contrib/python-zstandard/tests/test_data_structures.py

import io

try:
    import unittest2 as unittest
except ImportError:
    import unittest

try:
    import hypothesis
    import hypothesis.strategies as strategies
except ImportError:
    hypothesis = None

import zstd

from . common import (
    make_cffi,
)


@make_cffi
class TestCompressionParameters(unittest.TestCase):
    def test_init_bad_arg_type(self):
        with self.assertRaises(TypeError):
            zstd.CompressionParameters()

        with self.assertRaises(TypeError):
            zstd.CompressionParameters(0, 1)

    def test_bounds(self):
        zstd.CompressionParameters(zstd.WINDOWLOG_MIN,
                                   zstd.CHAINLOG_MIN,
                                   zstd.HASHLOG_MIN,
                                   zstd.SEARCHLOG_MIN,
                                   zstd.SEARCHLENGTH_MIN,
                                   zstd.TARGETLENGTH_MIN,
                                   zstd.STRATEGY_FAST)

        zstd.CompressionParameters(zstd.WINDOWLOG_MAX,
                                   zstd.CHAINLOG_MAX,
                                   zstd.HASHLOG_MAX,
                                   zstd.SEARCHLOG_MAX,
                                   zstd.SEARCHLENGTH_MAX,
                                   zstd.TARGETLENGTH_MAX,
                                   zstd.STRATEGY_BTOPT)

    def test_get_compression_parameters(self):
        p = zstd.get_compression_parameters(1)
        self.assertIsInstance(p, zstd.CompressionParameters)

        self.assertEqual(p.window_log, 19)

    def test_members(self):
        p = zstd.CompressionParameters(10, 6, 7, 4, 5, 8, 1)
        self.assertEqual(p.window_log, 10)
        self.assertEqual(p.chain_log, 6)
        self.assertEqual(p.hash_log, 7)
        self.assertEqual(p.search_log, 4)
        self.assertEqual(p.search_length, 5)
        self.assertEqual(p.target_length, 8)
        self.assertEqual(p.strategy, 1)


@make_cffi
class TestFrameParameters(unittest.TestCase):
    def test_invalid_type(self):
        with self.assertRaises(TypeError):
            zstd.get_frame_parameters(None)

        with self.assertRaises(TypeError):
            zstd.get_frame_parameters(u'foobarbaz')

    def test_invalid_input_sizes(self):
        with self.assertRaisesRegexp(zstd.ZstdError, 'not enough data for frame'):
            zstd.get_frame_parameters(b'')

        with self.assertRaisesRegexp(zstd.ZstdError, 'not enough data for frame'):
            zstd.get_frame_parameters(zstd.FRAME_HEADER)

    def test_invalid_frame(self):
        with self.assertRaisesRegexp(zstd.ZstdError, 'Unknown frame descriptor'):
            zstd.get_frame_parameters(b'foobarbaz')

    def test_attributes(self):
        params = zstd.get_frame_parameters(zstd.FRAME_HEADER + b'\x00\x00')
        self.assertEqual(params.content_size, 0)
        self.assertEqual(params.window_size, 1024)
        self.assertEqual(params.dict_id, 0)
        self.assertFalse(params.has_checksum)

        # Lowest 2 bits indicate a dictionary and length. Here, the dict id is 1 byte.
        params = zstd.get_frame_parameters(zstd.FRAME_HEADER + b'\x01\x00\xff')
        self.assertEqual(params.content_size, 0)
        self.assertEqual(params.window_size, 1024)
        self.assertEqual(params.dict_id, 255)
        self.assertFalse(params.has_checksum)

        # Lowest 3rd bit indicates if checksum is present.
        params = zstd.get_frame_parameters(zstd.FRAME_HEADER + b'\x04\x00')
        self.assertEqual(params.content_size, 0)
        self.assertEqual(params.window_size, 1024)
        self.assertEqual(params.dict_id, 0)
        self.assertTrue(params.has_checksum)

        # Upper 2 bits indicate content size.
        params = zstd.get_frame_parameters(zstd.FRAME_HEADER + b'\x40\x00\xff\x00')
        self.assertEqual(params.content_size, 511)
        self.assertEqual(params.window_size, 1024)
        self.assertEqual(params.dict_id, 0)
        self.assertFalse(params.has_checksum)

