Neil Johnson
Official Sheffield ARMBand micro:bit program
microbit/microbit-dal/source/drivers/MicroBitMessageBus.cpp@0:b9164b348919, 2016-10-17 (annotated)
- Committer:
- MrBedfordVan
- Date:
- Mon Oct 17 12:41:20 2016 +0000
- Revision:
- 0:b9164b348919
Official Sheffield ARMBand Micro:bit program
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| MrBedfordVan | 0:b9164b348919 | 1 | /* |
| MrBedfordVan | 0:b9164b348919 | 2 | The MIT License (MIT) |
| MrBedfordVan | 0:b9164b348919 | 3 | |
| MrBedfordVan | 0:b9164b348919 | 4 | Copyright (c) 2016 British Broadcasting Corporation. |
| MrBedfordVan | 0:b9164b348919 | 5 | This software is provided by Lancaster University by arrangement with the BBC. |
| MrBedfordVan | 0:b9164b348919 | 6 | |
| MrBedfordVan | 0:b9164b348919 | 7 | Permission is hereby granted, free of charge, to any person obtaining a |
| MrBedfordVan | 0:b9164b348919 | 8 | copy of this software and associated documentation files (the "Software"), |
| MrBedfordVan | 0:b9164b348919 | 9 | to deal in the Software without restriction, including without limitation |
| MrBedfordVan | 0:b9164b348919 | 10 | the rights to use, copy, modify, merge, publish, distribute, sublicense, |
| MrBedfordVan | 0:b9164b348919 | 11 | and/or sell copies of the Software, and to permit persons to whom the |
| MrBedfordVan | 0:b9164b348919 | 12 | Software is furnished to do so, subject to the following conditions: |
| MrBedfordVan | 0:b9164b348919 | 13 | |
| MrBedfordVan | 0:b9164b348919 | 14 | The above copyright notice and this permission notice shall be included in |
| MrBedfordVan | 0:b9164b348919 | 15 | all copies or substantial portions of the Software. |
| MrBedfordVan | 0:b9164b348919 | 16 | |
| MrBedfordVan | 0:b9164b348919 | 17 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| MrBedfordVan | 0:b9164b348919 | 18 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| MrBedfordVan | 0:b9164b348919 | 19 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
| MrBedfordVan | 0:b9164b348919 | 20 | THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| MrBedfordVan | 0:b9164b348919 | 21 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
| MrBedfordVan | 0:b9164b348919 | 22 | FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
| MrBedfordVan | 0:b9164b348919 | 23 | DEALINGS IN THE SOFTWARE. |
| MrBedfordVan | 0:b9164b348919 | 24 | */ |
| MrBedfordVan | 0:b9164b348919 | 25 | |
| MrBedfordVan | 0:b9164b348919 | 26 | /** |
| MrBedfordVan | 0:b9164b348919 | 27 | * Class definition for the MicroBitMessageBus. |
| MrBedfordVan | 0:b9164b348919 | 28 | * |
| MrBedfordVan | 0:b9164b348919 | 29 | * The MicroBitMessageBus is the common mechanism to deliver asynchronous events on the |
| MrBedfordVan | 0:b9164b348919 | 30 | * MicroBit platform. It serves a number of purposes: |
| MrBedfordVan | 0:b9164b348919 | 31 | * |
| MrBedfordVan | 0:b9164b348919 | 32 | * 1) It provides an eventing abstraction that is independent of the underlying substrate. |
| MrBedfordVan | 0:b9164b348919 | 33 | * |
| MrBedfordVan | 0:b9164b348919 | 34 | * 2) It provides a mechanism to decouple user code from trusted system code |
| MrBedfordVan | 0:b9164b348919 | 35 | * i.e. the basis of a message passing nano kernel. |
| MrBedfordVan | 0:b9164b348919 | 36 | * |
| MrBedfordVan | 0:b9164b348919 | 37 | * 3) It allows a common high level eventing abstraction across a range of hardware types.e.g. buttons, BLE... |
| MrBedfordVan | 0:b9164b348919 | 38 | * |
| MrBedfordVan | 0:b9164b348919 | 39 | * 4) It provides a mechanim for extensibility - new devices added via I/O pins can have OO based |
| MrBedfordVan | 0:b9164b348919 | 40 | * drivers and communicate via the message bus with minima impact on user level languages. |
| MrBedfordVan | 0:b9164b348919 | 41 | * |
| MrBedfordVan | 0:b9164b348919 | 42 | * 5) It allows for the possiblility of event / data aggregation, which in turn can save energy. |
| MrBedfordVan | 0:b9164b348919 | 43 | * |
| MrBedfordVan | 0:b9164b348919 | 44 | * It has the following design principles: |
| MrBedfordVan | 0:b9164b348919 | 45 | * |
| MrBedfordVan | 0:b9164b348919 | 46 | * 1) Maintain a low RAM footprint where possible |
| MrBedfordVan | 0:b9164b348919 | 47 | * |
| MrBedfordVan | 0:b9164b348919 | 48 | * 2) Make few assumptions about the underlying platform, but allow optimizations where possible. |
| MrBedfordVan | 0:b9164b348919 | 49 | */ |
| MrBedfordVan | 0:b9164b348919 | 50 | #include "MicroBitConfig.h" |
| MrBedfordVan | 0:b9164b348919 | 51 | #include "MicroBitMessageBus.h" |
| MrBedfordVan | 0:b9164b348919 | 52 | #include "MicroBitFiber.h" |
| MrBedfordVan | 0:b9164b348919 | 53 | #include "ErrorNo.h" |
| MrBedfordVan | 0:b9164b348919 | 54 | |
| MrBedfordVan | 0:b9164b348919 | 55 | /** |
| MrBedfordVan | 0:b9164b348919 | 56 | * Default constructor. |
