add new functions to retrieve file descriptors from nodes, io formats and tasks

include/villas/io.h

@@ -86,6 +86,7 @@ void io_rewind(struct io *io);
 
 int io_flush(struct io *io);
 
+int io_fd(struct io *io);
 
 int io_stream_open(struct io *io, const char *uri);
 
@@ -95,4 +96,6 @@ int io_stream_eof(struct io *io);
 
 void io_stream_rewind(struct io *io);
 
+int io_stream_fd(struct io *io);
+
 int io_stream_flush(struct io *io);

include/villas/io_format.h

@@ -70,6 +70,9 @@ struct io_format {
 	 * @see rewind()
 	 */
 	void (*rewind)(struct io *io);
+	
+	/** Get a file descriptor which can be used with select / poll */
+	int (*fd)(struct io *io);
 
 	/** Flush buffered data to disk.
 	 *

include/villas/node.h

@@ -125,6 +125,8 @@ int node_read(struct node *n, struct sample *smps[], unsigned cnt);
 
 int node_write(struct node *n, struct sample *smps[], unsigned cnt);
 
+int node_fd(struct node *n);
+
 /** Parse an array or single node and checks if they exist in the "nodes" section.
  *
  * Examples:

include/villas/node_type.h

@@ -146,6 +146,9 @@ struct node_type {
 	 * @param n	A pointer to the node object.
 	 */
 	int (*reverse)(struct node *n);
+	
+	/** Return a file descriptor which can be used by poll / select to detect the availability of new data. */
+	int (*fd)(struct node *n);
 };
 
 /** Initialize all registered node type subsystems.

include/villas/task.h

@@ -68,4 +68,6 @@ uint64_t task_wait_until_next_period(struct task *t);
  *
  * @param until A pointer to a time in the future.
  */
-int task_wait_until(struct task *t, const struct timespec *until);
+int task_wait_until(struct task *t, const struct timespec *until);
+
+int task_fd(struct task *t);

lib/io.c

@@ -177,6 +177,19 @@ void io_stream_rewind(struct io *io)
 	}
 }
 
+int io_stream_fd(struct io *io)
+{
+	switch (io->mode) {
+		case IO_MODE_ADVIO:
+			return afileno(io->advio.input);
+		case IO_MODE_STDIO:
+			return fileno(io->stdio.input);
+		case IO_MODE_CUSTOM:
+			return -1;
+	}
+}
+
+
 int io_open(struct io *io, const char *uri)
 {
 	return io->_vt->open
@@ -212,6 +225,13 @@ void io_rewind(struct io *io)
 		: io_stream_rewind(io);
 }
 
+int io_fd(struct io *io)
+{
+	return io->_vt->fd
+		? io->_vt->fd(io)
+		: io_stream_fd(io);
+}
+
 int io_print(struct io *io, struct sample *smps[], unsigned cnt)
 {
 	int ret;

lib/node.c

@@ -288,6 +288,11 @@ int node_reverse(struct node *n)
 	return n->_vt->reverse ? n->_vt->reverse(n) : -1;
 }
 
+int node_fd(struct node *n)
+{
+	return n->_vt->fd ? n->_vt->fd(n) : -1;
+}
+
 int node_parse_list(struct list *list, json_t *cfg, struct list *all)
 {
 	struct node *node;

lib/task.c

@@ -115,7 +115,6 @@ uint64_t task_wait_until_next_period(struct task *t)
 	return runs;
 }
 
-
 int task_wait_until(struct task *t, const struct timespec *until)
 {
 	int ret;
@@ -154,4 +153,13 @@ retry:	ret = clock_nanosleep(t->clock, TIMER_ABSTIME, until, NULL);
 #endif
 	
 	return 0;
+}
+
+int task_fd(struct task *t)
+{
+#if PERIODIC_TASK_IMPL == TIMERFD
+	return t->fd;
+#else
+	return -1;
+#endif
 }