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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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from __future__ import absolute_import
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from cStringIO import StringIO
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# make GzipFile faster:
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from gzip import U32, LOWU32, FEXTRA, FCOMMENT, FNAME, FHCRC
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from gzip import FEXTRA, FCOMMENT, FNAME, FHCRC
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# we want a \n preserved, break on \n only splitlines.
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__all__ = ["GzipFile"]
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from bzrlib import symbol_versioning
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__all__ = ["GzipFile", "bytes_to_gzip"]
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"""Return i as an unsigned integer, assuming it fits in 32 bits.
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If it's >= 2GB when viewed as a 32-bit unsigned int, return a long.
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"""Return the low-order 32 bits of an int, as a non-negative int."""
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return i & 0xFFFFFFFFL
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def bytes_to_gzip(bytes, 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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"""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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"""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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'\037\213' # self.fileobj.write('\037\213') # magic header
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'\010' # self.fileobj.write('\010') # compression method
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# fname = self.filename[:-3]
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'\x00' # self.fileobj.write(chr(flags))
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'\0\0\0\0' # write32u(self.fileobj, long(time.time()))
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'\002' # self.fileobj.write('\002')
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'\377' # self.fileobj.write('\377')
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'' # self.fileobj.write(fname + '\000')
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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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crc = crc32(chunk, crc)
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total_len += len(chunk)
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zbytes = compress.compress(chunk)
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result.append(compress.flush())
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# size may exceed 2GB, or even 4GB
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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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class GzipFile(gzip.GzipFile):
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Yes, its only 1.6 seconds, but they add up.
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def _add_read_data(self, data):
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# temp var for len(data) and switch to +='s.
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self.crc = zlib.crc32(data, self.crc)
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self.extrasize += len_data
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def __init__(self, *args, **kwargs):
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symbol_versioning.warn(
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symbol_versioning.deprecated_in((2, 3, 0))
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% 'bzrlib.tuned_gzip.GzipFile',
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DeprecationWarning, stacklevel=2)
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gzip.GzipFile.__init__(self, *args, **kwargs)
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if sys.version_info >= (2, 7, 4):
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def _add_read_data(self, data):
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# temp var for len(data) and switch to +='s.
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self.crc = zlib.crc32(data, self.crc) & 0xffffffffL
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offset = self.offset - self.extrastart
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self.extrabuf = self.extrabuf[offset:] + data
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self.extrasize = self.extrasize + len_data
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self.extrastart = self.offset
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self.size = self.size + len_data
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def _add_read_data(self, data):
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# temp var for len(data) and switch to +='s.
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self.crc = zlib.crc32(data, self.crc)
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self.extrabuf += data
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self.extrasize += len_data
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self.size += len_data
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def _write_gzip_header(self):
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"""A tuned version of gzip._write_gzip_header
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We have some extra constrains that plain Gzip does not.
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1) We want to write the whole blob at once. rather than multiple
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1) We want to write the whole blob at once. rather than multiple
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calls to fileobj.write().
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2) We never have a filename
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3) We don't care about the time
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'' # self.fileobj.write(fname + '\000')
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def _read(self, size=1024):
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# various optimisations:
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# reduces lsprof count from 2500 to
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# 8337 calls in 1272, 365 internal
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if self.fileobj is None:
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raise EOFError, "Reached EOF"
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# If the _new_member flag is set, we have to
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# jump to the next member, if there is one.
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# First, check if we're at the end of the file;
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# if so, it's time to stop; no more members to read.
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next_header_bytes = self.fileobj.read(10)
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if next_header_bytes == '':
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if sys.version_info < (2, 7, 4):
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def _read(self, size=1024):
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# various optimisations:
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# reduces lsprof count from 2500 to
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# 8337 calls in 1272, 365 internal
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if self.fileobj is None:
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raise EOFError, "Reached EOF"
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self._read_gzip_header(next_header_bytes)
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self.decompress = zlib.decompressobj(-zlib.MAX_WBITS)
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self._new_member = False
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# Read a chunk of data from the file
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buf = self.fileobj.read(size)
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# If the EOF has been reached, flush the decompression object
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# and mark this object as finished.
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self._add_read_data(self.decompress.flush())
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assert len(self.decompress.unused_data) >= 8, "what does flush do?"
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self._gzip_tail = self.decompress.unused_data[0:8]
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# tell the driving read() call we have stuffed all the data
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raise EOFError, 'Reached EOF'
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self._add_read_data(self.decompress.decompress(buf))
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if self.decompress.unused_data != "":
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# Ending case: we've come to the end of a member in the file,
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# so seek back to the start of the data for the next member which
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# is the length of the decompress objects unused data - the first
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# 8 bytes for the end crc and size records.
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# so seek back to the start of the unused data, finish up
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# this member, and read a new gzip header.