| MrBedfordVan | 0:b9164b348919 | 57 | * |
| MrBedfordVan | 0:b9164b348919 | 58 | * Adds itself as a fiber component, and also configures itself to be the |
| MrBedfordVan | 0:b9164b348919 | 59 | * default EventModel if defaultEventBus is NULL. |
| MrBedfordVan | 0:b9164b348919 | 60 | */ |
| MrBedfordVan | 0:b9164b348919 | 61 | MicroBitMessageBus::MicroBitMessageBus() |
| MrBedfordVan | 0:b9164b348919 | 62 | { |
| MrBedfordVan | 0:b9164b348919 | 63 | this->listeners = NULL; |
| MrBedfordVan | 0:b9164b348919 | 64 | this->evt_queue_head = NULL; |
| MrBedfordVan | 0:b9164b348919 | 65 | this->evt_queue_tail = NULL; |
| MrBedfordVan | 0:b9164b348919 | 66 | this->queueLength = 0; |
| MrBedfordVan | 0:b9164b348919 | 67 | |
| MrBedfordVan | 0:b9164b348919 | 68 | fiber_add_idle_component(this); |
| MrBedfordVan | 0:b9164b348919 | 69 | |
| MrBedfordVan | 0:b9164b348919 | 70 | if(EventModel::defaultEventBus == NULL) |
| MrBedfordVan | 0:b9164b348919 | 71 | EventModel::defaultEventBus = this; |
| MrBedfordVan | 0:b9164b348919 | 72 | } |
| MrBedfordVan | 0:b9164b348919 | 73 | |
| MrBedfordVan | 0:b9164b348919 | 74 | /** |
| MrBedfordVan | 0:b9164b348919 | 75 | * Invokes a callback on a given MicroBitListener |
| MrBedfordVan | 0:b9164b348919 | 76 | * |
| MrBedfordVan | 0:b9164b348919 | 77 | * Internal wrapper function, used to enable |
| MrBedfordVan | 0:b9164b348919 | 78 | * parameterised callbacks through the fiber scheduler. |
| MrBedfordVan | 0:b9164b348919 | 79 | */ |
| MrBedfordVan | 0:b9164b348919 | 80 | void async_callback(void *param) |
| MrBedfordVan | 0:b9164b348919 | 81 | { |
| MrBedfordVan | 0:b9164b348919 | 82 | MicroBitListener *listener = (MicroBitListener *)param; |
| MrBedfordVan | 0:b9164b348919 | 83 | |
| MrBedfordVan | 0:b9164b348919 | 84 | // OK, now we need to decide how to behave depending on our configuration. |
| MrBedfordVan | 0:b9164b348919 | 85 | // If this a fiber f already active within this listener then check our |
| MrBedfordVan | 0:b9164b348919 | 86 | // configuration to determine the correct course of action. |
| MrBedfordVan | 0:b9164b348919 | 87 | // |
| MrBedfordVan | 0:b9164b348919 | 88 | |
| MrBedfordVan | 0:b9164b348919 | 89 | if (listener->flags & MESSAGE_BUS_LISTENER_BUSY) |
| MrBedfordVan | 0:b9164b348919 | 90 | { |
| MrBedfordVan | 0:b9164b348919 | 91 | // Drop this event, if that's how we've been configured. |
| MrBedfordVan | 0:b9164b348919 | 92 | if (listener->flags & MESSAGE_BUS_LISTENER_DROP_IF_BUSY) |
| MrBedfordVan | 0:b9164b348919 | 93 | return; |
| MrBedfordVan | 0:b9164b348919 | 94 | |
| MrBedfordVan | 0:b9164b348919 | 95 | // Queue this event up for later, if that's how we've been configured. |
| MrBedfordVan | 0:b9164b348919 | 96 | if (listener->flags & MESSAGE_BUS_LISTENER_QUEUE_IF_BUSY) |
| MrBedfordVan | 0:b9164b348919 | 97 | { |
| MrBedfordVan | 0:b9164b348919 | 98 | listener->queue(listener->evt); |
| MrBedfordVan | 0:b9164b348919 | 99 | return; |
| MrBedfordVan | 0:b9164b348919 | 100 | } |
| MrBedfordVan | 0:b9164b348919 | 101 | } |
| MrBedfordVan | 0:b9164b348919 | 102 | |
| MrBedfordVan | 0:b9164b348919 | 103 | // Determine the calling convention for the callback, and invoke... |
| MrBedfordVan | 0:b9164b348919 | 104 | // C++ is really bad at this! Especially as the ARM compiler is yet to support C++ 11 :-/ |
| MrBedfordVan | 0:b9164b348919 | 105 | |
| MrBedfordVan | 0:b9164b348919 | 106 | // Record that we have a fiber going into this listener... |
| MrBedfordVan | 0:b9164b348919 | 107 | listener->flags |= MESSAGE_BUS_LISTENER_BUSY; |
| MrBedfordVan | 0:b9164b348919 | 108 | |
| MrBedfordVan | 0:b9164b348919 | 109 | while (1) |
| MrBedfordVan | 0:b9164b348919 | 110 | { |
| MrBedfordVan | 0:b9164b348919 | 111 | // Firstly, check for a method callback into an object. |
| MrBedfordVan | 0:b9164b348919 | 112 | if (listener->flags & MESSAGE_BUS_LISTENER_METHOD) |
| MrBedfordVan | 0:b9164b348919 | 113 | listener->cb_method->fire(listener->evt); |
| MrBedfordVan | 0:b9164b348919 | 114 | |
| MrBedfordVan | 0:b9164b348919 | 115 | // Now a parameterised C function |
| MrBedfordVan | 0:b9164b348919 | 116 | else if (listener->flags & MESSAGE_BUS_LISTENER_PARAMETERISED) |
| MrBedfordVan | 0:b9164b348919 | 117 | listener->cb_param(listener->evt, listener->cb_arg); |
| MrBedfordVan | 0:b9164b348919 | 118 | |
| MrBedfordVan | 0:b9164b348919 | 119 | // We must have a plain C function |
| MrBedfordVan | 0:b9164b348919 | 120 | else |
| MrBedfordVan | 0:b9164b348919 | 121 | listener->cb(listener->evt); |
| MrBedfordVan | 0:b9164b348919 | 122 | |
| MrBedfordVan | 0:b9164b348919 | 123 | // If there are more events to process, dequeue the next one and process it. |
| MrBedfordVan | 0:b9164b348919 | 124 | if ((listener->flags & MESSAGE_BUS_LISTENER_QUEUE_IF_BUSY) && listener->evt_queue) |
