unix: change uv_backend_timeout() prototype

* change return value to signed int
* constify loop argument

include/uv.h

@@ -262,16 +262,26 @@ 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).
+ * Get backend file descriptor. 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.
+ * See test/test-embed.c for an example.
+ *
+ * Note that embedding a kqueue fd in another kqueue pollset doesn't work on
+ * all platforms. It's not an error to add the fd but it never generates
+ * events.
  */
 UV_EXTERN int uv_backend_fd(const uv_loop_t*);
-UV_EXTERN unsigned int uv_backend_timeout(uv_loop_t*);
+
+/*
+ * Get the poll timeout. The return value is in milliseconds, or -1 for no
+ * timeout.
+ */
+UV_EXTERN int uv_backend_timeout(const uv_loop_t*);
 
 
 /*

src/unix/core.c

@@ -253,7 +253,7 @@ int uv_backend_fd(const uv_loop_t* loop) {
 }
 
 
-unsigned int uv_backend_timeout(uv_loop_t* loop) {
+int uv_backend_timeout(const uv_loop_t* loop) {
   if (!uv__has_active_handles(loop) && !uv__has_active_reqs(loop))
     return 0;
 

src/unix/internal.h

@@ -163,7 +163,7 @@ int uv_pipe_listen(uv_pipe_t* handle, int backlog, uv_connection_cb cb);
 
 /* timer */
 void uv__run_timers(uv_loop_t* loop);
-unsigned int uv__next_timeout(uv_loop_t* loop);
+int uv__next_timeout(const uv_loop_t* loop);
 
 /* signal */
 void uv__signal_close(uv_signal_t* handle);

src/unix/timer.c

@@ -102,13 +102,14 @@ int64_t uv_timer_get_repeat(uv_timer_t* handle) {
 }
 
 
-unsigned int uv__next_timeout(uv_loop_t* loop) {
-  uv_timer_t* handle;
+int uv__next_timeout(const uv_loop_t* loop) {
+  const uv_timer_t* handle;
 
-  handle = RB_MIN(uv__timers, &loop->timer_handles);
+  /* RB_MIN expects a non-const tree root. That's okay, it doesn't modify it. */
+  handle = RB_MIN(uv__timers, (struct uv__timers*) &loop->timer_handles);
 
   if (handle == NULL)
-    return (unsigned int) -1; /* block indefinitely */
+    return -1; /* block indefinitely */
 
   if (handle->timeout <= loop->time)
     return 0;

src/win/core.c

@@ -176,7 +176,7 @@ int uv_backend_fd(const uv_loop_t* loop) {
 }
 
 
-unsigned int uv_backend_timeout(uv_loop_t* loop) {
+int uv_backend_timeout(const uv_loop_t* loop) {
   return 0;
 }
 

test/test-embed.c

@@ -61,7 +61,7 @@ static int embed_timer_called;
 static void embed_thread_runner(void* arg) {
   int r;
   int fd;
-  unsigned int timeout;
+  int timeout;
 
   while (!embed_closed) {
     fd = uv_backend_fd(uv_default_loop());