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/* Copyright 2015 greenbytes GmbH (https://www.greenbytes.de)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <assert.h>
#include <stddef.h>
#include <httpd.h>
#include <http_core.h>
#include "h2_task.h"
#include "h2_task_queue.h"
static void tq_grow(h2_task_queue *q, int nlen);
static void tq_swap(h2_task_queue *q, int i, int j);
static int tq_bubble_up(h2_task_queue *q, int i, int top,
h2_tq_cmp *cmp, void *ctx);
static int tq_bubble_down(h2_task_queue *q, int i, int bottom,
h2_tq_cmp *cmp, void *ctx);
h2_task_queue *h2_tq_create(apr_pool_t *pool, int capacity)
{
h2_task_queue *q = apr_pcalloc(pool, sizeof(h2_task_queue));
if (q) {
q->pool = pool;
tq_grow(q, capacity);
q->nelts = 0;
}
return q;
}
int h2_tq_empty(h2_task_queue *q)
{
return q->nelts == 0;
}
void h2_tq_add(h2_task_queue *q, int sid, h2_tq_cmp *cmp, void *ctx)
{
int i;
if (q->nelts >= q->nalloc) {
tq_grow(q, q->nalloc * 2);
}
i = (q->head + q->nelts) % q->nalloc;
q->elts[i] = sid;
++q->nelts;
/* bubble it to the front of the queue */
tq_bubble_up(q, i, q->head, cmp, ctx);
}
int h2_tq_remove(h2_task_queue *q, int sid)
{
int i;
for (i = 0; i < q->nelts; ++i) {
if (sid == q->elts[(q->head + i) % q->nalloc]) {
break;
}
}
if (i < q->nelts) {
++i;
for (; i < q->nelts; ++i) {
q->elts[(q->head+i-1)%q->nalloc] = q->elts[(q->head+i)%q->nalloc];
}
--q->nelts;
return 1;
}
return 0;
}
void h2_tq_sort(h2_task_queue *q, h2_tq_cmp *cmp, void *ctx)
{
/* Assume that changes in ordering are minimal. This needs,
* best case, q->nelts - 1 comparisions to check that nothing
* changed.
*/
if (q->nelts > 0) {
int i, ni, prev, last;
/* Start at the end of the queue and create a tail of sorted
* entries. Make that tail one element longer in each iteration.
*/
last = i = (q->head + q->nelts - 1) % q->nalloc;
while (i != q->head) {
prev = (q->nalloc + i - 1) % q->nalloc;
ni = tq_bubble_up(q, i, prev, cmp, ctx);
if (ni == prev) {
/* i bubbled one up, bubble the new i down, which
* keeps all tasks below i sorted. */
tq_bubble_down(q, i, last, cmp, ctx);
}
i = prev;
};
}
}
int h2_tq_shift(h2_task_queue *q)
{
int sid;
if (q->nelts <= 0) {
return 0;
}
sid = q->elts[q->head];
q->head = (q->head + 1) % q->nalloc;
q->nelts--;
return sid;
}
static void tq_grow(h2_task_queue *q, int nlen)
{
AP_DEBUG_ASSERT(q->nalloc <= nlen);
if (nlen > q->nalloc) {
int *nq = apr_pcalloc(q->pool, sizeof(h2_task *) * nlen);
if (q->nelts > 0) {
int l = ((q->head + q->nelts) % q->nalloc) - q->head;
memmove(nq, q->elts + q->head, sizeof(int) * l);
if (l < q->nelts) {
/* elts wrapped, append elts in [0, remain] to nq */
int remain = q->nelts - l;
memmove(nq + l, q->elts, sizeof(int) * remain);
}
}
q->elts = nq;
q->nalloc = nlen;
q->head = 0;
}
}
static void tq_swap(h2_task_queue *q, int i, int j)
{
int x = q->elts[i];
q->elts[i] = q->elts[j];
q->elts[j] = x;
}
static int tq_bubble_up(h2_task_queue *q, int i, int top,
h2_tq_cmp *cmp, void *ctx)
{
int prev;
while (((prev = (q->nalloc + i - 1) % q->nalloc), i != top)
&& (*cmp)(q->elts[i], q->elts[prev], ctx) < 0) {
tq_swap(q, prev, i);
i = prev;
}
return i;
}
static int tq_bubble_down(h2_task_queue *q, int i, int bottom,
h2_tq_cmp *cmp, void *ctx)
{
int next;
while (((next = (q->nalloc + i + 1) % q->nalloc), i != bottom)
&& (*cmp)(q->elts[i], q->elts[next], ctx) > 0) {
tq_swap(q, next, i);
i = next;
}
return i;
}
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