From 65d27b2d0ebce997b1706a4dde9a46d5ffc67154 Mon Sep 17 00:00:00 2001
From: Christopher Haster <chaster@utexas.edu>
Date: Fri, 5 Aug 2016 19:04:21 -0500
Subject: [PATCH] Moved to statically allocated Semaphores in mbed
 implementation

Used static buffer + placement new + reinterpret cast to allow
static allocation of the C++ Semaphore class in C. An assertion
is used to protect against invalid size, although this should be
changed to a static-assertion if available.
---
 equeue_mbed.cpp | 20 ++++++++++----------
 equeue_sema.h   |  2 +-
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/equeue_mbed.cpp b/equeue_mbed.cpp
index 4c3563b..05d13b9 100644
--- a/equeue_mbed.cpp
+++ b/equeue_mbed.cpp
@@ -63,26 +63,26 @@ void equeue_mutex_unlock(equeue_mutex_t *m) {
 // Semaphore operations
 #ifdef MBED_CONF_RTOS_PRESENT
 
-static inline Semaphore *sema(equeue_sema_t *s) {
-    return static_cast<Semaphore*>(*s);
-}
-
 int equeue_sema_create(equeue_sema_t *s) {
-    *s = new Semaphore(0);
-    return sema(s) ? 0 : -1;
+    MBED_ASSERT(sizeof(equeue_sema_t) >= sizeof(Semaphore));
+    new (s) Semaphore(0);
+    return 0;
 }
 
 void equeue_sema_destroy(equeue_sema_t *s) {
-    delete sema(s);
+    reinterpret_cast<Semaphore*>(s)->~Semaphore();
 }
 
 void equeue_sema_signal(equeue_sema_t *s) {
-    sema(s)->release();
+    reinterpret_cast<Semaphore*>(s)->release();
 }
 
 bool equeue_sema_wait(equeue_sema_t *s, int ms) {
-    int t = sema(s)->wait(ms < 0 ? osWaitForever : ms);
-    return t > 0;
+    if (ms < 0) {
+        ms = osWaitForever;
+    }
+
+    return (reinterpret_cast<Semaphore*>(s)->wait(ms) > 0);
 }
 
 #else
diff --git a/equeue_sema.h b/equeue_sema.h
index 91ccd8d..80c0b60 100644
--- a/equeue_sema.h
+++ b/equeue_sema.h
@@ -23,7 +23,7 @@ extern "C" {
 typedef sem_t equeue_sema_t;
 #elif defined(__MBED__)
 #ifdef MBED_CONF_RTOS_PRESENT
-typedef void *equeue_sema_t;
+typedef unsigned equeue_sema_t[8];
 #else
 typedef bool equeue_sema_t;
 #endif