Method read

client/blockcache/bcache/manage.go:213–264

(key string, offset uint64, len uint32)

}

func (bm *bcacheManager) read(key string, offset uint64, len uint32) (io.ReadCloser, error) {
	var err error
	bgTime := stat.BeginStat()
	defer func() {
		stat.EndStat("GetCache:Read", err, bgTime, 1)
		if err == nil {
			stat.StatBandWidth("GetCache:Read", len)
		}
	}()
	metaBgTime := stat.BeginStat()
	bm.Lock()
	element, ok := bm.bcacheKeys[key]
	bm.Unlock()
	stat.EndStat("GetCache:Read:GetMeta", nil, metaBgTime, 1)
	log.LogDebugf("Trace read. ok =%v", ok)
	if ok {
		item := element.Value.(*cacheItem)
		f, err := bm.load(key)
		if os.IsNotExist(err) {
			bm.Lock()
			delete(bm.bcacheKeys, key)
			bm.Unlock()
			d := bm.selectDiskKv(key)
			atomic.AddInt64(&d.usedSize, -int64(item.size))
			atomic.AddInt64(&d.usedCount, -1)
			return nil, os.ErrNotExist
		}
		if err != nil {
			return nil, err
		}
		defer f.Close()
		size := item.size
		log.LogDebugf("read. offset =%v,len=%v size=%v", offset, len, size)
		if uint32(offset)+len > size {
			len = size - uint32(offset)
		}
		dataBgTime := stat.BeginStat()
		buf := make([]byte, len)
		n, err := f.ReadAt(buf, int64(offset))
		stat.EndStat("GetCache:Read:ReadData", err, dataBgTime, 1)
		if err != nil {
			return nil, err
		} else {
			// decrypt
			encryptXOR(buf[:n])
			return io.NopCloser(bytes.NewBuffer(buf[:n])), nil
		}
	} else {
		err = os.ErrNotExist
	}
	return nil, err
}

func (bm *bcacheManager) load(key string) (ReadCloser, error) {
	if len(bm.bstore) == 0 {