no_os_lf256fifo.c

/***************************************************************************//**
 *   @file   no_os_lf256fifo.c
 *   @brief  SPSC lock-free fifo of fixed size (256), specialized for UART.
 *   @author Darius Berghe (darius.berghe@analog.com)
********************************************************************************
 *   @copyright
 * Copyright 2020(c) Analog Devices, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * 3. Neither the name of Analog Devices, Inc. nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY ANALOG DEVICES, INC. “AS IS” AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL ANALOG DEVICES, INC. BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*******************************************************************************/
#include <errno.h>
#include "no_os_lf256fifo.h"
#include "no_os_alloc.h"

/**
 * @struct lf256fifo
 * @brief Structure holding the fifo element parameters.
 */
struct lf256fifo {
	uint8_t * data; // pointer to memory area where the buffer will be allocated
	uint8_t ffilled; // the index where the data starts
	uint8_t fempty; // the index where empty/non-used area starts
};

/**
 * @brief Initialize and allocate a lock-free 256 FIFO.
 * @param fifo - pointer to a fifo descriptor pointer.
 * @return 0 if successful, negative error code otherwise.
 */
int lf256fifo_init(struct lf256fifo **fifo)
{
	if (fifo == NULL)
		return -EINVAL;

	struct lf256fifo *b = no_os_calloc(1, sizeof(struct lf256fifo));
	if (b == NULL)
		return -ENOMEM;

	b->data = no_os_calloc(1, 256);
	if (b->data == NULL) {
		no_os_free(b);
		return -ENOMEM;
	}

	*fifo = b;

	return 0;
}

/**
 * @brief Test whether fifo is full.
 * @param fifo - pointer to fifo descriptor.
 * @return true if fifo is full, false if not full.
 */
bool lf256fifo_is_full(struct lf256fifo *fifo)
{
	return (fifo->fempty + 1) ==
	       fifo->ffilled; // intended overflow at 256 (data size is 256)
}

/**
* @brief Test whether fifo is empty.
* @param fifo - pointer to fifo descriptor.
* @return true if fifo is empty, false if not empty.
*/
bool lf256fifo_is_empty(struct lf256fifo *fifo)
{
	return fifo->fempty == fifo->ffilled;
}

/**
* @brief Read char from fifo.
* @param fifo - pointer to fifo descriptor.
* @param c - pointer to memory where the char element is read.
* @return 0 if successful, -1 if buffer empty.
*/
int lf256fifo_read(struct lf256fifo * fifo, uint8_t *c)
{
	if (lf256fifo_is_empty(fifo))
		return -1; // buffer empty

	*c = fifo->data[fifo->ffilled];
	fifo->ffilled++; // intended overflow at 256 (data size is 256)

	return 0;
}

/**
* @brief Write char to fifo.
* @param fifo - pointer to fifo descriptor.
* @param c - char element to write.
* @return 0 if successful, -1 if buffer full.
*/
int lf256fifo_write(struct lf256fifo *fifo, uint8_t c)
{
	if (lf256fifo_is_full(fifo))
		return -1; // buffer full

	fifo->data[fifo->fempty] = c;
	fifo->fempty++; // intended overflow at 256 (data size is 256)

	return 0; // return success
}

/**
* @brief Flush the fifo.
* @param fifo - pointer to fifo descriptor.
* @return void
*/
void lf256fifo_flush(struct lf256fifo *fifo)
{
	fifo->ffilled = fifo->fempty;
}

/**
* @brief Remove the fifo
* @param fifo - pointer to fifo descriptor.
* @return void
*/
void lf256fifo_remove(struct lf256fifo *fifo)
{
	if (fifo && fifo->data)
		no_os_free(fifo->data);
}