Add queue_peek to the kernel (written by Mike Sevakis), and use it to improve upon my previous commit.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@15336 a1c6a512-1295-4272-9138-f99709370657

2 files changed, 23 insertions, 0 deletions

diff --git a/firmware/export/kernel.h b/firmware/export/kernel.h
index a72e004b33..041f846380 100644
--- a/firmware/export/kernel.h
+++ b/firmware/export/kernel.h
@@ -219,6 +219,7 @@ extern void queue_reply(struct event_queue *q, intptr_t retval);
 extern bool queue_in_queue_send(struct event_queue *q);
 #endif /* HAVE_EXTENDED_MESSAGING_AND_NAME */
 extern bool queue_empty(const struct event_queue* q);
+extern bool queue_peek(struct event_queue *q, struct queue_event *ev);
 extern void queue_clear(struct event_queue* q);
 extern void queue_remove_from_head(struct event_queue *q, long id);
 extern int queue_count(const struct event_queue *q);
diff --git a/firmware/kernel.c b/firmware/kernel.c
index 006a06dfe0..25249c6148 100644
--- a/firmware/kernel.c
+++ b/firmware/kernel.c
@@ -537,6 +537,28 @@ bool queue_empty(const struct event_queue* q)
     return ( q->read == q->write );
 }
 
+bool queue_peek(struct event_queue *q, struct queue_event *ev)
+{
+    if (q->read == q->write)
+         return false;
+
+    bool have_msg = false;
+
+    int oldlevel = set_irq_level(HIGHEST_IRQ_LEVEL);
+    corelock_lock(&q->cl);
+
+    if (q->read != q->write)
+    {
+        *ev = q->events[q->read & QUEUE_LENGTH_MASK];
+        have_msg = true;
+    }
+
+    corelock_unlock(&q->cl);
+    set_irq_level(oldlevel);
+
+    return have_msg;
+}
+
 void queue_clear(struct event_queue* q)
 {
     int oldlevel;