a correct implementation of filer

go/filer/filer_in_leveldb.go

@@ -0,0 +1,70 @@
+package filer
+
+import (
+	"bytes"
+	"code.google.com/p/weed-fs/go/glog"
+	"github.com/syndtr/goleveldb/leveldb"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+type FileListInLevelDb struct {
+	db *leveldb.DB
+}
+
+func NewFileListInLevelDb(dir string) (fl *FileListInLevelDb, err error) {
+	fl = &FileListInLevelDb{}
+	if fl.db, err = leveldb.OpenFile(dir, nil); err != nil {
+		return
+	}
+	return
+}
+
+func genKey(dirId DirectoryId, fileName string) []byte {
+	ret := make([]byte, 0, 4+len(fileName))
+	for i := 3; i >= 0; i-- {
+		ret = append(ret, byte(dirId>>(uint(i)*8)))
+	}
+	ret = append(ret, []byte(fileName)...)
+	return ret
+}
+
+func (fl *FileListInLevelDb) CreateFile(dirId DirectoryId, fileName string, fid string) (err error) {
+	glog.V(4).Infoln("directory", dirId, "fileName", fileName, "fid", fid)
+	return fl.db.Put(genKey(dirId, fileName), []byte(fid), nil)
+}
+func (fl *FileListInLevelDb) DeleteFile(dirId DirectoryId, fileName string) (fid string, err error) {
+	if fid, err = fl.FindFile(dirId, fileName); err != nil {
+		return
+	}
+	err = fl.db.Delete(genKey(dirId, fileName), nil)
+	return fid, err
+}
+func (fl *FileListInLevelDb) FindFile(dirId DirectoryId, fileName string) (fid string, err error) {
+	data, e := fl.db.Get(genKey(dirId, fileName), nil)
+	if e != nil {
+		return "", e
+	}
+	return string(data), nil
+}
+func (fl *FileListInLevelDb) ListFiles(dirId DirectoryId, lastFileName string, limit int) (files []FileEntry) {
+	glog.V(4).Infoln("directory", dirId, "lastFileName", lastFileName, "limit", limit)
+	dirKey := genKey(dirId, "")
+	iter := fl.db.NewIterator(&util.Range{Start: genKey(dirId, lastFileName)}, nil)
+	limitCounter := -1
+	for iter.Next() {
+		limitCounter++
+		if limit > 0 {
+			if limitCounter > limit {
+				break
+			}
+		}
+		key := iter.Key()
+		if !bytes.HasPrefix(key, dirKey) {
+			break
+		}
+		fileName := key[len(dirKey):]
+		files = append(files, FileEntry{Name: string(fileName), Id: FileId(string(iter.Value()))})
+	}
+	iter.Release()
+	return
+}