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)
            # part is in bytes, but we need to read up to the first null
            #  byte.
            if sys.version_info >= (2,6):
                null_byte = bytes([0])
            else:
                null_byte = chr(0)
            config = part.split(null_byte, 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()