Added Redis storage adapter

README.md

@@ -47,3 +47,12 @@ Example: s3://mybucket/
 ```
 
 You can specify the bucket and also a prefix for the storage. That way you even could use one bucket for different instances of CloudKeys Go. In case you're migrating from the old version you need to set the path to `/`.
+
+### Redis
+
+If you want to utilize a Redis storage server or even a Redis cluster you can choose this storage type. Authentication is supported as well as selecting the database to use. Aditionally you can set a prefix for the keys.
+
+```
+Schema:  redis+tcp://auth:<password>@127.0.0.1:6379/<db>?timeout=10s&maxidle=1&prefix=<prefix>
+Example: redis+tcp://auth:mypass@redis.example.com:6379/5?prefix=cloudkeys::
+```

storageRedis.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/xuyu/goredis"
+)
+
+func init() {
+	registerStorage("redis+tcp", newRedisStorage)
+	registerStorage("redis+udp", newRedisStorage)
+}
+
+// RedisStorage implements a storage option for redis server
+type RedisStorage struct {
+	conn   *goredis.Redis
+	prefix string
+}
+
+// NewRedisStorage checks config, creates the path and initializes a RedisStorage
+func newRedisStorage(u *url.URL) (storageAdapter, error) {
+	client, err := goredis.DialURL(strings.Replace(u.String(), "redis+", "", -1))
+	if err != nil {
+		return nil, err
+	}
+
+	return &RedisStorage{
+		conn:   client,
+		prefix: u.Query().Get("prefix"),
+	}, nil
+}
+
+// Write store the data of a dataObject into the storage
+func (r *RedisStorage) Write(identifier string, data io.Reader) error {
+	d, err := ioutil.ReadAll(data)
+	if err != nil {
+		return err
+	}
+
+	return r.conn.Set(r.prefix+identifier, string(d), 0, 0, false, false)
+}
+
+// Read reads the data of a dataObject from the storage
+func (r *RedisStorage) Read(identifier string) (io.Reader, error) {
+	content, err := r.conn.Get(r.prefix + identifier)
+	return bytes.NewReader(content), err
+}
+
+// IsPresent checks for the presence of an userfile identifier
+func (r *RedisStorage) IsPresent(identifier string) bool {
+	e, err := r.conn.Exists(r.prefix + identifier)
+	if err != nil {
+		fmt.Printf("ERR: %s\n", err)
+	}
+	return e && err == nil
+}
+
+// Backup creates a backup of the old data
+func (r *RedisStorage) Backup(identifier string) error {
+	ts := strconv.FormatInt(time.Now().Unix(), 10)
+	data, err := r.Read(identifier)
+	if err != nil {
+		return err
+	}
+
+	return r.Write(identifier+":backup:"+ts, data)
+}