| MrBedfordVan | 0:b9164b348919 | 125 | { |
| MrBedfordVan | 0:b9164b348919 | 126 | MicroBitEventQueueItem *item = listener->evt_queue; |
| MrBedfordVan | 0:b9164b348919 | 127 | |
| MrBedfordVan | 0:b9164b348919 | 128 | listener->evt = item->evt; |
| MrBedfordVan | 0:b9164b348919 | 129 | listener->evt_queue = listener->evt_queue->next; |
| MrBedfordVan | 0:b9164b348919 | 130 | delete item; |
| MrBedfordVan | 0:b9164b348919 | 131 | |
| MrBedfordVan | 0:b9164b348919 | 132 | // We spin the scheduler here, to preven any particular event handler from continuously holding onto resources. |
| MrBedfordVan | 0:b9164b348919 | 133 | schedule(); |
| MrBedfordVan | 0:b9164b348919 | 134 | } |
| MrBedfordVan | 0:b9164b348919 | 135 | else |
| MrBedfordVan | 0:b9164b348919 | 136 | break; |
| MrBedfordVan | 0:b9164b348919 | 137 | } |
| MrBedfordVan | 0:b9164b348919 | 138 | |
| MrBedfordVan | 0:b9164b348919 | 139 | // The fiber of exiting... clear our state. |
| MrBedfordVan | 0:b9164b348919 | 140 | listener->flags &= ~MESSAGE_BUS_LISTENER_BUSY; |
| MrBedfordVan | 0:b9164b348919 | 141 | } |
| MrBedfordVan | 0:b9164b348919 | 142 | |
| MrBedfordVan | 0:b9164b348919 | 143 | /** |
| MrBedfordVan | 0:b9164b348919 | 144 | * Queue the given event for processing at a later time. |
| MrBedfordVan | 0:b9164b348919 | 145 | * Add the given event at the tail of our queue. |
| MrBedfordVan | 0:b9164b348919 | 146 | * |
| MrBedfordVan | 0:b9164b348919 | 147 | * @param The event to queue. |
| MrBedfordVan | 0:b9164b348919 | 148 | */ |
| MrBedfordVan | 0:b9164b348919 | 149 | void MicroBitMessageBus::queueEvent(MicroBitEvent &evt) |
| MrBedfordVan | 0:b9164b348919 | 150 | { |
| MrBedfordVan | 0:b9164b348919 | 151 | int processingComplete; |
| MrBedfordVan | 0:b9164b348919 | 152 | |
| MrBedfordVan | 0:b9164b348919 | 153 | MicroBitEventQueueItem *prev = evt_queue_tail; |
| MrBedfordVan | 0:b9164b348919 | 154 | |
| MrBedfordVan | 0:b9164b348919 | 155 | // Now process all handler regsitered as URGENT. |
| MrBedfordVan | 0:b9164b348919 | 156 | // These pre-empt the queue, and are useful for fast, high priority services. |
| MrBedfordVan | 0:b9164b348919 | 157 | processingComplete = this->process(evt, true); |
| MrBedfordVan | 0:b9164b348919 | 158 | |
| MrBedfordVan | 0:b9164b348919 | 159 | // If we've already processed all event handlers, we're all done. |
| MrBedfordVan | 0:b9164b348919 | 160 | // No need to queue the event. |
| MrBedfordVan | 0:b9164b348919 | 161 | if (processingComplete) |
| MrBedfordVan | 0:b9164b348919 | 162 | return; |
| MrBedfordVan | 0:b9164b348919 | 163 | |
| MrBedfordVan | 0:b9164b348919 | 164 | // If we need to queue, but there is no space, then there's nothg we can do. |
| MrBedfordVan | 0:b9164b348919 | 165 | if (queueLength >= MESSAGE_BUS_LISTENER_MAX_QUEUE_DEPTH) |
| MrBedfordVan | 0:b9164b348919 | 166 | return; |
| MrBedfordVan | 0:b9164b348919 | 167 | |
| MrBedfordVan | 0:b9164b348919 | 168 | // Otherwise, we need to queue this event for later processing... |
| MrBedfordVan | 0:b9164b348919 | 169 | // We queue this event at the tail of the queue at the point where we entered queueEvent() |
| MrBedfordVan | 0:b9164b348919 | 170 | // This is important as the processing above *may* have generated further events, and |
| MrBedfordVan | 0:b9164b348919 | 171 | // we want to maintain ordering of events. |
| MrBedfordVan | 0:b9164b348919 | 172 | MicroBitEventQueueItem *item = new MicroBitEventQueueItem(evt); |
| MrBedfordVan | 0:b9164b348919 | 173 | |
| MrBedfordVan | 0:b9164b348919 | 174 | // The queue was empty when we entered this function, so queue our event at the start of the queue. |
| MrBedfordVan | 0:b9164b348919 | 175 | __disable_irq(); |
| MrBedfordVan | 0:b9164b348919 | 176 | |
| MrBedfordVan | 0:b9164b348919 | 177 | if (prev == NULL) |
| MrBedfordVan | 0:b9164b348919 | 178 | { |
| MrBedfordVan | 0:b9164b348919 | 179 | item->next = evt_queue_head; |
| MrBedfordVan | 0:b9164b348919 | 180 | evt_queue_head = item; |
| MrBedfordVan | 0:b9164b348919 | 181 | } |
| MrBedfordVan | 0:b9164b348919 | 182 | else |
| MrBedfordVan | 0:b9164b348919 | 183 | { |
| MrBedfordVan | 0:b9164b348919 | 184 | item->next = prev->next; |
| MrBedfordVan | 0:b9164b348919 | 185 | prev->next = item; |
| MrBedfordVan | 0:b9164b348919 | 186 | } |
| MrBedfordVan | 0:b9164b348919 | 187 | |
| MrBedfordVan | 0:b9164b348919 | 188 | if (item->next == NULL) |
| MrBedfordVan | 0:b9164b348919 | 189 | evt_queue_tail = item; |
| MrBedfordVan | 0:b9164b348919 | 190 | |
| MrBedfordVan | 0:b9164b348919 | 191 | queueLength++; |
| MrBedfordVan | 0:b9164b348919 | 192 | |
| MrBedfordVan | 0:b9164b348919 | 193 | __enable_irq(); |
| MrBedfordVan | 0:b9164b348919 | 194 | } |
| MrBedfordVan | 0:b9164b348919 | 195 | |
| MrBedfordVan | 0:b9164b348919 | 196 | /** |
