Mbed OS Reference | equeue.h Source File

 
 /*
  * Flexible event queue for dispatching events
  *
  * Copyright (c) 2016-2019 ARM Limited
  * SPDX-License-Identifier: Apache-2.0
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 #ifndef EQUEUE_H
 #define EQUEUE_H
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 // Platform specific files
 #include "events/internal/equeue_platform.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 /**
  * \addtogroup events-public-api
  * @{
  */
 
 // The minimum size of an event
 // This size is guaranteed to fit events created by event_call
 #define EQUEUE_EVENT_SIZE (sizeof(struct equeue_event) + 2*sizeof(void*))
 
 // Internal event structure
 struct equeue_event {
     unsigned size;
     uint16_t generation;
     uint8_t id;
 
     struct equeue_event *next;
     struct equeue_event *sibling;
     struct equeue_event **ref;
 
     unsigned target;
     int period;
     void (*dtor)(void *);
 
     void (*cb)(void *);
     // data follows
 };
 
 // Event queue structure
 typedef struct equeue {
     struct equeue_event *queue;
     unsigned tick;
 
     uint16_t generation;
     bool break_requested;
 
     unsigned char *buffer;
     unsigned npw2;
     void *allocated;
 
     struct equeue_event *chunks;
     struct equeue_slab {
         size_t size;
         unsigned char *data;
     } slab;
 
     struct equeue_background {
         bool active;
         void (*update)(void *timer, int ms);
         void *timer;
     } background;
 
     equeue_sema_t eventsema;
     equeue_mutex_t queuelock;
     equeue_mutex_t memlock;
 } equeue_t;
 
 
 // Queue lifetime operations
 //
 // Creates and destroys an event queue. The event queue either allocates a
 // buffer of the specified size with malloc or uses a user provided buffer
 // if constructed with equeue_create_inplace.
 //
 // If the event queue creation fails, equeue_create returns a negative,
 // platform-specific error code.
 //
 // If queues are chained, it is needed to unchain them first, before calling destroy,
 // or call the destroy function on queues in order that chained queues are destroyed first.
 int equeue_create(equeue_t *queue, size_t size);
 int equeue_create_inplace(equeue_t *queue, size_t size, void *buffer);
 void equeue_destroy(equeue_t *queue);
 
 // Dispatch events
 //
 // Executes events until the specified milliseconds have passed. If ms is
 // negative, equeue_dispatch will dispatch events indefinitely or until
 // equeue_break is called on this queue.
 //
 // When called with a finite timeout, the equeue_dispatch function is
 // guaranteed to terminate. When called with a timeout of 0, the
 // equeue_dispatch does not wait and is irq safe.
 void equeue_dispatch(equeue_t *queue, int ms);
 
 // Break out of a running event loop
 //
 // Forces the specified event queue's dispatch loop to terminate. Pending
 // events may finish executing, but no new events will be executed.
 void equeue_break(equeue_t *queue);
 
 // Simple event calls
 //
 // The specified callback will be executed in the context of the event queue's
 // dispatch loop. When the callback is executed depends on the call function.
 //
 // equeue_call       - Immediately post an event to the queue
 // equeue_call_in    - Post an event after a specified time in milliseconds
 // equeue_call_every - Post an event periodically every milliseconds
 //
 // All equeue_call functions are irq safe and can act as a mechanism for
 // moving events out of irq contexts.
 //
 // The return value is a unique id that represents the posted event and can
 // be passed to equeue_cancel. If there is not enough memory to allocate the
 // event, equeue_call returns an id of 0.
 int equeue_call(equeue_t *queue, void (*cb)(void *), void *data);
 int equeue_call_in(equeue_t *queue, int ms, void (*cb)(void *), void *data);
 int equeue_call_every(equeue_t *queue, int ms, void (*cb)(void *), void *data);
 
 // Allocate memory for events
 //
 // The equeue_alloc function allocates an event that can be manually dispatched
 // with equeue_post. The equeue_dealloc function may be used to free an event
 // that has not been posted. Once posted, an event's memory is managed by the
 // event queue and should not be deallocated.
 //
 // Both equeue_alloc and equeue_dealloc are irq safe.
 //
 // The equeue allocator is designed to minimize jitter in interrupt contexts as
 // well as avoid memory fragmentation on small devices. The allocator achieves
 // both constant-runtime and zero-fragmentation for fixed-size events, however
 // grows linearly as the quantity of different sized allocations increases.
 //
 // The equeue_alloc function returns a pointer to the event's allocated memory
 // and acts as a handle to the underlying event. If there is not enough memory
 // to allocate the event, equeue_alloc returns null.
 void *equeue_alloc(equeue_t *queue, size_t size);
 void equeue_dealloc(equeue_t *queue, void *event);
 
