X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fnetwork%2Fpoll.c;h=f6f9050effd9df1f7c1ffd4b4f2d0b293295d2de;hb=77a5fef919c5e2668991b9ae6e3e44a9901835e8;hp=b50cb835d83ee2a05d9c715a5cf94acaf10a0387;hpb=057e689f92d55d9b3e5889a18e749b62f1fe3924;p=vlc

diff --git a/src/network/poll.c b/src/network/poll.c
index b50cb835d8..f6f9050eff 100644
--- a/src/network/poll.c
+++ b/src/network/poll.c
@@ -21,20 +21,32 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  *****************************************************************************/
 
-#include <vlc/vlc.h>
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
 
-#ifndef HAVE_POLL
+#include <vlc_common.h>
+#include <vlc_network.h>
+
+#ifdef HAVE_POLL
+struct pollfd;
+
+int vlc_poll (struct pollfd *fds, unsigned nfds, int timeout)
+{
+    (void)fds; (void)nfds; (void)timeout;
+    abort ();
+}
+#else /* !HAVE_POLL */
 #include <string.h>
 #include <stdlib.h>
 #include <vlc_network.h>
 
-int poll (struct pollfd *fds, unsigned nfds, int timeout)
+int vlc_poll (struct pollfd *fds, unsigned nfds, int timeout)
 {
     fd_set rdset, wrset, exset;
     struct timeval tv = { 0, 0 };
     int val = -1;
 
-
     FD_ZERO (&rdset);
     FD_ZERO (&wrset);
     FD_ZERO (&exset);
@@ -44,8 +56,26 @@ int poll (struct pollfd *fds, unsigned nfds, int timeout)
         if (val < fd)
             val = fd;
 
-        /* I assume the OS has a solution select overflow if it does not have
-         * poll(). If it did not, we are screwed anyway. */
+        /* With POSIX, FD_SET & FD_ISSET are not defined if fd is negative or
+	 * bigger or equal than FD_SETSIZE. That is one of the reasons why VLC
+	 * uses poll() rather than select(). Most POSIX systems implement
+	 * fd_set has a bit field with no sanity checks. This is especially bad
+	 * on systems (such as BSD) that have no process open files limit by
+	 * default, such that it is quite feasible to get fd >= FD_SETSIZE.
+	 * The next instructions will result in a buffer overflow if run on
+	 * a POSIX system, and the later FD_ISSET will do undefined memory
+	 * access.
+	 *
+	 * With Winsock, fd_set is a table of integers. This is awfully slow.
+	 * However, FD_SET and FD_ISSET silently and safely discard
+	 * overflows. If it happens we will loose socket events. Note that
+	 * most (if not all) Winsock SOCKET handles are actually bigger than
+	 * FD_SETSIZE in terms of absolute value - they are not POSIX file
+	 * descriptors. From Vista, there is a much nicer WSAPoll(), but Mingw
+	 * is yet to support it.
+	 *
+	 * With BeOS, the situation is unknown (FIXME: document).
+	 */
         if (fds[i].events & POLLIN)
             FD_SET (fd, &rdset);
         if (fds[i].events & POLLOUT)
@@ -61,7 +91,7 @@ int poll (struct pollfd *fds, unsigned nfds, int timeout)
         tv.tv_usec = d.rem * 1000;
     }
 
-    val = select (val + 1, &rdset, &wrset, NULL,
+    val = select (val + 1, &rdset, &wrset, &exset,
                   (timeout >= 0) ? &tv : NULL);
     if (val == -1)
         return -1;