This bug surfaced in 1.6.2 and does not affect code in any other released version of Asterisk. It manifested itself as SIP qualify not happening when it should, causing peers to go unreachable. This was debugged down to scheduler entries sometimes not getting executed when they were supposed to, which was in turn caused by an error in the heap code. The problem only sometimes occurs, and it is due to the logic for removing an entry in the heap from an arbitrary location (not just popping off the top). The scheduler performs this operation frequently when entries are removed before they run (when ast_sched_del() is used). In a normal pop off of the top of the heap, a node is taken off the bottom, placed at the top, and then bubbled down until the max heap property is restored (see max_heapify()). This same logic was used for removing an arbitrary node from the middle of the heap. Unfortunately, that logic is full of fail. This patch fixes that by fully restoring the max heap property when a node is thrown into the middle of the heap. Instead of just pushing it down as appropriate, it first pushes it up as high as it will go, and _then_ pushes it down. Lastly, fix a minor problem in ast_heap_verify(), which is only used for debugging. If a parent and child node have the same value, that is not an error. The only error is if a parent's value is less than its children. A huge thanks goes out to cappucinoking for debugging this down to the scheduler, and then producing an ast_heap test case that demonstrated the breakage. That made it very easy for me to focus on the heap logic and produce a fix. Open source projects are awesome. (closes issue #16936) Reported by: ib2 Tested by: cappucinoking, crjw (closes issue #17277) Reported by: cappucinoking Patches: heap-fix.rev2.diff uploaded by russell (license 2) Tested by: cappucinoking, russell git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@261496 65c4cc65-6c06-0410-ace0-fbb531ad65f3
323 lines
5.8 KiB
C
323 lines
5.8 KiB
C
/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 2009, Digium, Inc.
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*
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* Russell Bryant <russell@digium.com>
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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/*! \file
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*
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* \brief Max Heap data structure
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*
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* \author Russell Bryant <russell@digium.com>
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*/
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#include "asterisk.h"
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ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
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#include "asterisk/heap.h"
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#include "asterisk/utils.h"
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#include "asterisk/cli.h"
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struct ast_heap {
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ast_rwlock_t lock;
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ast_heap_cmp_fn cmp_fn;
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ssize_t index_offset;
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size_t cur_len;
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size_t avail_len;
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void **heap;
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};
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static inline int left_node(int i)
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{
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return 2 * i;
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}
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static inline int right_node(int i)
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{
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return 2 * i + 1;
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}
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static inline int parent_node(int i)
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{
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return i / 2;
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}
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static inline void *heap_get(struct ast_heap *h, int i)
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{
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return h->heap[i - 1];
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}
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static inline ssize_t get_index(struct ast_heap *h, void *elm)
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{
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ssize_t *index;
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if (h->index_offset < 0) {
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return -1;
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}
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index = elm + h->index_offset;
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return *index;
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}
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static inline void heap_set(struct ast_heap *h, int i, void *elm)
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{
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h->heap[i - 1] = elm;
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if (h->index_offset >= 0) {
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ssize_t *index = elm + h->index_offset;
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*index = i;
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}
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}
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int ast_heap_verify(struct ast_heap *h)
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{
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unsigned int i;
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for (i = 1; i <= (h->cur_len / 2); i++) {
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int l = left_node(i);
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int r = right_node(i);
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if (l <= h->cur_len) {
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if (h->cmp_fn(heap_get(h, i), heap_get(h, l)) < 0) {
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return -1;
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}
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}
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if (r <= h->cur_len) {
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if (h->cmp_fn(heap_get(h, i), heap_get(h, r)) < 0) {
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return -1;
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}
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}
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}
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return 0;
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}
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#ifdef MALLOC_DEBUG
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struct ast_heap *_ast_heap_create(unsigned int init_height, ast_heap_cmp_fn cmp_fn,
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ssize_t index_offset, const char *file, int lineno, const char *func)
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#else
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struct ast_heap *ast_heap_create(unsigned int init_height, ast_heap_cmp_fn cmp_fn,
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ssize_t index_offset)
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#endif
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{
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struct ast_heap *h;
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if (!cmp_fn) {
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ast_log(LOG_ERROR, "A comparison function must be provided\n");
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return NULL;
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}
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if (!init_height) {
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init_height = 8;
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}
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if (!(h =
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#ifdef MALLOC_DEBUG
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__ast_calloc(1, sizeof(*h), file, lineno, func)
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#else
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ast_calloc(1, sizeof(*h))
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#endif
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)) {
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return NULL;
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}
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h->cmp_fn = cmp_fn;
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h->index_offset = index_offset;
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h->avail_len = (1 << init_height) - 1;
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if (!(h->heap =
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#ifdef MALLOC_DEBUG
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__ast_calloc(1, h->avail_len * sizeof(void *), file, lineno, func)
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#else
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ast_calloc(1, h->avail_len * sizeof(void *))
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#endif
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)) {
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ast_free(h);
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return NULL;
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}
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ast_rwlock_init(&h->lock);
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return h;
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}
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struct ast_heap *ast_heap_destroy(struct ast_heap *h)
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{
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ast_free(h->heap);
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h->heap = NULL;
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ast_rwlock_destroy(&h->lock);
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ast_free(h);
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return NULL;
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}
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/*!
