MemberFunctionCallback.h

00001 /*
00002 The MIT License (MIT)
00003 
00004 Copyright (c) 2016 British Broadcasting Corporation.
00005 This software is provided by Lancaster University by arrangement with the BBC.
00006 
00007 Permission is hereby granted, free of charge, to any person obtaining a
00008 copy of this software and associated documentation files (the "Software"),
00009 to deal in the Software without restriction, including without limitation
00010 the rights to use, copy, modify, merge, publish, distribute, sublicense,
00011 and/or sell copies of the Software, and to permit persons to whom the
00012 Software is furnished to do so, subject to the following conditions:
00013 
00014 The above copyright notice and this permission notice shall be included in
00015 all copies or substantial portions of the Software.
00016 
00017 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
00018 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
00019 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
00020 THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
00021 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
00022 FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
00023 DEALINGS IN THE SOFTWARE.
00024 */
00025 
00026 #ifndef MEMBER_FUNCTION_CALLBACK_H
00027 #define MEMBER_FUNCTION_CALLBACK_H
00028 
00029 #include "mbed.h"
00030 #include "MicroBitConfig.h"
00031 #include "MicroBitEvent.h"
00032 #include "MicroBitCompat.h"
00033 
00034 /**
00035   * Class definition for a MemberFunctionCallback.
00036   *
00037   * C++ member functions (also known as methods) have a more complex
00038   * representation than normal C functions. This class allows a reference to
00039   * a C++ member function to be stored then called at a later date.
00040   *
00041   * This class is used extensively by the MicroBitMessageBus to deliver
00042   * events to C++ methods.
00043   */
00044 class MemberFunctionCallback
00045 {
00046     private:
00047     void* object;
00048     uint32_t method[4];
00049     void (*invoke)(void *object, uint32_t *method, MicroBitEvent e);
00050     template <typename T> static void methodCall(void* object, uint32_t*method, MicroBitEvent e);
00051 
00052     public:
00053 
00054     /**
00055       * Constructor. Creates a MemberFunctionCallback based on a pointer to given method.
00056       *
00057       * @param object The object the callback method should be invooked on.
00058       *
00059       * @param method The method to invoke.
00060       */
00061     template <typename T> MemberFunctionCallback(T* object, void (T::*method)(MicroBitEvent e));
00062 
00063     /**
00064       * A comparison of two MemberFunctionCallback objects.
00065       *
00066       * @return true if the given MemberFunctionCallback is equivalent to this one, false otherwise.
00067       */
00068     bool operator==(const MemberFunctionCallback &mfc);
00069 
00070     /**
00071       * Calls the method reference held by this MemberFunctionCallback.
00072       *
00073       * @param e The event to deliver to the method
00074       */
00075     void fire(MicroBitEvent e);
00076 };
00077 
00078 /**
00079   * Constructor. Creates a MemberFunctionCallback based on a pointer to given method.
00080   *
00081   * @param object The object the callback method should be invooked on.
00082   *
00083   * @param method The method to invoke.
00084   */
00085 template <typename T>
00086 MemberFunctionCallback::MemberFunctionCallback(T* object, void (T::*method)(MicroBitEvent e))
00087 {
00088     this->object = object;
00089     memclr(this->method, sizeof(this->method));
00090     memcpy(this->method, &method, sizeof(method));
00091     invoke = &MemberFunctionCallback::methodCall<T>;
00092 }
00093 
00094 /**
00095   * A template used to create a static method capable of invoking a C++ member function (method)
00096   * based on the given parameters.
00097   *
00098   * @param object The object the callback method should be invooked on.
00099   *
00100   * @param method The method to invoke.
00101   *
00102   * @param method The MicroBitEvent to supply to the given member function.
00103   */
00104 template <typename T>
00105 void MemberFunctionCallback::methodCall(void *object, uint32_t *method, MicroBitEvent e)
00106 {
00107     T* o = (T*)object;
00108     void (T::*m)(MicroBitEvent);
00109     memcpy(&m, method, sizeof(m));
00110 
00111     (o->*m)(e);
00112 }
00113 
00114 #endif