Method readEntry

recovery_reader.go:38–94

readEntry will read an Entry from disk.

(off int64)

// readEntry will read an Entry from disk.
func (fr *fileRecovery) readEntry(off int64) (e *core.Entry, err error) {
	var size int64 = core.MaxEntryHeaderSize
	// Since core.MaxEntryHeaderSize may be larger than the actual Header, it needs to be calculated
	if off+size > fr.size {
		size = fr.size - off
	}

	buf := make([]byte, size)
	_, err = fr.fd.Seek(off, 0)
	if err != nil {
		return nil, err
	}

	_, err = fr.fd.Read(buf)
	if err != nil {
		return nil, err
	}

	e = new(core.Entry)
	headerSize, err := e.ParseMeta(buf)
	if err != nil {
		return nil, err
	}

	if e.IsZero() {
		return nil, nil
	}

	headerBuf := buf[:headerSize]
	remainingBuf := buf[headerSize:]

	payloadSize := e.Meta.PayloadSize()
	dataBuf := make([]byte, payloadSize)
	excessSize := size - headerSize

	if payloadSize <= excessSize {
		copy(dataBuf, remainingBuf[:payloadSize])
	} else {
		copy(dataBuf, remainingBuf)
		_, err := fr.fd.Read(dataBuf[excessSize:])
		if err != nil {
			return nil, err
		}
	}

	err = e.ParsePayload(dataBuf)
	if err != nil {
		return nil, err
	}

	crc := e.GetCrc(headerBuf)
	if crc != e.Meta.Crc {
		return nil, ErrCrc
	}

	return e, nil
}