/brz/remove-bazaar

# Copyright (C) 2006-2011 Canonical Ltd

# Written by Robert Collins <robert.collins@canonical.com>

#

# 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

"""Legacy breezy specific gzip tunings."""

import struct

import zlib

__all__ = ["chunks_to_gzip"]

def U32(i):

    """Return i as an unsigned integer, assuming it fits in 32 bits.

    If it's >= 2GB when viewed as a 32-bit unsigned int, return a long.

    """

    if i < 0:

        i += 1 << 32

    return i

def LOWU32(i):

    """Return the low-order 32 bits of an int, as a non-negative int."""

    return i & 0xFFFFFFFF

def chunks_to_gzip(chunks, factory=zlib.compressobj,

                   level=zlib.Z_DEFAULT_COMPRESSION, method=zlib.DEFLATED,

                   width=-zlib.MAX_WBITS, mem=zlib.DEF_MEM_LEVEL,

                   crc32=zlib.crc32):

    """Create a gzip file containing chunks and return its content.

    :param chunks: An iterable of strings. Each string can have arbitrary

        layout.

    """

    result = [

        b'\037\213'  # self.fileobj.write('\037\213')  # magic header

        b'\010'      # self.fileobj.write('\010')      # compression method

                     # fname = self.filename[:-3]

                     # flags = 0

                     # if fname:

                     #     flags = FNAME

        b'\x00'      # self.fileobj.write(chr(flags))

        b'\0\0\0\0'  # write32u(self.fileobj, long(time.time()))

        b'\002'      # self.fileobj.write('\002')

        b'\377'      # self.fileobj.write('\377')

                     # if fname:

        b''  # self.fileobj.write(fname + '\000')

        ]

    # using a compressobj avoids a small header and trailer that the compress()

    # utility function adds.

    compress = factory(level, method, width, mem, 0)

    crc = 0

    total_len = 0

    for chunk in chunks:

        crc = crc32(chunk, crc)

        total_len += len(chunk)

        zbytes = compress.compress(chunk)

        if zbytes:

            result.append(zbytes)

    result.append(compress.flush())

    # size may exceed 2GB, or even 4GB

    result.append(struct.pack("<LL", LOWU32(crc), LOWU32(total_len)))

    return result