Add coio_wait() to public C API

Extract bsdsocket_io_wait() from bsdsocket.cc to public C API.
This very simple patch allow to use Tarantool event machine in
stored C procedures.

Other changes: replace fiber_wakeup() with fiber_call() here to save extra
               event loop iteration.

src/coio.cc

@@ -705,3 +705,42 @@ coio_waitpid(pid_t pid)
 	return status;
 }
 
+/* Values of COIO_READ(WRITE) must equal to EV_READ(WRITE) */
+static_assert(COIO_READ == (int) EV_READ, "TNT_IO_READ");
+static_assert(COIO_WRITE == (int) EV_WRITE, "TNT_IO_WRITE");
+
+struct coio_wdata {
+	struct fiber *fiber;
+	int revents;
+};
+
+static void
+coio_wait_cb(struct ev_loop *loop, ev_io *watcher, int revents)
+{
+	(void) loop;
+	struct coio_wdata *wdata = (struct coio_wdata *) watcher->data;
+	wdata->revents = revents;
+	fiber_call(wdata->fiber);
+}
+
+int
+coio_wait(int fd, int events, double timeout)
+{
+	struct ev_io io;
+	coio_init(&io, fd);
+	ev_io_init(&io, coio_wait_cb, fd, events);
+	struct coio_wdata wdata = {
+		/* .fiber =   */ fiber(),
+		/* .revents = */ 0
+	};
+	io.data = &wdata;
+
+	/* A special hack to work with zero timeout */
+	ev_set_priority(&io, EV_MAXPRI);
+	ev_io_start(loop(), &io);
+
+	fiber_yield_timeout(timeout);
+
+	ev_io_stop(loop(), &io);
+	return wdata.revents;
+}

src/coio.h

@@ -32,6 +32,7 @@
  */
 #include "evio.h"
 #include "fiber.h"
+#include "trivia/util.h"
 
 /**
  * Co-operative I/O
@@ -183,5 +184,28 @@ coio_stat_stat_timeout(ev_stat *stat, ev_tstamp delay);
 int
 coio_waitpid(pid_t pid);
 
+/** \cond public */
+
+enum {
+	/** READ event */
+	COIO_READ  = 0x1,
+	/** WRITE event */
+	COIO_WRITE = 0x2,
+};
+
+/**
+ * Wait until READ or WRITE event on socket (\a fd). Yields.
+ * \param fd - non-blocking socket file description
+ * \param events - requested events to wait.
+ * Combination of TNT_IO_READ | TNT_IO_WRITE bit flags.
+ * \param timeoout - timeout in seconds.
+ * \retval 0 - timeout
+ * \retval >0 - returned events. Combination of TNT_IO_READ | TNT_IO_WRITE
+ * bit flags.
+ */
+API_EXPORT int
+coio_wait(int fd, int event, double timeout);
+
+/** \endcond public */
 
 #endif /* TARANTOOL_COIO_H_INCLUDED */

src/lua/bsdsocket.cc

@@ -49,6 +49,7 @@ extern "C" {
 #include <lualib.h>
 }
 
+#include <coio.h>
 #include <coeio.h>
 #include <fiber.h>
 #include <scoped_guard.h>
@@ -379,21 +380,6 @@ bsdsocket_nonblock(int fh, int mode)
 	return mode ? 1 : 0;
 }
 
-struct bsdsocket_io_wdata {
-	struct fiber *fiber;
-	int io;
-};
-
-static void
-bsdsocket_io(struct ev_loop *loop, ev_io *watcher, int revents)
-{
-	(void) loop;
-	struct bsdsocket_io_wdata *wdata =
-		(struct bsdsocket_io_wdata *)watcher->data;
-	wdata->io = revents;
-	fiber_wakeup(wdata->fiber);
-}
-
 static int
 lbox_bsdsocket_iowait(struct lua_State *L)
 {
@@ -401,35 +387,7 @@ lbox_bsdsocket_iowait(struct lua_State *L)
 	int events = lua_tointeger(L, 2);
 	ev_tstamp timeout = lua_tonumber(L, 3);
 
-	switch (events) {
-	case 0:
-		events = EV_READ;
-		break;
-	case 1:
-		events = EV_WRITE;
-		break;
-	case 2:
-		events = EV_READ | EV_WRITE;
-		break;
-	default:
-		assert(false);
-	}
-
-	struct ev_io io;
-	ev_io_init(&io, bsdsocket_io, fh, events);
-	struct bsdsocket_io_wdata wdata = { fiber(), 0 };
-	io.data = &wdata;
-	ev_set_priority(&io, EV_MAXPRI);
-	ev_io_start(loop(), &io);
-
-	fiber_yield_timeout(timeout);
-	ev_io_stop(loop(), &io);
-
-	int ret = 0;
-	if (wdata.io & EV_READ)
-		ret |= 1;
-	if (wdata.io & EV_WRITE)
-		ret |= 2;
+	int ret = coio_wait(fh, events, timeout);
 
 	lua_pushinteger(L, ret);
 	return 1;

src/lua/bsdsocket.lua

@@ -270,20 +270,20 @@ local function wait_safely(self, what, timeout)
     self.waiters[fid] = true
     local res = internal.iowait(fd, what, timeout)
     self.waiters[fid] = nil
-    fiber.testcancel()
     if res == 0 then
         self._errno = boxerrno.ETIMEDOUT
         return 0
     end
+    fiber.testcancel()
     return res
 end
 
 socket_methods.readable = function(self, timeout)
-    return wait_safely(self, 0, timeout) ~= 0
+    return wait_safely(self, 1, timeout) ~= 0
 end
 
 socket_methods.wait = function(self, timeout)
-    local wres = wait_safely(self, 2, timeout)
+    local wres = wait_safely(self, 3, timeout)
     local res = ''
     if bit.band(wres, 1) ~= 0 then
         res = res .. 'R'
@@ -295,7 +295,7 @@ socket_methods.wait = function(self, timeout)
 end
 
 socket_methods.writable = function(self, timeout)
-    return wait_safely(self, 1, timeout) ~= 0
+    return wait_safely(self, 2, timeout) ~= 0
 end
 
 socket_methods.listen = function(self, backlog)

src/trivia/CMakeLists.txt

 set(api_headers
     ${CMAKE_CURRENT_BINARY_DIR}/config.h
     ${CMAKE_SOURCE_DIR}/src/say.h
+    ${CMAKE_SOURCE_DIR}/src/coio.h
     ${CMAKE_SOURCE_DIR}/src/coeio.h
     ${CMAKE_SOURCE_DIR}/src/lua/utils.h
     ${CMAKE_SOURCE_DIR}/src/box/txn.h