Implement TryWait for hsSemaphore

Sources/Plasma/CoreLib/hsThread.h

@@ -157,6 +157,7 @@ public:
     hsSemaphore(int initialValue=0, const char* name=nil);
     ~hsSemaphore();
 
+    hsBool      TryWait();
     hsBool      Wait(hsMilliseconds timeToWait = kPosInfinity32);
     void        Signal();
 };

Sources/Plasma/CoreLib/hsThread_Unix.cpp

@@ -316,6 +316,18 @@ hsSemaphore::~hsSemaphore()
 #endif
 }
 
+hsBool hsSemaphore::TryWait()
+{
+#ifdef USE_SEMA
+    int status = ::sem_trywait(fPSema);
+    return status != E_AGAIN;
+#else
+    int status = ::pthread_mutex_trylock(&fPMutex);
+    hsThrowIfOSErr(status);
+    return status==EBUSY ? false : true;
+#endif
+}
+
 hsBool hsSemaphore::Wait(hsMilliseconds timeToWait)
 {
 #ifdef USE_SEMA  // SHOULDN'T THIS USE timeToWait??!?!? -rje

Sources/Plasma/CoreLib/hsThread_Win.cpp

@@ -170,6 +170,13 @@ hsSemaphore::~hsSemaphore()
     ::CloseHandle(fSemaH);
 }
 
+hsBool hsSemaphore::TryWait()
+{
+    DWORD result = ::WaitForSingleObject(fSemaH, 0);
+    hsAssert(result != WAIT_ABANDONED, "hsSemaphore -> Abandoned Semaphore");
+    return result == WAIT_OBJECT_0;
+}
+
 hsBool hsSemaphore::Wait(hsMilliseconds timeToWait)
 {
     if (timeToWait == kPosInfinity32)