| MrBedfordVan | 0:b9164b348919 | 197 | * Extract the next event from the front of the event queue (if present). |
| MrBedfordVan | 0:b9164b348919 | 198 | * |
| MrBedfordVan | 0:b9164b348919 | 199 | * @return a pointer to the MicroBitEventQueueItem that is at the head of the list. |
| MrBedfordVan | 0:b9164b348919 | 200 | */ |
| MrBedfordVan | 0:b9164b348919 | 201 | MicroBitEventQueueItem* MicroBitMessageBus::dequeueEvent() |
| MrBedfordVan | 0:b9164b348919 | 202 | { |
| MrBedfordVan | 0:b9164b348919 | 203 | MicroBitEventQueueItem *item = NULL; |
| MrBedfordVan | 0:b9164b348919 | 204 | |
| MrBedfordVan | 0:b9164b348919 | 205 | __disable_irq(); |
| MrBedfordVan | 0:b9164b348919 | 206 | |
| MrBedfordVan | 0:b9164b348919 | 207 | if (evt_queue_head != NULL) |
| MrBedfordVan | 0:b9164b348919 | 208 | { |
| MrBedfordVan | 0:b9164b348919 | 209 | item = evt_queue_head; |
| MrBedfordVan | 0:b9164b348919 | 210 | evt_queue_head = item->next; |
| MrBedfordVan | 0:b9164b348919 | 211 | |
| MrBedfordVan | 0:b9164b348919 | 212 | if (evt_queue_head == NULL) |
| MrBedfordVan | 0:b9164b348919 | 213 | evt_queue_tail = NULL; |
| MrBedfordVan | 0:b9164b348919 | 214 | |
| MrBedfordVan | 0:b9164b348919 | 215 | queueLength--; |
| MrBedfordVan | 0:b9164b348919 | 216 | } |
| MrBedfordVan | 0:b9164b348919 | 217 | |
| MrBedfordVan | 0:b9164b348919 | 218 | __enable_irq(); |
| MrBedfordVan | 0:b9164b348919 | 219 | |
| MrBedfordVan | 0:b9164b348919 | 220 | |
| MrBedfordVan | 0:b9164b348919 | 221 | return item; |
| MrBedfordVan | 0:b9164b348919 | 222 | } |
| MrBedfordVan | 0:b9164b348919 | 223 | |
| MrBedfordVan | 0:b9164b348919 | 224 | /** |
| MrBedfordVan | 0:b9164b348919 | 225 | * Cleanup any MicroBitListeners marked for deletion from the list. |
| MrBedfordVan | 0:b9164b348919 | 226 | * |
| MrBedfordVan | 0:b9164b348919 | 227 | * @return The number of listeners removed from the list. |
| MrBedfordVan | 0:b9164b348919 | 228 | */ |
| MrBedfordVan | 0:b9164b348919 | 229 | int MicroBitMessageBus::deleteMarkedListeners() |
| MrBedfordVan | 0:b9164b348919 | 230 | { |
| MrBedfordVan | 0:b9164b348919 | 231 | MicroBitListener *l, *p; |
| MrBedfordVan | 0:b9164b348919 | 232 | int removed = 0; |
| MrBedfordVan | 0:b9164b348919 | 233 | |
| MrBedfordVan | 0:b9164b348919 | 234 | l = listeners; |
| MrBedfordVan | 0:b9164b348919 | 235 | p = NULL; |
| MrBedfordVan | 0:b9164b348919 | 236 | |
| MrBedfordVan | 0:b9164b348919 | 237 | // Walk this list of event handlers. Delete any that match the given listener. |
| MrBedfordVan | 0:b9164b348919 | 238 | while (l != NULL) |
| MrBedfordVan | 0:b9164b348919 | 239 | { |
| MrBedfordVan | 0:b9164b348919 | 240 | if ((l->flags & MESSAGE_BUS_LISTENER_DELETING) && !(l->flags & MESSAGE_BUS_LISTENER_BUSY)) |
| MrBedfordVan | 0:b9164b348919 | 241 | { |
| MrBedfordVan | 0:b9164b348919 | 242 | if (p == NULL) |
| MrBedfordVan | 0:b9164b348919 | 243 | listeners = l->next; |
| MrBedfordVan | 0:b9164b348919 | 244 | else |
| MrBedfordVan | 0:b9164b348919 | 245 | p->next = l->next; |
| MrBedfordVan | 0:b9164b348919 | 246 | |
| MrBedfordVan | 0:b9164b348919 | 247 | // delete the listener. |
| MrBedfordVan | 0:b9164b348919 | 248 | MicroBitListener *t = l; |
| MrBedfordVan | 0:b9164b348919 | 249 | l = l->next; |
| MrBedfordVan | 0:b9164b348919 | 250 | |
| MrBedfordVan | 0:b9164b348919 | 251 | delete t; |
| MrBedfordVan | 0:b9164b348919 | 252 | removed++; |
| MrBedfordVan | 0:b9164b348919 | 253 | |
| MrBedfordVan | 0:b9164b348919 | 254 | continue; |
| MrBedfordVan | 0:b9164b348919 | 255 | } |
| MrBedfordVan | 0:b9164b348919 | 256 | |
| MrBedfordVan | 0:b9164b348919 | 257 | p = l; |
| MrBedfordVan | 0:b9164b348919 | 258 | l = l->next; |
| MrBedfordVan | 0:b9164b348919 | 259 | } |
| MrBedfordVan | 0:b9164b348919 | 260 | |
| MrBedfordVan | 0:b9164b348919 | 261 | return removed; |
| MrBedfordVan | 0:b9164b348919 | 262 | } |
| MrBedfordVan | 0:b9164b348919 | 263 | |
| MrBedfordVan | 0:b9164b348919 | 264 | /** |
| MrBedfordVan | 0:b9164b348919 | 265 | * Periodic callback from MicroBit. |
| MrBedfordVan | 0:b9164b348919 | 266 | * |
| MrBedfordVan | 0:b9164b348919 | 267 | * Process at least one event from the event queue, if it is not empty. |
| MrBedfordVan | 0:b9164b348919 | 268 | * We then continue processing events until something appears on the runqueue. |
| MrBedfordVan | 0:b9164b348919 | 269 | */ |
| MrBedfordVan | 0:b9164b348919 | 270 | void MicroBitMessageBus::idleTick() |
| MrBedfordVan | 0:b9164b348919 | 271 | { |
| MrBedfordVan | 0:b9164b348919 | 272 | // Clear out any listeners marked for deletion |
| MrBedfordVan | 0:b9164b348919 | 273 | this->deleteMarkedListeners(); |
| MrBedfordVan | 0:b9164b348919 | 274 | |
| MrBedfordVan | 0:b9164b348919 | 275 | MicroBitEventQueueItem *item = this->dequeueEvent(); |
| MrBedfordVan | 0:b9164b348919 | 276 | |
