Initial clone in from local subversion server

Common.cpp

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+#include "Common.h"
+#include <iostream>
+
+SharedCanvas2D::SharedCanvas2D()
+{
+    this->canvas = NULL;
+}
+
+SharedCanvas2D::~SharedCanvas2D()
+{
+    this->releaseCanvas();
+}
+
+/**
+ * @brief Return a pointer to the SDL_Surface pointer held by this shared canvas
+ * @return SDL_Surface *
+ */
+SDL_Surface *SharedCanvas2D::getCanvas()
+{
+    return this->canvas;
+}
+
+/**
+ * @brief Set the canvas pointer to the given object, and increment its refcount
+ * @param obj A SharedCanvas2D object whose surface you want to share
+ * @return 0 on success, 1 on failure
+ */
+int SharedCanvas2D::shareCanvas(SharedCanvas2D *obj)
+{
+    if ( obj == NULL || this->canvas != NULL || obj->getCanvas() == NULL ) {
+	std::cerr << "Unable to share canvas from object " << obj << "\n";
+	return 1;
+    }
+    this->canvas = obj->getCanvas();
+    this->canvas->refcount += 1;
+    return 0;
+}
+
+/**
+ * @brief Set the canvas pointer to the given object, and increment its refcount
+ * @param obj A SDL_Surface pointer who you want to share
+ * @return 0 on success, 1 on failure
+ */
+int SharedCanvas2D::shareCanvas(SDL_Surface *obj)
+{
+  if ( obj == NULL ) {
+    return 1;
+  }
+
+  this->canvas = obj;
+  obj->refcount += 1;
+  return 0;
+}
+
+/**
+ * @fn SharedCanvas2D::releaseCanvas
+ * @brief Decrement the refcount of the canvas we're currently sharing, and release it
+ * @return 0 on success, 1 on failure
+ */
+int SharedCanvas2D::releaseCanvas()
+{
+    if ( this->canvas == NULL ) {
+	return 0;
+    }
+    if ( this->canvas->refcount >= 2 ) {
+	this->canvas->refcount -= 1;
+	this->canvas = NULL;
+	return 1;
+    } else if ( this->canvas->refcount == 1 ) {
+	SDL_FreeSurface(this->canvas);
+	return 1;
+    }
+    // do nothing if canvas refcount == 0 (thou shalt not double free)
+    return 0;
+}