From f9324000fa761ae63d418a2274ac97688b9290f9 Mon Sep 17 00:00:00 2001
From: Steffen Vogel <post@steffenvogel.de>
Date: Wed, 30 Aug 2017 00:22:58 +0200
Subject: [PATCH] add new functions to retrieve file descriptors from nodes, io
 formats and tasks

---
 include/villas/io.h        |  3 +++
 include/villas/io_format.h |  3 +++
 include/villas/node.h      |  2 ++
 include/villas/node_type.h |  3 +++
 include/villas/task.h      |  4 +++-
 lib/io.c                   | 20 ++++++++++++++++++++
 lib/node.c                 |  5 +++++
 lib/task.c                 | 10 +++++++++-
 8 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/include/villas/io.h b/include/villas/io.h
index 969daca15..c22976bbf 100644
--- a/include/villas/io.h
+++ b/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);
diff --git a/include/villas/io_format.h b/include/villas/io_format.h
index d82bd5c17..7bca9954f 100644
--- a/include/villas/io_format.h
+++ b/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.
 	 *
diff --git a/include/villas/node.h b/include/villas/node.h
index ed49c6098..0eeeb7cbc 100644
--- a/include/villas/node.h
+++ b/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:
diff --git a/include/villas/node_type.h b/include/villas/node_type.h
index 3b00957a3..09330eb4a 100644
--- a/include/villas/node_type.h
+++ b/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.
diff --git a/include/villas/task.h b/include/villas/task.h
index 518ae46ba..71d1b3a1c 100644
--- a/include/villas/task.h
+++ b/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);
\ No newline at end of file
+int task_wait_until(struct task *t, const struct timespec *until);
+
+int task_fd(struct task *t);
\ No newline at end of file
diff --git a/lib/io.c b/lib/io.c
index 6abf70bff..4dedc1873 100644
--- a/lib/io.c
+++ b/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;
diff --git a/lib/node.c b/lib/node.c
index a7bcf971d..a2be6ab0f 100644
--- a/lib/node.c
+++ b/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;
diff --git a/lib/task.c b/lib/task.c
index d6e46ee16..bf2dcf20b 100644
--- a/lib/task.c
+++ b/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
 }
\ No newline at end of file