| MrBedfordVan | 0:b9164b348919 | 277 | // Whilst there are events to process and we have no useful other work to do, pull them off the queue and process them. |
| MrBedfordVan | 0:b9164b348919 | 278 | while (item) |
| MrBedfordVan | 0:b9164b348919 | 279 | { |
| MrBedfordVan | 0:b9164b348919 | 280 | // send the event to all standard event listeners. |
| MrBedfordVan | 0:b9164b348919 | 281 | this->process(item->evt); |
| MrBedfordVan | 0:b9164b348919 | 282 | |
| MrBedfordVan | 0:b9164b348919 | 283 | // Free the queue item. |
| MrBedfordVan | 0:b9164b348919 | 284 | delete item; |
| MrBedfordVan | 0:b9164b348919 | 285 | |
| MrBedfordVan | 0:b9164b348919 | 286 | // If we have created some useful work to do, we stop processing. |
| MrBedfordVan | 0:b9164b348919 | 287 | // This helps to minimise the number of blocked fibers we create at any point in time, therefore |
| MrBedfordVan | 0:b9164b348919 | 288 | // also reducing the RAM footprint. |
| MrBedfordVan | 0:b9164b348919 | 289 | if(!scheduler_runqueue_empty()) |
| MrBedfordVan | 0:b9164b348919 | 290 | break; |
| MrBedfordVan | 0:b9164b348919 | 291 | |
| MrBedfordVan | 0:b9164b348919 | 292 | // Pull the next event to process, if there is one. |
| MrBedfordVan | 0:b9164b348919 | 293 | item = this->dequeueEvent(); |
| MrBedfordVan | 0:b9164b348919 | 294 | } |
| MrBedfordVan | 0:b9164b348919 | 295 | } |
| MrBedfordVan | 0:b9164b348919 | 296 | |
| MrBedfordVan | 0:b9164b348919 | 297 | /** |
| MrBedfordVan | 0:b9164b348919 | 298 | * Queues the given event to be sent to all registered recipients. |
| MrBedfordVan | 0:b9164b348919 | 299 | * |
| MrBedfordVan | 0:b9164b348919 | 300 | * @param evt The event to send. |
| MrBedfordVan | 0:b9164b348919 | 301 | * |
| MrBedfordVan | 0:b9164b348919 | 302 | * @code |
| MrBedfordVan | 0:b9164b348919 | 303 | * MicroBitMessageBus bus; |
| MrBedfordVan | 0:b9164b348919 | 304 | * |
| MrBedfordVan | 0:b9164b348919 | 305 | * // Creates and sends the MicroBitEvent using bus. |
| MrBedfordVan | 0:b9164b348919 | 306 | * MicrobitEvent evt(MICROBIT_ID_BUTTON_A, MICROBIT_BUTTON_EVT_CLICK); |
| MrBedfordVan | 0:b9164b348919 | 307 | * |
| MrBedfordVan | 0:b9164b348919 | 308 | * // Creates the MicrobitEvent, but delays the sending of that event. |
| MrBedfordVan | 0:b9164b348919 | 309 | * MicrobitEvent evt1(MICROBIT_ID_BUTTON_A, MICROBIT_BUTTON_EVT_CLICK, CREATE_ONLY); |
| MrBedfordVan | 0:b9164b348919 | 310 | * |
| MrBedfordVan | 0:b9164b348919 | 311 | * bus.send(evt1); |
| MrBedfordVan | 0:b9164b348919 | 312 | * |
| MrBedfordVan | 0:b9164b348919 | 313 | * // This has the same effect! |
| MrBedfordVan | 0:b9164b348919 | 314 | * evt1.fire() |
| MrBedfordVan | 0:b9164b348919 | 315 | * @endcode |
| MrBedfordVan | 0:b9164b348919 | 316 | */ |
| MrBedfordVan | 0:b9164b348919 | 317 | int MicroBitMessageBus::send(MicroBitEvent evt) |
| MrBedfordVan | 0:b9164b348919 | 318 | { |
| MrBedfordVan | 0:b9164b348919 | 319 | // We simply queue processing of the event until we're scheduled in normal thread context. |
| MrBedfordVan | 0:b9164b348919 | 320 | // We do this to avoid the possibility of executing event handler code in IRQ context, which may bring |
| MrBedfordVan | 0:b9164b348919 | 321 | // hidden race conditions to kids code. Queuing all events ensures causal ordering (total ordering in fact). |
| MrBedfordVan | 0:b9164b348919 | 322 | this->queueEvent(evt); |
| MrBedfordVan | 0:b9164b348919 | 323 | return MICROBIT_OK; |
| MrBedfordVan | 0:b9164b348919 | 324 | } |
| MrBedfordVan | 0:b9164b348919 | 325 | |
| MrBedfordVan | 0:b9164b348919 | 326 | /** |
| MrBedfordVan | 0:b9164b348919 | 327 | * Internal function, used to deliver the given event to all relevant recipients. |
| MrBedfordVan | 0:b9164b348919 | 328 | * Normally, this is called once an event has been removed from the event queue. |
| MrBedfordVan | 0:b9164b348919 | 329 | * |
| MrBedfordVan | 0:b9164b348919 | 330 | * @param evt The event to send. |
| MrBedfordVan | 0:b9164b348919 | 331 | * |
| MrBedfordVan | 0:b9164b348919 | 332 | * @param urgent The type of listeners to process (optional). If set to true, only listeners defined as urgent and non-blocking will be processed |
| MrBedfordVan | 0:b9164b348919 | 333 | * otherwise, all other (standard) listeners will be processed. Defaults to false. |
| MrBedfordVan | 0:b9164b348919 | 334 | * |
| MrBedfordVan | 0:b9164b348919 | 335 | * @return 1 if all matching listeners were processed, 0 if further processing is required. |
| MrBedfordVan | 0:b9164b348919 | 336 | * |
| MrBedfordVan | 0:b9164b348919 | 337 | * @note It is recommended that all external code uses the send() function instead of this function, |
| MrBedfordVan | 0:b9164b348919 | 338 | * or the constructors provided by MicrobitEvent. |
| MrBedfordVan | 0:b9164b348919 | 339 | */ |
