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  • Committer: Andrew Bennetts
  • Date: 2009-07-27 05:35:00 UTC
  • mfrom: (4570 +trunk)
  • mto: (4634.6.29 2.0)
  • mto: This revision was merged to the branch mainline in revision 4680.
  • Revision ID: andrew.bennetts@canonical.com-20090727053500-q76zsn2dx33jhmj5
Merge bzr.dev.

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bzrlib/tuned_gzip.py
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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"""Bzrlib specific gzip tunings. We plan to feed these to the upstream gzip."""
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    width=-zlib.MAX_WBITS, mem=zlib.DEF_MEM_LEVEL,
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    crc32=zlib.crc32):
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    """Create a gzip file containing bytes and return its content."""
 
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    return chunks_to_gzip([bytes])
 
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def chunks_to_gzip(chunks, factory=zlib.compressobj,
 
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    level=zlib.Z_DEFAULT_COMPRESSION, method=zlib.DEFLATED,
 
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    width=-zlib.MAX_WBITS, mem=zlib.DEF_MEM_LEVEL,
 
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    crc32=zlib.crc32):
 
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    """Create a gzip file containing chunks and return its content.
 
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    :param chunks: An iterable of strings. Each string can have arbitrary
 
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        layout.
 
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    """
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    result = [
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        '\037\213'  # self.fileobj.write('\037\213')  # magic header
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        '\010'      # self.fileobj.write('\010')      # compression method
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    # using a compressobj avoids a small header and trailer that the compress()
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    # utility function adds.
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    compress = factory(level, method, width, mem, 0)
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    result.append(compress.compress(bytes))
 
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    crc = 0
 
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    total_len = 0
 
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    for chunk in chunks:
 
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        crc = crc32(chunk, crc)
 
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        total_len += len(chunk)
 
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        zbytes = compress.compress(chunk)
 
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        if zbytes:
 
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            result.append(zbytes)
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    result.append(compress.flush())
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    result.append(struct.pack("<L", LOWU32(crc32(bytes))))
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    # size may exceed 2GB, or even 4GB
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    result.append(struct.pack("<L", LOWU32(len(bytes))))
 
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    result.append(struct.pack("<LL", LOWU32(crc), LOWU32(total_len)))
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    return ''.join(result)
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