Background resolver.

osdep/BackgroundResolver.hpp

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+/*
+ * ZeroTier One - Network Virtualization Everywhere
+ * Copyright (C) 2011-2015  ZeroTier, Inc.
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ * --
+ *
+ * ZeroTier may be used and distributed under the terms of the GPLv3, which
+ * are available at: http://www.gnu.org/licenses/gpl-3.0.html
+ *
+ * If you would like to embed ZeroTier into a commercial application or
+ * redistribute it in a modified binary form, please contact ZeroTier Networks
+ * LLC. Start here: http://www.zerotier.com/
+ */
+
+#ifndef ZT_BACKGROUNDRESOLVER_HPP
+#define ZT_BACKGROUNDRESOLVER_HPP
+
+#include <vector>
+#include <string>
+
+#include "../node/Constants.hpp"
+#include "../node/Mutex.hpp"
+#include "../node/InetAddress.hpp"
+#include "../node/NonCopyable.hpp"
+#include "Thread.hpp"
+
+namespace ZeroTier {
+
+class BackgroundResolverJob;
+
+/**
+ * A simple background resolver
+ */
+class BackgroundResolver : NonCopyable
+{
+	friend class BackgroundResolverJob;
+
+public:
+	/**
+	 * Construct a new resolver
+	 *
+	 * resolveNow() must be called to actually initiate background resolution.
+	 *
+	 * @param name Name to resolve
+	 */
+	BackgroundResolver(const char *name);
+
+	~BackgroundResolver();
+
+	/**
+	 * @return Most recent resolver results or empty vector if none
+	 */
+	std::vector<InetAddress> get() const;
+
+	/**
+	 * Launch a background resolve job now
+	 *
+	 * If a resolve job is currently in progress, it is aborted and another
+	 * job is started.
+	 *
+	 * Note that jobs can't actually be aborted due to the limitations of the
+	 * ancient synchronous OS resolver APIs. As a result, in progress jobs
+	 * that are aborted are simply abandoned. Don't call this too frequently
+	 * or background threads might pile up.
+	 *
+	 * @param callback Callback function to receive notification or NULL if none
+	 * @praam arg Second argument to callback function
+	 */
+	void resolveNow(void (*callback)(BackgroundResolver *,void *),void *arg);
+
+	/**
+	 * Abort (abandon) any current resolve jobs
+	 */
+	void abort();
+
+	/**
+	 * @return True if a background job is in progress
+	 */
+	inline bool running() const
+	{
+		Mutex::Lock _l(_lock);
+		return (_job != (BackgroundResolverJob *)0);
+	}
+
+	/**
+	 * Wait for pending job to complete (if any)
+	 */
+	inline void wait() const
+	{
+		Thread t;
+		{
+			Mutex::Lock _l(_lock);
+			if (!_job)
+				return;
+			t = _jobThread;
+		}
+		Thread::join(t);
+	}
+
+private:
+	void _postResult(const std::vector<InetAddress> &ips);
+
+	std::string _name;
+	BackgroundResolverJob *_job;
+	Thread _jobThread;
+	void (*_callback)(BackgroundResolver *,void *);
+	void *_arg;
+	std::vector<InetAddress> _ips;
+	Mutex _lock;
+};
+
+} // namespace ZeroTier
+
+#endif