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# (The number of bytes to seek back is the length of the unused
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# data, minus 8 because those 8 bytes are part of this member.
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seek_length = len (self.decompress.unused_data) - 8
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# we read too much data
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self.fileobj.seek(-seek_length, 1)
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# If the _new_member flag is set, we have to
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# jump to the next member, if there is one.
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# First, check if we're at the end of the file;
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# if so, it's time to stop; no more members to read.
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next_header_bytes = self.fileobj.read(10)
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if next_header_bytes == '':
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raise EOFError, "Reached EOF"
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self._read_gzip_header(next_header_bytes)
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self.decompress = zlib.decompressobj(-zlib.MAX_WBITS)
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self._new_member = False
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# Read a chunk of data from the file
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buf = self.fileobj.read(size)
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# If the EOF has been reached, flush the decompression object
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# and mark this object as finished.
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self._add_read_data(self.decompress.flush())
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if len(self.decompress.unused_data) < 8:
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raise AssertionError("what does flush do?")
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self._gzip_tail = self.decompress.unused_data[0:8]
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elif seek_length < 0:
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# we haven't read enough to check the checksum.
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assert -8 < seek_length, "too great a seek."
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buf = self.fileobj.read(-seek_length)
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self._gzip_tail = self.decompress.unused_data + buf
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self._gzip_tail = self.decompress.unused_data
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# Check the CRC and file size, and set the flag so we read
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# a new member on the next call
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self._new_member = True
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"""tuned to reduce function calls and eliminate file seeking:
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reduces lsprof count from 800 to 288
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avoid U32 call by using struct format L
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# We've read to the end of the file, so we should have 8 bytes of
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# unused data in the decompressor. If we don't, there is a corrupt file.
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# We use these 8 bytes to calculate the CRC and the recorded file size.
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# We then check the that the computed CRC and size of the
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# uncompressed data matches the stored values. Note that the size
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# stored is the true file size mod 2**32.
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assert len(self._gzip_tail) == 8, "gzip trailer is incorrect length."
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crc32, isize = struct.unpack("<LL", self._gzip_tail)
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# note that isize is unsigned - it can exceed 2GB
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if crc32 != U32(self.crc):
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raise IOError, "CRC check failed %d %d" % (crc32, U32(self.crc))
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elif isize != LOWU32(self.size):
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raise IOError, "Incorrect length of data produced"
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# tell the driving read() call we have stuffed all the data
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raise EOFError, 'Reached EOF'
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self._add_read_data(self.decompress.decompress(buf))
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if self.decompress.unused_data != "":
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# Ending case: we've come to the end of a member in the file,
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# so seek back to the start of the data for the next member
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# which is the length of the decompress objects unused data -
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# the first 8 bytes for the end crc and size records.
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# so seek back to the start of the unused data, finish up
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# this member, and read a new gzip header.
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# (The number of bytes to seek back is the length of the unused
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# data, minus 8 because those 8 bytes are part of this member.
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seek_length = len (self.decompress.unused_data) - 8
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# we read too much data
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self.fileobj.seek(-seek_length, 1)
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self._gzip_tail = self.decompress.unused_data[0:8]
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elif seek_length < 0:
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# we haven't read enough to check the checksum.
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if not (-8 < seek_length):
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raise AssertionError("too great a seek")
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buf = self.fileobj.read(-seek_length)
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self._gzip_tail = self.decompress.unused_data + buf
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self._gzip_tail = self.decompress.unused_data
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# Check the CRC and file size, and set the flag so we read
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# a new member on the next call
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self._new_member = True
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"""tuned to reduce function calls and eliminate file seeking:
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reduces lsprof count from 800 to 288
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avoid U32 call by using struct format L
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# We've read to the end of the file, so we should have 8 bytes of
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# unused data in the decompressor. If we don't, there is a corrupt
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# file. We use these 8 bytes to calculate the CRC and the recorded
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# file size. We then check the that the computed CRC and size of
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# the uncompressed data matches the stored values. Note that the
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# size stored is the true file size mod 2**32.
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if not (len(self._gzip_tail) == 8):
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raise AssertionError("gzip trailer is incorrect length.")
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crc32, isize = struct.unpack("<LL", self._gzip_tail)
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# note that isize is unsigned - it can exceed 2GB
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if crc32 != U32(self.crc):
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raise IOError, "CRC check failed %d %d" % (crc32, U32(self.crc))
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elif isize != LOWU32(self.size):
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raise IOError, "Incorrect length of data produced"
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def _read_gzip_header(self, bytes=None):
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"""Supply bytes if the minimum header size is already read.
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:param bytes: 10 bytes of header data.
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"""starting cost: 300 in 3998
added
removed
bzrlib/tuned_gzip.py
