use poll() instead of select() when available

Signed-off-by: Julien Danjou <julien@danjou.info>

configure.ac

@@ -116,6 +116,8 @@ AC_PREREQ([2.59c], [], [AC_SUBST([htmldir], [m4_ifset([AC_PACKAGE_TARNAME],
 
 XCB_CHECK_DOXYGEN()
 
+AC_CHECK_FUNC(poll, [AC_DEFINE(USE_POLL, 1, [poll() function is available])], )
+
 XCB_EXTENSION(Composite, "yes")
 XCB_EXTENSION(Damage, "yes")
 XCB_EXTENSION(DPMS, "yes")

src/xcb_conn.c

@@ -31,12 +31,16 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <netinet/in.h>
-#include <sys/select.h>
 #include <fcntl.h>
 #include <errno.h>
 
 #include "xcb.h"
 #include "xcbint.h"
+#if USE_POLL
+#include <poll.h>
+#else
+#include <sys/select.h>
+#endif
 
 typedef struct {
     uint8_t  status;
@@ -258,7 +262,11 @@ void _xcb_conn_shutdown(xcb_connection_t *c)
 int _xcb_conn_wait(xcb_connection_t *c, pthread_cond_t *cond, struct iovec **vector, int *count)
 {
     int ret;
+#if USE_POLL
+    struct pollfd fd;
+#else
     fd_set rfds, wfds;
+#endif
 
     /* If the thing I should be doing is already being done, wait for it. */
     if(count ? c->out.writing : c->in.reading)
@@ -267,20 +275,38 @@ int _xcb_conn_wait(xcb_connection_t *c, pthread_cond_t *cond, struct iovec **vec
         return 1;
     }
 
+#if USE_POLL
+    memset(&fd, 0, sizeof(fd));
+    fd.fd = c->fd;
+    fd.events = POLLIN;
+#else
     FD_ZERO(&rfds);
     FD_SET(c->fd, &rfds);
+#endif
     ++c->in.reading;
 
+#if USE_POLL
+    if(count)
+    {
+        fd.events |= POLLOUT;
+        ++c->out.writing;
+    }
+#else
     FD_ZERO(&wfds);
     if(count)
     {
         FD_SET(c->fd, &wfds);
         ++c->out.writing;
     }
+#endif
 
     pthread_mutex_unlock(&c->iolock);
     do {
+#if USE_POLL
+    ret = poll(&fd, 1, -1);
+#else
 	ret = select(c->fd + 1, &rfds, &wfds, 0, 0);
+#endif
     } while (ret == -1 && errno == EINTR);
     if (ret < 0)
     {
@@ -291,10 +317,18 @@ int _xcb_conn_wait(xcb_connection_t *c, pthread_cond_t *cond, struct iovec **vec
 
     if(ret)
     {
+#if USE_POLL
+        if((fd.revents & POLLIN) == POLLIN)
+#else
         if(FD_ISSET(c->fd, &rfds))
+#endif
             ret = ret && _xcb_in_read(c);
 
+#if USE_POLL
+        if((fd.revents & POLLOUT) == POLLOUT)
+#else
         if(FD_ISSET(c->fd, &wfds))
+#endif
             ret = ret && write_vec(c, vector, count);
     }
 

src/xcb_in.c

@@ -30,12 +30,16 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <stdio.h>
-#include <sys/select.h>
 #include <errno.h>
 
 #include "xcb.h"
 #include "xcbext.h"
 #include "xcbint.h"
+#if USE_POLL
+#include <poll.h>
+#else
+#include <sys/select.h>
+#endif
 
 #define XCB_ERROR 0
 #define XCB_REPLY 1
@@ -268,12 +272,22 @@ static int read_block(const int fd, void *buf, const ssize_t len)
             done += ret;
         if(ret < 0 && errno == EAGAIN)
         {
+#if USE_POLL
+            struct pollfd pfd;
+            pfd.fd = fd;
+            pfd.events = POLLIN;
+            pfd.revents = 0;
+            do {
+                ret = poll(&pfd, 1, -1);
+            } while (ret == -1 && errno == EINTR);
+#else
             fd_set fds;
             FD_ZERO(&fds);
             FD_SET(fd, &fds);
 	    do {
 		ret = select(fd + 1, &fds, 0, 0, 0);
 	    } while (ret == -1 && errno == EINTR);
+#endif
         }
         if(ret <= 0)
             return ret;