design patterns - Non-OS Specific FD(File Descriptor) for C/C++ -
linux treated file, network socket. but, windows not. , common files , network sockets treated "fd". if code should not rely on operating system, how should write?
i think below..
#ifndef invalid_socket #define invalid_socket (-1) #endif class descriptor { private: int m_fd; public: descriptor() : m_fd(invalid_socket) { } virtual ~descriptor() { this->close(); } virtual bool isvalid(); virtual bool close() = 0; virtual int getno() { return m_fd; } }; enum elistenflags { e_listen_read = 1, e_listen_write = 2, e_listen_error = 4, e_listen_nonblock = 8 }; class asyncdescriptor : public descriptor { // epoll (for linux) or iocp (for windows) or select, poll... public: virtual bool listen(descriptor* pdesc, int listenflags) = 0; virtual bool dizzy(descriptor* pdesc, int dizzyflags) = 0; virtual bool wait(std::list<descriptor*>& listout) = 0; virtual bool list(std::list<descriptor*>& listout) = 0; virtual bool getflags(descriptor* pdesc, int* flagoutput) = 0; }; class socketdescriptor : public descriptor { // omitted....... }; // details omitted below ... how can implement it???! :(
you cannot (getting non-os specific file descriptor, or portably dealing network sockets without os support). file descriptors & network sockets operating system specific thing (or in posix standard). c standard library (from c99 or c11 standards) not know them. fileno(3) posix 2001 (and in posix 2008).
if coding in c++, might use framework libraries poco or qt (or perhaps boost) wrapping os services (e.g. linux, macosx, windows, android) , providing unified abstractions. if coding in c, consider glib and/or gio (from gnome/gtk).
btw, want multiplexing ability (like poll(2) syscall provides on linux & posix), , operating system specific. consider using event loop library, e.g. libev or libevent (or use event loop facilities qt, poco, gtk or glib)
notice c & c++ different languages, , both can exist on implementations without networking facilities (e.g. computers without network abilities, embedded systems, etc...).
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