func (r *Reader) readRawBlock(bh blockHandle, checksum bool) ([]byte, error) {
data := r.bpool.Get(int(bh.length + blockTrailerLen))
if _, err := r.reader.ReadAt(data, int64(bh.offset)); err != nil && err != io.EOF {
return nil, err
}
if checksum || r.checksum {
if !verifyChecksum(data) {
return nil, errors.New("leveldb/table: Reader: invalid block (checksum mismatch)")
}
}
switch data[bh.length] {
case blockTypeNoCompression:
data = data[:bh.length]
case blockTypeSnappyCompression:
decLen, err := snappy.DecodedLen(data[:bh.length])
if err != nil {
return nil, err
}
tmp := data
data, err = snappy.Decode(r.bpool.Get(decLen), tmp[:bh.length])
r.bpool.Put(tmp)
if err != nil {
return nil, err
}
default:
return nil, fmt.Errorf("leveldb/table: Reader: unknown block compression type: %d", data[bh.length])
}
return data, nil
}
// decodeDataBlock assumes r.hdr[0] to be either blockCompressed or
// blockUncompressed.
func (r *reader) decodeBlock() error {
// read compressed block data and determine if uncompressed data is too
// large.
buf, err := r.readBlock()
if err != nil {
return err
}
declen := len(buf[4:])
if r.hdr[0] == blockCompressed {
declen, err = snappy.DecodedLen(buf[4:])
if err != nil {
return err
}
}
if declen > MaxBlockSize {
return fmt.Errorf("decoded block data too large %d > %d", declen, MaxBlockSize)
}
// decode data and verify its integrity using the little-endian crc32
// preceding encoded data
crc32le, blockdata := buf[:4], buf[4:]
if r.hdr[0] == blockCompressed {
r.dst, err = snappy.Decode(r.dst, blockdata)
if err != nil {
return err
}
blockdata = r.dst
}
if r.verifyChecksum {
checksum := unmaskChecksum(uint32(crc32le[0]) | uint32(crc32le[1])<<8 | uint32(crc32le[2])<<16 | uint32(crc32le[3])<<24)
actualChecksum := crc32.Checksum(blockdata, crcTable)
if checksum != actualChecksum {
return fmt.Errorf("checksum does not match %x != %x", checksum, actualChecksum)
}
}
_, err = r.buf.Write(blockdata)
return err
}