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inc/drivers/MicroBitMessageBus.h@1:8aa5cdb4ab67, 2016-04-07 (annotated)

Committer:
Jonathan Austin
Date:
Thu Apr 07 01:33:22 2016 +0100
Revision:
1:8aa5cdb4ab67
Child:
41:da05ec75cd5d
Synchronized with git rev 55cb9199

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Jonathan Austin 1:8aa5cdb4ab67 1 /*
Jonathan Austin 1:8aa5cdb4ab67 2 The MIT License (MIT)
Jonathan Austin 1:8aa5cdb4ab67 3
Jonathan Austin 1:8aa5cdb4ab67 4 Copyright (c) 2016 British Broadcasting Corporation.
Jonathan Austin 1:8aa5cdb4ab67 5 This software is provided by Lancaster University by arrangement with the BBC.
Jonathan Austin 1:8aa5cdb4ab67 6
Jonathan Austin 1:8aa5cdb4ab67 7 Permission is hereby granted, free of charge, to any person obtaining a
Jonathan Austin 1:8aa5cdb4ab67 8 copy of this software and associated documentation files (the "Software"),
Jonathan Austin 1:8aa5cdb4ab67 9 to deal in the Software without restriction, including without limitation
Jonathan Austin 1:8aa5cdb4ab67 10 the rights to use, copy, modify, merge, publish, distribute, sublicense,
Jonathan Austin 1:8aa5cdb4ab67 11 and/or sell copies of the Software, and to permit persons to whom the
Jonathan Austin 1:8aa5cdb4ab67 12 Software is furnished to do so, subject to the following conditions:
Jonathan Austin 1:8aa5cdb4ab67 13
Jonathan Austin 1:8aa5cdb4ab67 14 The above copyright notice and this permission notice shall be included in
Jonathan Austin 1:8aa5cdb4ab67 15 all copies or substantial portions of the Software.
Jonathan Austin 1:8aa5cdb4ab67 16
Jonathan Austin 1:8aa5cdb4ab67 17 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
Jonathan Austin 1:8aa5cdb4ab67 18 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
Jonathan Austin 1:8aa5cdb4ab67 19 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
Jonathan Austin 1:8aa5cdb4ab67 20 THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
Jonathan Austin 1:8aa5cdb4ab67 21 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
Jonathan Austin 1:8aa5cdb4ab67 22 FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
Jonathan Austin 1:8aa5cdb4ab67 23 DEALINGS IN THE SOFTWARE.
Jonathan Austin 1:8aa5cdb4ab67 24 */
Jonathan Austin 1:8aa5cdb4ab67 25
Jonathan Austin 1:8aa5cdb4ab67 26 #ifndef MICROBIT_MESSAGE_BUS_H
Jonathan Austin 1:8aa5cdb4ab67 27 #define MICROBIT_MESSAGE_BUS_H
Jonathan Austin 1:8aa5cdb4ab67 28
Jonathan Austin 1:8aa5cdb4ab67 29 #include "mbed.h"
Jonathan Austin 1:8aa5cdb4ab67 30 #include "MicroBitConfig.h"
Jonathan Austin 1:8aa5cdb4ab67 31 #include "MicroBitComponent.h"
Jonathan Austin 1:8aa5cdb4ab67 32 #include "MicroBitEvent.h"
Jonathan Austin 1:8aa5cdb4ab67 33 #include "MicroBitListener.h"
Jonathan Austin 1:8aa5cdb4ab67 34 #include "EventModel.h"
Jonathan Austin 1:8aa5cdb4ab67 35
Jonathan Austin 1:8aa5cdb4ab67 36 /**
Jonathan Austin 1:8aa5cdb4ab67 37 * Class definition for the MicroBitMessageBus.
Jonathan Austin 1:8aa5cdb4ab67 38 *
Jonathan Austin 1:8aa5cdb4ab67 39 * The MicroBitMessageBus is the common mechanism to deliver asynchronous events on the
Jonathan Austin 1:8aa5cdb4ab67 40 * MicroBit platform. It serves a number of purposes:
Jonathan Austin 1:8aa5cdb4ab67 41 *
Jonathan Austin 1:8aa5cdb4ab67 42 * 1) It provides an eventing abstraction that is independent of the underlying substrate.
Jonathan Austin 1:8aa5cdb4ab67 43 *
Jonathan Austin 1:8aa5cdb4ab67 44 * 2) It provides a mechanism to decouple user code from trusted system code
Jonathan Austin 1:8aa5cdb4ab67 45 * i.e. the basis of a message passing nano kernel.