| MrBedfordVan | 0:b9164b348919 | 340 | int MicroBitMessageBus::process(MicroBitEvent &evt, bool urgent) |
| MrBedfordVan | 0:b9164b348919 | 341 | { |
| MrBedfordVan | 0:b9164b348919 | 342 | MicroBitListener *l; |
| MrBedfordVan | 0:b9164b348919 | 343 | int complete = 1; |
| MrBedfordVan | 0:b9164b348919 | 344 | bool listenerUrgent; |
| MrBedfordVan | 0:b9164b348919 | 345 | |
| MrBedfordVan | 0:b9164b348919 | 346 | l = listeners; |
| MrBedfordVan | 0:b9164b348919 | 347 | while (l != NULL) |
| MrBedfordVan | 0:b9164b348919 | 348 | { |
| MrBedfordVan | 0:b9164b348919 | 349 | if((l->id == evt.source || l->id == MICROBIT_ID_ANY) && (l->value == evt.value || l->value == MICROBIT_EVT_ANY)) |
| MrBedfordVan | 0:b9164b348919 | 350 | { |
| MrBedfordVan | 0:b9164b348919 | 351 | // If we're running under the fiber scheduler, then derive the THREADING_MODE for the callback based on the |
| MrBedfordVan | 0:b9164b348919 | 352 | // metadata in the listener itself. |
| MrBedfordVan | 0:b9164b348919 | 353 | if (fiber_scheduler_running()) |
| MrBedfordVan | 0:b9164b348919 | 354 | listenerUrgent = (l->flags & MESSAGE_BUS_LISTENER_IMMEDIATE) == MESSAGE_BUS_LISTENER_IMMEDIATE; |
| MrBedfordVan | 0:b9164b348919 | 355 | else |
| MrBedfordVan | 0:b9164b348919 | 356 | listenerUrgent = true; |
| MrBedfordVan | 0:b9164b348919 | 357 | |
| MrBedfordVan | 0:b9164b348919 | 358 | // If we should process this event hander in this pass, then activate the listener. |
| MrBedfordVan | 0:b9164b348919 | 359 | if(listenerUrgent == urgent && !(l->flags & MESSAGE_BUS_LISTENER_DELETING)) |
| MrBedfordVan | 0:b9164b348919 | 360 | { |
| MrBedfordVan | 0:b9164b348919 | 361 | l->evt = evt; |
| MrBedfordVan | 0:b9164b348919 | 362 | |
| MrBedfordVan | 0:b9164b348919 | 363 | // OK, if this handler has regisitered itself as non-blocking, we just execute it directly... |
| MrBedfordVan | 0:b9164b348919 | 364 | // This is normally only done for trusted system components. |
| MrBedfordVan | 0:b9164b348919 | 365 | // Otherwise, we invoke it in a 'fork on block' context, that will automatically create a fiber |
| MrBedfordVan | 0:b9164b348919 | 366 | // should the event handler attempt a blocking operation, but doesn't have the overhead |
| MrBedfordVan | 0:b9164b348919 | 367 | // of creating a fiber needlessly. (cool huh?) |
| MrBedfordVan | 0:b9164b348919 | 368 | if (l->flags & MESSAGE_BUS_LISTENER_NONBLOCKING || !fiber_scheduler_running()) |
| MrBedfordVan | 0:b9164b348919 | 369 | async_callback(l); |
| MrBedfordVan | 0:b9164b348919 | 370 | else |
| MrBedfordVan | 0:b9164b348919 | 371 | invoke(async_callback, l); |
| MrBedfordVan | 0:b9164b348919 | 372 | } |
| MrBedfordVan | 0:b9164b348919 | 373 | else |
| MrBedfordVan | 0:b9164b348919 | 374 | { |
| MrBedfordVan | 0:b9164b348919 | 375 | complete = 0; |
| MrBedfordVan | 0:b9164b348919 | 376 | } |
| MrBedfordVan | 0:b9164b348919 | 377 | } |
| MrBedfordVan | 0:b9164b348919 | 378 | |
| MrBedfordVan | 0:b9164b348919 | 379 | l = l->next; |
| MrBedfordVan | 0:b9164b348919 | 380 | } |
| MrBedfordVan | 0:b9164b348919 | 381 | |
| MrBedfordVan | 0:b9164b348919 | 382 | return complete; |
| MrBedfordVan | 0:b9164b348919 | 383 | } |
| MrBedfordVan | 0:b9164b348919 | 384 | |
| MrBedfordVan | 0:b9164b348919 | 385 | /** |
| MrBedfordVan | 0:b9164b348919 | 386 | * Add the given MicroBitListener to the list of event handlers, unconditionally. |
| MrBedfordVan | 0:b9164b348919 | 387 | * |
| MrBedfordVan | 0:b9164b348919 | 388 | * @param listener The MicroBitListener to add. |
| MrBedfordVan | 0:b9164b348919 | 389 | * |
| MrBedfordVan | 0:b9164b348919 | 390 | * @return MICROBIT_OK if the listener is valid, MICROBIT_INVALID_PARAMETER otherwise. |
| MrBedfordVan | 0:b9164b348919 | 391 | */ |
| MrBedfordVan | 0:b9164b348919 | 392 | int MicroBitMessageBus::add(MicroBitListener *newListener) |
| MrBedfordVan | 0:b9164b348919 | 393 | { |
| MrBedfordVan | 0:b9164b348919 | 394 | MicroBitListener *l, *p; |
| MrBedfordVan | 0:b9164b348919 | 395 | int methodCallback; |
| MrBedfordVan | 0:b9164b348919 | 396 | |
| MrBedfordVan | 0:b9164b348919 | 397 | //handler can't be NULL! |
| MrBedfordVan | 0:b9164b348919 | 398 | if (newListener == NULL) |
| MrBedfordVan | 0:b9164b348919 | 399 | return MICROBIT_INVALID_PARAMETER; |
| MrBedfordVan | 0:b9164b348919 | 400 | |
| MrBedfordVan | 0:b9164b348919 | 401 | l = listeners; |
| MrBedfordVan | 0:b9164b348919 | 402 | |
| MrBedfordVan | 0:b9164b348919 | 403 | // Firstly, we treat a listener as an idempotent operation. Ensure we don't already have this handler |
| MrBedfordVan | 0:b9164b348919 | 404 | // registered in a that will already capture these events. If we do, silently ignore. |
| MrBedfordVan | 0:b9164b348919 | 405 | |
| MrBedfordVan | 0:b9164b348919 | 406 | // We always check the ID, VALUE and CB_METHOD fields. |
