Added initial support for Dreamcast (thanks HERO!)

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%40510

src/thread/dc/SDL_syscond.c

@@ -0,0 +1,223 @@
+/*
+    SDL - Simple DirectMedia Layer
+    Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002  Sam Lantinga
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Library General Public License for more details.
+
+    You should have received a copy of the GNU Library General Public
+    License along with this library; if not, write to the Free
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+    Sam Lantinga
+    slouken@libsdl.org
+*/
+
+#ifdef SAVE_RCSID
+static char rcsid =
+ "@(#) $Id$";
+#endif
+
+/* An implementation of condition variables using semaphores and mutexes */
+/*
+   This implementation borrows heavily from the BeOS condition variable
+   implementation, written by Christopher Tate and Owen Smith.  Thanks!
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "SDL_error.h"
+#include "SDL_thread.h"
+
+struct SDL_cond
+{
+	SDL_mutex *lock;
+	int waiting;
+	int signals;
+	SDL_sem *wait_sem;
+	SDL_sem *wait_done;
+};
+
+/* Create a condition variable */
+SDL_cond * SDL_CreateCond(void)
+{
+	SDL_cond *cond;
+
+	cond = (SDL_cond *) malloc(sizeof(SDL_cond));
+	if ( cond ) {
+		cond->lock = SDL_CreateMutex();
+		cond->wait_sem = SDL_CreateSemaphore(0);
+		cond->wait_done = SDL_CreateSemaphore(0);
+		cond->waiting = cond->signals = 0;
+		if ( ! cond->lock || ! cond->wait_sem || ! cond->wait_done ) {
+			SDL_DestroyCond(cond);
+			cond = NULL;
+		}
+	} else {
+		SDL_OutOfMemory();
+	}
+	return(cond);
+}
+
+/* Destroy a condition variable */
+void SDL_DestroyCond(SDL_cond *cond)
+{
+	if ( cond ) {
+		if ( cond->wait_sem ) {
+			SDL_DestroySemaphore(cond->wait_sem);
+		}
+		if ( cond->wait_done ) {
+			SDL_DestroySemaphore(cond->wait_done);
+		}
+		if ( cond->lock ) {
+			SDL_DestroyMutex(cond->lock);
+		}
+		free(cond);
+	}
+}
+
+/* Restart one of the threads that are waiting on the condition variable */
+int SDL_CondSignal(SDL_cond *cond)
+{
+	if ( ! cond ) {
+		SDL_SetError("Passed a NULL condition variable");
+		return -1;
+	}
+
+	/* If there are waiting threads not already signalled, then
+	   signal the condition and wait for the thread to respond.
+	*/
+	SDL_LockMutex(cond->lock);
+	if ( cond->waiting > cond->signals ) {
+		++cond->signals;
+		SDL_SemPost(cond->wait_sem);
+		SDL_UnlockMutex(cond->lock);
+		SDL_SemWait(cond->wait_done);
+	} else {
+		SDL_UnlockMutex(cond->lock);
+	}
+
+	return 0;
+}
+
+/* Restart all threads that are waiting on the condition variable */
+int SDL_CondBroadcast(SDL_cond *cond)
+{
+	if ( ! cond ) {
+		SDL_SetError("Passed a NULL condition variable");
+		return -1;
+	}
+
+	/* If there are waiting threads not already signalled, then
+	   signal the condition and wait for the thread to respond.
+	*/
+	SDL_LockMutex(cond->lock);
+	if ( cond->waiting > cond->signals ) {
+		int i, num_waiting;
+
+		num_waiting = (cond->waiting - cond->signals);
+		cond->signals = cond->waiting;
+		for ( i=0; i<num_waiting; ++i ) {
+			SDL_SemPost(cond->wait_sem);
+		}
+		/* Now all released threads are blocked here, waiting for us.
+		   Collect them all (and win fabulous prizes!) :-)
+		 */
+		SDL_UnlockMutex(cond->lock);
+		for ( i=0; i<num_waiting; ++i ) {
+			SDL_SemWait(cond->wait_done);
+		}
+	} else {
+		SDL_UnlockMutex(cond->lock);
+	}
+
+	return 0;
+}
+
+/* Wait on the condition variable for at most 'ms' milliseconds.
+   The mutex must be locked before entering this function!
+   The mutex is unlocked during the wait, and locked again after the wait.
+
+Typical use:
+
+Thread A:
+	SDL_LockMutex(lock);
+	while ( ! condition ) {
+		SDL_CondWait(cond);
+	}
+	SDL_UnlockMutex(lock);
+
+Thread B:
+	SDL_LockMutex(lock);
+	...
+	condition = true;
+	...
+	SDL_UnlockMutex(lock);
+ */
+int SDL_CondWaitTimeout(SDL_cond *cond, SDL_mutex *mutex, Uint32 ms)
+{
+	int retval;
+
+	if ( ! cond ) {
+		SDL_SetError("Passed a NULL condition variable");
+		return -1;
+	}
+
+	/* Obtain the protection mutex, and increment the number of waiters.
+	   This allows the signal mechanism to only perform a signal if there
+	   are waiting threads.
+	 */
+	SDL_LockMutex(cond->lock);
+	++cond->waiting;
+	SDL_UnlockMutex(cond->lock);
+
+	/* Unlock the mutex, as is required by condition variable semantics */
+	SDL_UnlockMutex(mutex);
+
+	/* Wait for a signal */
+	if ( ms == SDL_MUTEX_MAXWAIT ) {
+		retval = SDL_SemWait(cond->wait_sem);
+	} else {
+		retval = SDL_SemWaitTimeout(cond->wait_sem, ms);
+	}
+
+	/* Let the signaler know we have completed the wait, otherwise
+           the signaler can race ahead and get the condition semaphore
+           if we are stopped between the mutex unlock and semaphore wait,
+           giving a deadlock.  See the following URL for details:
+        http://www-classic.be.com/aboutbe/benewsletter/volume_III/Issue40.html
+	*/
+	SDL_LockMutex(cond->lock);
+	if ( cond->signals > 0 ) {
+		/* If we timed out, we need to eat a condition signal */
+		if ( retval > 0 ) {
+			SDL_SemWait(cond->wait_sem);
+		}
+		/* We always notify the signal thread that we are done */
+		SDL_SemPost(cond->wait_done);
+
+		/* Signal handshake complete */
+		--cond->signals;
+	}
+	--cond->waiting;
+	SDL_UnlockMutex(cond->lock);
+
+	/* Lock the mutex, as is required by condition variable semantics */
+	SDL_LockMutex(mutex);
+
+	return retval;
+}
+
+/* Wait on the condition variable forever */
+int SDL_CondWait(SDL_cond *cond, SDL_mutex *mutex)
+{
+	return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT);
+}