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Add an implementation of the heap data structure. 

A heap is a convenient data structure for implementing a priority queue.

Code from svn/asterisk/team/russell/heap/.

Review: http://reviewboard.digium.com/r/160/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@176632 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Russell Bryant 2009-02-17 20:51:10 +00:00
parent 47913cab6d
commit bb03ef8d47
3 changed files with 503 additions and 1 deletions
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218
include/asterisk/heap.h Normal file
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/*
* Asterisk -- An open source telephony toolkit.
*
* Copyright (C) 2009, Digium, Inc.
*
* Russell Bryant <russell@digium.com>
*
* See http://www.asterisk.org for more information about
* the Asterisk project. Please do not directly contact
* any of the maintainers of this project for assistance;
* the project provides a web site, mailing lists and IRC
* channels for your use.
*
* This program is free software, distributed under the terms of
* the GNU General Public License Version 2. See the LICENSE file
* at the top of the source tree.
*/
/*!
* \file
* \brief Max Heap data structure
* \author Russell Bryant <russell@digium.com>
*/
#ifndef __AST_HEAP_H__
#define __AST_HEAP_H__
/*!
* \brief A max heap.
*
* \note Thread-safety is left to the user of the API. The heap API provides
* no locking of its own. If the heap will be accessed by multiple threads,
* then a lock must be used to ensure that only a single operation is
* done on the heap at a time. For the sake of convenience, a lock is
* provided for the user of the API to use if another lock is not already
* available to protect the heap.
*/
struct ast_heap;
/*!
* \brief Function type for comparing nodes in a heap
*
* \param elm1 the first element
* \param elm2 the second element
*
* \retval negative if elm1 < elm2
* \retval 0 if elm1 == elm2
* \retval positive if elm1 > elm2
*
* \note This implementation is of a max heap. However, if a min heap is
* desired, simply swap the return values of this function.
*/
typedef int (*ast_heap_cmp_fn)(void *elm1, void *elm2);
/*!
* \brief Create a max heap
*
* \param init_height The initial height of the heap to allocate space for.
* To start out, there will be room for (2 ^ init_height) - 1 entries.
* However, the heap will grow as needed.
* \param cmp_fn The function that should be used to compare elements in the heap.
* \param index_offset This parameter is optional, but must be provided to be able
* to use ast_heap_remove(). This is the number of bytes into the element
* where an ssize_t has been made available for the heap's internal
* use. The heap will use this field to keep track of the element's current
* position in the heap. The offsetof() macro is useful for providing a
* proper value for this argument. If ast_heap_remove() will not be used,
* then a negative value can be provided to indicate that no field for an
* offset has been allocated.
*
* Example Usage:
*
* \code
*
* struct myobj {
* int foo;
* int bar;
* char stuff[8];
* char things[8];
* ssize_t __heap_index;
* };
*
* ...
*
* static int myobj_cmp(void *obj1, void *obj2);
*
* ...
*
* struct ast_heap *h;
*
* h = ast_heap_create(8, myobj_cmp, offsetof(struct myobj, __heap_index));
*
* \endcode
*
* \return An instance of a max heap
*/
struct ast_heap *ast_heap_create(unsigned int init_height, ast_heap_cmp_fn cmp_fn,
ssize_t index_offset);
/*!
* \brief Destroy a max heap
*
* \param h the heap to destroy
*
* \return NULL for convenience
*/
struct ast_heap *ast_heap_destroy(struct ast_heap *h);
/*!
* \brief Push an element on to a heap
*
* \param h the heap being added to
* \param elm the element being put on the heap
*
* \retval 0 success
* \retval non-zero failure
*/
int ast_heap_push(struct ast_heap *h, void *elm);
/*!
* \brief Pop the max element off of the heap
*
* \param h the heap
*
* \return this will return the element on the top of the heap, which has the
* largest value according to the element comparison function that was
* provided when the heap was created. The element will be removed before
* being returned.
*/
void *ast_heap_pop(struct ast_heap *h);
/*!
* \brief Remove a specific element from a heap
*
* \param h the heap to remove from
* \param elm the element to remove
*
* \return elm, if the removal was successful, or NULL if it failed
*
* \note the index_offset parameter to ast_heap_create() is required to be able
* to use this function.
*/
void *ast_heap_remove(struct ast_heap *h, void *elm);
/*!
* \brief Peek at an element on a heap
*
* \param h the heap
* \param index index of the element to return. The first element is at index 1,
* and the last element is at the index == the size of the heap.
*
* \return an element at the specified index on the heap. This element will \b not
* be removed before being returned.
*
* \note If this function is being used in combination with ast_heap_size() for
* purposes of traversing the heap, the heap must be locked for the entire
* duration of the traversal.
*/
void *ast_heap_peek(struct ast_heap *h, unsigned int index);
/*!
* \brief Get the current size of a heap
*
* \param h the heap
*
* \return the number of elements currently in the heap
*/
size_t ast_heap_size(struct ast_heap *h);
/*!
* \brief Write-Lock a heap
*
* \arg h the heap
*
* A lock is provided for convenience. It can be assumed that none of the
* ast_heap API calls are thread safe. This lock does not have to be used
* if another one is already available to protect the heap.
*
* \return see the documentation for pthread_rwlock_wrlock()
*/
int ast_heap_wrlock(struct ast_heap *h);
/*!
* \brief Read-Lock a heap
*
* \arg h the heap
*
* A lock is provided for convenience. It can be assumed that none of the
* ast_heap API calls are thread safe. This lock does not have to be used
* if another one is already available to protect the heap.
*
* \return see the documentation for pthread_rwlock_rdlock()
*/
int ast_heap_rdlock(struct ast_heap *h);
/*!
* \brief Unlock a heap
*
* \arg h the heap
*
* \return see the documentation for pthread_rwlock_unlock()
*/
int ast_heap_unlock(struct ast_heap *h);
/*!
* \brief Verify that a heap has been properly constructed
*
* \param h a heap
*
* \retval 0 success
* \retval non-zero failure
*
* \note This function is mostly for debugging purposes. It traverses an existing
* heap and verifies that every node is properly placed relative to its children.
*/
int ast_heap_verify(struct ast_heap *h);
#endif /* __AST_HEAP_H__ */

