add uv_run_once()

include/uv.h

@@ -212,6 +212,11 @@ UV_EXTERN uv_loop_t* uv_default_loop(void);
  */
 UV_EXTERN int uv_run (uv_loop_t*);
 
+/*
+ * This function polls for new events without blocking.
+ */
+UV_EXTERN int uv_run_once (uv_loop_t*);
+
 /*
  * Manually modify the event loop's reference count. Useful if the user wants
  * to have a handle or timeout that doesn't keep the loop alive.

src/unix/core.c

@@ -202,6 +202,12 @@ int uv_run(uv_loop_t* loop) {
 }
 
 
+int uv_run_once(uv_loop_t* loop) {
+  ev_run(loop->ev, EVRUN_NOWAIT);
+  return 0;
+}
+
+
 void uv__handle_init(uv_loop_t* loop, uv_handle_t* handle,
     uv_handle_type type) {
   loop->counters.handle_init++;

src/win/core.c

@@ -192,9 +192,8 @@ static void uv_poll_ex(uv_loop_t* loop, int block) {
   }
 }
 
-
-#define UV_LOOP(loop, poll)                                                   \
-  while ((loop)->refs > 0) {                                                  \
+#define UV_LOOP_ONCE(loop, poll)                                              \
+  do {                                                                        \
     uv_update_time((loop));                                                   \
     uv_process_timers((loop));                                                \
                                                                               \
@@ -219,9 +218,24 @@ static void uv_poll_ex(uv_loop_t* loop, int block) {
                  (loop)->refs > 0);                                           \
                                                                               \
     uv_check_invoke((loop));                                                  \
+  } while (0);
+
+#define UV_LOOP(loop, poll)                                                   \
+  while ((loop)->refs > 0) {                                                  \
+    UV_LOOP_ONCE(loop, poll)                                                  \
   }
 
 
+int uv_run_once(uv_loop_t* loop) {
+  if (pGetQueuedCompletionStatusEx) {
+    UV_LOOP_ONCE(loop, uv_poll_ex);
+  } else {
+    UV_LOOP_ONCE(loop, uv_poll);
+  }
+  return 0;
+}
+
+
 int uv_run(uv_loop_t* loop) {
   if (pGetQueuedCompletionStatusEx) {
     UV_LOOP(loop, uv_poll_ex);

test/test-run-once.c

@@ -0,0 +1,44 @@
+/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "uv.h"
+#include "task.h"
+
+static idle_counter = 0;
+
+static void idle_cb(uv_idle_t* handle, int status) {
+  ASSERT(handle != NULL);
+  ASSERT(status == 0);
+  idle_counter ++;
+}
+
+
+TEST_IMPL(run_once) {
+  int n;
+  uv_idle_t h;
+  uv_idle_init(uv_default_loop(), &h);
+  uv_idle_start(&h, idle_cb);
+  for (n = 0; n < 500; n++) {
+    uv_run_once(uv_default_loop());
+  }
+  ASSERT(n == 500);
+  return 0;
+}