| MrBedfordVan | 0:b9164b348919 | 407 | // If we have a callback to a method, check the cb_method class. Otherwise, the cb function point is sufficient. |
| MrBedfordVan | 0:b9164b348919 | 408 | while (l != NULL) |
| MrBedfordVan | 0:b9164b348919 | 409 | { |
| MrBedfordVan | 0:b9164b348919 | 410 | methodCallback = (newListener->flags & MESSAGE_BUS_LISTENER_METHOD) && (l->flags & MESSAGE_BUS_LISTENER_METHOD); |
| MrBedfordVan | 0:b9164b348919 | 411 | |
| MrBedfordVan | 0:b9164b348919 | 412 | if (l->id == newListener->id && l->value == newListener->value && (methodCallback ? *l->cb_method == *newListener->cb_method : l->cb == newListener->cb)) |
| MrBedfordVan | 0:b9164b348919 | 413 | { |
| MrBedfordVan | 0:b9164b348919 | 414 | // We have a perfect match for this event listener already registered. |
| MrBedfordVan | 0:b9164b348919 | 415 | // If it's marked for deletion, we simply resurrect the listener, and we're done. |
| MrBedfordVan | 0:b9164b348919 | 416 | // Either way, we return an error code, as the *new* listener should be released... |
| MrBedfordVan | 0:b9164b348919 | 417 | if(l->flags & MESSAGE_BUS_LISTENER_DELETING) |
| MrBedfordVan | 0:b9164b348919 | 418 | l->flags &= ~MESSAGE_BUS_LISTENER_DELETING; |
| MrBedfordVan | 0:b9164b348919 | 419 | |
| MrBedfordVan | 0:b9164b348919 | 420 | return MICROBIT_NOT_SUPPORTED; |
| MrBedfordVan | 0:b9164b348919 | 421 | } |
| MrBedfordVan | 0:b9164b348919 | 422 | |
| MrBedfordVan | 0:b9164b348919 | 423 | l = l->next; |
| MrBedfordVan | 0:b9164b348919 | 424 | } |
| MrBedfordVan | 0:b9164b348919 | 425 | |
| MrBedfordVan | 0:b9164b348919 | 426 | // We have a valid, new event handler. Add it to the list. |
| MrBedfordVan | 0:b9164b348919 | 427 | // if listeners is null - we can automatically add this listener to the list at the beginning... |
| MrBedfordVan | 0:b9164b348919 | 428 | if (listeners == NULL) |
| MrBedfordVan | 0:b9164b348919 | 429 | { |
| MrBedfordVan | 0:b9164b348919 | 430 | listeners = newListener; |
| MrBedfordVan | 0:b9164b348919 | 431 | MicroBitEvent(MICROBIT_ID_MESSAGE_BUS_LISTENER, newListener->id); |
| MrBedfordVan | 0:b9164b348919 | 432 | |
| MrBedfordVan | 0:b9164b348919 | 433 | return MICROBIT_OK; |
| MrBedfordVan | 0:b9164b348919 | 434 | } |
| MrBedfordVan | 0:b9164b348919 | 435 | |
| MrBedfordVan | 0:b9164b348919 | 436 | // We maintain an ordered list of listeners. |
| MrBedfordVan | 0:b9164b348919 | 437 | // The chain is held stictly in increasing order of ID (first level), then value code (second level). |
| MrBedfordVan | 0:b9164b348919 | 438 | // Find the correct point in the chain for this event. |
| MrBedfordVan | 0:b9164b348919 | 439 | // Adding a listener is a rare occurance, so we just walk the list... |
| MrBedfordVan | 0:b9164b348919 | 440 | |
| MrBedfordVan | 0:b9164b348919 | 441 | p = listeners; |
| MrBedfordVan | 0:b9164b348919 | 442 | l = listeners; |
| MrBedfordVan | 0:b9164b348919 | 443 | |
| MrBedfordVan | 0:b9164b348919 | 444 | while (l != NULL && l->id < newListener->id) |
| MrBedfordVan | 0:b9164b348919 | 445 | { |
| MrBedfordVan | 0:b9164b348919 | 446 | p = l; |
| MrBedfordVan | 0:b9164b348919 | 447 | l = l->next; |
| MrBedfordVan | 0:b9164b348919 | 448 | } |
| MrBedfordVan | 0:b9164b348919 | 449 | |
| MrBedfordVan | 0:b9164b348919 | 450 | while (l != NULL && l->id == newListener->id && l->value < newListener->value) |
| MrBedfordVan | 0:b9164b348919 | 451 | { |
| MrBedfordVan | 0:b9164b348919 | 452 | p = l; |
| MrBedfordVan | 0:b9164b348919 | 453 | l = l->next; |
| MrBedfordVan | 0:b9164b348919 | 454 | } |
| MrBedfordVan | 0:b9164b348919 | 455 | |
| MrBedfordVan | 0:b9164b348919 | 456 | //add at front of list |
| MrBedfordVan | 0:b9164b348919 | 457 | if (p == listeners && (newListener->id < p->id || (p->id == newListener->id && p->value > newListener->value))) |
| MrBedfordVan | 0:b9164b348919 | 458 | { |
| MrBedfordVan | 0:b9164b348919 | 459 | newListener->next = p; |
| MrBedfordVan | 0:b9164b348919 | 460 | |
| MrBedfordVan | 0:b9164b348919 | 461 | //this new listener is now the front! |
| MrBedfordVan | 0:b9164b348919 | 462 | listeners = newListener; |
| MrBedfordVan | 0:b9164b348919 | 463 | } |
| MrBedfordVan | 0:b9164b348919 | 464 | |
| MrBedfordVan | 0:b9164b348919 | 465 | //add after p |
| MrBedfordVan | 0:b9164b348919 | 466 | else |
| MrBedfordVan | 0:b9164b348919 | 467 | { |
| MrBedfordVan | 0:b9164b348919 | 468 | newListener->next = p->next; |
| MrBedfordVan | 0:b9164b348919 | 469 | p->next = newListener; |
| MrBedfordVan | 0:b9164b348919 | 470 | } |
| MrBedfordVan | 0:b9164b348919 | 471 | |
| MrBedfordVan | 0:b9164b348919 | 472 | MicroBitEvent(MICROBIT_ID_MESSAGE_BUS_LISTENER, newListener->id); |
| MrBedfordVan | 0:b9164b348919 | 473 | return MICROBIT_OK; |
| MrBedfordVan | 0:b9164b348919 | 474 | } |
| MrBedfordVan | 0:b9164b348919 | 475 | |
