def read_next_chunk(self, lazy):
# Check for EOF:
ncode_records_minus_one_buf = self._stream.read(1)
if not ncode_records_minus_one_buf:
return None
# Code track (run length encoded):
(ncode_records_minus_one, ) = struct.unpack(
"<B", ncode_records_minus_one_buf)
ncode_records = ncode_records_minus_one + 1
codes = np.empty(256, np.uint16)
cursor = 0
for i in xrange(ncode_records):
repeat_minus_one, code = struct.unpack("<BH", self._stream.read(3))
codes[cursor:cursor + repeat_minus_one + 1] = code
cursor += repeat_minus_one + 1
assert cursor == 256
# Data bytes (delta encoded and packed into variable-length integers):
# Record where these start so we can find it again in get_chunk().
self._offsets.append(self._stream.tell())
(ncompressed_words, ) = struct.unpack("<H", self._stream.read(2))
compressed_data = self._stream.read(ncompressed_words * 2)
if lazy:
data_chunk = None
else:
# This is the slow part of loading data:
data_chunk = _decompress_crw_chunk(compressed_data,
ncompressed_words, self._nchans)
return codes, data_chunk
def read_next_chunk(self, lazy):
# Check for EOF:
ncode_records_minus_one_buf = self._stream.read(1)
if not ncode_records_minus_one_buf:
return None
# Code track (run length encoded):
(ncode_records_minus_one,) = struct.unpack("<B",
ncode_records_minus_one_buf)
ncode_records = ncode_records_minus_one + 1
codes = np.empty(256, np.uint16)
cursor = 0
for i in xrange(ncode_records):
repeat_minus_one, code = struct.unpack("<BH", self._stream.read(3))
codes[cursor:cursor + repeat_minus_one + 1] = code
cursor += repeat_minus_one + 1
assert cursor == 256
# Data bytes (delta encoded and packed into variable-length integers):
# Record where these start so we can find it again in get_chunk().
self._offsets.append(self._stream.tell())
(ncompressed_words,) = struct.unpack("<H", self._stream.read(2))
compressed_data = self._stream.read(ncompressed_words * 2)
if lazy:
data_chunk = None
else:
# This is the slow part of loading data:
data_chunk = _decompress_crw_chunk(compressed_data,
ncompressed_words,
self._nchans)
return codes, data_chunk
def get_chunk(self, chunk_number):
self._stream.seek(self._offsets[chunk_number])
(ncompressed_words, ) = struct.unpack("<H", self._stream.read(2))
return _decompress_crw_chunk(self._stream.read(ncompressed_words * 2),
ncompressed_words, self._nchans)
def get_chunk(self, chunk_number):
self._stream.seek(self._offsets[chunk_number])
(ncompressed_words,) = struct.unpack("<H", self._stream.read(2))
return _decompress_crw_chunk(self._stream.read(ncompressed_words * 2),
ncompressed_words,
self._nchans)
