| 39 | } |
| 40 | |
| 41 | func (this *FileReader) ReadAt(b []byte, offset int64) (n int, err error) { |
| 42 | if offset >= this.fileHeader.MaxOffset() { |
| 43 | err = io.EOF |
| 44 | return |
| 45 | } |
| 46 | |
| 47 | blockInfo, ok := this.fileHeader.BlockAt(offset) |
| 48 | if !ok { |
| 49 | err = errors.New("could not find block at '" + types.String(offset) + "'") |
| 50 | return |
| 51 | } |
| 52 | |
| 53 | var delta = offset - blockInfo.OriginOffsetFrom |
| 54 | var bFrom = blockInfo.BFileOffsetFrom + delta |
| 55 | var bTo = blockInfo.BFileOffsetTo |
| 56 | if bFrom > bTo { |
| 57 | err = errors.New("invalid block information") |
| 58 | return |
| 59 | } |
| 60 | |
| 61 | var bufLen = len(b) |
| 62 | if int64(bufLen) > bTo-bFrom { |
| 63 | bufLen = int(bTo - bFrom) |
| 64 | } |
| 65 | |
| 66 | AckReadThread() |
| 67 | n, err = this.fp.ReadAt(b[:bufLen], bFrom) |
| 68 | ReleaseReadThread() |
| 69 | |
| 70 | return |
| 71 | } |
| 72 | |
| 73 | func (this *FileReader) Reset(fileHeader *FileHeader) { |
| 74 | this.fileHeader = fileHeader |