From ab1ec8e46423f4814999a88b9f29f0592c13552d Mon Sep 17 00:00:00 2001
From: Glenn Maynard <gmaynard@users.sourceforge.net>
Date: Fri, 13 Dec 2002 06:18:09 +0000
Subject: [PATCH] Add some lock handling stuff for the sound code.

---
 stepmania/src/RageThreads.cpp | 79 +++++++++++++++++++++++++++++++++++
 stepmania/src/RageThreads.h   | 36 ++++++++++++++++
 2 files changed, 115 insertions(+)
 create mode 100644 stepmania/src/RageThreads.cpp
 create mode 100644 stepmania/src/RageThreads.h

diff --git a/stepmania/src/RageThreads.cpp b/stepmania/src/RageThreads.cpp
new file mode 100644
index 0000000000..c98e3760a9
--- /dev/null
+++ b/stepmania/src/RageThreads.cpp
@@ -0,0 +1,79 @@
+/*
+ * If you're going to use threads, remember this: 
+ *
+ * Threads suck.
+ *
+ * If there's any way to avoid them, take it!  Threaded code an order of
+ * magnitude more complicated, harder to debug and harder to make robust.
+ *
+ * That said, here are a few helpers for when they're unavoidable.  (Use
+ * SDL for the rest.)
+ */
+
+#include "stdafx.h"
+
+#include "RageThreads.h"
+
+RageMutex::RageMutex()
+{
+	Locked = 0;
+	mut = SDL_CreateMutex();
+	mutwait = SDL_CreateMutex();
+}
+
+RageMutex::~RageMutex()
+{
+	SDL_DestroyMutex(mut);
+	SDL_DestroyMutex(mutwait);
+}
+
+void RageMutex::Lock()
+{
+	while(1)
+	{
+		SDL_LockMutex(mut);
+		if(!Locked || LockedBy == SDL_ThreadID())
+		{
+			if(!Locked)
+			{
+				/* This mutex is now locked. */
+				SDL_LockMutex(mutwait);
+				LockedBy = SDL_ThreadID();
+			} /* (else it was already locked and we're just increasing the counter) */
+			Locked++;
+			SDL_UnlockMutex(mut);
+			return;
+		}
+
+		SDL_UnlockMutex(mut);
+
+		/* Someone else is locking it.  Wait until it's available and try again. */
+		SDL_LockMutex(mutwait);
+		SDL_UnlockMutex(mutwait);
+	}
+}
+
+void RageMutex::Unlock()
+{
+	SDL_LockMutex(mut);
+	ASSERT(Locked);
+	ASSERT(LockedBy == SDL_ThreadID());
+
+	Locked--;
+	if(!Locked)
+	{
+		LockedBy = 0;
+		SDL_UnlockMutex(mutwait);
+	}
+
+	SDL_UnlockMutex(mut);
+}
+
+/*
+-----------------------------------------------------------------------------
+ File: RageThreads
+
+ Copyright (c) 2001-2002 by the person(s) listed below.  All rights reserved.
+    Glenn Maynard
+-----------------------------------------------------------------------------
+*/
diff --git a/stepmania/src/RageThreads.h b/stepmania/src/RageThreads.h
new file mode 100644
index 0000000000..3f3fd42232
--- /dev/null
+++ b/stepmania/src/RageThreads.h
@@ -0,0 +1,36 @@
+#ifndef RAGE_THREADS_H
+#define RAGE_THREADS_H
+
+#include "SDL_Thread.h"
+
+/* Mutex class that follows the behavior of Windows mutexes: if the same
+ * thread locks the same mutex twice, we just increase a refcount; a mutex
+ * is considered unlocked when the refcount reaches zero.  This is more
+ * convenient, though much slower on some archs.  (We don't have any tightly-
+ * coupled threads, so that's OK.) */
+class RageMutex
+{
+	Uint32 LockedBy;
+	int Locked;
+	SDL_mutex *mut, *mutwait;
+
+public:
+	void Lock();
+	void Unlock();
+	RageMutex();
+	~RageMutex();
+};
+
+/* Lock a mutex on construction, unlock it on destruction.  Helps for functions
+ * with more than one return path. */
+class LockMutex
+{
+	RageMutex &mutex;
+
+public:
+	LockMutex(RageMutex &mut): mutex(mut) { mutex.Lock(); }
+	~LockMutex() { mutex.Unlock(); }
+	LockMutex(LockMutex &cpy): mutex(cpy.mutex) { mutex.Lock(); }
+};
+
+#endif