ctrump/common/queue.c

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/* -*- coding:utf-8 -*- 
 Copyright (c) 2009, Fixstars Corporation
 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.
 
   * Neither the name of Fixstars Corporation 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 THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT OWNER OR CONTRIBUTORS 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 "ctrump/common/queue.h"
#include <stdlib.h>
#include <string.h>

void
ctrump_queue_init(struct ctrump_queue *q, size_t nelem, size_t elem_size)
{
    q->head = 0;
    q->tail = 0;
    q->rem = nelem;
    q->elem_size = elem_size;
    q->size = nelem;
    q->elements = malloc(elem_size*nelem);
}

void
ctrump_queue_realloc(struct ctrump_queue *q)
{
    size_t new_size = q->size * 2U;
    size_t elem_size = q->elem_size;
    void *new_buf = malloc(q->elem_size * new_size);
    char *ep = (char*)q->elements;
    unsigned int rem = q->rem;

    if (rem == q->size) {
        q->head = q->tail = 0;
        q->rem = new_size;
    } else if (q->head > q->tail) {
        size_t copy_elem = q->head - q->tail;
        memcpy(new_buf, ep + q->tail*elem_size, copy_elem*elem_size);
        q->tail = 0;
        q->head = copy_elem;
        q->rem = new_size - copy_elem;
    } else /* q->head <= q->tail */ {
        unsigned int nelem = q->size - q->tail + q->head;
        unsigned int tail_copy = (q->size - q->tail)*elem_size;
        memcpy(new_buf, ep + q->tail, tail_copy);
        memcpy((char*)new_buf + tail_copy,
               ep, q->head * elem_size);

        q->tail = 0;
        q->head = nelem;
        q->rem = new_size - nelem;
    }

    free(q->elements);
    q->elements = new_buf;
    q->size = new_size;
}

void
ctrump_queue_destroy(struct ctrump_queue *q)
{
    free(q->elements);
}

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