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Diff: inc/types/ManagedType.h
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- 1:8aa5cdb4ab67
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/inc/types/ManagedType.h Thu Apr 07 01:33:22 2016 +0100 @@ -0,0 +1,279 @@ +/* +The MIT License (MIT) + +Copyright (c) 2016 British Broadcasting Corporation. +This software is provided by Lancaster University by arrangement with the BBC. + +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 MICROBIT_MANAGED_TYPE_H +#define MICROBIT_MANAGED_TYPE_H + +#include "MicroBitConfig.h" + +/** + * Class definition for a Generic Managed Type. + * + * Represents a reference counted object. + * + * @note When the destructor is called, delete is called on the object - implicitly calling the given objects destructor. + */ +template <class T> +class ManagedType +{ +protected: + + int *ref; + +public: + + T *object; + + /** + * Constructor for the managed type, given a class space T. + * + * @param object the object that you would like to be ref counted - of class T + * + * @code + * T object = new T(); + * ManagedType<T> mt(t); + * @endcode + */ + ManagedType(T* object); + + /** + * Default constructor for the managed type, given a class space T. + */ + ManagedType(); + + /** + * Copy constructor for the managed type, given a class space T. + * + * @param t another managed type instance of class type T. + * + * @code + * T* object = new T(); + * ManagedType<T> mt(t); + * ManagedType<T> mt1(mt); + * @endcode + */ + ManagedType(const ManagedType<T> &t); + + /** + * Destructor for the managed type, given a class space T. + */ + ~ManagedType(); + + /** + * Copy-assign member function for the managed type, given a class space. + * + * @code + * T* object = new T(); + * ManagedType<T> mt(t); + * ManagedType<T> mt1 = mt; + * @endcode + */ + ManagedType<T>& operator = (const ManagedType<T>&i); + + /** + * Returns the references to this ManagedType. + * + * @code + * T* object = new T(); + * ManagedType<T> mt(t); + * ManagedType<T> mt1(mt); + * + * mt.getReferences // this will be 2! + * @endcode + */ + int getReferences(); + + /** + * De-reference operator overload. This makes modifying ref-counted POD + * easier. + * + * @code + * ManagedType<int> x = 0; + * *x = 1; // mutates the ref-counted integer + * @endcode + */ + T& operator*() { + return *object; + } + + /** + * Method call operator overload. This forwards the call to the underlying + * object. + * + * @code + * ManagedType<T> x = new T(); + * x->m(); // resolves to T::m + */ + T* operator->() { + if (object == NULL) + microbit_panic(MICROBIT_NULL_DEREFERENCE); + return object; + } + + /** + * Shorthand for `x.operator->()` + */ + T* get() { + return object; + } + + /** + * A simple inequality overload to compare two ManagedType instances. + */ + bool operator!=(const ManagedType<T>& x) { + return !(this == x); + } + + /** + * A simple equality overload to compare two ManagedType instances. + */ + bool operator==(const ManagedType<T>& x) { + return this->object == x.object; + } +}; + +/** + * Constructor for the managed type, given a class space T. + * + * @param object the object that you would like to be ref counted - of class T + * + * @code + * T object = new T(); + * ManagedType<T> mt(t); + * @endcode + */ +template<typename T> +ManagedType<T>::ManagedType(T* object) +{ + this->object = object; + ref = (int *)malloc(sizeof(int)); + *ref = 1; +} + +/** + * Default constructor for the managed type, given a class space T. + */ +template<typename T> +ManagedType<T>::ManagedType() +{ + this->object = NULL; + ref = (int *)malloc(sizeof(int)); + *ref = 0; +} + +/** + * Copy constructor for the managed type, given a class space T. + * + * @param t another managed type instance of class type T. + * + * @code + * T* object = new T(); + * ManagedType<T> mt(t); + * ManagedType<T> mt1(mt); + * @endcode + */ +template<typename T> +ManagedType<T>::ManagedType(const ManagedType<T> &t) +{ + this->object = t.object; + this->ref = t.ref; + (*ref)++; +} + +/** + * Destructor for the managed type, given a class space T. + */ +template<typename T> +ManagedType<T>::~ManagedType() +{ + // Special case - we were created using a default constructor, and never assigned a value. + if (*ref == 0) + { + // Simply destroy our reference counter and we're done. + free(ref); + } + + // Normal case - we have a valid piece of data. + // Decrement our reference counter and free all allocated memory if we're deleting the last reference. + else if (--(*ref) == 0) + { + delete object; + free(ref); + } +} + +/** + * Copy-assign member function for the managed type, given a class space. + * + * @code + * T* object = new T(); + * ManagedType<T> mt(t); + * ManagedType<T> mt1 = mt; + * @endcode + */ +template<typename T> +ManagedType<T>& ManagedType<T>::operator = (const ManagedType<T>&t) +{ + if (this == &t) + return *this; + + // Special case - we were created using a default constructor, and never assigned a value. + if (*ref == 0) + { + // Simply destroy our reference counter, as we're about to adopt another. + free(ref); + } + + else if (--(*ref) == 0) + { + delete object; + free(ref); + } + + object = t.object; + ref = t.ref; + + (*ref)++; + + return *this; +} + +/** + * Returns the references to this ManagedType. + * + * @code + * T* object = new T(); + * ManagedType<T> mt(t); + * ManagedType<T> mt1(mt); + * + * mt.getReferences // this will be 2! + * @endcode + */ +template<typename T> +int ManagedType<T>::getReferences() +{ + return (*ref); +} +#endif