unix: add uv_backend_fd() and uv_backend_timeout()

This can be used in conjuction with uv_run_once() to poll in one thread and run
the event loop's event callbacks in another.

Useful for embedding libuv's event loop in another event loop.

include/uv.h

@@ -261,6 +261,18 @@ UV_EXTERN void uv_unref(uv_handle_t*);
 UV_EXTERN void uv_update_time(uv_loop_t*);
 UV_EXTERN int64_t uv_now(uv_loop_t*);
 
+/*
+ * Get backend file descriptor and get polling timeout for it.
+ * (only kqueue, epoll and event ports are supported).
+ *
+ * This can be used in conjuction with uv_run_once() to poll in one thread and
+ * run the event loop's event callbacks in another.
+ *
+ * Useful for embedding libuv's event loop in another event loop.
+ */
+UV_EXTERN int uv_backend_fd(const uv_loop_t*);
+UV_EXTERN unsigned int uv_backend_timeout(uv_loop_t*);
+
 
 /*
  * Should return a buffer that libuv can use to read data into.

src/unix/core.c

@@ -248,7 +248,12 @@ void uv_loop_delete(uv_loop_t* loop) {
 }
 
 
-static unsigned int uv__poll_timeout(uv_loop_t* loop) {
+int uv_backend_fd(const uv_loop_t* loop) {
+  return loop->backend_fd;
+}
+
+
+unsigned int uv_backend_timeout(uv_loop_t* loop) {
   if (!uv__has_active_handles(loop) && !uv__has_active_reqs(loop))
     return 0;
 
@@ -268,7 +273,7 @@ static int uv__run(uv_loop_t* loop) {
   uv__run_idle(loop);
   uv__run_prepare(loop);
   uv__run_pending(loop);
-  uv__io_poll(loop, uv__poll_timeout(loop));
+  uv__io_poll(loop, uv_backend_timeout(loop));
   uv__run_check(loop);
   uv__run_closing_handles(loop);
   return uv__has_active_handles(loop) || uv__has_active_reqs(loop);

src/win/core.c

@@ -171,6 +171,16 @@ void uv_loop_delete(uv_loop_t* loop) {
 }
 
 
+int uv_backend_fd(const uv_loop_t* loop) {
+  return uv__new_artificial_error(UV_ENOSYS);
+}
+
+
+unsigned int uv_backend_timeout(uv_loop_t* loop) {
+  return 0;
+}
+
+
 static void uv_poll(uv_loop_t* loop, int block) {
   BOOL success;
   DWORD bytes, timeout;

test/test-embed.c

@@ -0,0 +1,132 @@
+/* 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"
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#ifndef HAVE_KQUEUE
+# if __APPLE__ || __DragonFly__ || __FreeBSD__ || __OpenBSD__ || __NetBSD__
+#  define HAVE_KQUEUE 1
+# endif
+#endif
+
+#ifndef HAVE_EPOLL
+# if defined(__linux__)
+#  define HAVE_EPOLL 1
+# endif
+#endif
+
+#if defined(HAVE_KQUEUE) || defined(HAVE_EPOLL)
+
+#if defined(HAVE_KQUEUE)
+# include <sys/types.h>
+# include <sys/event.h>
+# include <sys/time.h>
+#endif
+
+#if defined(HAVE_EPOLL)
+# include <sys/epoll.h>
+#endif
+
+static uv_thread_t embed_thread;
+static uv_sem_t embed_sem;
+static uv_timer_t embed_timer;
+static uv_async_t embed_async;
+static volatile int embed_closed;
+
+static int embed_timer_called;
+
+
+static void embed_thread_runner(void* arg) {
+  int r;
+  int fd;
+  unsigned int timeout;
+
+  while (!embed_closed) {
+    fd = uv_backend_fd(uv_default_loop());
+    timeout = uv_backend_timeout(uv_default_loop());
+
+    do {
+#if defined(HAVE_KQUEUE)
+      struct timespec ts;
+      ts.tv_sec = timeout / 1000;
+      ts.tv_nsec = (timeout % 1000) * 1000000;
+      r = kevent(fd, NULL, 0, NULL, 0, &ts);
+#elif defined(HAVE_EPOLL)
+      r = epoll_wait(fd, NULL, 0, timeout);
+#endif
+    } while (r == -1 && errno == EINTR);
+    uv_async_send(&embed_async);
+    uv_sem_wait(&embed_sem);
+  }
+}
+
+
+static void embed_cb(uv_async_t* async, int status) {
+  uv_run_once(uv_default_loop());
+
+  uv_sem_post(&embed_sem);
+}
+
+
+static void embed_timer_cb(uv_timer_t* timer, int status) {
+  embed_timer_called++;
+  embed_closed = 1;
+
+  uv_close((uv_handle_t*) &embed_async, NULL);
+}
+#endif
+
+
+TEST_IMPL(embed) {
+#if defined(HAVE_KQUEUE) || defined(HAVE_EPOLL)
+  uv_loop_t* external;
+
+  external = uv_loop_new();
+  ASSERT(external != NULL);
+
+  embed_timer_called = 0;
+  embed_closed = 0;
+
+  uv_async_init(external, &embed_async, embed_cb);
+
+  /* Start timer in default loop */
+  uv_timer_init(uv_default_loop(), &embed_timer);
+  uv_timer_start(&embed_timer, embed_timer_cb, 250, 0);
+
+  /* Start worker that will interrupt external loop */
+  uv_sem_init(&embed_sem, 0);
+  uv_thread_create(&embed_thread, embed_thread_runner, NULL);
+
+  /* But run external loop */
+  uv_run(external);
+
+  uv_thread_join(&embed_thread);
+  uv_loop_delete(external);
+
+  ASSERT(embed_timer_called == 1);
+#endif
+
+  return 0;
+}

test/test-list.h

@@ -124,6 +124,7 @@ TEST_DECLARE   (pipe_ref3)
 TEST_DECLARE   (pipe_ref4)
 TEST_DECLARE   (process_ref)
 TEST_DECLARE   (active)
+TEST_DECLARE   (embed)
 TEST_DECLARE   (async)
 TEST_DECLARE   (get_currentexe)
 TEST_DECLARE   (process_title)
@@ -363,6 +364,8 @@ TASK_LIST_START
 
   TEST_ENTRY  (active)
 
+  TEST_ENTRY  (embed)
+
   TEST_ENTRY  (async)
 
   TEST_ENTRY  (get_currentexe)

uv.gyp

@@ -250,6 +250,7 @@
         'test/test-cwd-and-chdir.c',
         'test/test-delayed-accept.c',
         'test/test-error.c',
+        'test/test-embed.c',
         'test/test-fail-always.c',
         'test/test-fs.c',
         'test/test-fs-event.c',