2
main/Makefile
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@ -18,7 +18,7 @@ all: asterisk
include $(ASTTOPDIR)/Makefile.moddir_rules
OBJS= tcptls.o io.o sched.o logger.o frame.o loader.o config.o channel.o \
translate.o file.o pbx.o cli.o md5.o term.o \
translate.o file.o pbx.o cli.o md5.o term.o heap.o \
ulaw.o alaw.o callerid.o fskmodem.o image.o app.o \
cdr.o tdd.o acl.o rtp.o udptl.o manager.o asterisk.o \
dsp.o chanvars.o indications.o autoservice.o db.o privacy.o \

284
main/heap.c Normal file
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/*
* Asterisk -- An open source telephony toolkit.
*
* Copyright (C) 2009, Digium, Inc.
*
* Russell Bryant <russell@digium.com>
*
* See http://www.asterisk.org for more information about
* the Asterisk project. Please do not directly contact
* any of the maintainers of this project for assistance;
* the project provides a web site, mailing lists and IRC
* channels for your use.
*
* This program is free software, distributed under the terms of
* the GNU General Public License Version 2. See the LICENSE file
* at the top of the source tree.
*/
/*! \file
*
* \brief Max Heap data structure
*
* \author Russell Bryant <russell@digium.com>
*/
#include "asterisk.h"
ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
#include "asterisk/heap.h"
#include "asterisk/utils.h"
#include "asterisk/cli.h"
struct ast_heap {
ast_rwlock_t lock;
ast_heap_cmp_fn cmp_fn;
ssize_t index_offset;
size_t cur_len;
size_t avail_len;
void **heap;
};
static inline int left_node(int i)
{
return 2 * i;
}
static inline int right_node(int i)
{
return 2 * i + 1;
}
static inline int parent_node(int i)
{
return i / 2;
}
static inline void *heap_get(struct ast_heap *h, int i)
{
return h->heap[i - 1];
}
static inline ssize_t get_index(struct ast_heap *h, void *elm)
{
ssize_t *index;
if (h->index_offset < 0) {
return -1;
}
index = elm + h->index_offset;
return *index;
}
static inline void heap_set(struct ast_heap *h, int i, void *elm)
{
h->heap[i - 1] = elm;
if (h->index_offset >= 0) {
ssize_t *index = elm + h->index_offset;
*index = i;
}
}
int ast_heap_verify(struct ast_heap *h)
{
unsigned int i;
for (i = 1; i <= (h->cur_len / 2); i++) {
int l = left_node(i);
int r = right_node(i);
if (l <= h->cur_len) {
if (h->cmp_fn(heap_get(h, i), heap_get(h, l)) <= 0) {
return -1;
}
}
if (r <= h->cur_len) {
if (h->cmp_fn(heap_get(h, i), heap_get(h, r)) <= 0) {
return -1;
}
}
}
return 0;
}
struct ast_heap *ast_heap_create(unsigned int init_height, ast_heap_cmp_fn cmp_fn,
ssize_t index_offset)
{
struct ast_heap *h;
if (!cmp_fn) {