Jonathan Austin 1:8aa5cdb4ab67 46 *
Jonathan Austin 1:8aa5cdb4ab67 47 * 3) It allows a common high level eventing abstraction across a range of hardware types.e.g. buttons, BLE...
Jonathan Austin 1:8aa5cdb4ab67 48 *
Jonathan Austin 1:8aa5cdb4ab67 49 * 4) It provides a mechanim for extensibility - new devices added via I/O pins can have OO based
Jonathan Austin 1:8aa5cdb4ab67 50 * drivers and communicate via the message bus with minima impact on user level languages.
Jonathan Austin 1:8aa5cdb4ab67 51 *
Jonathan Austin 1:8aa5cdb4ab67 52 * 5) It allows for the possiblility of event / data aggregation, which in turn can save energy.
Jonathan Austin 1:8aa5cdb4ab67 53 *
Jonathan Austin 1:8aa5cdb4ab67 54 * It has the following design principles:
Jonathan Austin 1:8aa5cdb4ab67 55 *
Jonathan Austin 1:8aa5cdb4ab67 56 * 1) Maintain a low RAM footprint where possible
Jonathan Austin 1:8aa5cdb4ab67 57 *
Jonathan Austin 1:8aa5cdb4ab67 58 * 2) Make few assumptions about the underlying platform, but allow optimizations where possible.
Jonathan Austin 1:8aa5cdb4ab67 59 */
Jonathan Austin 1:8aa5cdb4ab67 60 class MicroBitMessageBus : public EventModel, public MicroBitComponent
Jonathan Austin 1:8aa5cdb4ab67 61 {
Jonathan Austin 1:8aa5cdb4ab67 62 public:
Jonathan Austin 1:8aa5cdb4ab67 63
Jonathan Austin 1:8aa5cdb4ab67 64 /**
Jonathan Austin 1:8aa5cdb4ab67 65 * Default constructor.
Jonathan Austin 1:8aa5cdb4ab67 66 *
Jonathan Austin 1:8aa5cdb4ab67 67 * Adds itself as a fiber component, and also configures itself to be the
Jonathan Austin 1:8aa5cdb4ab67 68 * default EventModel if defaultEventBus is NULL.
Jonathan Austin 1:8aa5cdb4ab67 69 */
Jonathan Austin 1:8aa5cdb4ab67 70 MicroBitMessageBus();
Jonathan Austin 1:8aa5cdb4ab67 71
Jonathan Austin 1:8aa5cdb4ab67 72 /**
Jonathan Austin 1:8aa5cdb4ab67 73 * Queues the given event to be sent to all registered recipients.
Jonathan Austin 1:8aa5cdb4ab67 74 *
Jonathan Austin 1:8aa5cdb4ab67 75 * @param evt The event to send.
Jonathan Austin 1:8aa5cdb4ab67 76 *
Jonathan Austin 1:8aa5cdb4ab67 77 * @code
Jonathan Austin 1:8aa5cdb4ab67 78 * MicroBitMessageBus bus;
Jonathan Austin 1:8aa5cdb4ab67 79 *
Jonathan Austin 1:8aa5cdb4ab67 80 * // Creates and sends the MicroBitEvent using bus.
Jonathan Austin 1:8aa5cdb4ab67 81 * MicrobitEvent evt(MICROBIT_ID_BUTTON_A, MICROBIT_BUTTON_EVT_CLICK);
Jonathan Austin 1:8aa5cdb4ab67 82 *
Jonathan Austin 1:8aa5cdb4ab67 83 * // Creates the MicrobitEvent, but delays the sending of that event.
Jonathan Austin 1:8aa5cdb4ab67 84 * MicrobitEvent evt1(MICROBIT_ID_BUTTON_A, MICROBIT_BUTTON_EVT_CLICK, CREATE_ONLY);
Jonathan Austin 1:8aa5cdb4ab67 85 *
Jonathan Austin 1:8aa5cdb4ab67 86 * bus.send(evt1);
Jonathan Austin 1:8aa5cdb4ab67 87 *
Jonathan Austin 1:8aa5cdb4ab67 88 * // This has the same effect!
