From 57d292d962d0de1b35febec71aa1a185e4b461b1 Mon Sep 17 00:00:00 2001
From: Alexander Chemeris <Alexander.Chemeris@gmail.com>
Date: Thu, 9 Sep 2010 18:00:49 +0400
Subject: [PATCH] Better documentation and error reporting for ThreadSemaphore.

---
 public-trunk/CommonLibs/Threads.cpp | 65 ++++++++++++++++++++++++++---
 public-trunk/CommonLibs/Threads.h   | 43 +++++++++++++++----
 2 files changed, 93 insertions(+), 15 deletions(-)

diff --git a/public-trunk/CommonLibs/Threads.cpp b/public-trunk/CommonLibs/Threads.cpp
index 184c271..0449710 100644
--- a/public-trunk/CommonLibs/Threads.cpp
+++ b/public-trunk/CommonLibs/Threads.cpp
@@ -28,6 +28,7 @@
 #include "Threads.h"
 #include "Timeval.h"
 
+#include <errno.h>
 
 using namespace std;
 
@@ -96,14 +97,66 @@ void Signal::wait(Mutex& wMutex, unsigned timeout) const
 	pthread_cond_timedwait(&mSignal,&wMutex.mMutex,&waitTime);
 }
 
-/** Wait for semaphore to be signaled with timeout.
-* @returns 0 on success, -1 on error or timeout.
-*/
-int ThreadSemaphore::wait(unsigned timeout) const
+ThreadSemaphore::Result ThreadSemaphore::wait(unsigned timeoutMs)
 {
-	Timeval then(timeout);
+	Timeval then(timeoutMs);
 	struct timespec waitTime = then.timespec();
-	return sem_timedwait(&mSem,&waitTime);
+	int s;
+	while ((s = sem_timedwait(&mSem,&waitTime)) == -1 && errno == EINTR)
+		continue;
+
+	if (s == -1)
+	{
+		if (errno == ETIMEDOUT)
+		{
+			return TSEM_TIMEOUT;
+		}
+		return TSEM_ERROR;
+	}
+	return TSEM_OK;
+}
+
+ThreadSemaphore::Result ThreadSemaphore::wait()
+{
+	int s;
+	while ((s = sem_wait(&mSem)) == -1 && errno == EINTR)
+		continue;
+
+	if (s == -1)
+	{
+		return TSEM_ERROR;
+	}
+	return TSEM_OK;
+}
+
+ThreadSemaphore::Result ThreadSemaphore::trywait() 
+{
+	int s;
+	while ((s = sem_trywait(&mSem)) == -1 && errno == EINTR)
+		continue;
+
+	if (s == -1)
+	{
+		if (errno == EAGAIN)
+		{
+			return TSEM_TIMEOUT;
+		}
+		return TSEM_ERROR;
+	}
+	return TSEM_OK;
+}
+
+ThreadSemaphore::Result ThreadSemaphore::post()
+{
+	if (sem_post(&mSem) != 0)
+	{
+		if (errno == EOVERFLOW)
+		{
+			return TSEM_OVERFLOW;
+		}
+		return TSEM_ERROR;
+	}
+	return TSEM_OK;
 }
 
 void Thread::start(void *(*task)(void*), void *arg)
diff --git a/public-trunk/CommonLibs/Threads.h b/public-trunk/CommonLibs/Threads.h
index 6bb57bf..9015be8 100644
--- a/public-trunk/CommonLibs/Threads.h
+++ b/public-trunk/CommonLibs/Threads.h
@@ -126,30 +126,55 @@ class ThreadSemaphore {
 
 	private:
 
-	mutable sem_t mSem;
+	sem_t mSem;
 
 	public:
 
-	ThreadSemaphore(int pshared = 0, unsigned value = 0) { assert(sem_init(&mSem,pshared,value)!=-1); }
+	enum Result {
+		TSEM_OK,       ///< Success.
+		TSEM_TIMEOUT,  ///< wait() or trywait() timed out.
+		TSEM_OVERFLOW, ///< post() overflows a semaphore
+		TSEM_ERROR     ///< Generic error.
+	};
+
+	/** Create and initialize semaphore.
+	* @param[in] value - initial semaphore value.
+	*/
+	ThreadSemaphore(unsigned value = 0)
+	{
+		int s = sem_init(&mSem,0,value);
+		assert(s == 0);
+	}
 
 	~ThreadSemaphore() { sem_destroy(&mSem); }
 
 	/** Wait for semaphore to be signaled with timeout.
-	* @returns 0 on success, -1 on error or timeout.
+	* @param[in] timeoutMs - timeout in milliseconds
+	*
+	* @retval TSEM_OK on success.
+	* @retval TSEM_TIMEOUT on timeout.
+	* @retval TSEM_ERROR on error.
 	*/
-	int wait (unsigned timeout) const;
+	Result wait(unsigned timeoutMs);
 
 	/** Wait for semaphore to be signaled infinitely.
-	* @returns 0 on success, -1 on error.
+	* @retval TSEM_OK on success.
+	* @retval TSEM_ERROR on error.
 	*/
-	int wait() const { return sem_wait(&mSem); }
+	Result wait();
 
 	/** Check if semaphore has been signaled and disarm it.
-	* @returns 0 if semaphore has been signaled, -1 in other cases.
+	* @retval TSEM_OK is semaphore is signaled.
+	* @retval TSEM_TIMEOUT if semaphore is not signaled.
+	* @retval TSEM_ERROR on error.
 	*/
-	int trywait() const { return sem_trywait(&mSem); }
+	Result trywait();
 
-	int post() { return sem_post (&mSem); }
+	/** Signal semaphore.
+	* @retval TSEM_OK on success.
+	* @retval TSEM_ERROR on error.
+	*/
+	Result post();
 
 };