webkitgtk-2.16.5HEADwebkitgtk-2.16.5master

1 files changed, 132 insertions, 0 deletions

diff --git a/Source/WTF/wtf/RefCounter.h b/Source/WTF/wtf/RefCounter.h
new file mode 100644
index 000000000..b1aad5603
--- /dev/null
+++ b/Source/WTF/wtf/RefCounter.h
@@ -0,0 +1,132 @@
+/*
+ * Copyright (C) 2014 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef RefCounter_h
+#define RefCounter_h
+
+#include <functional>
+#include <wtf/Noncopyable.h>
+#include <wtf/RefPtr.h>
+
+namespace WTF {
+
+enum class RefCounterEvent { Decrement, Increment };
+
+template<typename T>
+class RefCounter {
+    WTF_MAKE_NONCOPYABLE(RefCounter);
+
+    class Count {
+        WTF_MAKE_NONCOPYABLE(Count);
+    public:
+        void ref();
+        void deref();
+
+    private:
+        friend class RefCounter;
+
+        Count(RefCounter& refCounter)
+            : m_refCounter(&refCounter)
+            , m_value(0)
+        {
+        }
+
+        RefCounter* m_refCounter;
+        size_t m_value;
+    };
+
+public:
+    using Token = RefPtr<Count>;
+    using ValueChangeFunction = std::function<void (RefCounterEvent)>;
+
+    RefCounter(ValueChangeFunction = nullptr);
+    ~RefCounter();
+
+    Token count() const
+    {
+        return m_count;
+    }
+
+    size_t value() const
+    {
+        return m_count->m_value;
+    }
+
+private:
+    ValueChangeFunction m_valueDidChange;
+    Count* m_count;
+};
+
+template<typename T>
+inline void RefCounter<T>::Count::ref()
+{
+    ++m_value;
+    if (m_refCounter && m_refCounter->m_valueDidChange)
+        m_refCounter->m_valueDidChange(RefCounterEvent::Increment);
+}
+
+template<typename T>
+inline void RefCounter<T>::Count::deref()
+{
+    ASSERT(m_value);
+
+    --m_value;
+    if (m_refCounter && m_refCounter->m_valueDidChange)
+        m_refCounter->m_valueDidChange(RefCounterEvent::Decrement);
+
+    // The Count object is kept alive so long as either the RefCounter that created it remains
+    // allocated, or so long as its reference count is non-zero.
+    // If the RefCounter has already been deallocted then delete the Count when its reference
+    // count reaches zero.
+    if (!m_refCounter && !m_value)
+        delete this;
+}
+
+template<typename T>
+inline RefCounter<T>::RefCounter(ValueChangeFunction valueDidChange)
+    : m_valueDidChange(valueDidChange)
+    , m_count(new Count(*this))
+{
+}
+
+template<typename T>
+inline RefCounter<T>::~RefCounter()
+{
+    // The Count object is kept alive so long as either the RefCounter that created it remains
+    // allocated, or so long as its reference count is non-zero.
+    // If the reference count of the Count is already zero then delete it now, otherwise
+    // clear its m_refCounter pointer.
+    if (m_count->m_value)
+        m_count->m_refCounter = nullptr;
+    else
+        delete m_count;
+}
+
+} // namespace WTF
+
+using WTF::RefCounter;
+using WTF::RefCounterEvent;
+
+#endif // RefCounter_h