~bzr-pqm/bzr/bzr.dev

# Copyright (C) 2006 by Canonical Ltd

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

"""Tests for tuned_gzip."""

# do not use bzrlib test cases here - this should be suitable for sending

# upstream.

from cStringIO import StringIO

from unittest import TestCase

import zlib

from bzrlib import tuned_gzip

class FakeDecompress(object):

    """A fake decompressor for testing GzipFile."""

    def __init__(self):

        self.unused_data=''

    def decompress(self, buf):

        """Return an empty string as though we are at eof."""

        # note that the zlib module *overwrites* unused data 

        # on writes after EOF.

        self.unused_data = buf

        return ''

class TestFakeDecompress(TestCase):

    """We use a fake decompressor to test GzipFile.

    This class tests the behaviours we want from it.

    """

    def test_decompress(self):

        # decompressing returns no data.

        decompress = FakeDecompress()

        self.assertEqual('', decompress.decompress('0'))

    def test_unused_data(self):

        # after decompressing, we have 1 unused byte.

        # this is normally set by decompressors when they

        # detect the end of a compressed stream.

        decompress = FakeDecompress()

        decompress.decompress('0')

        self.assertEqual('0', decompress.unused_data)

        # decompressing again (when the short read is read)

        # will give us the latest input in the unused_data

        # this is arguably a bug in zlib but ...

        decompress.decompress('1234567')

        self.assertEqual('1234567', decompress.unused_data)

class TestGzip(TestCase):

    def test__read_short_remainder(self):

        # a _read call at the end of a compressed hunk should

        # read more bytes if there is less than 8 bytes (the 

        # gzip trailer) unread.

        stream = StringIO('\0\0\0\0\0\0\0\0')

        myfile = tuned_gzip.GzipFile(fileobj=stream)

        # disable the _new_member check, we are microtesting.

        myfile._new_member = False

        myfile.crc = zlib.crc32('')

        myfile.decompress = FakeDecompress()

        myfile.size = 0

        myfile._read(1)

        # all the data should have been read now

        self.assertEqual('', stream.read())

        # and it should be new member time in the stream.

        self.failUnless(myfile._new_member)