ast_log(LOG_ERROR, "A comparison function must be provided\n");
return NULL;
}
if (!init_height) {
init_height = 8;
}
if (!(h = ast_calloc(1, sizeof(*h)))) {
return NULL;
}
h->cmp_fn = cmp_fn;
h->index_offset = index_offset;
h->avail_len = (1 << init_height) - 1;
if (!(h->heap = ast_calloc(1, h->avail_len * sizeof(void *)))) {
ast_free(h);
return NULL;
}
ast_rwlock_init(&h->lock);
return h;
}
struct ast_heap *ast_heap_destroy(struct ast_heap *h)
{
ast_free(h->heap);
h->heap = NULL;
ast_rwlock_destroy(&h->lock);
ast_free(h);
return NULL;
}
/*!
* \brief Add a row of additional storage for the heap.
*/
static int grow_heap(struct ast_heap *h)
{
h->avail_len = h->avail_len * 2 + 1;
if (!(h->heap = ast_realloc(h->heap, h->avail_len * sizeof(void *)))) {
h->cur_len = h->avail_len = 0;
return -1;
}
return 0;
}
static inline void heap_swap(struct ast_heap *h, int i, int j)
{
void *tmp;
tmp = heap_get(h, i);
heap_set(h, i, heap_get(h, j));
heap_set(h, j, tmp);
}
static inline void max_heapify(struct ast_heap *h, int i)
{
for (;;) {
int l = left_node(i);
int r = right_node(i);
int max;
if (l <= h->cur_len && h->cmp_fn(heap_get(h, l), heap_get(h, i)) > 0) {
max = l;
} else {
max = i;
}
if (r <= h->cur_len && h->cmp_fn(heap_get(h, r), heap_get(h, max)) > 0) {
max = r;
}
if (max == i) {
break;
}
heap_swap(h, i, max);
i = max;
}
}
int ast_heap_push(struct ast_heap *h, void *elm)
{
int i;
if (h->cur_len == h->avail_len && grow_heap(h)) {
return -1;
}
heap_set(h, ++(h->cur_len), elm);
for (i = h->cur_len;
i > 1 && h->cmp_fn(heap_get(h, parent_node(i)), heap_get(h, i)) < 0;
i = parent_node(i)) {
heap_swap(h, i, parent_node(i));
}
return 0;
}
static void *_ast_heap_remove(struct ast_heap *h, unsigned int index)
{
void *ret;
if (!index || index > h->cur_len) {
return NULL;
}
ret = heap_get(h, index);
heap_set(h, index, heap_get(h, (h->cur_len)--));
max_heapify(h, index);
return ret;
}
void *ast_heap_remove(struct ast_heap *h, void *elm)
{
ssize_t i = get_index(h, elm);
if (i == -1) {
return NULL;
}
return _ast_heap_remove(h, i);
}
void *ast_heap_pop(struct ast_heap *h)
{
return _ast_heap_remove(h, 1);
}
void *ast_heap_peek(struct ast_heap *h, unsigned int index)
{
if (!h->cur_len || !index || index > h->cur_len) {
return NULL;
}
return heap_get(h, index);
}
size_t ast_heap_size(struct ast_heap *h)
{
return h->cur_len;
}
int ast_heap_wrlock(struct ast_heap *h)
{
return ast_rwlock_wrlock(&h->lock);
}
int ast_heap_rdlock(struct ast_heap *h)
{
return ast_rwlock_rdlock(&h->lock);
}
int ast_heap_unlock(struct ast_heap *h)
{
return ast_rwlock_unlock(&h->lock);
}