Implement a simple resource lock (threading)

In this initial implementation Locks are no-ops on platforms other than
Windows.

src/Lock.h

@@ -0,0 +1,114 @@
+/* <!-- copyright */
+/*
+ * aria2 - The high speed download utility
+ *
+ * Copyright (C) 2013 Nils Maier
+ *
+ * This program 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
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
+ */
+/* copyright --> */
+#ifndef D_LOCK_H
+#define D_LOCK_H
+
+#if defined(_WIN32)
+#include <windows.h>
+#elif defined(ENABLE_PTHREAD)
+#include <pthread.h>
+#endif
+
+
+namespace aria2 {
+
+class Lock {
+private:
+#if defined(_WIN32)
+  ::CRITICAL_SECTION section_;
+#elif defined(ENABLE_PTHREAD)
+  ::pthread_mutex_t mutex_;
+#endif
+
+public:
+  Lock() {
+#if defined(_WIN32)
+    ::InitializeCriticalSection(&section_);
+#elif defined(ENABLE_PTHREAD)
+    mutex_ = PTHREAD_RECURSIVE_MUTEX_INITIALIZER;
+#endif
+  }
+
+  ~Lock() {
+#if defined(_WIN32)
+    ::DeleteCriticalSection(&section_);
+#elif defined(ENABLE_PTHREAD)
+    ::pthread_mutex_destroy(&mutex_);
+#endif
+  }
+
+  inline void aquire() {
+#if defined(_WIN32)
+    ::EnterCriticalSection(&section_);
+#elif defined(ENABLE_PTHREAD)
+    ::pthread_mutex_lock(&mutex_);
+#endif
+  }
+
+  inline bool tryAquire() {
+#if defined(_WIN32)
+    return ::TryEnterCriticalSection(&section_) == TRUE;
+#elif defined(ENABLE_PTHREAD)
+    return ::pthread_mutex_trylock(&mutex_) == 0;
+#else
+    return true;
+#endif
+  }
+
+  inline void release() {
+#if defined(_WIN32)
+    ::LeaveCriticalSection(&section_);
+#elif defined(ENABLE_PTHREAD)
+    ::pthread_mutex_unlock(&mutex_);
+#endif
+  }
+
+};
+
+class LockGuard {
+private:
+  Lock& lock_;
+public:
+  inline LockGuard(Lock& lock) : lock_(lock) {
+    lock_.aquire();
+  }
+  inline ~LockGuard() {
+    lock_.release();
+  }
+};
+
+} // namespace aria2
+
+#endif // D_LOCK_H

src/Makefile.am

@@ -250,7 +250,8 @@ SRCS =  option_processing.cc\
 	HttpRequestConnectChain.h\
 	HttpProxyRequestConnectChain.h\
 	FtpNegotiationConnectChain.h\
-	FtpTunnelRequestConnectChain.h
+	FtpTunnelRequestConnectChain.h\
+	Lock.h
 
 # Android NDK R8e does not provide ftruncate64. Use assembly code from
 # android source code and link it.