.File
	nm       *NeedleMap

	accessChannel chan int
}

func NewVolume(dirname string, id uint32) (v *Volume) {
	var e os.Error
	v = &Volume{dir: dirname, Id: id, nm: NewNeedleMap()}
	fileName := strconv.Uitoa64(uint64(v.Id))
	v.dataFile, e = os.OpenFile(path.Join(v.dir, fileName+".dat"), os.O_RDWR|os.O_CREATE, 0644)
	if e != nil {
		log.Fatalf("New Volume [ERROR] %s\n", e)
	}
	indexFile, ie := os.OpenFile(path.Join(v.dir, fileName+".idx"), os.O_RDWR|os.O_CREATE, 0644)
	if ie != nil {
		log.Fatalf("New Volume [ERROR] %s\n", ie)
	}
	v.nm = LoadNeedleMap(indexFile)

	v.accessChannel = make(chan int, 1)
	v.accessChannel <- 0

	return
}
func (v *Volume) Size() int64 {
	stat, e := v.dataFile.Stat()
	if e == nil {
		return stat.Size
	}
	return -1
}
func (v *Volume) Close() {
	close(v.accessChannel)
	v.nm.Close()
	v.dataFile.Close()
}

func (v *Volume) write(n *Needle) {
	counter := <-v.accessChannel
	offset, _ := v.dataFile.Seek(0, 2)
	n.Append(v.dataFile)
	nv, ok := v.nm.get(n.Key)
	if !ok || int64(nv.Offset)*8 < offset {
		v.nm.put(n.Key, uint32(offset/8), n.Size)
	}
	v.accessChannel <- counter + 1
}
func (v *Volume) read(n *Needle) {
	counter := <-v.accessChannel
	nv, ok := v.nm.get(n.Key)
	if ok && nv.Offset > 0 {
		v.dataFile.Seek(int64(nv.Offset)*8, 0)
		n.Read(v.dataFile, nv.Size)
	}
	v.accessChannel <- counter + 1
}