 // Configure an allocated event
 //
 // equeue_event_delay  - Millisecond delay before dispatching an event
 // equeue_event_period - Millisecond period for repeating dispatching an event
 // equeue_event_dtor   - Destructor to run when the event is deallocated
 void equeue_event_delay(void *event, int ms);
 void equeue_event_period(void *event, int ms);
 void equeue_event_dtor(void *event, void (*dtor)(void *));
 
 // Post an event onto the event queue
 //
 // The equeue_post function takes a callback and a pointer to an event
 // allocated by equeue_alloc. The specified callback will be executed in the
 // context of the event queue's dispatch loop with the allocated event
 // as its argument.
 //
 // The equeue_post function is irq safe and can act as a mechanism for
 // moving events out of irq contexts.
 //
 // The return value is a unique id that represents the posted event and can
 // be passed to equeue_cancel.
 int equeue_post(equeue_t *queue, void (*cb)(void *), void *event);
 
 // Post an user allocated event onto the event queue
 //
 // The equeue_post_user_allocated function takes a callback and a pointer
 // to an event allocated by user. The specified callback will be executed
 // in the context of the event queue's dispatch loop with the allocated
 // event as its argument.
 //
 // The equeue_post_user_allocated function is irq safe and can act as
 // a mechanism for moving events out of irq contexts.
 void equeue_post_user_allocated(equeue_t *queue, void (*cb)(void *), void *event);
 
 // Cancel an in-flight event
 //
 // Attempts to cancel an event referenced by the unique id returned from
 // equeue_call or equeue_post. It is safe to call equeue_cancel after an event
 // has already been dispatched.
 //
 // The equeue_cancel function is irq safe.
 //
 // If called while the event queue's dispatch loop is active in another thread,
 // equeue_cancel does not guarantee that the event will not execute after it returns as
 // the event may have already begun executing.
 // Returning true guarantees that cancel succeeded and event will not execute.
 // Returning false if invalid id or already started executing.
 bool equeue_cancel(equeue_t *queue, int id);
 
 // Cancel an in-flight user allocated event
 //
 // Attempts to cancel an event referenced by its address.
 // It is safe to call equeue_cancel_user_allocated after an event
 // has already been dispatched.
 //
 // The equeue_cancel_user_allocated function is irq safe.
 //
 // If called while the event queue's dispatch loop is active,
 // equeue_cancel_user_allocated does not guarantee that the event
 // will not not execute after it returns as the event may have
 // already begun executing.
 bool equeue_cancel_user_allocated(equeue_t *queue, void *event);
 
 // Query how much time is left for delayed event
 //
 //  If event is delayed, this function can be used to query how much time
 //  is left until the event is due to be dispatched.
 //
 //  This function is irq safe.
 //
 int equeue_timeleft(equeue_t *q, int id);
 
 // Query how much time is left for delayed user allocated event
 //
 //  If event is delayed, this function can be used to query how much time
 //  is left until the event is due to be dispatched.
 //
 //  This function is irq safe.
 //
 int equeue_timeleft_user_allocated(equeue_t *q, void *event);
 
 // Background an event queue onto a single-shot timer
 //
 // The provided update function will be called to indicate when the queue
 // should be dispatched. A negative timeout will be passed to the update
 // function when the timer is no longer needed.
 //
 // Passing a null update function disables the existing timer.
 //
 // The equeue_background function allows an event queue to take advantage
 // of hardware timers or even other event loops, allowing an event queue to
 // be effectively backgrounded.
 void equeue_background(equeue_t *queue,
                        void (*update)(void *timer, int ms), void *timer);
 
 // Chain an event queue onto another event queue
 //
 // After chaining a queue to a target, calling equeue_dispatch on the
 // target queue will also dispatch events from this queue. The queues
 // use their own buffers and events must be managed independently.
 //
 // Passing a null queue as the target will unchain the existing queue.
 //
 // The equeue_chain function allows multiple equeues to be composed, sharing
 // the context of a dispatch loop while still being managed independently.
 //
 // If the event queue chaining fails, equeue_chain returns a negative,
 // platform-specific error code.
 int equeue_chain(equeue_t *queue, equeue_t *target);
 
 /** @}*/
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif
Important Information for this Arm website
