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import unittest
import zstandard as zstd
class TestDecompressor_decompress(unittest.TestCase):
def test_empty_input(self):
dctx = zstd.ZstdDecompressor()
with self.assertRaisesRegex(
zstd.ZstdError, "error determining content size from frame header"
):
dctx.decompress(b"")
def test_invalid_input(self):
dctx = zstd.ZstdDecompressor()
with self.assertRaisesRegex(
zstd.ZstdError, "error determining content size from frame header"
):
dctx.decompress(b"foobar")
def test_input_types(self):
cctx = zstd.ZstdCompressor(level=1)
compressed = cctx.compress(b"foo")
mutable_array = bytearray(len(compressed))
mutable_array[:] = compressed
sources = [
memoryview(compressed),
bytearray(compressed),
mutable_array,
]
dctx = zstd.ZstdDecompressor()
for source in sources:
self.assertEqual(dctx.decompress(source), b"foo")
def test_no_content_size_in_frame(self):
cctx = zstd.ZstdCompressor(write_content_size=False)
compressed = cctx.compress(b"foobar")
dctx = zstd.ZstdDecompressor()
with self.assertRaisesRegex(
zstd.ZstdError, "could not determine content size in frame header"
):
dctx.decompress(compressed)
def test_content_size_present(self):
cctx = zstd.ZstdCompressor()
compressed = cctx.compress(b"foobar")
dctx = zstd.ZstdDecompressor()
decompressed = dctx.decompress(compressed)
self.assertEqual(decompressed, b"foobar")
def test_empty_roundtrip(self):
cctx = zstd.ZstdCompressor()
compressed = cctx.compress(b"")
dctx = zstd.ZstdDecompressor()
decompressed = dctx.decompress(compressed)
self.assertEqual(decompressed, b"")
def test_max_output_size(self):
cctx = zstd.ZstdCompressor(write_content_size=False)
source = b"foobar" * 256
compressed = cctx.compress(source)
dctx = zstd.ZstdDecompressor()
# Will fit into buffer exactly the size of input.
decompressed = dctx.decompress(compressed, max_output_size=len(source))
self.assertEqual(decompressed, source)
# Input size - 1 fails
with self.assertRaisesRegex(
zstd.ZstdError, "decompression error: did not decompress full frame"
):
dctx.decompress(compressed, max_output_size=len(source) - 1)
# Input size + 1 works
decompressed = dctx.decompress(
compressed, max_output_size=len(source) + 1
)
self.assertEqual(decompressed, source)
# A much larger buffer works.
decompressed = dctx.decompress(
compressed, max_output_size=len(source) * 64
)
self.assertEqual(decompressed, source)
def test_stupidly_large_output_buffer(self):
cctx = zstd.ZstdCompressor(write_content_size=False)
compressed = cctx.compress(b"foobar" * 256)
dctx = zstd.ZstdDecompressor()
# Will get OverflowError on some Python distributions that can't
# handle really large integers.
with self.assertRaises((MemoryError, OverflowError)):
dctx.decompress(compressed, max_output_size=2**62)
def test_dictionary(self):
samples = []
for i in range(128):
samples.append(b"foo" * 64)
samples.append(b"bar" * 64)
samples.append(b"foobar" * 64)
samples.append(b"qwert" * 64)
samples.append(b"yuiop" * 64)
samples.append(b"asdfg" * 64)
samples.append(b"hijkl" * 64)
d = zstd.train_dictionary(8192, samples)
orig = b"foobar" * 16384
cctx = zstd.ZstdCompressor(level=1, dict_data=d)
compressed = cctx.compress(orig)
dctx = zstd.ZstdDecompressor(dict_data=d)
decompressed = dctx.decompress(compressed)
self.assertEqual(decompressed, orig)
def test_dictionary_multiple(self):
samples = []
for i in range(128):
samples.append(b"foo" * 64)
samples.append(b"bar" * 64)
samples.append(b"foobar" * 64)
samples.append(b"qwert" * 64)
samples.append(b"yuiop" * 64)
samples.append(b"asdfg" * 64)
samples.append(b"hijkl" * 64)
d = zstd.train_dictionary(8192, samples)
sources = (b"foobar" * 8192, b"foo" * 8192, b"bar" * 8192)
compressed = []
cctx = zstd.ZstdCompressor(level=1, dict_data=d)
for source in sources:
compressed.append(cctx.compress(source))
dctx = zstd.ZstdDecompressor(dict_data=d)
for i in range(len(sources)):
decompressed = dctx.decompress(compressed[i])
self.assertEqual(decompressed, sources[i])
def test_max_window_size(self):
with open(__file__, "rb") as fh:
source = fh.read()
# If we write a content size, the decompressor engages single pass
# mode and the window size doesn't come into play.
cctx = zstd.ZstdCompressor(write_content_size=False)
frame = cctx.compress(source)
dctx = zstd.ZstdDecompressor(max_window_size=2**zstd.WINDOWLOG_MIN)
with self.assertRaisesRegex(
zstd.ZstdError,
"decompression error: Frame requires too much memory",
):
dctx.decompress(frame, max_output_size=len(source))
def test_explicit_default_params(self):
cctx = zstd.ZstdCompressor(level=1)
compressed = cctx.compress(b"foo")
dctx = zstd.ZstdDecompressor(
dict_data=None,
max_window_size=0,
format=zstd.FORMAT_ZSTD1,
)
self.assertEqual(dctx.decompress(compressed), b"foo")
def test_multiple_frames(self):
cctx = zstd.ZstdCompressor()
foo = cctx.compress(b"foo")
bar = cctx.compress(b"bar")
dctx = zstd.ZstdDecompressor()
self.assertEqual(dctx.decompress(foo + bar), b"foo")
self.assertEqual(
dctx.decompress(foo + bar, allow_extra_data=True), b"foo"
)
with self.assertRaisesRegex(
zstd.ZstdError,
"ZstdDecompressor.read_across_frames=True is not yet implemented",
):
dctx.decompress(foo + bar, read_across_frames=True)
with self.assertRaisesRegex(
zstd.ZstdError,
"%d bytes of unused data, which is disallowed" % len(bar),
):
dctx.decompress(foo + bar, allow_extra_data=False)
def test_junk_after_frame(self):
cctx = zstd.ZstdCompressor()
frame = cctx.compress(b"foo")
dctx = zstd.ZstdDecompressor()
self.assertEqual(dctx.decompress(frame + b"junk"), b"foo")
self.assertEqual(
dctx.decompress(frame + b"junk", allow_extra_data=True), b"foo"
)
with self.assertRaisesRegex(
zstd.ZstdError, "4 bytes of unused data, which is disallowed"
):
dctx.decompress(frame + b"junk", allow_extra_data=False)
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