Jonathan Austin 1:8aa5cdb4ab67 89 * evt1.fire()
Jonathan Austin 1:8aa5cdb4ab67 90 * @endcode
Jonathan Austin 1:8aa5cdb4ab67 91 */
Jonathan Austin 1:8aa5cdb4ab67 92 virtual int send(MicroBitEvent evt);
Jonathan Austin 1:8aa5cdb4ab67 93
Jonathan Austin 1:8aa5cdb4ab67 94 /**
Jonathan Austin 1:8aa5cdb4ab67 95 * Internal function, used to deliver the given event to all relevant recipients.
Jonathan Austin 1:8aa5cdb4ab67 96 * Normally, this is called once an event has been removed from the event queue.
Jonathan Austin 1:8aa5cdb4ab67 97 *
Jonathan Austin 1:8aa5cdb4ab67 98 * @param evt The event to send.
Jonathan Austin 1:8aa5cdb4ab67 99 *
Jonathan Austin 1:8aa5cdb4ab67 100 * @param urgent The type of listeners to process (optional). If set to true, only listeners defined as urgent and non-blocking will be processed
Jonathan Austin 1:8aa5cdb4ab67 101 * otherwise, all other (standard) listeners will be processed. Defaults to false.
Jonathan Austin 1:8aa5cdb4ab67 102 *
Jonathan Austin 1:8aa5cdb4ab67 103 * @return 1 if all matching listeners were processed, 0 if further processing is required.
Jonathan Austin 1:8aa5cdb4ab67 104 *
Jonathan Austin 1:8aa5cdb4ab67 105 * @note It is recommended that all external code uses the send() function instead of this function,
Jonathan Austin 1:8aa5cdb4ab67 106 * or the constructors provided by MicrobitEvent.
Jonathan Austin 1:8aa5cdb4ab67 107 */
Jonathan Austin 1:8aa5cdb4ab67 108 int process(MicroBitEvent &evt, bool urgent = false);
Jonathan Austin 1:8aa5cdb4ab67 109
Jonathan Austin 1:8aa5cdb4ab67 110 /**
Jonathan Austin 1:8aa5cdb4ab67 111 * Returns the microBitListener with the given position in our list.
Jonathan Austin 1:8aa5cdb4ab67 112 *
Jonathan Austin 1:8aa5cdb4ab67 113 * @param n The position in the list to return.
Jonathan Austin 1:8aa5cdb4ab67 114 *
Jonathan Austin 1:8aa5cdb4ab67 115 * @return the MicroBitListener at postion n in the list, or NULL if the position is invalid.
Jonathan Austin 1:8aa5cdb4ab67 116 */
Jonathan Austin 1:8aa5cdb4ab67 117 virtual MicroBitListener *elementAt(int n);
Jonathan Austin 1:8aa5cdb4ab67 118
Jonathan Austin 1:8aa5cdb4ab67 119 /**
Jonathan Austin 1:8aa5cdb4ab67 120 * Destructor for MicroBitMessageBus, where we deregister this instance from the array of fiber components.
Jonathan Austin 1:8aa5cdb4ab67 121 */
Jonathan Austin 1:8aa5cdb4ab67 122 ~MicroBitMessageBus();
Jonathan Austin 1:8aa5cdb4ab67 123
Jonathan Austin 1:8aa5cdb4ab67 124 /**
Jonathan Austin 1:8aa5cdb4ab67 125 * Add the given MicroBitListener to the list of event handlers, unconditionally.
Jonathan Austin 1:8aa5cdb4ab67 126 *
Jonathan Austin 1:8aa5cdb4ab67 127 * @param listener The MicroBitListener to add.
Jonathan Austin 1:8aa5cdb4ab67 128 *
Jonathan Austin 1:8aa5cdb4ab67 129 * @return MICROBIT_OK if the listener is valid, MICROBIT_INVALID_PARAMETER otherwise.
Jonathan Austin 1:8aa5cdb4ab67 130 */
Jonathan Austin 1:8aa5cdb4ab67 131 virtual int add(MicroBitListener *newListener);
Jonathan Austin 1:8aa5cdb4ab67 132
Jonathan Austin 1:8aa5cdb4ab67 133 /**
Jonathan Austin 1:8aa5cdb4ab67 134 * Remove the given MicroBitListener from the list of event handlers.
Jonathan Austin 1:8aa5cdb4ab67 135 *
Jonathan Austin 1:8aa5cdb4ab67 136 * @param listener The MicroBitListener to remove.
Jonathan Austin 1:8aa5cdb4ab67 137 *
Jonathan Austin 1:8aa5cdb4ab67 138 * @return MICROBIT_OK if the listener is valid, MICROBIT_INVALID_PARAMETER otherwise.
