Fix race condition with a std::string access

The downloading thread was writing to a std::string while the main
thread was trying to draw it, for example. Now access to the label
caption is guarded with a mutex.

Should fix crashes while downloading updates.

1 files changed, 94 insertions, 0 deletions

diff --git a/src/utils/mutex.h b/src/utils/mutex.h
new file mode 100644
index 00000000..6c35987c
--- /dev/null
+++ b/src/utils/mutex.h
@@ -0,0 +1,94 @@
+/*
+ *  The Mana World
+ *  Copyright 2008 The Mana World Development Team
+ *
+ *  This file is part of The Mana World.
+ *
+ *  The Mana World is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  any later version.
+ *
+ *  The Mana World 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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with The Mana World; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef TMW_MUTEX_H
+#define TMW_MUTEX_H
+
+#include <SDL_thread.h>
+
+#include "../log.h"
+
+/**
+ * A mutex provides mutual exclusion of access to certain data that is
+ * accessed by multiple threads.
+ */
+class Mutex
+{
+public:
+    Mutex();
+    ~Mutex();
+
+    void lock();
+    void unlock();
+
+private:
+    SDL_mutex *mMutex;
+};
+
+/**
+ * A convenience class for locking a mutex.
+ */
+class MutexLocker
+{
+public:
+    MutexLocker(Mutex mutex);
+    ~MutexLocker();
+
+private:
+    Mutex mMutex;
+};
+
+
+inline Mutex::Mutex()
+{
+    mMutex = SDL_CreateMutex();
+}
+
+inline Mutex::~Mutex()
+{
+    SDL_DestroyMutex(mMutex);
+}
+
+inline void Mutex::lock()
+{
+    if (SDL_mutexP(mMutex) == -1)
+        logger->log("Mutex locking failed: %s", SDL_GetError());
+}
+
+inline void Mutex::unlock()
+{
+    if (SDL_mutexV(mMutex) == -1)
+        logger->log("Mutex unlocking failed: %s", SDL_GetError());
+}
+
+
+inline MutexLocker::MutexLocker(Mutex mutex):
+    mMutex(mutex)
+{
+    mMutex.lock();
+}
+
+inline MutexLocker::~MutexLocker()
+{
+    mMutex.unlock();
+}
+
+#endif // TMW_MUTEX_H