rpm2cpio.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Lightweight RPM to CPIO converter.
# Copyright © 2008-2013 Rudá Moura
#

'''Extract cpio archive from RPM package.

rpm2cpio converts the RPM on standard input or first parameter to a CPIO archive on standard output.

Usage:
rpm2cpio < adjtimex-1.20-2.1.i386.rpm  | cpio -it
./sbin/adjtimex
./usr/share/doc/adjtimex-1.20
./usr/share/doc/adjtimex-1.20/COPYING
./usr/share/doc/adjtimex-1.20/COPYRIGHT
./usr/share/doc/adjtimex-1.20/README
./usr/share/man/man8/adjtimex.8.gz
133 blocks
'''

import sys
import StringIO
import gzip
import subprocess

try:
    import lzma
except ImportError:
    HAS_LZMA_MODULE = False
else:
    HAS_LZMA_MODULE = True

RPM_MAGIC = '\xed\xab\xee\xdb'
GZIP_MAGIC = '\x1f\x8b'
XZ_MAGIC = '\xfd7zXZ\x00'

def gzip_decompress(data):
    gzstream = StringIO.StringIO(data)
    gzipper = gzip.GzipFile(fileobj=gzstream)
    data = gzipper.read()
    return data

def xz_decompress(data):
    if HAS_LZMA_MODULE:
        return lzma.decompress(data)
    unxz = subprocess.Popen(['unxz'],
                            stdin=subprocess.PIPE,
                            stdout=subprocess.PIPE)
    data = unxz.communicate(input=data)[0]
    return data

def rpm2cpio(stream_in=sys.stdin, stream_out=sys.stdout):
    lead = stream_in.read(96)
    if lead[0:4] != RPM_MAGIC:
        raise IOError, 'the input is not a RPM package'
    data = stream_in.read()
    decompress = None
    idx = data.find(XZ_MAGIC)
    if idx != -1:
        decompress = xz_decompress
        pos = idx
    idx = data.find(GZIP_MAGIC)
    if idx != -1 and decompress is None:
        decompress = gzip_decompress
        pos = idx
    if decompress is None:
        raise IOError, 'could not find compressed cpio archive'
    data = decompress(data[pos:])
    stream_out.write(data)

if __name__ == '__main__':
    if sys.argv[1:]:
        try:
            fin = open(sys.argv[1])
            rpm2cpio(fin)
            fin.close()
        except IOError, e:
            print 'Error:', sys.argv[1], e
    else:
        try:
            rpm2cpio()
        except IOError, e:
            print 'Error:', e