osdep: add poll shim for macOS

This implements a poll-compatible interface, backed by select on macOS,
suitable for polling on device files - which are not supported by
macOS's implementation of poll. This is a (long-standing) bug in macOS,
so hopefully we can eventually remove this shim.

osdep/polldev.c

@@ -0,0 +1,75 @@
+/*
+ * poll shim that supports device files on macOS.
+ *
+ * This file is part of mpv.
+ *
+ * mpv is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * mpv is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdlib.h>
+#include <poll.h>
+#include <sys/select.h>
+#include <stdio.h>
+
+#include "osdep/polldev.h"
+
+int polldev(struct pollfd fds[], nfds_t nfds, int timeout) {
+#ifdef __APPLE__
+    int maxfd = 0;
+    fd_set readfds, writefds, errorfds;
+    FD_ZERO(&readfds);
+    FD_ZERO(&writefds);
+    FD_ZERO(&errorfds);
+    for (size_t i = 0; i < nfds; ++i) {
+        struct pollfd *fd = &fds[i];
+        if (fd->fd > maxfd) {
+            maxfd = fd->fd;
+        }
+        if ((fd->events & POLLIN)) {
+            FD_SET(fd->fd, &readfds);
+        }
+        if ((fd->events & POLLOUT)) {
+            FD_SET(fd->fd, &writefds);
+        }
+        if ((fd->events & POLLERR)) {
+            FD_SET(fd->fd, &errorfds);
+        }
+    }
+    struct timeval _timeout = {
+        .tv_sec = timeout / 1000,
+        .tv_usec = (timeout % 1000) * 1000
+    };
+    int n = select(maxfd + 1, &readfds, &writefds, &errorfds,
+        timeout != -1 ? &_timeout : NULL);
+    if (n < 0) {
+        return n;
+    }
+    for (size_t i = 0; i < nfds; ++i) {
+        struct pollfd *fd = &fds[i];
+        fd->revents = 0;
+        if (FD_ISSET(fd->fd, &readfds)) {
+            fd->revents |= POLLIN;
+        }
+        if (FD_ISSET(fd->fd, &writefds)) {
+            fd->revents |= POLLOUT;
+        }
+        if (FD_ISSET(fd->fd, &errorfds)) {
+            fd->revents |= POLLERR;
+        }
+    }
+    return n;
+#else
+    return poll(fds, nfds, timeout);
+#endif
+}

osdep/polldev.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include <poll.h>
+
+// Behaves like poll(3) but works for device files on macOS.
+// Only supports POLLIN, POLLOUT, and POLLERR.
+int polldev(struct pollfd fds[], nfds_t nfds, int timeout);

wscript_build.py

@@ -476,6 +476,7 @@ def build(ctx):
         ( "osdep/timer.c" ),
         ( timer_c ),
         ( "osdep/threads.c" ),
+        ( "osdep/polldev.c",                     "posix" ),
 
         ( "osdep/ar/HIDRemote.m",                "apple-remote" ),
         ( "osdep/macosx_application.m",          "cocoa" ),