uint8_t what[] = {0xA8, 0x78, 0x0A, 0x21, 0x6A} ; uint8_t repl[] = {0xE8, 0x78, 0x0A, 0x21, 0x6A};
    size_t count;
    file=fopen("fw","rb");
    fileout=fopen("fw_changed","wb");
    count = replace(file, fileout, what, repl, sizeof(what));