--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/thread/riscos/SDL_syssem.c	Fri Sep 17 13:20:10 2004 +0000
@@ -0,0 +1,216 @@
+/*
+    SDL - Simple DirectMedia Layer
+    Copyright (C) 1997-2004 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
+*/
+
+/* RISC OS doesn't have semiphores so use code based on generic implementation */
+
+#ifdef SAVE_RCSID
+static char rcsid =
+ "@(#) $Id$";
+#endif
+
+/* An implementation of semaphores using mutexes and condition variables */
+
+#include <stdlib.h>
+
+#include "SDL_error.h"
+#include "SDL_timer.h"
+#include "SDL_thread.h"
+
+#include "SDL_systhread_c.h"
+
+#ifdef DISABLE_THREADS
+
+SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
+{
+	SDL_SetError("SDL not configured with thread support");
+	return (SDL_sem *)0;
+}
+
+void SDL_DestroySemaphore(SDL_sem *sem)
+{
+	return;
+}
+
+int SDL_SemTryWait(SDL_sem *sem)
+{
+	SDL_SetError("SDL not configured with thread support");
+	return -1;
+}
+
+int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
+{
+	SDL_SetError("SDL not configured with thread support");
+	return -1;
+}
+
+int SDL_SemWait(SDL_sem *sem)
+{
+	SDL_SetError("SDL not configured with thread support");
+	return -1;
+}
+
+Uint32 SDL_SemValue(SDL_sem *sem)
+{
+	return 0;
+}
+
+int SDL_SemPost(SDL_sem *sem)
+{
+	SDL_SetError("SDL not configured with thread support");
+	return -1;
+}
+
+#else
+
+struct SDL_semaphore
+{
+	Uint32 count;
+	Uint32 waiters_count;
+	SDL_mutex *count_lock;
+	SDL_cond *count_nonzero;
+};
+
+SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
+{
+	SDL_sem *sem;
+
+	sem = (SDL_sem *)malloc(sizeof(*sem));
+	if ( ! sem ) {
+		SDL_OutOfMemory();
+		return(0);
+	}
+	sem->count = initial_value;
+	sem->waiters_count = 0;
+
+	sem->count_lock = SDL_CreateMutex();
+	sem->count_nonzero = SDL_CreateCond();
+	if ( ! sem->count_lock || ! sem->count_nonzero ) {
+		SDL_DestroySemaphore(sem);
+		return(0);
+	}
+
+	return(sem);
+}
+
+/* WARNING:
+   You cannot call this function when another thread is using the semaphore.
+*/
+void SDL_DestroySemaphore(SDL_sem *sem)
+{
+	if ( sem ) {
+		sem->count = 0xFFFFFFFF;
+		while ( sem->waiters_count > 0) {
+			SDL_CondSignal(sem->count_nonzero);
+			SDL_Delay(10);
+		}
+		SDL_DestroyCond(sem->count_nonzero);
+		SDL_mutexP(sem->count_lock);
+		SDL_mutexV(sem->count_lock);
+		SDL_DestroyMutex(sem->count_lock);
+		free(sem);
+	}
+}
+
+int SDL_SemTryWait(SDL_sem *sem)
+{
+	int retval;
+
+	if ( ! sem ) {
+		SDL_SetError("Passed a NULL semaphore");
+		return -1;
+	}
+
+	retval = SDL_MUTEX_TIMEDOUT;
+	SDL_LockMutex(sem->count_lock);
+	if ( sem->count > 0 ) {
+		--sem->count;
+		retval = 0;
+	}
+	SDL_UnlockMutex(sem->count_lock);
+
+	return retval;
+}
+
+int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
+{
+	int retval;
+
+	if ( ! sem ) {
+		SDL_SetError("Passed a NULL semaphore");
+		return -1;
+	}
+
+	/* A timeout of 0 is an easy case */
+	if ( timeout == 0 ) {
+		return SDL_SemTryWait(sem);
+	}
+
+	SDL_LockMutex(sem->count_lock);
+	++sem->waiters_count;
+	retval = 0;
+	while ( (sem->count == 0) && (retval != SDL_MUTEX_TIMEDOUT) ) {
+		retval = SDL_CondWaitTimeout(sem->count_nonzero,
+		                             sem->count_lock, timeout);
+	}
+	--sem->waiters_count;
+	--sem->count;
+	SDL_UnlockMutex(sem->count_lock);
+
+	return retval;
+}
+
+int SDL_SemWait(SDL_sem *sem)
+{
+	return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
+}
+
+Uint32 SDL_SemValue(SDL_sem *sem)
+{
+	Uint32 value;
+	
+	value = 0;
+	if ( sem ) {
+		SDL_LockMutex(sem->count_lock);
+		value = sem->count;
+		SDL_UnlockMutex(sem->count_lock);
+	}
+	return value;
+}
+
+int SDL_SemPost(SDL_sem *sem)
+{
+	if ( ! sem ) {
+		SDL_SetError("Passed a NULL semaphore");
+		return -1;
+	}
+
+	SDL_LockMutex(sem->count_lock);
+	if ( sem->waiters_count > 0 ) {
+		SDL_CondSignal(sem->count_nonzero);
+	}
+	++sem->count;
+	SDL_UnlockMutex(sem->count_lock);
+
+	return 0;
+}
+
+#endif /* DISABLE_THREADS */