spdylay/lib/spdylay_pq.c

/*
 * Spdylay - SPDY Library
 *
 * Copyright (c) 2012 Tatsuhiro Tsujikawa
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
#include "spdylay_pq.h"

int spdylay_pq_init(spdylay_pq *pq, spdylay_compar compar)
{
  pq->capacity = 4096;
  pq->q = malloc(pq->capacity * sizeof(void*));
  if(pq->q == NULL) {
    return SPDYLAY_ERR_NOMEM;
  }
  pq->length = 0;
  pq->compar = compar;
  return 0;
}

void spdylay_pq_free(spdylay_pq *pq)
{
  free(pq->q);
  pq->q = NULL;
}

static void swap(spdylay_pq *pq, size_t i, size_t j)
{
  void *t = pq->q[i];
  pq->q[i] = pq->q[j];
  pq->q[j] = t;
}

static void bubble_up(spdylay_pq *pq, size_t index)
{
  if(index == 0) {
    return;
  } else {
    size_t parent = (index-1)/2;
    if(pq->compar(pq->q[parent], pq->q[index]) > 0) {
      swap(pq, parent, index);
      bubble_up(pq, parent);
    }
  }
}

int spdylay_pq_push(spdylay_pq *pq, void *item)
{
  if(pq->capacity <= pq->length) {
    void *nq;
    nq = realloc(pq->q, (pq->capacity*2) * sizeof(void*));
    if(nq == NULL) {
      return SPDYLAY_ERR_NOMEM;
    }
    pq->capacity *= 2;
    pq->q = nq;
  }
  pq->q[pq->length] = item;
  ++pq->length;
  bubble_up(pq, pq->length-1);
  return 0;
}

void* spdylay_pq_top(spdylay_pq *pq)
{
  if(pq->length == 0) {
    return NULL;
  } else {
    return pq->q[0];
  }
}

static void bubble_down(spdylay_pq *pq, size_t index)
{
  size_t lchild = index*2+1;
  size_t minindex = index;
  size_t i, j;
  for(i = 0; i < 2; ++i) {
    j = lchild+i;
    if(j >= pq->length) {
      break;
    }
    if(pq->compar(pq->q[minindex], pq->q[j]) > 0) {
      minindex = j;
    }
  }
  if(minindex != index) {
    swap(pq, index, minindex);
    bubble_down(pq, minindex);
  }
}

void spdylay_pq_pop(spdylay_pq *pq)
{
  if(pq->length > 0) {
    pq->q[0] = pq->q[pq->length-1];
    --pq->length;
    bubble_down(pq, 0);
  }
}

int spdylay_pq_empty(spdylay_pq *pq)
{
  return pq->length == 0;
}

size_t spdylay_pq_size(spdylay_pq *pq)
{
  return pq->length;
}