local ZPOS64_T unz64local_SearchCentralDir64()

in zlib/contrib/minizip/unzip.c [383:477]
69 lines of code
26 McCabe index (conditional complexity)

local ZPOS64_T unz64local_SearchCentralDir64(const zlib_filefunc64_32_def* pzlib_filefunc_def,
                                             voidpf filestream) {
    unsigned char* buf;
    ZPOS64_T uSizeFile;
    ZPOS64_T uBackRead;
    ZPOS64_T uMaxBack=0xffff; /* maximum size of global comment */
    ZPOS64_T uPosFound=CENTRALDIRINVALID;
    uLong uL;
                ZPOS64_T relativeOffset;

    if (ZSEEK64(*pzlib_filefunc_def,filestream,0,ZLIB_FILEFUNC_SEEK_END) != 0)
        return CENTRALDIRINVALID;


    uSizeFile = ZTELL64(*pzlib_filefunc_def,filestream);

    if (uMaxBack>uSizeFile)
        uMaxBack = uSizeFile;

    buf = (unsigned char*)ALLOC(BUFREADCOMMENT+4);
    if (buf==NULL)
        return CENTRALDIRINVALID;

    uBackRead = 4;
    while (uBackRead<uMaxBack)
    {
        uLong uReadSize;
        ZPOS64_T uReadPos;
        int i;
        if (uBackRead+BUFREADCOMMENT>uMaxBack)
            uBackRead = uMaxBack;
        else
            uBackRead+=BUFREADCOMMENT;
        uReadPos = uSizeFile-uBackRead ;

        uReadSize = ((BUFREADCOMMENT+4) < (uSizeFile-uReadPos)) ?
                     (BUFREADCOMMENT+4) : (uLong)(uSizeFile-uReadPos);
        if (ZSEEK64(*pzlib_filefunc_def,filestream,uReadPos,ZLIB_FILEFUNC_SEEK_SET)!=0)
            break;

        if (ZREAD64(*pzlib_filefunc_def,filestream,buf,uReadSize)!=uReadSize)
            break;

        for (i=(int)uReadSize-3; (i--)>0;)
            if (((*(buf+i))==0x50) && ((*(buf+i+1))==0x4b) &&
                ((*(buf+i+2))==0x06) && ((*(buf+i+3))==0x07))
            {
                uPosFound = uReadPos+(unsigned)i;
                break;
            }

        if (uPosFound!=CENTRALDIRINVALID)
            break;
    }
    free(buf);
    if (uPosFound == CENTRALDIRINVALID)
        return CENTRALDIRINVALID;

    /* Zip64 end of central directory locator */
    if (ZSEEK64(*pzlib_filefunc_def,filestream, uPosFound,ZLIB_FILEFUNC_SEEK_SET)!=0)
        return CENTRALDIRINVALID;

    /* the signature, already checked */
    if (unz64local_getLong(pzlib_filefunc_def,filestream,&uL)!=UNZ_OK)
        return CENTRALDIRINVALID;

    /* number of the disk with the start of the zip64 end of central directory */
    if (unz64local_getLong(pzlib_filefunc_def,filestream,&uL)!=UNZ_OK)
        return CENTRALDIRINVALID;
    if (uL != 0)
        return CENTRALDIRINVALID;

    /* relative offset of the zip64 end of central directory record */
    if (unz64local_getLong64(pzlib_filefunc_def,filestream,&relativeOffset)!=UNZ_OK)
        return CENTRALDIRINVALID;

    /* total number of disks */
    if (unz64local_getLong(pzlib_filefunc_def,filestream,&uL)!=UNZ_OK)
        return CENTRALDIRINVALID;
    if (uL != 1)
        return CENTRALDIRINVALID;

    /* Goto end of central directory record */
    if (ZSEEK64(*pzlib_filefunc_def,filestream, relativeOffset,ZLIB_FILEFUNC_SEEK_SET)!=0)
        return CENTRALDIRINVALID;

     /* the signature */
    if (unz64local_getLong(pzlib_filefunc_def,filestream,&uL)!=UNZ_OK)
        return CENTRALDIRINVALID;

    if (uL != 0x06064b50)
        return CENTRALDIRINVALID;

    return relativeOffset;
}