Implement metadata cache, metadata cache is used by top level donut right now. Rename trove as data cache

We should use it internally everywhere.

pkg/donut/cache/data/data_test.go

@@ -0,0 +1,45 @@
+/*
+ * Minimalist Object Storage, (C) 2015 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package data
+
+import (
+	"testing"
+
+	. "github.com/minio/check"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type MySuite struct{}
+
+var _ = Suite(&MySuite{})
+
+func (s *MySuite) TestCache(c *C) {
+	cache := NewCache(1000, 0)
+	data := []byte("Hello, world!")
+	ok := cache.Set("filename", data)
+
+	c.Assert(ok, Equals, true)
+	storedata, ok := cache.Get("filename")
+
+	c.Assert(ok, Equals, true)
+	c.Assert(data, DeepEquals, storedata)
+
+	cache.Delete("filename")
+	_, ok = cache.Get("filename")
+	c.Assert(ok, Equals, false)
+}