From 7dd9ac6be0e8e24d4fec5d9bdbd2cab96ef597b5 Mon Sep 17 00:00:00 2001
From: Ludwig Ortmann <ludwig.ortmann@fu-berlin.de>
Date: Fri, 5 Jul 2013 19:22:29 +0200
Subject: [PATCH 1/3] Add msg_try_receive

---
 core/include/msg.h | 10 ++++++++++
 core/msg.c         | 15 +++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/core/include/msg.h b/core/include/msg.h
index c8770b7a8d..78db899b43 100644
--- a/core/include/msg.h
+++ b/core/include/msg.h
@@ -90,6 +90,16 @@ int msg_send_int(msg_t *m, unsigned int target_pid);
  */
 int msg_receive(msg_t *m);
 
+/**
+ * @brief Try to receive a message.
+ *
+ * This function does not block if no message can be received.
+ * @param m pointer to preallocated msg
+ *
+ * @return 1 if a message was received, -1 otherwise.
+ */
+int msg_try_receive(msg_t *m);
+
 /**
  * @brief Send a message, block until reply received.
  *
diff --git a/core/msg.c b/core/msg.c
index 9e621027f9..0c494cc843 100644
--- a/core/msg.c
+++ b/core/msg.c
@@ -184,7 +184,17 @@ int msg_reply_int(msg_t *m, msg_t *reply)
     return 1;
 }
 
+int msg_try_receive(msg_t *m)
+{
+    return _msg_receive(m, false);
+}
+
 int msg_receive(msg_t *m)
+{
+    return _msg_receive(m, true);
+}
+
+int _msg_receive(msg_t *m, block)
 {
     dINT();
     DEBUG("%s: msg_receive.\n", active_thread->name);
@@ -197,6 +207,11 @@ int msg_receive(msg_t *m)
         n = cib_get(&(me->msg_queue));
     }
 
+    /* no message, fail */
+    if ((!block) && (n == -1)) {
+        return -1;
+    }
+
     if (n >= 0) {
         DEBUG("%s: msg_receive(): We've got a queued message.\n", active_thread->name);
         *m = me->msg_array[n];

From 96cbf4019e7249346173f0cbdf51f3b9bbc3b42a Mon Sep 17 00:00:00 2001
From: Christian Mehlis <mehlis@inf.fu-berlin.de>
Date: Fri, 5 Jul 2013 23:34:11 +0200
Subject: [PATCH 2/3] make internal function static

---
 core/msg.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/core/msg.c b/core/msg.c
index 0c494cc843..de16b8a323 100644
--- a/core/msg.c
+++ b/core/msg.c
@@ -28,6 +28,9 @@
 //#define ENABLE_DEBUG
 #include "debug.h"
 
+static int _msg_receive(msg_t *m, int block);
+
+
 static int queue_msg(tcb_t *target, msg_t *m)
 {
     int n = cib_put(&(target->msg_queue));
@@ -194,7 +197,7 @@ int msg_receive(msg_t *m)
     return _msg_receive(m, true);
 }
 
-int _msg_receive(msg_t *m, block)
+static int _msg_receive(msg_t *m, block)
 {
     dINT();
     DEBUG("%s: msg_receive.\n", active_thread->name);

From 190e24116ded56275cc104ecbed01a9e9764011f Mon Sep 17 00:00:00 2001
From: Christian Mehlis <mehlis@inf.fu-berlin.de>
Date: Tue, 9 Jul 2013 13:41:08 +0200
Subject: [PATCH 3/3] use int explicitly

---
 core/msg.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/core/msg.c b/core/msg.c
index de16b8a323..52e6e1dc30 100644
--- a/core/msg.c
+++ b/core/msg.c
@@ -189,15 +189,15 @@ int msg_reply_int(msg_t *m, msg_t *reply)
 
 int msg_try_receive(msg_t *m)
 {
-    return _msg_receive(m, false);
+    return _msg_receive(m, 0);
 }
 
 int msg_receive(msg_t *m)
 {
-    return _msg_receive(m, true);
+    return _msg_receive(m, 1);
 }
 
-static int _msg_receive(msg_t *m, block)
+static int _msg_receive(msg_t *m, int block)
 {
     dINT();
     DEBUG("%s: msg_receive.\n", active_thread->name);