133 lines
4.1 KiB
C
133 lines
4.1 KiB
C
#include <inttypes.h>
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/**
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* @file
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* Prototypes and structures for the ring buffer module.
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*/
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#ifndef RINGBUFFER_H
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#define RINGBUFFER_H
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/**
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* The size of a ring buffer.
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* Due to the design only <tt> RING_BUFFER_SIZE-1 </tt> items
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* can be contained in the buffer.
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* The buffer size must be a power of two.
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*/
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#define RING_BUFFER_SIZE 512
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#if (RING_BUFFER_SIZE & (RING_BUFFER_SIZE - 1)) != 0
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#error "RING_BUFFER_SIZE must be a power of two"
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#endif
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/**
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* The type which is used to hold the size
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* and the indicies of the buffer.
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* Must be able to fit \c RING_BUFFER_SIZE .
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*/
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typedef uint32_t ring_buffer_size_t;
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/**
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* Used as a modulo operator
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* as <tt> a % b = (a & (b 鈭<> 1)) </tt>
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* where \c a is a positive index in the buffer and
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* \c b is the (power of two) size of the buffer.
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*/
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#define RING_BUFFER_MASK (RING_BUFFER_SIZE-1)
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/**
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* Simplifies the use of <tt>struct ring_buffer_t</tt>.
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*/
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typedef struct ring_buffer_t ring_buffer_t;
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/**
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* Structure which holds a ring buffer.
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* The buffer contains a buffer array
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* as well as metadata for the ring buffer.
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*/
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struct ring_buffer_t {
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/** Buffer memory. */
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char buffer[RING_BUFFER_SIZE];
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/** Index of tail. */
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ring_buffer_size_t tail_index;
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/** Index of head. */
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ring_buffer_size_t head_index;
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};
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/**
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* Initializes the ring buffer pointed to by <em>buffer</em>.
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* This function can also be used to empty/reset the buffer.
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* @param buffer The ring buffer to initialize.
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*/
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void ring_buffer_init(ring_buffer_t *buffer);
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/**
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* Adds a byte to a ring buffer.
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* @param buffer The buffer in which the data should be placed.
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* @param data The byte to place.
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*/
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void ring_buffer_queue(ring_buffer_t *buffer, uint8_t data);
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/**
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* Adds an array of bytes to a ring buffer.
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* @param buffer The buffer in which the data should be placed.
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* @param data A pointer to the array of bytes to place in the queue.
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* @param size The size of the array.
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*/
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void ring_buffer_queue_arr(ring_buffer_t *buffer, const uint8_t *data, ring_buffer_size_t size);
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/**
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* Returns the oldest byte in a ring buffer.
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* @param buffer The buffer from which the data should be returned.
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* @param data A pointer to the location at which the data should be placed.
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* @return 1 if data was returned; 0 otherwise.
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*/
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ring_buffer_size_t ring_buffer_dequeue(ring_buffer_t *buffer, uint8_t *data);
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/**
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* Returns the <em>len</em> oldest bytes in a ring buffer.
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* @param buffer The buffer from which the data should be returned.
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* @param data A pointer to the array at which the data should be placed.
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* @param len The maximum number of bytes to return.
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* @return The number of bytes returned.
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*/
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ring_buffer_size_t ring_buffer_dequeue_arr(ring_buffer_t *buffer, uint8_t *data, ring_buffer_size_t len);
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/**
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* Peeks a ring buffer, i.e. returns an element without removing it.
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* @param buffer The buffer from which the data should be returned.
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* @param data A pointer to the location at which the data should be placed.
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* @param index The index to peek.
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* @return 1 if data was returned; 0 otherwise.
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*/
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ring_buffer_size_t ring_buffer_peek(ring_buffer_t *buffer, uint8_t *data, ring_buffer_size_t index);
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/**
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* Returns whether a ring buffer is empty.
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* @param buffer The buffer for which it should be returned whether it is empty.
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* @return 1 if empty; 0 otherwise.
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*/
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inline ring_buffer_size_t ring_buffer_is_empty(ring_buffer_t *buffer) {
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return (buffer->head_index == buffer->tail_index);
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}
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/**
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* Returns whether a ring buffer is full.
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* @param buffer The buffer for which it should be returned whether it is full.
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* @return 1 if full; 0 otherwise.
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*/
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inline ring_buffer_size_t ring_buffer_is_full(ring_buffer_t *buffer) {
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return ((buffer->head_index - buffer->tail_index) & RING_BUFFER_MASK) == RING_BUFFER_MASK;
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}
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/**
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* Returns the number of items in a ring buffer.
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* @param buffer The buffer for which the number of items should be returned.
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* @return The number of items in the ring buffer.
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*/
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inline ring_buffer_size_t ring_buffer_num_items(ring_buffer_t *buffer) {
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return ((buffer->head_index - buffer->tail_index) & RING_BUFFER_MASK);
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}
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#endif /* RINGBUFFER_H */
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