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* \brief Add a row of additional storage for the heap.
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*/
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static int grow_heap(struct ast_heap *h
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#ifdef MALLOC_DEBUG
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, const char *file, int lineno, const char *func
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#endif
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)
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{
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h->avail_len = h->avail_len * 2 + 1;
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if (!(h->heap =
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#ifdef MALLOC_DEBUG
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__ast_realloc(h->heap, h->avail_len * sizeof(void *), file, lineno, func)
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#else
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ast_realloc(h->heap, h->avail_len * sizeof(void *))
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#endif
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)) {
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h->cur_len = h->avail_len = 0;
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return -1;
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}
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return 0;
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}
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static inline void heap_swap(struct ast_heap *h, int i, int j)
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{
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void *tmp;
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tmp = heap_get(h, i);
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heap_set(h, i, heap_get(h, j));
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heap_set(h, j, tmp);
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}
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static inline void max_heapify(struct ast_heap *h, int i)
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{
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for (;;) {
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int l = left_node(i);
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int r = right_node(i);
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int max;
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if (l <= h->cur_len && h->cmp_fn(heap_get(h, l), heap_get(h, i)) > 0) {
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max = l;
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} else {
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max = i;
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}
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if (r <= h->cur_len && h->cmp_fn(heap_get(h, r), heap_get(h, max)) > 0) {
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max = r;
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}
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if (max == i) {
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break;
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}
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heap_swap(h, i, max);
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i = max;
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}
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}
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static int bubble_up(struct ast_heap *h, int i)
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{
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while (i > 1 && h->cmp_fn(heap_get(h, parent_node(i)), heap_get(h, i)) < 0) {
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heap_swap(h, i, parent_node(i));
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i = parent_node(i);
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}
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return i;
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}
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#ifdef MALLOC_DEBUG
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int _ast_heap_push(struct ast_heap *h, void *elm, const char *file, int lineno, const char *func)
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#else
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int ast_heap_push(struct ast_heap *h, void *elm)
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#endif
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{
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if (h->cur_len == h->avail_len && grow_heap(h
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#ifdef MALLOC_DEBUG
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, file, lineno, func
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#endif
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)) {
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return -1;
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}
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heap_set(h, ++(h->cur_len), elm);
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bubble_up(h, h->cur_len);
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return 0;
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}
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static void *_ast_heap_remove(struct ast_heap *h, unsigned int index)
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{
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void *ret;
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if (!index || index > h->cur_len) {
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return NULL;
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}
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ret = heap_get(h, index);
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heap_set(h, index, heap_get(h, (h->cur_len)--));
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index = bubble_up(h, index);
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max_heapify(h, index);
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return ret;
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}
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void *ast_heap_remove(struct ast_heap *h, void *elm)
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{
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ssize_t i = get_index(h, elm);
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if (i == -1) {
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return NULL;
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}
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return _ast_heap_remove(h, i);
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}
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void *ast_heap_pop(struct ast_heap *h)
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{
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return _ast_heap_remove(h, 1);
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}
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void *ast_heap_peek(struct ast_heap *h, unsigned int index)
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{
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if (!h->cur_len || !index || index > h->cur_len) {
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return NULL;
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}
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return heap_get(h, index);
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}
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size_t ast_heap_size(struct ast_heap *h)
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{
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return h->cur_len;
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}
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int __ast_heap_wrlock(struct ast_heap *h, const char *file, const char *func, int line)
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{
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return __ast_rwlock_wrlock(&h->lock, "&h->lock", file, line, func);
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}
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int __ast_heap_rdlock(struct ast_heap *h, const char *file, const char *func, int line)
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{
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return __ast_rwlock_rdlock(&h->lock, "&h->lock", file, line, func);
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}
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int __ast_heap_unlock(struct ast_heap *h, const char *file, const char *func, int line)
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{
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return __ast_rwlock_unlock(&h->lock, "&h->lock", file, line, func);
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}
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