From ba94e035face3deb032b902853f7be7f81a9a1b9 Mon Sep 17 00:00:00 2001
From: Corey Richardson <corey@octayn.net>
Date: Sun, 14 Oct 2012 11:35:44 -0400
Subject: [PATCH] Implement semaphores on POSIX

---
 Thread.c | 39 ++++++++++++++++++++++++---------------
 Thread.h |  3 +--
 2 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/Thread.c b/Thread.c
index 2e1eef6..e730906 100644
--- a/Thread.c
+++ b/Thread.c
@@ -1,4 +1,5 @@
-/** @file Thread.c
+/** 
+ * @file Thread.c
  * @brief Threading functions and synchronization primitives.
  */
 
@@ -6,6 +7,8 @@
 
 #ifdef WINDOWS
 	#include <Windows.h>
+#elif defined POSIX
+	#include <errno.h>
 #endif
 
 /**
@@ -137,53 +140,59 @@ void SAL_Mutex_Release(SAL_Mutex mutex) {
 /**
  * Create a new semaphore.
  *
- * @return a new semaphore
+ * @returns a new semaphore, NULL on failure
  */
 SAL_Semaphore SAL_Semaphore_Create(void) {
 	#ifdef WINDOWS
 		return CreateSemaphore(NULL, 0, 4294967295, NULL);
 	#elif defined POSIX
-    
+		sem_t *sem = Allocate(sem_t);
+		if (sem_init(sem, 0 /* shared between threads */, 0) != 0) {
+			return NULL;
+		}
+		return sem;
 	#endif
 }
 
 /**
  * Free a semaphore.
  * 
- * @param semaphore to free.
+ * @param semaphore to free
+ * @warning Don't free a semaphor that is still in use (being waited on)
  */
-void SAL_Semaphore_Free(SAL_Semaphore Semaphore) {
+void SAL_Semaphore_Free(SAL_Semaphore semaphore) {
 	#ifdef WINDOWS
-		CloseHandle(Semaphore);
+		CloseHandle(semaphore);
 	#elif defined POSIX
-
+		sem_destroy(semaphore);
+		Free(semaphore);
 	#endif
 }
 
 /**
  * Decrement a semaphore.
  * 
- * @param semaphore to decrement.
+ * @param semaphore to decrement
  *
  * @warning This function will block if the semaphore count is zero.
  */
-void SAL_Semaphore_Decrement(SAL_Semaphore Semaphore) {
+void SAL_Semaphore_Decrement(SAL_Semaphore semaphore) {
 	#ifdef WINDOWS
-		WaitForSingleObject(Semaphore, INFINITE);
+		WaitForSingleObject(semaphore, INFINITE);
 	#elif defined POSIX
-
+		while (sem_wait(semaphore) == -1 && errno == EINTR);
 	#endif
 }
 
 /**
  * Increment a semaphore.
  * 
- * @param semaphore to increment.
+ * @param semaphore to increment
  */
-void SAL_Semaphore_Increment(SAL_Semaphore Semaphore) {
+void SAL_Semaphore_Increment(SAL_Semaphore semaphore) {
 	#ifdef WINDOWS
-		ReleaseSemaphore(Semaphore, 1, NULL);
+		ReleaseSemaphore(semaphore, 1, NULL);
 	#elif defined POSIX
-
+		sem_post(semaphore);
 	#endif
 }
diff --git a/Thread.h b/Thread.h
index f2e495e..58d1b65 100644
--- a/Thread.h
+++ b/Thread.h
@@ -10,13 +10,12 @@
 	typedef void* SAL_Semaphore;
 #elif defined POSIX
 	#include <pthread.h>
-	#include <errno.h>
     
 	typedef void* (*SAL_Thread_StartAddress)(void* SAL_Thread_StartParameter);
 	typedef pthread_t SAL_Thread;
 	
 	typedef pthread_mutex_t* SAL_Mutex;
-    typedef pthread_cond_t* SAL_Semaphore;
+    typedef sem_t* SAL_Semaphore;
 #endif
 
 public SAL_Thread SAL_Thread_Create(SAL_Thread_StartAddress startAddress, void* startParameter);