| MrBedfordVan | 0:b9164b348919 | 476 | /** |
| MrBedfordVan | 0:b9164b348919 | 477 | * Remove the given MicroBitListener from the list of event handlers. |
| MrBedfordVan | 0:b9164b348919 | 478 | * |
| MrBedfordVan | 0:b9164b348919 | 479 | * @param listener The MicroBitListener to remove. |
| MrBedfordVan | 0:b9164b348919 | 480 | * |
| MrBedfordVan | 0:b9164b348919 | 481 | * @return MICROBIT_OK if the listener is valid, MICROBIT_INVALID_PARAMETER otherwise. |
| MrBedfordVan | 0:b9164b348919 | 482 | */ |
| MrBedfordVan | 0:b9164b348919 | 483 | int MicroBitMessageBus::remove(MicroBitListener *listener) |
| MrBedfordVan | 0:b9164b348919 | 484 | { |
| MrBedfordVan | 0:b9164b348919 | 485 | MicroBitListener *l; |
| MrBedfordVan | 0:b9164b348919 | 486 | int removed = 0; |
| MrBedfordVan | 0:b9164b348919 | 487 | |
| MrBedfordVan | 0:b9164b348919 | 488 | //handler can't be NULL! |
| MrBedfordVan | 0:b9164b348919 | 489 | if (listener == NULL) |
| MrBedfordVan | 0:b9164b348919 | 490 | return MICROBIT_INVALID_PARAMETER; |
| MrBedfordVan | 0:b9164b348919 | 491 | |
| MrBedfordVan | 0:b9164b348919 | 492 | l = listeners; |
| MrBedfordVan | 0:b9164b348919 | 493 | |
| MrBedfordVan | 0:b9164b348919 | 494 | // Walk this list of event handlers. Delete any that match the given listener. |
| MrBedfordVan | 0:b9164b348919 | 495 | while (l != NULL) |
| MrBedfordVan | 0:b9164b348919 | 496 | { |
| MrBedfordVan | 0:b9164b348919 | 497 | if ((listener->flags & MESSAGE_BUS_LISTENER_METHOD) == (l->flags & MESSAGE_BUS_LISTENER_METHOD)) |
| MrBedfordVan | 0:b9164b348919 | 498 | { |
| MrBedfordVan | 0:b9164b348919 | 499 | if(((listener->flags & MESSAGE_BUS_LISTENER_METHOD) && (*l->cb_method == *listener->cb_method)) || |
| MrBedfordVan | 0:b9164b348919 | 500 | ((!(listener->flags & MESSAGE_BUS_LISTENER_METHOD) && l->cb == listener->cb))) |
| MrBedfordVan | 0:b9164b348919 | 501 | { |
| MrBedfordVan | 0:b9164b348919 | 502 | if ((listener->id == MICROBIT_ID_ANY || listener->id == l->id) && (listener->value == MICROBIT_EVT_ANY || listener->value == l->value)) |
| MrBedfordVan | 0:b9164b348919 | 503 | { |
| MrBedfordVan | 0:b9164b348919 | 504 | // Found a match. mark this to be removed from the list. |
| MrBedfordVan | 0:b9164b348919 | 505 | l->flags |= MESSAGE_BUS_LISTENER_DELETING; |
| MrBedfordVan | 0:b9164b348919 | 506 | removed++; |
| MrBedfordVan | 0:b9164b348919 | 507 | } |
| MrBedfordVan | 0:b9164b348919 | 508 | } |
| MrBedfordVan | 0:b9164b348919 | 509 | } |
| MrBedfordVan | 0:b9164b348919 | 510 | |
| MrBedfordVan | 0:b9164b348919 | 511 | l = l->next; |
| MrBedfordVan | 0:b9164b348919 | 512 | } |
| MrBedfordVan | 0:b9164b348919 | 513 | |
| MrBedfordVan | 0:b9164b348919 | 514 | if (removed > 0) |
| MrBedfordVan | 0:b9164b348919 | 515 | return MICROBIT_OK; |
| MrBedfordVan | 0:b9164b348919 | 516 | else |
| MrBedfordVan | 0:b9164b348919 | 517 | return MICROBIT_INVALID_PARAMETER; |
| MrBedfordVan | 0:b9164b348919 | 518 | } |
| MrBedfordVan | 0:b9164b348919 | 519 | |
| MrBedfordVan | 0:b9164b348919 | 520 | /** |
| MrBedfordVan | 0:b9164b348919 | 521 | * Returns the microBitListener with the given position in our list. |
| MrBedfordVan | 0:b9164b348919 | 522 | * |
| MrBedfordVan | 0:b9164b348919 | 523 | * @param n The position in the list to return. |
| MrBedfordVan | 0:b9164b348919 | 524 | * |
| MrBedfordVan | 0:b9164b348919 | 525 | * @return the MicroBitListener at postion n in the list, or NULL if the position is invalid. |
| MrBedfordVan | 0:b9164b348919 | 526 | */ |
| MrBedfordVan | 0:b9164b348919 | 527 | MicroBitListener* MicroBitMessageBus::elementAt(int n) |
| MrBedfordVan | 0:b9164b348919 | 528 | { |
| MrBedfordVan | 0:b9164b348919 | 529 | MicroBitListener *l = listeners; |
| MrBedfordVan | 0:b9164b348919 | 530 | |
| MrBedfordVan | 0:b9164b348919 | 531 | while (n > 0) |
| MrBedfordVan | 0:b9164b348919 | 532 | { |
| MrBedfordVan | 0:b9164b348919 | 533 | if (l == NULL) |
| MrBedfordVan | 0:b9164b348919 | 534 | return NULL; |
| MrBedfordVan | 0:b9164b348919 | 535 | |
| MrBedfordVan | 0:b9164b348919 | 536 | n--; |
| MrBedfordVan | 0:b9164b348919 | 537 | l = l->next; |
| MrBedfordVan | 0:b9164b348919 | 538 | } |
| MrBedfordVan | 0:b9164b348919 | 539 | |
| MrBedfordVan | 0:b9164b348919 | 540 | return l; |
| MrBedfordVan | 0:b9164b348919 | 541 | } |
| MrBedfordVan | 0:b9164b348919 | 542 | |
| MrBedfordVan | 0:b9164b348919 | 543 | /** |
| MrBedfordVan | 0:b9164b348919 | 544 | * Destructor for MicroBitMessageBus, where we deregister this instance from the array of fiber components. |
| MrBedfordVan | 0:b9164b348919 | 545 | */ |
| MrBedfordVan | 0:b9164b348919 | 546 | MicroBitMessageBus::~MicroBitMessageBus() |
| MrBedfordVan | 0:b9164b348919 | 547 | { |
| MrBedfordVan | 0:b9164b348919 | 548 | fiber_remove_idle_component(this); |
| MrBedfordVan | 0:b9164b348919 | 549 | } |