def test_compression(self):
# test that we can add compressed chunks
compressor = snappy.StreamCompressor()
data = b"\0" * 50
compressed_data = snappy.compress(data)
crc = struct.pack("<L", snappy._masked_crc32c(data))
self.assertEqual(crc, b"\x8f)H\xbd")
self.assertEqual(len(compressed_data), 6)
self.assertEqual(compressor.add_chunk(data, compress=True),
b"\xff\x06\x00\x00sNaPpY"
b"\x00\x0a\x00\x00" + crc + compressed_data)
# test that we can add uncompressed chunks
data = b"\x01" * 50
crc = struct.pack("<L", snappy._masked_crc32c(data))
self.assertEqual(crc, b"\xb2\x14)\x8a")
self.assertEqual(compressor.add_chunk(data, compress=False),
b"\x01\x36\x00\x00" + crc + data)
# test that we can add more data than will fit in one chunk
data = b"\x01" * (snappy._CHUNK_MAX * 2 - 5)
crc1 = struct.pack("<L",
snappy._masked_crc32c(data[:snappy._CHUNK_MAX]))
self.assertEqual(crc1, b"h#6\x8e")
crc2 = struct.pack("<L",
snappy._masked_crc32c(data[snappy._CHUNK_MAX:]))
self.assertEqual(crc2, b"q\x8foE")
self.assertEqual(compressor.add_chunk(data, compress=False),
b"\x01\x04\x00\x01" + crc1 + data[:snappy._CHUNK_MAX] +
b"\x01\xff\xff\x00" + crc2 + data[snappy._CHUNK_MAX:])
def test_decompression(self):
# test that we check for the initial stream identifier
data = b"\x01" * 50
self.assertRaises(snappy.UncompressError,
snappy.StreamDecompressor().decompress,
b"\x01\x36\x00\00" +
struct.pack("<L", snappy._masked_crc32c(data)) + data)
self.assertEqual(
snappy.StreamDecompressor().decompress(
b"\xff\x06\x00\x00sNaPpY"
b"\x01\x36\x00\x00" +
struct.pack("<L", snappy._masked_crc32c(data)) + data),
data)
decompressor = snappy.StreamDecompressor()
decompressor.decompress(b"\xff\x06\x00\x00sNaPpY")
self.assertEqual(
decompressor.copy().decompress(
b"\x01\x36\x00\x00" +
struct.pack("<L", snappy._masked_crc32c(data)) + data),
data)
# test that we throw errors for unknown unskippable chunks
self.assertRaises(snappy.UncompressError,
decompressor.copy().decompress, b"\x03\x01\x00\x00")
# test that we skip unknown skippable chunks
self.assertEqual(b"",
decompressor.copy().decompress(b"\xfe\x01\x00\x00"))
# test that we check CRCs
compressed_data = snappy.compress(data)
real_crc = struct.pack("<L", snappy._masked_crc32c(data))
fake_crc = os.urandom(4)
self.assertRaises(snappy.UncompressError,
decompressor.copy().decompress,
b"\x00\x0a\x00\x00" + fake_crc + compressed_data)
self.assertEqual(
decompressor.copy().decompress(
b"\x00\x0a\x00\x00" + real_crc + compressed_data),
data)
# test that we buffer when we don't have enough
uncompressed_data = os.urandom(100)
compressor = snappy.StreamCompressor()
compressed_data = (compressor.compress(uncompressed_data[:50]) +
compressor.compress(uncompressed_data[50:]))
for split1 in range(len(compressed_data) - 1):
for split2 in range(split1, len(compressed_data)):
decompressor = snappy.StreamDecompressor()
self.assertEqual(
(decompressor.decompress(compressed_data[:split1]) +
decompressor.decompress(compressed_data[split1:split2]) +
decompressor.decompress(compressed_data[split2:])),
uncompressed_data)
