ref counting for pointers

1 files changed, 129 insertions, 0 deletions

diff --git a/src/FbTk/RefCount.hh b/src/FbTk/RefCount.hh
new file mode 100644
index 0000000..f437837
--- /dev/null
+++ b/src/FbTk/RefCount.hh
@@ -0,0 +1,129 @@
+// RefCount.hh for FbTk - Fluxbox Toolkit
+// Copyright (c) 2002 Henrik Kinnunen (fluxgen at users.sourceforge.net)
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#ifndef FBTK_REFCOUNT_HH
+#define FBTK_REFCOUNT_HH
+
+namespace FbTk {
+
+/// holds a pointer with reference counting, similar to std:auto_ptr
+template <typename Pointer>
+class RefCount {
+public:
+    RefCount();
+    explicit RefCount(Pointer *p);
+    explicit RefCount(RefCount<Pointer> &copy);
+    explicit RefCount(const RefCount<Pointer> &copy);
+    ~RefCount();
+    RefCount<Pointer> &operator = (const RefCount<Pointer> &copy);
+    RefCount<Pointer> &operator = (Pointer *p);
+    Pointer *operator * () const { return get(); } 
+    Pointer *operator -> () const { return get(); }
+    Pointer *get() const { return m_data; }
+    /// @return number of referenses
+    unsigned int usedBy() const { return (m_refcount != 0 ? *m_refcount : 0); }
+private:
+    /// increase referense count
+    void incRefCount();
+    /// decrease referense count
+    void decRefCount();
+    Pointer *m_data; ///< data holder
+    mutable unsigned int *m_refcount; ///< holds reference counting
+};
+
+// implementation
+
+template <typename Pointer>
+RefCount<Pointer>::RefCount():m_data(0), m_refcount(new unsigned int(0)) {
+
+}
+
+template <typename Pointer>
+RefCount<Pointer>::RefCount(RefCount<Pointer> &copy):
+    m_data(copy.m_data),
+    m_refcount(copy.m_refcount) {
+    incRefCount();
+}
+
+template <typename Pointer>
+RefCount<Pointer>::RefCount(Pointer *p):m_data(p), m_refcount(new unsigned int(0)) {
+    incRefCount();
+}
+
+template <typename Pointer>
+RefCount<Pointer>::RefCount(const RefCount<Pointer> &copy):
+    m_data(copy.m_data),
+    m_refcount(copy.m_refcount) {
+    incRefCount();
+}
+
+template <typename Pointer>
+RefCount<Pointer>::~RefCount() {
+    decRefCount();
+}
+
+template <typename Pointer>
+RefCount<Pointer> &RefCount<Pointer>::operator = (const RefCount<Pointer> &copy) {
+    decRefCount(); // dec current ref count
+    m_refcount = copy.m_refcount; // set new ref count
+    m_data = copy.m_data; // set new data pointer
+    incRefCount(); // inc new ref count 
+    return *this;
+}
+
+template <typename Pointer>
+RefCount<Pointer> &RefCount<Pointer>::operator = (Pointer *p) {
+    decRefCount();
+    m_data = p;
+    if (m_refcount == 0)
+        m_refcount = new unsigned int(0);
+    incRefCount();
+}
+
+template <typename Pointer>
+void RefCount<Pointer>::decRefCount() {
+    if (m_refcount == 0)
+        return;
+    if (*m_refcount == 0) { // already zero, then delete refcount
+        delete m_refcount;
+        m_refcount = 0;
+        return;
+    }
+    (*m_refcount)--;
+    if (*m_refcount == 0) { // destroy m_data and m_refcount if nobody else is using this
+        if (m_data != 0)
+            delete m_data;
+        m_data = 0;
+        delete m_refcount;
+        m_refcount = 0;
+    }
+}
+
+template <typename Pointer>
+void RefCount<Pointer>::incRefCount() {
+    if (m_refcount == 0)
+        return;
+    (*m_refcount)++;
+}
+
+}; // end namespace FbTk
+
+#endif // FBTK_REFCOUNT_HH