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/*
* jabberd - Jabber Open Source Server
* Copyright (c) 2002 Jeremie Miller, Thomas Muldowney,
* Ryan Eatmon, Robert Norris
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA02111-1307USA
*/
/* priority queues */
#include "pqueue.h"
#include "pool.h"
#include <stdio.h> /* to get NULL */
#include <assert.h>
typedef struct _pqueue_node_st *_pqueue_node_t;
struct _pqueue_node_st {
void *data;
int priority;
_pqueue_node_t next;
_pqueue_node_t prev;
};
struct _pqueue_st {
pool_t p;
_pqueue_node_t cache;
_pqueue_node_t front;
_pqueue_node_t back;
int size;
};
pqueue_t pqueue_new(pool_t p) {
pqueue_t q;
q = (pqueue_t) pmalloco(p, sizeof(struct _pqueue_st));
q->p = p;
return q;
}
void pqueue_push(pqueue_t q, void *data, int priority) {
_pqueue_node_t qn, scan;
assert((q != NULL));
q->size++;
/* node from the cache, or make a new one */
qn = q->cache;
if(qn != NULL)
q->cache = qn->next;
else
qn = (_pqueue_node_t) pmalloc(q->p, sizeof(struct _pqueue_node_st));
qn->data = data;
qn->priority = priority;
qn->next = NULL;
qn->prev = NULL;
/* first one */
if(q->back == NULL && q->front == NULL) {
q->back = qn;
q->front = qn;
return;
}
/* find the first node with priority <= to us */
for(scan = q->back; scan != NULL && scan->priority > priority; scan = scan->next);
/* didn't find one, so we have top priority - push us on the front */
if(scan == NULL) {
qn->prev = q->front;
qn->prev->next = qn;
q->front = qn;
return;
}
/* push us in front of scan */
qn->next = scan;
qn->prev = scan->prev;
if(scan->prev != NULL)
scan->prev->next = qn;
else
q->back = qn;
scan->prev = qn;
}
void *pqueue_pull(pqueue_t q) {
void *data;
_pqueue_node_t qn;
assert((q != NULL));
if(q->front == NULL)
return NULL;
data = q->front->data;
qn = q->front;
if(qn->prev != NULL)
qn->prev->next = NULL;
q->front = qn->prev;
/* node to cache for later reuse */
qn->next = q->cache;
q->cache = qn;
if(q->front == NULL)
q->back = NULL;
q->size--;
return data;
}
int pqueue_size(pqueue_t q) {
return q->size;
}
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