Added a README file regarding WinRT support

To note, this file is currently formatted with CRLF line endings, rather than
LF, to allow the file to be viewed with Notepad.

src/thread/pthread/SDL_sysmutex.c

@@ -0,0 +1,193 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2014 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+#include "../../SDL_internal.h"
+
+#define _GNU_SOURCE
+#include <pthread.h>
+#include <errno.h>
+
+#include "SDL_thread.h"
+
+#if !SDL_THREAD_PTHREAD_RECURSIVE_MUTEX && \
+    !SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
+#define FAKE_RECURSIVE_MUTEX 1
+#endif
+
+struct SDL_mutex
+{
+    pthread_mutex_t id;
+#if FAKE_RECURSIVE_MUTEX
+    int recursive;
+    pthread_t owner;
+#endif
+};
+
+SDL_mutex *
+SDL_CreateMutex(void)
+{
+    SDL_mutex *mutex;
+    pthread_mutexattr_t attr;
+
+    /* Allocate the structure */
+    mutex = (SDL_mutex *) SDL_calloc(1, sizeof(*mutex));
+    if (mutex) {
+        pthread_mutexattr_init(&attr);
+#if SDL_THREAD_PTHREAD_RECURSIVE_MUTEX
+        pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
+#elif SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
+        pthread_mutexattr_setkind_np(&attr, PTHREAD_MUTEX_RECURSIVE_NP);
+#else
+        /* No extra attributes necessary */
+#endif
+        if (pthread_mutex_init(&mutex->id, &attr) != 0) {
+            SDL_SetError("pthread_mutex_init() failed");
+            SDL_free(mutex);
+            mutex = NULL;
+        }
+    } else {
+        SDL_OutOfMemory();
+    }
+    return (mutex);
+}
+
+void
+SDL_DestroyMutex(SDL_mutex * mutex)
+{
+    if (mutex) {
+        pthread_mutex_destroy(&mutex->id);
+        SDL_free(mutex);
+    }
+}
+
+/* Lock the mutex */
+int
+SDL_LockMutex(SDL_mutex * mutex)
+{
+#if FAKE_RECURSIVE_MUTEX
+    pthread_t this_thread;
+#endif
+
+    if (mutex == NULL) {
+        return SDL_SetError("Passed a NULL mutex");
+    }
+
+#if FAKE_RECURSIVE_MUTEX
+    this_thread = pthread_self();
+    if (mutex->owner == this_thread) {
+        ++mutex->recursive;
+    } else {
+        /* The order of operations is important.
+           We set the locking thread id after we obtain the lock
+           so unlocks from other threads will fail.
+         */
+        if (pthread_mutex_lock(&mutex->id) == 0) {
+            mutex->owner = this_thread;
+            mutex->recursive = 0;
+        } else {
+            return SDL_SetError("pthread_mutex_lock() failed");
+        }
+    }
+#else
+    if (pthread_mutex_lock(&mutex->id) < 0) {
+        return SDL_SetError("pthread_mutex_lock() failed");
+    }
+#endif
+    return 0;
+}
+
+int
+SDL_TryLockMutex(SDL_mutex * mutex)
+{
+    int retval;
+#if FAKE_RECURSIVE_MUTEX
+    pthread_t this_thread;
+#endif
+
+    if (mutex == NULL) {
+        return SDL_SetError("Passed a NULL mutex");
+    }
+
+    retval = 0;
+#if FAKE_RECURSIVE_MUTEX
+    this_thread = pthread_self();
+    if (mutex->owner == this_thread) {
+        ++mutex->recursive;
+    } else {
+        /* The order of operations is important.
+         We set the locking thread id after we obtain the lock
+         so unlocks from other threads will fail.
+         */
+        if (pthread_mutex_lock(&mutex->id) == 0) {
+            mutex->owner = this_thread;
+            mutex->recursive = 0;
+        } else if (errno == EBUSY) {
+            retval = SDL_MUTEX_TIMEDOUT;
+        } else {
+            retval = SDL_SetError("pthread_mutex_trylock() failed");
+        }
+    }
+#else
+    if (pthread_mutex_trylock(&mutex->id) != 0) {
+        if (errno == EBUSY) {
+            retval = SDL_MUTEX_TIMEDOUT;
+        } else {
+            retval = SDL_SetError("pthread_mutex_trylock() failed");
+        }
+    }
+#endif
+    return retval;
+}
+
+int
+SDL_UnlockMutex(SDL_mutex * mutex)
+{
+    if (mutex == NULL) {
+        return SDL_SetError("Passed a NULL mutex");
+    }
+
+#if FAKE_RECURSIVE_MUTEX
+    /* We can only unlock the mutex if we own it */
+    if (pthread_self() == mutex->owner) {
+        if (mutex->recursive) {
+            --mutex->recursive;
+        } else {
+            /* The order of operations is important.
+               First reset the owner so another thread doesn't lock
+               the mutex and set the ownership before we reset it,
+               then release the lock semaphore.
+             */
+            mutex->owner = 0;
+            pthread_mutex_unlock(&mutex->id);
+        }
+    } else {
+        return SDL_SetError("mutex not owned by this thread");
+    }
+
+#else
+    if (pthread_mutex_unlock(&mutex->id) < 0) {
+        return SDL_SetError("pthread_mutex_unlock() failed");
+    }
+#endif /* FAKE_RECURSIVE_MUTEX */
+
+    return 0;
+}
+
+/* vi: set ts=4 sw=4 expandtab: */