easy_install.py 文件源码

def extract_wininst_cfg(dist_filename):
    """Extract configuration data from a bdist_wininst .exe

    Returns a ConfigParser.RawConfigParser, or None
    """
    f = open(dist_filename, 'rb')
    try:
        endrec = zipfile._EndRecData(f)
        if endrec is None:
            return None

        prepended = (endrec[9] - endrec[5]) - endrec[6]
        if prepended < 12:  # no wininst data here
            return None
        f.seek(prepended - 12)

        from setuptools.compat import StringIO, ConfigParser
        import struct

        tag, cfglen, bmlen = struct.unpack("<iii", f.read(12))
        if tag not in (0x1234567A, 0x1234567B):
            return None  # not a valid tag

        f.seek(prepended - (12 + cfglen))
        cfg = ConfigParser.RawConfigParser(
            {'version': '', 'target_version': ''})
        try:
            part = f.read(cfglen)
            # Read up to the first null byte.
            config = part.split(b'\0', 1)[0]
            # Now the config is in bytes, but for RawConfigParser, it should
            #  be text, so decode it.
            config = config.decode(sys.getfilesystemencoding())
            cfg.readfp(StringIO(config))
        except ConfigParser.Error:
            return None
        if not cfg.has_section('metadata') or not cfg.has_section('Setup'):
            return None
        return cfg

    finally:
        f.close()