dulwich/dulwich/tests/compat/test_pack.py

# test_pack.py -- Compatibility tests for git packs.
# Copyright (C) 2010 Google, Inc.
#
# Dulwich is dual-licensed under the Apache License, Version 2.0 and the GNU
# General Public License as public by the Free Software Foundation; version 2.0
# or (at your option) any later version. You can redistribute it and/or
# modify it under the terms of either of these two licenses.
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# You should have received a copy of the licenses; if not, see
# <http://www.gnu.org/licenses/> for a copy of the GNU General Public License
# and <http://www.apache.org/licenses/LICENSE-2.0> for a copy of the Apache
# License, Version 2.0.
#

"""Compatibility tests for git packs."""


import binascii
import os
import re
import shutil
import tempfile

from dulwich.pack import (
    write_pack,
    )
from dulwich.objects import (
    Blob,
    )
from dulwich.tests import (
    SkipTest,
    )
from dulwich.tests.test_pack import (
    a_sha,
    pack1_sha,
    PackTests,
    )
from dulwich.tests.compat.utils import (
    require_git_version,
    run_git_or_fail,
    )

_NON_DELTA_RE = re.compile(b'non delta: (?P<non_delta>\\d+) objects')


def _git_verify_pack_object_list(output):
    pack_shas = set()
    for line in output.splitlines():
        sha = line[:40]
        try:
            binascii.unhexlify(sha)
        except (TypeError, binascii.Error):
            continue  # non-sha line
        pack_shas.add(sha)
    return pack_shas


class TestPack(PackTests):
    """Compatibility tests for reading and writing pack files."""

    def setUp(self):
        require_git_version((1, 5, 0))
        super(TestPack, self).setUp()
        self._tempdir = tempfile.mkdtemp()
        self.addCleanup(shutil.rmtree, self._tempdir)

    def test_copy(self):
        with self.get_pack(pack1_sha) as origpack:
            self.assertSucceeds(origpack.index.check)
            pack_path = os.path.join(self._tempdir, "Elch")
            write_pack(pack_path, origpack.pack_tuples())
            output = run_git_or_fail(['verify-pack', '-v', pack_path])
            orig_shas = set(o.id for o in origpack.iterobjects())
            self.assertEqual(orig_shas, _git_verify_pack_object_list(output))

    def test_deltas_work(self):
        with self.get_pack(pack1_sha) as orig_pack:
            orig_blob = orig_pack[a_sha]
            new_blob = Blob()
            new_blob.data = orig_blob.data + b'x'
            all_to_pack = list(orig_pack.pack_tuples()) + [(new_blob, None)]
        pack_path = os.path.join(self._tempdir, 'pack_with_deltas')
        write_pack(pack_path, all_to_pack, deltify=True)
        output = run_git_or_fail(['verify-pack', '-v', pack_path])
        self.assertEqual(set(x[0].id for x in all_to_pack),
                         _git_verify_pack_object_list(output))
        # We specifically made a new blob that should be a delta
        # against the blob a_sha, so make sure we really got only 3
        # non-delta objects:
        got_non_delta = int(_NON_DELTA_RE.search(output).group('non_delta'))
        self.assertEqual(
            3, got_non_delta,
            'Expected 3 non-delta objects, got %d' % got_non_delta)

    def test_delta_medium_object(self):
        # This tests an object set that will have a copy operation
        # 2**20 in size.
        with self.get_pack(pack1_sha) as orig_pack:
            orig_blob = orig_pack[a_sha]
            new_blob = Blob()
            new_blob.data = orig_blob.data + (b'x' * 2 ** 20)
            new_blob_2 = Blob()
            new_blob_2.data = new_blob.data + b'y'
            all_to_pack = list(orig_pack.pack_tuples()) + [(new_blob, None),
                                                           (new_blob_2, None)]
        pack_path = os.path.join(self._tempdir, 'pack_with_deltas')
        write_pack(pack_path, all_to_pack, deltify=True)
        output = run_git_or_fail(['verify-pack', '-v', pack_path])
        self.assertEqual(set(x[0].id for x in all_to_pack),
                         _git_verify_pack_object_list(output))
        # We specifically made a new blob that should be a delta
        # against the blob a_sha, so make sure we really got only 3
        # non-delta objects:
        got_non_delta = int(_NON_DELTA_RE.search(output).group('non_delta'))
        self.assertEqual(
            3, got_non_delta,
            'Expected 3 non-delta objects, got %d' % got_non_delta)
        # We expect one object to have a delta chain length of two
        # (new_blob_2), so let's verify that actually happens:
        self.assertIn(b'chain length = 2', output)

    # This test is SUPER slow: over 80 seconds on a 2012-era
    # laptop. This is because SequenceMatcher is worst-case quadratic
    # on the input size. It's impractical to produce deltas for
    # objects this large, but it's still worth doing the right thing
    # when it happens.
    def test_delta_large_object(self):
        # This tests an object set that will have a copy operation
        # 2**25 in size. This is a copy large enough that it requires
        # two copy operations in git's binary delta format.
        raise SkipTest('skipping slow, large test')
        with self.get_pack(pack1_sha) as orig_pack:
            new_blob = Blob()
            new_blob.data = 'big blob' + ('x' * 2 ** 25)
            new_blob_2 = Blob()
            new_blob_2.data = new_blob.data + 'y'
            all_to_pack = list(orig_pack.pack_tuples()) + [(new_blob, None),
                                                           (new_blob_2, None)]
        pack_path = os.path.join(self._tempdir, "pack_with_deltas")
        write_pack(pack_path, all_to_pack, deltify=True)
        output = run_git_or_fail(['verify-pack', '-v', pack_path])
        self.assertEqual(set(x[0].id for x in all_to_pack),
                         _git_verify_pack_object_list(output))
        # We specifically made a new blob that should be a delta
        # against the blob a_sha, so make sure we really got only 4
        # non-delta objects:
        got_non_delta = int(_NON_DELTA_RE.search(output).group('non_delta'))
        self.assertEqual(
            4, got_non_delta,
            'Expected 4 non-delta objects, got %d' % got_non_delta)