This is so we can avoid linking utilities with socket libraries (see
commit 8b778634).
When using sockets, we need to replace close(), because Windows'
close() can't cope with socket file descriptors. But replacing it
always would pull in the socket stuff again. Define close() to call
function pointer w32_close_function, which is initially _close.
Rename posix_close() to w32_close_maybe_socket(). Make new
w32_socket_init() put it in w32_close_function.
Same for read() and write(): define read(), write() to call function
pointers w32_read_function, w32_write_function, initially _read(),
_write(); rename posix_read(), posix_write() to
w32_read_maybe_socket(), w32_write_maybe_socket(), and put them into
w32_read_function, w32_write_function in w32_socket_init().
Also call WSAStartup() there, and use that from loc_NTInit().
WSACleanup() now belongs next to w32_socket_init(). Don't bother,
just drop it, along with loc_NTTerm().
Put the Windows code into new open_locked() instead. It's ugly having
that in file.c, but the fakes are ugly too, and somewhat brittle.
Remove posix_open(), F_SETLK, F_RDLCK, F_WRLCK, struct flock, and
simplify fcntl().
Unlike POSIX sockets, Windows sockets are not file descriptors, but
"OS handles", with a completely separate set of functions.
However, Windows can create a file descriptor for a socket, and return
a file descriptor's underlying handle. Use that instead of wrapping
our own file descriptors around Windows file descriptors and sockets.
Remove the wrapping machinery: MAX_FDS, enum fdmap_io_type, struct
fdmap, fdmap[], nfd, get_fd(), free_fd(), set_fd(), lookup_handle(),
lookup_fd().
Rewrite SOCKET_FUNCTION(), posix_accept(), posix_socket(),
posix_close(), ftruncate(), posix_open(), posix_read(), posix_write(),
fcntl().
Remove FILE_FUNCTION(), posix_fstat(), posix_lseek(),
SHARED_FUNCTION(), and fileno(), because the system's functions now
work fine.
posix_fsync() is used only #ifdef _WIN32, remove it, and call
_commit() directly.
The old code stuffed WSA error codes into errno, which doesn't work.
Use new w32_set_winsock_errno() to retrieve, convert & stuff into
errno. Adapt inet_ntop() to set the WSA error code instead of errno,
so it can use w32_set_winsock_errno().
Move EWOULDBLOCK from sys/socket.h to w32misc.h, and drop unused
ENOTSOCK, EAFNOSUPPORT.
Use SOCKET rather than int in Windows-specific code.
F_GETFL always failed with WSAEINVAL. io_noblocking() always failed
without doing anything. Callers didn't check for failure, and newly
opened sockets remained blocking. But because because
WSAEventSelect() makes sockets non-blocking automatically, they became
non-blocking soon enough to keep things working.
Remove the broken code to query the non-blocking state, and just
return 0. Document why this works.
While there, simplify the F_SETFL case by using ioctlsocket() instead
of WSAIoctl().
posix_shutdown, posix_socket, socklen_t) [_WIN32]: Move socket
related externs to sys/socket.h.
(inet_ntop) [_WIN32]: Move extern to inet.h.
(tcp_listen): Remove the !WIN32 includes and use the revised
sys/socket.h, netinet/in.h, arpa/inet.h and netdb.h.
Move CANT_REACH() and return -1 into a default case.
Removes warnings for MinGW of potential missing cases.
(posix_accept, posix_socket) [_WIN32]: Switch handle to SOCKET
to match Windows call. Cast to an int for translation map.
Remove the extern posix_fileno().
(fileno) [_WIN32]: Replace system fileno() with a function that supports posix
file descriptors. Move #undef fileno to w32misc.h as the system define
is in stdio.h.
(rea) [_WIN32]: Add stdio.h for fileno() extern declaration and add misc.h
to ensure the WIN32 fixes to stdio.h are included.
[_WIN32]: New in.h, inet.h, netdb.h. Windows equivalent for POSIX
includes.
(tcp_connect): Use new include files and inet_ntop().
Allows tcp_connect() to compile when HAVE_GETADDRINFO is enabled.
SO_REUSEADDR code for _WIN32 from tcp_listen() to
posix_setsockopt().
[_WIN32] (posix_open): Switch to _sopen() for _sopen_s() as MinGW
does not support _sopen_s() yet.
[_WIN32] (posix_fd2socket): Fix typo.
