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package filer2
import ( "bytes" "context" "fmt" "io" "sync"
"github.com/chrislusf/seaweedfs/weed/glog" "github.com/chrislusf/seaweedfs/weed/pb/filer_pb" "github.com/chrislusf/seaweedfs/weed/util" "github.com/chrislusf/seaweedfs/weed/wdclient" )
type ChunkReadAt struct { masterClient *wdclient.MasterClient chunkViews []*ChunkView buffer []byte bufferOffset int64 lookupFileId func(fileId string) (targetUrl string, err error) readerLock sync.Mutex }
// var _ = io.ReaderAt(&ChunkReadAt{})
func NewChunkReaderAtFromClient(filerClient filer_pb.FilerClient, chunkViews []*ChunkView) *ChunkReadAt {
return &ChunkReadAt{ chunkViews: chunkViews, lookupFileId: func(fileId string) (targetUrl string, err error) { err = filerClient.WithFilerClient(func(client filer_pb.SeaweedFilerClient) error { vid := VolumeId(fileId) resp, err := client.LookupVolume(context.Background(), &filer_pb.LookupVolumeRequest{ VolumeIds: []string{vid}, }) if err != nil { return err }
locations := resp.LocationsMap[vid] if locations == nil || len(locations.Locations) == 0 { glog.V(0).Infof("failed to locate %s", fileId) return fmt.Errorf("failed to locate %s", fileId) }
volumeServerAddress := filerClient.AdjustedUrl(locations.Locations[0].Url)
targetUrl = fmt.Sprintf("http://%s/%s", volumeServerAddress, fileId)
return nil }) return }, bufferOffset: -1, } }
func (c *ChunkReadAt) ReadAt(p []byte, offset int64) (n int, err error) {
c.readerLock.Lock() defer c.readerLock.Unlock()
for n < len(p) && err == nil { readCount, readErr := c.doReadAt(p[n:], offset+int64(n)) n += readCount err = readErr if readCount == 0 { return n, nil } } return }
func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
var found bool for _, chunk := range c.chunkViews { if chunk.LogicOffset <= offset && offset < chunk.LogicOffset+int64(chunk.Size) { found = true if c.bufferOffset != chunk.LogicOffset { c.fetchChunkToBuffer(chunk) } break } } if !found { return 0, io.EOF }
n = copy(p, c.buffer[offset-c.bufferOffset:])
// fmt.Printf("> doReadAt [%d,%d), buffer:[%d,%d)\n", offset, offset+int64(n), c.bufferOffset, c.bufferOffset+int64(len(c.buffer)))
return
}
func (c *ChunkReadAt) fetchChunkToBuffer(chunkView *ChunkView) error {
// fmt.Printf("fetching %s [%d,%d)\n", chunkView.FileId, chunkView.LogicOffset, chunkView.LogicOffset+int64(chunkView.Size))
urlString, err := c.lookupFileId(chunkView.FileId) if err != nil { glog.V(1).Infof("operation LookupFileId %s failed, err: %v", chunkView.FileId, err) return err } var buffer bytes.Buffer err = util.ReadUrlAsStream(urlString, chunkView.CipherKey, chunkView.isGzipped, chunkView.IsFullChunk, chunkView.Offset, int(chunkView.Size), func(data []byte) { buffer.Write(data) }) if err != nil { glog.V(1).Infof("read %s failed, err: %v", chunkView.FileId, err) return err } c.buffer = buffer.Bytes() c.bufferOffset = chunkView.LogicOffset
glog.V(3).Infof("read %s [%d,%d)", chunkView.FileId, chunkView.LogicOffset, chunkView.LogicOffset+int64(chunkView.Size))
return nil }
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