Missing select family of functions

[flaub]

Looks like this belongs either in bsd42 or posix01.

From select(2) of Linux man pages:

/* According to POSIX.1-2001 */
#include <sys/select.h>

/* According to earlier standards */
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

int select(int nfds, fd_set *readfds, fd_set *writefds,
           fd_set *exceptfds, struct timeval *timeout);

void FD_CLR(int fd, fd_set *set);
int  FD_ISSET(int fd, fd_set *set);
void FD_SET(int fd, fd_set *set);
void FD_ZERO(fd_set *set);

From select(2) of BSD System Calls Manual:

     #include <sys/select.h>

     void
     FD_CLR(fd, fd_set *fdset);

     void
     FD_COPY(fd_set *fdset_orig, fd_set *fdset_copy);

     int
     FD_ISSET(fd, fd_set *fdset);

     void
     FD_SET(fd, fd_set *fdset);

     void
     FD_ZERO(fd_set *fdset);

     int
     select(int nfds, fd_set *restrict readfds, fd_set *restrict writefds, fd_set *restrict errorfds, struct timeval *restrict timeout);

And then on Windows, which only works for sockets:

int select(
  _In_    int                  nfds,
  _Inout_ fd_set               *readfds,
  _Inout_ fd_set               *writefds,
  _Inout_ fd_set               *exceptfds,
  _In_    const struct timeval *timeout
);

With FD_CLR, FD_ISSET, FD_SET, and FD_ZERO defined as macros on most (all?) platforms.

[flaub]

With this layer in place, it would be possible to extend the std::net::*Socket API to allow for cancelation of pending I/O operations (recv, recv_from, send, accept, etc). This would fix rust-lang/rust#23272 and mentioned in rust-lang/rfcs#957. The goal here would not be to allow non-blocking I/O in general per-se, but to simply provide a way for users to cleanly cancel blocking calls.

[alexcrichton]

Thanks for the report! Currently we're not trying to track all the missing APIs in liblibc, though, (there are quite a few!). You're more than welcome to add the bindings, however! If you make a PR against the main Rust repo then we can update the submodule here once that's landed.

[flaub]

Ok, I'll take a stab, thanks for the reply :)

[flaub]

I see now that many of the low level functions are actually implemented directly in libstd/sys.

[keepsimple1]

Is select available now in Rust std? I couldn't find it in the current Rust 1.59.