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https://github.com/smfsw/queue

Queue handling library (designed on Arduino)
https://github.com/smfsw/queue

arduino-library fifo lifo queue

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Queue handling library (designed on Arduino)

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# Queue [![Build Status](https://app.travis-ci.com/SMFSW/Queue.svg?branch=master)](https://app.travis-ci.com/SMFSW/Queue)



Queue handling library (designed on Arduino)



This library was designed for Arduino, yet may be compiled without change with gcc for other purposes/targets



Queue class has since start been called `Queue`. Unfortunately, on some platforms or when using FreeRTOS, Queue is already declared.

For compatibility purposes, `Queue` class has been renamed to `cppQueue`. Sorry for the inconvenience...



## Usage



- Declare a `cppQueue` instance `(size_t size_rec, uint16_t nb_recs=20, QueueType type=FIFO, bool overwrite=false, void * pQDat=NULL, size_t lenQDat=0)` (called `q` below):

  - `size_rec` - size of a record in the queue

  - `nb_recs` - number of records in the queue

  - `type` - queue implementation type: _FIFO_, _LIFO_

  - `overwrite` - overwrite previous records when queue is full if set to _true_

  - `pQDat` - pointer to static data queue

  - `lenQDat` - length of static data queue (in bytes)

- Push stuff to the queue using `q.push(void * rec)`

  - returns `true` if successfully pushed into queue

  - returns `false` is queue is full

- Pop stuff from the queue using `q.pop(void * rec)` or `q.pull(void * rec)`

  - returns `true` if successfully popped from queue

  - returns `false` if queue is empty

- Peek stuff from the queue using `q.peek(void * rec)`

  - returns `true` if successfully peeked from queue

  - returns `false` if queue is empty

- Drop stuff from the queue using `q.drop(void)`

  - returns `true` if successfully dropped from queue

  - returns `false` if queue is empty

- Peek stuff at index from the queue using `q.peekIdx(void * rec, uint16_t idx)`

  - returns `true` if successfully peeked from queue

  - returns `false` if index is out of range

  - warning: no associated drop function, not to use with `q.drop`

- Peek latest stored from the queue using `q.peekPrevious(void * rec)`

  - returns `true` if successfully peeked from queue

  - returns `false` if queue is empty

  - warning: no associated drop function, not to use with `q.drop`

  - note: only useful with FIFO implementation, use `q.peek` instead with a LIFO

- Other methods:

  - `q.isInitialized()`: `true` if initialized properly, `false` otherwise

  - `q.isEmpty()`: `true` if empty, `false` otherwise

  - `q.isFull()`: `true` if full, `false` otherwise

  - `q.sizeOf()`: queue size in bytes (returns 0 in case queue allocation failed)

  - `q.getCount()` or `q.nbRecs()`: number of records stored in the queue

  - `q.getRemainingCount()`: number of records left in the queue

  - `q.clean()` or `q.flush()`: remove all items in the queue



## Notes



- Interrupt safe automation is not implemented in the library. You have to manually disable/enable interrupts where required.

No implementation will be made as it would be an issue when using `peek`/`drop` methods with LIFO implementation:

if an item is put to the queue through interrupt between `peek` and `drop` calls, the `drop` call would drop the wrong (newer) item.

In this particular case, dropping decision must be made before re-enabling interrupts.



## Examples included



- [SimpleQueue.ino](examples/SimpleQueue/SimpleQueue.ino): Simple queue example (both LIFO FIFO implementations can be tested)

- [SimpleQueueStatic.ino](examples/SimpleQueueStatic/SimpleQueueStatic.ino): Simple queue example using static queue data array (both LIFO FIFO implementations can be tested)

- [PointersQueue.ino](examples/PointersQueue/PointersQueue.ino): Queue of string pointers for string processing

- [SerialQueue.ino](examples/SerialQueue/SerialQueue.ino): Print characters received from Serial to Serial after reception of EOT char

- [QueueDuplicates.ino](examples/QueueDuplicates/QueueDuplicates.ino): Simple test to test queue duplicates before pushing to queue

- [QueueIdxPeeking.ino](examples/QueueIdxPeeking/QueueIdxPeeking.ino): Simple test to test queue index picking

- [RolloverTest.ino](examples/RolloverTest/RolloverTest.ino): Simple test to test queue rollover (for lib testing purposes mainly)

- [LibTst.ino](examples/LibTst/LibTst.ino): flexible test (for lib testing purposes mainly)



## Documentation



Doxygen doc can be generated using "Doxyfile".



See [generated documentation](https://smfsw.github.io/Queue/)



## Release Notes



See [release notes](ReleaseNotes.md)



## See also



[cQueue](https://github.com/SMFSW/cQueue) - C implementation of this library