1 files changed, 156 insertions, 0 deletions
diff --git a/qpid/cpp/src/qpid/sys/CopyOnWriteArray.h b/qpid/cpp/src/qpid/sys/CopyOnWriteArray.h
new file mode 100644
index 0000000000..45a231dfd8
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+++ b/qpid/cpp/src/qpid/sys/CopyOnWriteArray.h
@@ -0,0 +1,156 @@
+#ifndef QPID_SYS_COPYONWRITEARRAY_H
+#define QPID_SYS_COPYONWRITEARRAY_H
+
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * 
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+ */
+
+#include "qpid/sys/Mutex.h"
+#include <algorithm>
+#include <vector>
+#include <boost/shared_ptr.hpp>
+
+namespace qpid {
+namespace sys {
+
+/**
+ * An array that copies on adding/removing element allowing lock-free
+ * iteration.
+ */
+template <class T>
+class CopyOnWriteArray
+{
+public:
+    typedef boost::shared_ptr<const std::vector<T> > ConstPtr;
+
+    CopyOnWriteArray() {}
+    CopyOnWriteArray(const CopyOnWriteArray& c) : array(c.array) {}
+
+    void add(T& t)
+    {
+        Mutex::ScopedLock l(lock);
+        ArrayPtr copy(array ? new std::vector<T>(*array) : new std::vector<T>());
+        copy->push_back(t);
+        array = copy;
+    }
+
+    bool remove(T& t)
+    {
+        Mutex::ScopedLock l(lock);
+        if (array && std::find(array->begin(), array->end(), t) != array->end()) {
+            ArrayPtr copy(new std::vector<T>(*array));
+            copy->erase(std::find(copy->begin(), copy->end(), t));
+            array = copy;
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    bool clear()
+    {
+        Mutex::ScopedLock l(lock);
+        if (array && !array->empty()) {
+            ArrayPtr copy;
+            array = copy;
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    template <class F>
+    bool add_unless(T& t, F f)
+    {
+        Mutex::ScopedLock l(lock);
+        if (array && std::find_if(array->begin(), array->end(), f) != array->end()) {
+            return false;
+        } else {
+            ArrayPtr copy(array ? new std::vector<T>(*array) : new std::vector<T>());
+            copy->push_back(t);
+            array = copy;
+            return true;
+        }
+    }
+
+    template <class F>
+    bool remove_if(F f)
+    {
+        Mutex::ScopedLock l(lock);
+        if (array && std::find_if(array->begin(), array->end(), f) != array->end()) {
+            ArrayPtr copy(new std::vector<T>(*array));
+            copy->erase(std::remove_if(copy->begin(), copy->end(), f), copy->end());
+            array = copy;
+            return true;
+        }
+        return false;
+    }
+
+    template <class TestFn, class ModifierFn>
+    bool modify_if(TestFn f, ModifierFn & m)
+    {
+        if (!array)
+            return false;
+        {
+            Mutex::ScopedLock l(lock);
+            if (std::find_if(array->begin(), array->end(), f) != array->end())
+            {
+                ArrayPtr copy(new std::vector<T>(*array));
+                m(*std::find_if(copy->begin(), copy->end(), f));
+                array = copy;
+                return true;
+            }
+        }
+        return false;
+    }
+
+    template <class F>
+    F for_each(F f)
+    {
+        ArrayPtr a;
+        {
+            Mutex::ScopedLock l(lock);
+            a = array;
+        }
+        if (!a) return f;
+        return std::for_each(a->begin(), a->end(), f);
+    }
+
+    ConstPtr snapshot()
+    {
+        ConstPtr a;
+        {
+            Mutex::ScopedLock l(lock);
+            a = array;
+        }
+        return a;
+    }
+
+private:
+    typedef boost::shared_ptr< std::vector<T> > ArrayPtr;
+    Mutex lock;
+    ArrayPtr array;
+};
+
+}}
+
+
+
+#endif  /*!QPID_SYS_COPYONWRITEARRAY_H*/