From b617378430c02fb3c8d58258ad11ad71af226e49 Mon Sep 17 00:00:00 2001
From: Sebastian Messmer <mail@smessmer.de>
Date: Sat, 3 Oct 2015 01:23:39 +0200
Subject: [PATCH] Add a lock library

---
 lock/ConditionBarrier.h | 37 +++++++++++++++++++++
 lock/LockPool.cpp       |  1 +
 lock/LockPool.h         | 73 +++++++++++++++++++++++++++++++++++++++++
 lock/MutexPoolLock.h    | 38 +++++++++++++++++++++
 4 files changed, 149 insertions(+)
 create mode 100644 lock/ConditionBarrier.h
 create mode 100644 lock/LockPool.cpp
 create mode 100644 lock/LockPool.h
 create mode 100644 lock/MutexPoolLock.h

diff --git a/lock/ConditionBarrier.h b/lock/ConditionBarrier.h
new file mode 100644
index 00000000..e776d5c8
--- /dev/null
+++ b/lock/ConditionBarrier.h
@@ -0,0 +1,37 @@
+#ifndef MESSMER_CPPUTILS_CONDITIONBARRIER_H
+#define MESSMER_CPPUTILS__CONDITIONBARRIER_H
+
+#include <mutex>
+#include <condition_variable>
+
+//TODO Test
+
+namespace cpputils {
+    // Like a condition variable, but without spurious wakeups.
+    // The waiting threads are only woken, when notify() is called.
+    // After a call to release(), future calls to wait() will not block anymore.
+    class ConditionBarrier {
+    public:
+        ConditionBarrier() :_mutex(), _cv(), _triggered(false) {
+        }
+
+        void wait() {
+            std::unique_lock<std::mutex> lock(_mutex);
+            _cv.wait(lock, [this] {
+                return _triggered;
+            });
+        }
+
+        void release() {
+            std::unique_lock<std::mutex> lock(_mutex);
+            _triggered = true;
+            _cv.notify_all();
+        }
+    private:
+        std::mutex _mutex;
+        std::condition_variable _cv;
+        bool _triggered;
+    };
+}
+
+#endif
diff --git a/lock/LockPool.cpp b/lock/LockPool.cpp
new file mode 100644
index 00000000..460417c7
--- /dev/null
+++ b/lock/LockPool.cpp
@@ -0,0 +1 @@
+#include "LockPool.h"
diff --git a/lock/LockPool.h b/lock/LockPool.h
new file mode 100644
index 00000000..2ddc2830
--- /dev/null
+++ b/lock/LockPool.h
@@ -0,0 +1,73 @@
+#ifndef MESSMER_CPPUTILS_LOCKPOOL_H
+#define MESSMER_CPPUTILS_LOCKPOOL_H
+
+#include <mutex>
+#include <condition_variable>
+#include <vector>
+#include <algorithm>
+#include "../assert/assert.h"
+#include "../macros.h"
+
+//TODO Test
+//TODO Rename package to synchronization
+//TODO Rename to MutexPool
+namespace cpputils {
+    template<class LockName>
+    class LockPool {
+    public:
+        LockPool();
+        void lock(const LockName &lock, std::unique_lock<std::mutex> *lockToFreeWhileWaiting = nullptr);
+        void release(const LockName &lock);
+
+    private:
+        bool _isLocked(const LockName &lock) const;
+
+        std::vector<LockName> _lockedLocks;
+        std::mutex _mutex;
+        std::condition_variable _cv;
+
+        DISALLOW_COPY_AND_ASSIGN(LockPool);
+    };
+    template<class LockName>
+    inline LockPool<LockName>::LockPool(): _lockedLocks(), _mutex(), _cv() {}
+
+    template<class LockName>
+    inline void LockPool<LockName>::lock(const LockName &lock, std::unique_lock<std::mutex> *lockToFreeWhileWaiting) {
+        std::cerr << "Aquiring lock " << lock.ToString() << std::endl;
+        std::unique_lock<std::mutex> mutexLock(_mutex); // TODO Is shared_lock enough here?
+        std::cerr << (void*)this << " Bquiring lock " << lock.ToString() << std::endl;
+        if (_isLocked(lock)) {
+            std::cerr << " is locked " << lock.ToString() << std::endl;
+            if(lockToFreeWhileWaiting != nullptr) {
+                lockToFreeWhileWaiting->unlock();
+            }
+            _cv.wait(mutexLock, [this, &lock]{
+                return !_isLocked(lock);
+            });
+            std::cerr << " reaquiring " << lock.ToString() << std::endl;
+            if(lockToFreeWhileWaiting != nullptr) {
+                lockToFreeWhileWaiting->lock();
+            }
+        }
+        std::cerr << "Lock acquired  " << lock.ToString() << std::endl;
+        _lockedLocks.push_back(lock);
+    }
+
+    template<class LockName>
+    inline bool LockPool<LockName>::_isLocked(const LockName &lock) const {
+        return std::find(_lockedLocks.begin(), _lockedLocks.end(), lock) != _lockedLocks.end();
+    }
+
+    template<class LockName>
+    inline void LockPool<LockName>::release(const LockName &lock) {
+        std::cerr << "Releasing lock "<<lock.ToString()<<std::endl;
+        std::unique_lock<std::mutex> mutexLock(_mutex);
+        auto found = std::find(_lockedLocks.begin(), _lockedLocks.end(), lock);
+        ASSERT(found != _lockedLocks.end(), "Lock given to release() was not locked");
+        _lockedLocks.erase(found);
+        _cv.notify_all();
+        std::cerr << "Lock released  "<<lock.ToString()<<std::endl;
+    }
+}
+
+#endif
diff --git a/lock/MutexPoolLock.h b/lock/MutexPoolLock.h
new file mode 100644
index 00000000..a77953c3
--- /dev/null
+++ b/lock/MutexPoolLock.h
@@ -0,0 +1,38 @@
+#ifndef MESSMER_CPPUTILS_LOCK_MUTEXPOOLLOCK_H
+#define MESSMER_CPPUTILS_LOCK_MUTEXPOOLLOCK_H
+
+#include "LockPool.h"
+
+namespace cpputils {
+    template<class LockName>
+    class MutexPoolLock {
+    public:
+        MutexPoolLock(LockPool<LockName> *pool, const LockName &lockName): _pool(pool), _lockName(lockName) {
+            _pool->lock(_lockName);
+        }
+
+        MutexPoolLock(LockPool<LockName> *pool, const LockName &lockName, std::unique_lock<std::mutex> *lockToFreeWhileWaiting)
+                : _pool(pool), _lockName(lockName) {
+            _pool->lock(_lockName, lockToFreeWhileWaiting);
+        }
+        
+        MutexPoolLock(MutexPoolLock &&rhs): _pool(rhs._pool), _lockName(rhs._lockName) {
+            rhs._pool = nullptr;
+        }
+
+        ~MutexPoolLock() {
+            if (_pool != nullptr) {
+                _pool->release(_lockName);
+                _pool = nullptr;
+            }
+        }
+
+    private:
+        LockPool<LockName> *_pool;
+        LockName _lockName;
+        
+        DISALLOW_COPY_AND_ASSIGN(MutexPoolLock);
+    };
+}
+
+#endif