libowfat/io/io_wantwrite.c

#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include "io_internal.h"
#ifdef HAVE_KQUEUE
#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#endif
#ifdef HAVE_EPOLL
#include <inttypes.h>
#include <sys/epoll.h>
#include <byte.h>
#endif
#ifdef HAVE_SIGIO
#include <sys/poll.h>
#endif
#ifdef HAVE_DEVPOLL
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/devpoll.h>
#endif

#ifdef DEBUG
#include <assert.h>
#else
#define assert(x)
#endif

/* IDEA: if someone calls io_dontwantwrite, do not do the syscall to
 * tell the kernel about it.  Only when a write event comes in and the
 * user has told us he does not want them, THEN tell the kernel we are
 * not interested.  In the typical protocol case of "write request, read
 * reply", this should save a lot of syscalls.
 * Now, if someone calls io_wantwrite, we might be in the situation that
 * canwrite is already set.  In that case, just enqueue the fd. */

void io_wantwrite_really(int64 d, io_entry* e) {
  int newfd;
  assert(!e->kernelwantwrite);	/* we should not be here if we already told the kernel we want to write */
  newfd=(!e->kernelwantread);
  io_wanted_fds+=newfd;
#ifdef HAVE_EPOLL
  if (io_waitmode==EPOLL) {
    struct epoll_event x;
    byte_zero(&x,sizeof(x));	// to shut up valgrind
    x.events=EPOLLOUT;
    if (e->kernelwantread) x.events|=EPOLLIN;
    x.data.fd=d;
    epoll_ctl(io_master,e->kernelwantread?EPOLL_CTL_MOD:EPOLL_CTL_ADD,d,&x);
  }
#endif
#ifdef HAVE_KQUEUE
  if (io_waitmode==KQUEUE) {
    struct kevent kev;
    struct timespec ts;
    EV_SET(&kev, d, EVFILT_WRITE, EV_ADD|EV_ENABLE, 0, 0, 0);
    ts.tv_sec=0; ts.tv_nsec=0;
    kevent(io_master,&kev,1,0,0,&ts);
  }
#endif
#ifdef HAVE_DEVPOLL
  if (io_waitmode==DEVPOLL) {
    struct pollfd x;
    x.fd=d;
    x.events=POLLOUT;
    if (e->wantread) x.events|=POLLIN;
    write(io_master,&x,sizeof(x));
  }
#endif
#ifdef HAVE_SIGIO
  if (io_waitmode==_SIGIO) {
    struct pollfd p;
    p.fd=d;
    p.events=POLLOUT;
    switch (poll(&p,1,0)) {
    case 1: e->canwrite=1; break;
    case 0: e->canwrite=0; break;
    case -1: return;
    }
    if (e->canwrite) {
      debug_printf(("io_wantwrite: enqueueing %lld in normal write queue before %ld\n",d,first_readable));
      e->next_write=first_writeable;
      first_writeable=d;
    }
  }
#endif
#ifdef __MINGW32__
  printf("e->wantwrite == %d\n",e->wantwrite);
  if (!e->wantwrite) {
    e->next_write=first_writeable;
    e->canwrite=1;
    first_writeable=d;
    printf("queueing write, setting first_writeable to %lld\n",d);
  }
#endif
  e->wantwrite=1;
  e->kernelwantwrite=1;
}

void io_wantwrite(int64 d) {
  io_entry* e=array_get(&io_fds,sizeof(io_entry),d);
  if (!e) return;
  if (e->wantwrite && e->kernelwantwrite) return;
  if (e->canwrite) {
    e->next_write=first_writeable;
    first_writeable=d;
    e->wantwrite=1;
    return;
  }
  /* the harder case: do as before */
  if (!e->kernelwantwrite) io_wantwrite_really(d, e); else e->wantwrite=1;
}