source: mainline/uspace/lib/c/generic/adt/dynamic_fifo.c@ 111d2d6

/*
 * Copyright (c) 2009 Lukas Mejdrech
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 THE AUTHOR 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.
 */

/** @addtogroup libc
 * @{
 */

/** @file
 * Dynamic first in first out positive integer queue implementation.
 */

#include <adt/dynamic_fifo.h>

#include <errno.h>
#include <malloc.h>
#include <mem.h>

/** Internal magic value for a consistency check. */
#define DYN_FIFO_MAGIC_VALUE    0x58627659

/** Returns the next queue index.
 *
 * The queue field is circular.
 *
 * @param[in] fifo      The dynamic queue.
 * @param[in] index     The actual index to be shifted.
 */
#define NEXT_INDEX(fifo, index) (((index) + 1) % ((fifo)->size + 1))

/** Checks if the queue is valid.
 *
 * @param[in] fifo      The dynamic queue.
 * @return              TRUE if the queue is valid.
 * @return              FALSE otherwise.
 */
static int dyn_fifo_is_valid(dyn_fifo_t *fifo)
{
        return fifo && (fifo->magic_value == DYN_FIFO_MAGIC_VALUE);
}

/** Initializes the dynamic queue.
 *
 * @param[in,out] fifo  The dynamic queue.
 * @param[in] size      The initial queue size.
 * @return              EOK on success.
 * @return              EINVAL if the queue is not valid.
 * @return              EBADMEM if the fifo parameter is NULL.
 * @return              ENOMEM if there is not enough memory left.
 */
int dyn_fifo_initialize(dyn_fifo_t *fifo, int size)
{
        if (!fifo)
                return EBADMEM;

        if (size <= 0)
                return EINVAL;

        fifo->items = (int *) malloc(sizeof(int) * size + 1);
        if (!fifo->items)
                return ENOMEM;

        fifo->size = size;
        fifo->head = 0;
        fifo->tail = 0;
        fifo->magic_value = DYN_FIFO_MAGIC_VALUE;

        return EOK;
}

/** Appends a new item to the queue end.
 *
 * @param[in,out] fifo  The dynamic queue.
 * @param[in] value     The new item value. Should be positive.
 * @param[in] max_size  The maximum queue size. The queue is not resized beyound
 *                      this limit. May be zero or negative to indicate no
 *                      limit.
 * @return              EOK on success.
 * @return              EINVAL if the queue is not valid.
 * @return              ENOMEM if there is not enough memory left.
 */
int dyn_fifo_push(dyn_fifo_t *fifo, int value, int max_size)
{
        int *new_items;

        if (!dyn_fifo_is_valid(fifo))
                return EINVAL;

        if (NEXT_INDEX(fifo, fifo->tail) == fifo->head) {
                if ((max_size > 0) && ((fifo->size * 2) > max_size)) {
                        if(fifo->size >= max_size)
                                return ENOMEM;
                } else {
                        max_size = fifo->size * 2;
                }

                new_items = realloc(fifo->items, sizeof(int) * max_size + 1);
                if (!new_items)
                        return ENOMEM;

                fifo->items = new_items;
                if (fifo->tail < fifo->head) {
                        if (fifo->tail < max_size - fifo->size) {
                                memcpy(fifo->items + fifo->size + 1,
                                    fifo->items, fifo->tail * sizeof(int));
                                fifo->tail += fifo->size + 1;
                        } else {
                                memcpy(fifo->items + fifo->size + 1,
                                    fifo->items,
                                    (max_size - fifo->size) * sizeof(int));
                                memcpy(fifo->items,
                                    fifo->items + max_size - fifo->size,
                                    fifo->tail - max_size + fifo->size);
                                fifo->tail -= max_size - fifo->size;
                        }
                }
                fifo->size = max_size;
        }

        fifo->items[fifo->tail] = value;
        fifo->tail = NEXT_INDEX(fifo, fifo->tail);
        return EOK;
}

/** Returns and excludes the first item in the queue.
 *
 * @param[in,out] fifo  The dynamic queue.
 * @return              Value of the first item in the queue.
 * @return              EINVAL if the queue is not valid.
 * @return              ENOENT if the queue is empty.
 */
int dyn_fifo_pop(dyn_fifo_t *fifo)
{
        int value;

        if (!dyn_fifo_is_valid(fifo))
                return EINVAL;

        if (fifo->head == fifo->tail)
                return ENOENT;

        value = fifo->items[fifo->head];
        fifo->head = NEXT_INDEX(fifo, fifo->head);
        return value;
}

/** Returns and keeps the first item in the queue.
 *
 * @param[in,out] fifo  The dynamic queue.
 * @return              Value of the first item in the queue.
 * @return              EINVAL if the queue is not valid.
 * @return              ENOENT if the queue is empty.
 */
int dyn_fifo_value(dyn_fifo_t *fifo)
{
        if (!dyn_fifo_is_valid(fifo))
                return EINVAL;

        if (fifo->head == fifo->tail)
                return ENOENT;

        return fifo->items[fifo->head];
}

/** Clears and destroys the queue.
 *
 * @param[in,out] fifo  The dynamic queue.
 * @return              EOK on success.
 * @return              EINVAL if the queue is not valid.
 */
int dyn_fifo_destroy(dyn_fifo_t *fifo)
{
        if (!dyn_fifo_is_valid(fifo))
                return EINVAL;

        free(fifo->items);
        fifo->magic_value = 0;
        return EOK;
}

/** @}
 */