Jonathan Austin 1:8aa5cdb4ab67 139 */
Jonathan Austin 1:8aa5cdb4ab67 140 virtual int remove(MicroBitListener *newListener);
Jonathan Austin 1:8aa5cdb4ab67 141
Jonathan Austin 1:8aa5cdb4ab67 142 private:
Jonathan Austin 1:8aa5cdb4ab67 143
Jonathan Austin 1:8aa5cdb4ab67 144 MicroBitListener *listeners; // Chain of active listeners.
Jonathan Austin 1:8aa5cdb4ab67 145 MicroBitEventQueueItem *evt_queue_head; // Head of queued events to be processed.
Jonathan Austin 1:8aa5cdb4ab67 146 MicroBitEventQueueItem *evt_queue_tail; // Tail of queued events to be processed.
Jonathan Austin 1:8aa5cdb4ab67 147 uint16_t nonce_val; // The last nonce issued.
Jonathan Austin 1:8aa5cdb4ab67 148 uint16_t queueLength; // The number of events currently waiting to be processed.
Jonathan Austin 1:8aa5cdb4ab67 149
Jonathan Austin 1:8aa5cdb4ab67 150 /**
Jonathan Austin 1:8aa5cdb4ab67 151 * Cleanup any MicroBitListeners marked for deletion from the list.
Jonathan Austin 1:8aa5cdb4ab67 152 *
Jonathan Austin 1:8aa5cdb4ab67 153 * @return The number of listeners removed from the list.
Jonathan Austin 1:8aa5cdb4ab67 154 */
Jonathan Austin 1:8aa5cdb4ab67 155 int deleteMarkedListeners();
Jonathan Austin 1:8aa5cdb4ab67 156
Jonathan Austin 1:8aa5cdb4ab67 157 /**
Jonathan Austin 1:8aa5cdb4ab67 158 * Queue the given event for processing at a later time.
Jonathan Austin 1:8aa5cdb4ab67 159 * Add the given event at the tail of our queue.
Jonathan Austin 1:8aa5cdb4ab67 160 *
Jonathan Austin 1:8aa5cdb4ab67 161 * @param The event to queue.
Jonathan Austin 1:8aa5cdb4ab67 162 */
Jonathan Austin 1:8aa5cdb4ab67 163 void queueEvent(MicroBitEvent &evt);
Jonathan Austin 1:8aa5cdb4ab67 164
Jonathan Austin 1:8aa5cdb4ab67 165 /**
Jonathan Austin 1:8aa5cdb4ab67 166 * Extract the next event from the front of the event queue (if present).
Jonathan Austin 1:8aa5cdb4ab67 167 *
Jonathan Austin 1:8aa5cdb4ab67 168 * @return a pointer to the MicroBitEventQueueItem that is at the head of the list.
Jonathan Austin 1:8aa5cdb4ab67 169 */
Jonathan Austin 1:8aa5cdb4ab67 170 MicroBitEventQueueItem* dequeueEvent();
Jonathan Austin 1:8aa5cdb4ab67 171
Jonathan Austin 1:8aa5cdb4ab67 172 /**
Jonathan Austin 1:8aa5cdb4ab67 173 * Periodic callback from MicroBit.
Jonathan Austin 1:8aa5cdb4ab67 174 *
Jonathan Austin 1:8aa5cdb4ab67 175 * Process at least one event from the event queue, if it is not empty.
Jonathan Austin 1:8aa5cdb4ab67 176 * We then continue processing events until something appears on the runqueue.
Jonathan Austin 1:8aa5cdb4ab67 177 */
Jonathan Austin 1:8aa5cdb4ab67 178 virtual void idleTick();
Jonathan Austin 1:8aa5cdb4ab67 179
Jonathan Austin 1:8aa5cdb4ab67 180 /**
Jonathan Austin 1:8aa5cdb4ab67 181 * Indicates whether or not we have any background work to do.
Jonathan Austin 1:8aa5cdb4ab67 182 *
Jonathan Austin 1:8aa5cdb4ab67 183 * @return 1 if there are any events waitingto be processed, 0 otherwise.
Jonathan Austin 1:8aa5cdb4ab67 184 */
Jonathan Austin 1:8aa5cdb4ab67 185 virtual int isIdleCallbackNeeded();
Jonathan Austin 1:8aa5cdb4ab67 186 };
Jonathan Austin 1:8aa5cdb4ab67 187
Jonathan Austin 1:8aa5cdb4ab67 188 #endif