# Queues

## Introduction

The standard library provides various queues implementations for various objects sizes. Queue objects aren't thread safe. It is defined inside `shelter/lib/include/std/queue.h` and implemented in `shelter/lib/src/std/queue.c`.

## Keyboard events queue

This queue is represented by the following object:
``` C
typedef struct {
  sh_kbd_EVENT *buffer;
  sh_uint32 capacity;
  sh_uint32 write_index;
} sh_queue_KBD_EVENT;
```

These queues automatically overwrite the oldest object when the caller try to push an object when the queue is full.

The API is as follows:
- `sh_queue_event_init(sh_queue_KBD_EVENT *q,sh_uint32 capacity)`: initialize a keyboard events queue, allocate the queue buffer
- `sh_queue_event_push(sh_queue_KBD_EVENT *q,sh_kbd_EVENT ev)`: push an event into the provided queue
- `sh_queue_event_destroy(sh_queue_KBD_EVENT *q)`: destroy the provided queue, free the queue buffer