add nowait option to bus_write

Signed-off-by: Mattias Andrée <maandree@operamail.com>

3 files changed, 29 insertions, 8 deletions

diff --git a/src/bus.c b/src/bus.c
index ff2abeb..0c121a6 100644
--- a/src/bus.c
+++ b/src/bus.c
@@ -126,6 +126,14 @@
 	(memcpy((bus)->message, msg, (strlen(msg) + 1) * sizeof(char)))
 
 
+/**
+ * If `flags & (bus_flag)`, this macro evalutes to `sys_flag`,
+ * otherwise this macro evalutes to 0.
+ */
+#define F(bus_flag, sys_flag)  \
+	((flags & (bus_flag)) ? sys_flag : 0)
+
+
 
 /**
  * Statement wrapper that goes to `fail` on failure
@@ -607,13 +615,16 @@ fail:
  * @param   bus      Bus information
  * @param   message  The message to write, may not be longer than
  *                   `BUS_MEMORY_SIZE` including the NUL-termination
+ * @param   flags    `BUS_NOWAIT` if this function shall fail if
+ *                   another process is currently running this
+ *                   procedure
  * @return           0 on success, -1 on error
  */
-int /* TODO nonblocking */
-bus_write(const bus_t *bus, const char *message)
+int
+bus_write(const bus_t *bus, const char *message, int flags /* TODO document in man page */)
 {
 	int state = 0, saved_errno;
-	if (acquire_semaphore(bus, X, SEM_UNDO) == -1)
+	if (acquire_semaphore(bus, X, SEM_UNDO | F(BUS_NOWAIT, IPC_NOWAIT)) == -1)
 		return -1;
 	t(zero_semaphore(bus, W, 0));
 	write_shared_memory(bus, message);
@@ -708,10 +719,11 @@ bus_poll_stop(const bus_t *bus)
 }
 
 
-const char * /* TODO nonblocking */
-bus_poll(bus_t *bus)
+const char *
+bus_poll(bus_t *bus, int flags)
 {
 	int state = 0, saved_errno;
+	(void) flags; /* TODO nonblocking */
 	if (!bus->first_poll) {
 		t(release_semaphore(bus, W, SEM_UNDO));  state++;
 		t(acquire_semaphore(bus, S, SEM_UNDO));  state++;
diff --git a/src/bus.h b/src/bus.h
index 52d0e98..ed1c5de 100644
--- a/src/bus.h
+++ b/src/bus.h
@@ -57,6 +57,12 @@
  */
 #define BUS_INTR    4
 
+/**
+ * Function shall fail with errno set to `EAGAIN`
+ * if the it would block and this flag is used
+ */
+#define BUS_NOWAIT  1
+
 
 
 /**
@@ -150,9 +156,12 @@ int bus_close(bus_t *bus);
  * @param   bus      Bus information
  * @param   message  The message to write, may not be longer than
  *                   `BUS_MEMORY_SIZE` including the NUL-termination
+ * @param   flags    `BUS_NOWAIT` if this function shall fail if
+ *                   another process is currently running this
+ *                   procedure
  * @return           0 on success, -1 on error
  */
-int bus_write(const bus_t *bus, const char *message);
+int bus_write(const bus_t *bus, const char *message, int flags);
 
 /**
  * Listen (in a loop, forever) for new message on a bus
@@ -181,7 +190,7 @@ int bus_read(const bus_t *bus, int (*callback)(const char *message, void *user_d
 
 int bus_poll_start(bus_t *bus);
 int bus_poll_stop(const bus_t *bus);
-const char *bus_poll(bus_t *bus);
+const char *bus_poll(bus_t *bus, int falgs);
 
 
 
diff --git a/src/cmdline.c b/src/cmdline.c
index d6df97a..03efdf3 100644
--- a/src/cmdline.c
+++ b/src/cmdline.c
@@ -148,7 +148,7 @@ main(int argc, char *argv[])
 	/* Broadcast a message on a bus. */
 	} else if ((argc == 4) && !strcmp(argv[1], "broadcast")) {
 		t(bus_open(&bus, argv[2], BUS_WRONLY));
-		t(bus_write(&bus, argv[3]));
+		t(bus_write(&bus, argv[3], 0));
 		t(bus_close(&bus));
 
 	} else