From a0f170eb2100291429d31a057977a88ece219519 Mon Sep 17 00:00:00 2001
From: Pixel <pixel@nobis-crew.org>
Date: Fri, 28 Jan 2011 08:23:41 -0800
Subject: Pretty much rewrote sbrk for simpler & safer usage. Mutex still don't
 work properly though. Have to understand that part from FreeRTOS.

---
 os/src/sbrk.c | 79 +++++++++++++++++++++++++++++++----------------------------
 1 file changed, 42 insertions(+), 37 deletions(-)

diff --git a/os/src/sbrk.c b/os/src/sbrk.c
index eca289a..df196f0 100644
--- a/os/src/sbrk.c
+++ b/os/src/sbrk.c
@@ -2,54 +2,59 @@
 #include <errno.h>
 #include <stdlib.h>
 
-#include "FreeRTOS.h"
-#include "task.h"
-#include "mpu_wrappers.h"
+#include <FreeRTOS.h>
+#include <task.h>
+#include <semphr.h>
+#include <mpu_wrappers.h>
 
-#include <osdebug.h>
+#include "osdebug.h"
 
 // Mostly stolen from mbed-freertos
 
-extern uintptr_t __heap_start, __heap_end;
-//extern uintptr_t __stack_start;
+extern uintptr_t __heap_start;
+extern uintptr_t __stack_start;
 
 /* Low-level bulk RAM allocator -- used by Newlib's Malloc */
-static void *heap_end = NULL;
+static void *heap_end = (void *) &__heap_start;
+
+#define USE_SBRK_MUTEX 0
+
+#if USE_SBRK_MUTEX
+static xSemaphoreHandle sbrk_sem;
+
+__attribute__((constructor)) static void sbrk_init() {
+    DBGOUT("Creating Mutex...");
+    sbrk_sem = xSemaphoreCreateMutex();
+}
+#endif
 
 void *_sbrk_r(struct _reent *ptr, ptrdiff_t incr)
 {
     void *prev_heap_end, *next_heap_end, *ret;
-//    void *stack_min = (void *)(__stack_start ? __stack_start : __heap_end);
-    void *stack_min = (void *)__heap_end;
-    
-    DBGOUT("_sbrk_r(%p, %u)\r\n", ptr, incr);
-
-    taskENTER_CRITICAL();
-    {
-        /* Initialize on first call */
-        if (heap_end == NULL)
-        {
-            heap_end = (void *)&__heap_start;
-        }
-
-        prev_heap_end = heap_end;
-
-        /* Align to always be on 8-byte boundaries */
-        next_heap_end = (void *)((((uintptr_t)heap_end + incr) + 7) & ~7);
-
-        /* Check if this allocation would exceed the end of the ram - would probably get into the stack first however */
-        if (next_heap_end > stack_min)
-        {
-            ptr->_errno = ENOMEM;
-            ret = NULL;
-        }
-        else
-        {
-            heap_end = next_heap_end;
-            ret = (void *)prev_heap_end;
-        }
+    void *stack_min = (void *) &__stack_start;
+
+#if USE_SBRK_MUTEX
+    xSemaphoreTake(sbrk_sem, portMAX_DELAY);
+#endif
+
+    prev_heap_end = heap_end;
+
+    /* Align to always be on 8-byte boundaries */
+    next_heap_end = (void *)((((uintptr_t)heap_end + incr) + 7) & ~7);
+
+    /* Check if this allocation would exceed the end of the ram - would probably get into the stack first however */
+    if (next_heap_end > stack_min) {
+        ptr->_errno = ENOMEM;
+        ret = NULL;
+    } else {
+        heap_end = next_heap_end;
+        ret = (void *)prev_heap_end;
     }
-    taskEXIT_CRITICAL();
+
+#if USE_SBRK_MUTEX
+    xSemaphoreGive(sbrk_sem);
+#endif
+
     return ret;
 }
 
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