def __write_record(self, record_type, data):
"""Write single physical record."""
length = len(data)
crc = crc32c.crc_update(crc32c.CRC_INIT, [record_type])
crc = crc32c.crc_update(crc, data)
crc = crc32c.crc_finalize(crc)
self.__writer.write(struct.pack(HEADER_FORMAT, crc, length, record_type))
self.__writer.write(data)
self.__position += HEADER_LENGTH + length
def __write_record(self, record_type, data):
"""Write single physical record."""
length = len(data)
crc = crc32c.crc_update(crc32c.CRC_INIT, [record_type])
crc = crc32c.crc_update(crc, data)
crc = crc32c.crc_finalize(crc)
self.__writer.write(
struct.pack(HEADER_FORMAT, _mask_crc(crc), length, record_type))
self.__writer.write(data)
self.__position += HEADER_LENGTH + length
def __try_read_record(self):
"""Try reading a record.
Returns:
(data, record_type) tuple.
Raises:
EOFError: when end of file was reached.
InvalidRecordError: when valid record could not be read.
"""
block_remaining = BLOCK_SIZE - self.__reader.tell() % BLOCK_SIZE
if block_remaining < HEADER_LENGTH:
return ('', RECORD_TYPE_NONE)
header = self.__reader.read(HEADER_LENGTH)
if len(header) != HEADER_LENGTH:
raise EOFError('Read %s bytes instead of %s' %
(len(header), HEADER_LENGTH))
(masked_crc, length,
record_type) = struct.unpack(HEADER_FORMAT, header)
crc = _unmask_crc(masked_crc)
if length + HEADER_LENGTH > block_remaining:
raise InvalidRecordError('Length is too big')
data = self.__reader.read(length)
if len(data) != length:
raise EOFError('Not enough data read. Expected: %s but got %s' %
(length, len(data)))
if record_type == RECORD_TYPE_NONE:
return ('', record_type)
actual_crc = crc32c.crc_update(crc32c.CRC_INIT, [record_type])
actual_crc = crc32c.crc_update(actual_crc, data)
actual_crc = crc32c.crc_finalize(actual_crc)
if actual_crc != crc:
raise InvalidRecordError('Data crc does not match')
return (data, record_type)
def __try_read_record(self):
"""Try reading a record.
Returns:
(data, record_type) tuple.
Raises:
EOFError: when end of file was reached.
InvalidRecordError: when valid record could not be read.
"""
block_remaining = BLOCK_SIZE - self.__reader.tell() % BLOCK_SIZE
if block_remaining < HEADER_LENGTH:
return ('', RECORD_TYPE_NONE)
header = self.__reader.read(HEADER_LENGTH)
if len(header) != HEADER_LENGTH:
raise EOFError('Read %s bytes instead of %s' %
(len(header), HEADER_LENGTH))
(masked_crc, length, record_type) = struct.unpack(HEADER_FORMAT, header)
crc = _unmask_crc(masked_crc)
if length + HEADER_LENGTH > block_remaining:
raise InvalidRecordError('Length is too big')
data = self.__reader.read(length)
if len(data) != length:
raise EOFError('Not enough data read. Expected: %s but got %s' %
(length, len(data)))
if record_type == RECORD_TYPE_NONE:
return ('', record_type)
actual_crc = crc32c.crc_update(crc32c.CRC_INIT, [record_type])
actual_crc = crc32c.crc_update(actual_crc, data)
actual_crc = crc32c.crc_finalize(actual_crc)
if actual_crc != crc:
raise InvalidRecordError('Data crc does not match')
return (data, record_type)
def _compute_python_crc(record_type, data):
"""Computes crc using naive python implementation."""
crc = crc32c.crc_update(crc32c.CRC_INIT, [record_type])
crc = crc32c.crc_update(crc, data)
return crc32c.crc_finalize(crc)
def _compute_python_crc(record_type, data): """Computes crc using naive python implementation.""" crc = crc32c.crc_update(crc32c.CRC_INIT, [record_type]) crc = crc32c.crc_update(crc, data) return crc32c.crc_finalize(crc)