示例#1
0
// readerForOffset returns a ReadCloser that reads some number of bytes and then EOF
// from the provided offset.  Seeing EOF doesn't mean the end of the whole file; just the
// chunk at that offset.  The caller must close the ReadCloser when done reading.
func (fr *FileReader) readerForOffset(off int64) (io.ReadCloser, error) {
	if off < 0 {
		panic("negative offset")
	}
	if off >= fr.size {
		return eofReader, nil
	}
	offRemain := off
	parts := fr.ss.Parts
	for len(parts) > 0 && parts[0].Size <= uint64(offRemain) {
		offRemain -= int64(parts[0].Size)
		parts = parts[1:]
	}
	if len(parts) == 0 {
		return eofReader, nil
	}
	p0 := parts[0]
	var rsc blobref.ReadSeekCloser
	var err error
	switch {
	case p0.BlobRef != nil && p0.BytesRef != nil:
		return nil, fmt.Errorf("part illegally contained both a blobRef and bytesRef")
	case p0.BlobRef == nil && p0.BytesRef == nil:
		return &nZeros{int(p0.Size - uint64(offRemain))}, nil
	case p0.BlobRef != nil:
		rsc, _, err = fr.fetcher.Fetch(p0.BlobRef)
	case p0.BytesRef != nil:
		rsc, err = NewFileReader(fr.fetcher, p0.BytesRef)
	}
	if err != nil {
		return nil, err
	}
	offRemain += int64(p0.Offset)
	if offRemain > 0 {
		newPos, err := rsc.Seek(offRemain, os.SEEK_SET)
		if err != nil {
			return nil, err
		}
		if newPos != offRemain {
			panic("Seek didn't work")
		}
	}
	return struct {
		io.Reader
		io.Closer
	}{
		io.LimitReader(rsc, int64(p0.Size)),
		rsc,
	}, nil
}
示例#2
0
func (fr *FileReader) readerFor(br *blobref.BlobRef, seekTo int64) (r io.Reader, err error) {
	if fr.crbr == br {
		return fr.cr, nil
	}
	fr.closeOpenBlobs()
	var rsc blobref.ReadSeekCloser
	if br != nil {
		rsc, _, err = fr.fetcher.Fetch(br)
		if err != nil {
			return
		}

		_, serr := rsc.Seek(int64(seekTo), os.SEEK_SET)
		if serr != nil {
			return nil, fmt.Errorf("schema: FileReader.Read seek error on blob %s: %v", br, serr)
		}

	} else {
		rsc = &zeroReader{}
	}
	fr.crbr = br
	fr.cr = rsc
	return rsc, nil
}
示例#3
0
// readerForOffset returns a ReadCloser that reads some number of bytes and then EOF
// from the provided offset.  Seeing EOF doesn't mean the end of the whole file; just the
// chunk at that offset.  The caller must close the ReadCloser when done reading.
func (fr *FileReader) readerForOffset(off int64) (io.ReadCloser, error) {
	if debug {
		log.Printf("(%p) readerForOffset %d + %d = %d", fr, fr.rootOff, off, fr.rootOff+off)
	}
	if off < 0 {
		panic("negative offset")
	}
	if off >= fr.size {
		return eofReader, nil
	}
	offRemain := off
	var skipped int64
	parts := fr.ss.Parts
	for len(parts) > 0 && parts[0].Size <= uint64(offRemain) {
		offRemain -= int64(parts[0].Size)
		skipped += int64(parts[0].Size)
		parts = parts[1:]
	}
	if len(parts) == 0 {
		return eofReader, nil
	}
	p0 := parts[0]
	var rsc blobref.ReadSeekCloser
	var err error
	switch {
	case p0.BlobRef != nil && p0.BytesRef != nil:
		return nil, fmt.Errorf("part illegally contained both a blobRef and bytesRef")
	case p0.BlobRef == nil && p0.BytesRef == nil:
		return &nZeros{int(p0.Size - uint64(offRemain))}, nil
	case p0.BlobRef != nil:
		rsc, _, err = fr.fetcher.Fetch(p0.BlobRef)
	case p0.BytesRef != nil:
		var ss *Superset
		ss, err = fr.getSuperset(p0.BytesRef)
		if err != nil {
			return nil, err
		}
		rsc, err = ss.NewFileReader(fr.fetcher)
		if err == nil {
			subFR := rsc.(*FileReader)
			subFR.parent = fr.rootReader()
			subFR.rootOff = fr.rootOff + skipped
		}
	}
	if err != nil {
		return nil, err
	}
	offRemain += int64(p0.Offset)
	if offRemain > 0 {
		newPos, err := rsc.Seek(offRemain, os.SEEK_SET)
		if err != nil {
			return nil, err
		}
		if newPos != offRemain {
			panic("Seek didn't work")
		}
	}
	return struct {
		io.Reader
		io.Closer
	}{
		io.LimitReader(rsc, int64(p0.Size)),
		rsc,
	}, nil
}