add file cache, thanks to gouki

+/**
+ * package: file
+ * User: gouki
+ * Date: 2013-10-22 - 14:22
+ */
+package cache
+
+import (
+	"bytes"
+	"crypto/md5"
+	"encoding/gob"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"reflect"
+	"strconv"
+	"time"
+)
+
+func init() {
+	Register("file", NewFileCache())
+}
+
+type FileCacheItem struct {
+	Data       interface{}
+	Lastaccess int64
+	Expired    int64
+}
+
+var (
+	FileCachePath           string = "cache"
+	FileCacheFileSuffix     string = ".bin"
+	FileCacheDirectoryLevel int    = 2
+	/**
+	 * 默认永不过期
+	 */
+	FileCacheEmbedExpiry int64 = 0
+)
+
+type FileCache struct {
+	CachePath      string
+	FileSuffix     string
+	DirectoryLevel int
+	EmbedExpiry    int
+}
+
+func NewFileCache() *FileCache {
+	//    return &FileCache{CachePath:FileCachePath, FileSuffix:FileCacheFileSuffix}
+	return &FileCache{}
+}
+
+func (this *FileCache) StartAndGC(config string) error {
+
+	var cfg map[string]string
+	json.Unmarshal([]byte(config), &cfg)
+	//fmt.Println(cfg)
+	if _, ok := cfg["CachePath"]; !ok {
+		cfg["CachePath"] = FileCachePath
+	}
+	if _, ok := cfg["FileSuffix"]; !ok {
+		cfg["FileSuffix"] = FileCacheFileSuffix
+	}
+	if _, ok := cfg["DirectoryLevel"]; !ok {
+		cfg["DirectoryLevel"] = strconv.Itoa(FileCacheDirectoryLevel)
+	}
+	if _, ok := cfg["EmbedExpiry"]; !ok {
+		cfg["EmbedExpiry"] = strconv.FormatInt(FileCacheEmbedExpiry, 10)
+	}
+	this.CachePath = cfg["CachePath"]
+	this.FileSuffix = cfg["FileSuffix"]
+	this.DirectoryLevel, _ = strconv.Atoi(cfg["DirectoryLevel"])
+	this.EmbedExpiry, _ = strconv.Atoi(cfg["EmbedExpiry"])
+
+	this.Init()
+	return nil
+}
+
+func (this *FileCache) Init() {
+	app := path.Dir(os.Args[0])
+	this.CachePath = path.Join(app, this.CachePath)
+	ok, err := exists(this.CachePath)
+	if err != nil { // print error
+		//fmt.Println(err)
+	}
+	if !ok {
+		if err = os.Mkdir(this.CachePath, os.ModePerm); err != nil {
+			//fmt.Println(err);
+		}
+	}
+	//fmt.Println(this.getCacheFileName("123456"));
+}
+
+func (this *FileCache) getCacheFileName(key string) string {
+	m := md5.New()
+	io.WriteString(m, key)
+	keyMd5 := hex.EncodeToString(m.Sum(nil))
+	cachePath := this.CachePath
+	//fmt.Println("cachepath : " , cachePath)
+	//fmt.Println("md5" , keyMd5);
+	switch this.DirectoryLevel {
+	case 2:
+		cachePath = path.Join(cachePath, keyMd5[0:2], keyMd5[2:4])
+	case 1:
+		cachePath = path.Join(cachePath, keyMd5[0:2])
+	}
+
+	ok, err := exists(cachePath)
+	if err != nil {
+		//fmt.Println(err)
+	}
+	if !ok {
+		if err = os.MkdirAll(cachePath, os.ModePerm); err != nil {
+			//fmt.Println(err);
+		}
+	}
+	return path.Join(cachePath, fmt.Sprintf("%s%s", keyMd5, this.FileSuffix))
+}
+
+func (this *FileCache) Get(key string) interface{} {
+	filename := this.getCacheFileName(key)
+	filedata, err := File_get_contents(filename)
+	//fmt.Println("get length:" , len(filedata));
+	if err != nil {
+		return ""
+	}
+	var to FileCacheItem
+	Gob_decode([]byte(filedata), &to)
+	if to.Expired < time.Now().Unix() {
+		return ""
+	}
+	return to.Data
+}
+
+func (this *FileCache) Put(key string, val interface{}, timeout int64) error {
+	filename := this.getCacheFileName(key)
+	var item FileCacheItem
+	item.Data = val
+	if timeout == FileCacheEmbedExpiry {
+		item.Expired = time.Now().Unix() + (86400 * 365 * 10) //10年
+	} else {
+		item.Expired = time.Now().Unix() + timeout
+	}
+	item.Expired = time.Now().Unix() + timeout
+	item.Lastaccess = time.Now().Unix()
+	data, err := Gob_encode(item)
+	if err != nil {
+		return err
+	}
+	err = File_put_contents(filename, data)
+	return err
+}
+
+func (this *FileCache) Delete(key string) error {
+	filename := this.getCacheFileName(key)
+	if ok, _ := exists(filename); ok {
+		return os.Remove(filename)
+	}
+	return nil
+}
+
+func (this *FileCache) Incr(key string) error {
+	data := this.Get(key)
+	var incr int
+	fmt.Println(reflect.TypeOf(data).Name())
+	if reflect.TypeOf(data).Name() != "int" {
+		incr = 0
+	} else {
+		incr = data.(int) + 1
+	}
+	this.Put(key, incr, FileCacheEmbedExpiry)
+	return nil
+}
+
+func (this *FileCache) Decr(key string) error {
+	data := this.Get(key)
+	var decr int
+	if reflect.TypeOf(data).Name() != "int" || data.(int)-1 <= 0 {
+		decr = 0
+	} else {
+		decr = data.(int) - 1
+	}
+	this.Put(key, decr, FileCacheEmbedExpiry)
+	return nil
+}
+
+func (this *FileCache) IsExist(key string) bool {
+	filename := this.getCacheFileName(key)
+	ret, _ := exists(filename)
+	return ret
+}
+
+func (this *FileCache) ClearAll() error {
+	//this.CachePath .递归删除
+
+	return nil
+}
+
+func exists(path string) (bool, error) {
+	_, err := os.Stat(path)
+	if err == nil {
+		return true, nil
+	}
+	if os.IsNotExist(err) {
+		return false, nil
+	}
+	return false, err
+}
+
+func File_get_contents(filename string) ([]byte, error) { //文件不存在时自动创建
+	f, err := os.OpenFile(filename, os.O_RDWR|os.O_CREATE, os.ModePerm)
+	if err != nil {
+		return []byte(""), err
+	}
+	defer f.Close()
+	stat, err := f.Stat()
+	if err != nil {
+		return []byte(""), err
+	}
+	data := make([]byte, stat.Size())
+	result, err := f.Read(data)
+	if int64(result) == stat.Size() {
+		return data, err
+	}
+	return []byte(""), err
+}
+
+func File_put_contents(filename string, content []byte) error {
+	fp, err := os.OpenFile(filename, os.O_RDWR|os.O_CREATE, os.ModePerm)
+	if err != nil {
+		return err
+	}
+	defer fp.Close()
+	_, err = fp.Write(content)
+	return err
+}
+func Gob_encode(data interface{}) ([]byte, error) {
+	buf := bytes.NewBuffer(nil)
+	enc := gob.NewEncoder(buf)
+	err := enc.Encode(data)
+	if err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), err
+}
+
+func Gob_decode(data []byte, to interface{}) error {
+	buf := bytes.NewBuffer(data)
+	dec := gob.NewDecoder(buf)
+	return dec.Decode(&to)
+}