        # Window descriptor is 2nd byte after frame header.
        params = zstd.get_frame_parameters(zstd.FRAME_HEADER + b'\x00\x40')
        self.assertEqual(params.content_size, 0)
        self.assertEqual(params.window_size, 262144)
        self.assertEqual(params.dict_id, 0)
        self.assertFalse(params.has_checksum)

        # Set multiple things.
        params = zstd.get_frame_parameters(zstd.FRAME_HEADER + b'\x45\x40\x0f\x10\x00')
        self.assertEqual(params.content_size, 272)
        self.assertEqual(params.window_size, 262144)
        self.assertEqual(params.dict_id, 15)
        self.assertTrue(params.has_checksum)


if hypothesis:
    s_windowlog = strategies.integers(min_value=zstd.WINDOWLOG_MIN,
                                      max_value=zstd.WINDOWLOG_MAX)
    s_chainlog = strategies.integers(min_value=zstd.CHAINLOG_MIN,
                                     max_value=zstd.CHAINLOG_MAX)
    s_hashlog = strategies.integers(min_value=zstd.HASHLOG_MIN,
                                    max_value=zstd.HASHLOG_MAX)
    s_searchlog = strategies.integers(min_value=zstd.SEARCHLOG_MIN,
                                      max_value=zstd.SEARCHLOG_MAX)
    s_searchlength = strategies.integers(min_value=zstd.SEARCHLENGTH_MIN,
                                         max_value=zstd.SEARCHLENGTH_MAX)
    s_targetlength = strategies.integers(min_value=zstd.TARGETLENGTH_MIN,
                                         max_value=zstd.TARGETLENGTH_MAX)
    s_strategy = strategies.sampled_from((zstd.STRATEGY_FAST,
                                          zstd.STRATEGY_DFAST,
                                          zstd.STRATEGY_GREEDY,
                                          zstd.STRATEGY_LAZY,
                                          zstd.STRATEGY_LAZY2,
                                          zstd.STRATEGY_BTLAZY2,
                                          zstd.STRATEGY_BTOPT))


    @make_cffi
    class TestCompressionParametersHypothesis(unittest.TestCase):
        @hypothesis.given(s_windowlog, s_chainlog, s_hashlog, s_searchlog,
                          s_searchlength, s_targetlength, s_strategy)
        def test_valid_init(self, windowlog, chainlog, hashlog, searchlog,
                            searchlength, targetlength, strategy):
            p = zstd.CompressionParameters(windowlog, chainlog, hashlog,
                                           searchlog, searchlength,
                                           targetlength, strategy)

            # Verify we can instantiate a compressor with the supplied values.
            # ZSTD_checkCParams moves the goal posts on us from what's advertised
            # in the constants. So move along with them.
            if searchlength == zstd.SEARCHLENGTH_MIN and strategy in (zstd.STRATEGY_FAST, zstd.STRATEGY_GREEDY):
                searchlength += 1
                p = zstd.CompressionParameters(windowlog, chainlog, hashlog,
                                searchlog, searchlength,
                                targetlength, strategy)
            elif searchlength == zstd.SEARCHLENGTH_MAX and strategy != zstd.STRATEGY_FAST:
                searchlength -= 1
                p = zstd.CompressionParameters(windowlog, chainlog, hashlog,
                                searchlog, searchlength,
                                targetlength, strategy)

            cctx = zstd.ZstdCompressor(compression_params=p)
            with cctx.write_to(io.BytesIO()):
                pass

        @hypothesis.given(s_windowlog, s_chainlog, s_hashlog, s_searchlog,
                          s_searchlength, s_targetlength, s_strategy)
        def test_estimate_compression_context_size(self, windowlog, chainlog,
                                                   hashlog, searchlog,
                                                   searchlength, targetlength,
                                                   strategy):
            p = zstd.CompressionParameters(windowlog, chainlog, hashlog,
                                searchlog, searchlength,
                                targetlength, strategy)
            size = zstd.estimate_compression_context_size(p)