// fillHeader fills in the header for the pending chunk.
func (w *Writer) fillHeader(last bool) {
	if w.i+headerSize > w.j || w.j > blockSize {
		panic("leveldb/journal: bad writer state")
	}
	if last {
		if w.first {
			w.buf[w.i+6] = fullChunkType
		} else {
			w.buf[w.i+6] = lastChunkType
		}
	} else {
		if w.first {
			w.buf[w.i+6] = firstChunkType
		} else {
			w.buf[w.i+6] = middleChunkType
		}
	}
	binary.LittleEndian.PutUint32(w.buf[w.i+0:w.i+4], util.NewCRC(w.buf[w.i+6:w.j]).Value())
	binary.LittleEndian.PutUint16(w.buf[w.i+4:w.i+6], uint16(w.j-w.i-headerSize))
}
Exemple #2
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func (w *Writer) writeBlock(buf *util.Buffer, compression opt.Compression) (bh blockHandle, err error) {
	// Compress the buffer if necessary.
	var b []byte
	if compression == opt.SnappyCompression {
		// Allocate scratch enough for compression and block trailer.
		if n := snappy.MaxEncodedLen(buf.Len()) + blockTrailerLen; len(w.compressionScratch) < n {
			w.compressionScratch = make([]byte, n)
		}
		var compressed []byte
		compressed, err = snappy.Encode(w.compressionScratch, buf.Bytes())
		if err != nil {
			return
		}
		n := len(compressed)
		b = compressed[:n+blockTrailerLen]
		b[n] = blockTypeSnappyCompression
	} else {
		tmp := buf.Alloc(blockTrailerLen)
		tmp[0] = blockTypeNoCompression
		b = buf.Bytes()
	}

	// Calculate the checksum.
	n := len(b) - 4
	checksum := util.NewCRC(b[:n]).Value()
	binary.LittleEndian.PutUint32(b[n:], checksum)

	// Write the buffer to the file.
	_, err = w.writer.Write(b)
	if err != nil {
		return
	}
	bh = blockHandle{w.offset, uint64(len(b) - blockTrailerLen)}
	w.offset += uint64(len(b))
	return
}
Exemple #3
0
func verifyChecksum(data []byte) bool {
	n := len(data) - 4
	checksum0 := binary.LittleEndian.Uint32(data[n:])
	checksum1 := util.NewCRC(data[:n]).Value()
	return checksum0 == checksum1
}
// nextChunk sets r.buf[r.i:r.j] to hold the next chunk's payload, reading the
// next block into the buffer if necessary.
func (r *Reader) nextChunk(first bool) error {
	for {
		if r.j+headerSize <= r.n {
			checksum := binary.LittleEndian.Uint32(r.buf[r.j+0 : r.j+4])
			length := binary.LittleEndian.Uint16(r.buf[r.j+4 : r.j+6])
			chunkType := r.buf[r.j+6]

			if checksum == 0 && length == 0 && chunkType == 0 {
				// Drop entire block.
				m := r.n - r.j
				r.i = r.n
				r.j = r.n
				return r.corrupt(m, "zero header", false)
			} else {
				m := r.n - r.j
				r.i = r.j + headerSize
				r.j = r.j + headerSize + int(length)
				if r.j > r.n {
					// Drop entire block.
					r.i = r.n
					r.j = r.n
					return r.corrupt(m, "chunk length overflows block", false)
				} else if r.checksum && checksum != util.NewCRC(r.buf[r.i-1:r.j]).Value() {
					// Drop entire block.
					r.i = r.n
					r.j = r.n
					return r.corrupt(m, "checksum mismatch", false)
				}
			}
			if first && chunkType != fullChunkType && chunkType != firstChunkType {
				m := r.j - r.i
				r.i = r.j
				// Report the error, but skip it.
				return r.corrupt(m+headerSize, "orphan chunk", true)
			}
			r.last = chunkType == fullChunkType || chunkType == lastChunkType
			return nil
		}

		// The last block.
		if r.n < blockSize && r.n > 0 {
			if !first {
				return r.corrupt(0, "missing chunk part", false)
			}
			r.err = io.EOF
			return r.err
		}

		// Read block.
		n, err := io.ReadFull(r.r, r.buf[:])
		if err != nil && err != io.EOF && err != io.ErrUnexpectedEOF {
			return err
		}
		if n == 0 {
			if !first {
				return r.corrupt(0, "missing chunk part", false)
			}
			r.err = io.EOF
			return r.err
		}
		r.i, r.j, r.n = 0, 0, n
	}
}