mount: add on disk caching

weed/util/chunk_cache/chunk_cache_in_memory.go

@@ -0,0 +1,36 @@
+package chunk_cache
+
+import (
+	"time"
+
+	"github.com/karlseguin/ccache"
+)
+
+// a global cache for recently accessed file chunks
+type ChunkCacheInMemory struct {
+	cache *ccache.Cache
+}
+
+func NewChunkCacheInMemory(maxEntries int64) *ChunkCacheInMemory {
+	pruneCount := maxEntries >> 3
+	if pruneCount <= 0 {
+		pruneCount = 500
+	}
+	return &ChunkCacheInMemory{
+		cache: ccache.New(ccache.Configure().MaxSize(maxEntries).ItemsToPrune(uint32(pruneCount))),
+	}
+}
+
+func (c *ChunkCacheInMemory) GetChunk(fileId string) []byte {
+	item := c.cache.Get(fileId)
+	if item == nil {
+		return nil
+	}
+	data := item.Value().([]byte)
+	item.Extend(time.Hour)
+	return data
+}
+
+func (c *ChunkCacheInMemory) SetChunk(fileId string, data []byte) {
+	c.cache.Set(fileId, data, time.Hour)
+}