Mon Aug 31 12:30:37 2015

Asterisk developer's documentation


heap.h File Reference

Max Heap data structure. More...

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Defines

#define ast_heap_rdlock(h)   __ast_heap_rdlock(h, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define ast_heap_unlock(h)   __ast_heap_unlock(h, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define ast_heap_wrlock(h)   __ast_heap_wrlock(h, __FILE__, __PRETTY_FUNCTION__, __LINE__)

Typedefs

typedef int(* ast_heap_cmp_fn )(void *elm1, void *elm2)
 Function type for comparing nodes in a heap.

Functions

int __ast_heap_rdlock (struct ast_heap *h, const char *file, const char *func, int line)
 Read-Lock a heap.
int __ast_heap_unlock (struct ast_heap *h, const char *file, const char *func, int line)
 Unlock a heap.
int __ast_heap_wrlock (struct ast_heap *h, const char *file, const char *func, int line)
 Write-Lock a heap.
struct ast_heapast_heap_create (unsigned int init_height, ast_heap_cmp_fn cmp_fn, ssize_t index_offset)
 Create a max heap.
struct ast_heapast_heap_destroy (struct ast_heap *h)
 Destroy a max heap.
void * ast_heap_peek (struct ast_heap *h, unsigned int index)
 Peek at an element on a heap.
void * ast_heap_pop (struct ast_heap *h)
 Pop the max element off of the heap.
int ast_heap_push (struct ast_heap *h, void *elm)
 Push an element on to a heap.
void * ast_heap_remove (struct ast_heap *h, void *elm)
 Remove a specific element from a heap.
size_t ast_heap_size (struct ast_heap *h)
 Get the current size of a heap.
int ast_heap_verify (struct ast_heap *h)
 Verify that a heap has been properly constructed.

Detailed Description

Max Heap data structure.

Author:
Russell Bryant <russell@digium.com>

Definition in file heap.h.


Define Documentation

#define ast_heap_rdlock (  )     __ast_heap_rdlock(h, __FILE__, __PRETTY_FUNCTION__, __LINE__)

Definition at line 251 of file heap.h.

Referenced by ast_timer_open().

#define ast_heap_unlock (  )     __ast_heap_unlock(h, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define ast_heap_wrlock (  )     __ast_heap_wrlock(h, __FILE__, __PRETTY_FUNCTION__, __LINE__)

Definition at line 250 of file heap.h.

Referenced by _ast_register_timing_interface(), and ast_unregister_timing_interface().


Typedef Documentation

typedef int(* ast_heap_cmp_fn)(void *elm1, void *elm2)

Function type for comparing nodes in a heap.

Parameters:
elm1 the first element
elm2 the second element
Return values:
negative if elm1 < elm2
0 if elm1 == elm2
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.
Since:
1.6.1

Definition at line 55 of file heap.h.


Function Documentation

int __ast_heap_rdlock ( struct ast_heap h,
const char *  file,
const char *  func,
int  line 
)

Read-Lock a heap.

Parameters:
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.

Returns:
see the documentation for pthread_rwlock_rdlock()
Since:
1.6.1

Definition at line 319 of file heap.c.

References __ast_rwlock_rdlock(), and ast_heap::lock.

00320 {
00321    return __ast_rwlock_rdlock(file, line, func, &h->lock, "&h->lock");
00322 }

int __ast_heap_unlock ( struct ast_heap h,
const char *  file,
const char *  func,
int  line 
)

Unlock a heap.

Parameters:
h the heap
Returns:
see the documentation for pthread_rwlock_unlock()
Since:
1.6.1

Definition at line 324 of file heap.c.

References __ast_rwlock_unlock(), and ast_heap::lock.

00325 {
00326    return __ast_rwlock_unlock(file, line, func, &h->lock, "&h->lock");
00327 }

int __ast_heap_wrlock ( struct ast_heap h,
const char *  file,
const char *  func,
int  line 
)

Write-Lock a heap.

Parameters:
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.

Returns:
see the documentation for pthread_rwlock_wrlock()
Since:
1.6.1

Definition at line 314 of file heap.c.

References __ast_rwlock_wrlock(), and ast_heap::lock.

00315 {
00316    return __ast_rwlock_wrlock(file, line, func, &h->lock, "&h->lock");
00317 }

struct ast_heap* ast_heap_create ( unsigned int  init_height,
ast_heap_cmp_fn  cmp_fn,
ssize_t  index_offset 
) [read]

Create a max heap.

Parameters:
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.
cmp_fn The function that should be used to compare elements in the heap.
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:

 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));
Returns:
An instance of a max heap
Since:
1.6.1

Definition at line 118 of file heap.c.

References __ast_calloc(), ast_calloc, ast_free, ast_log(), ast_rwlock_init, ast_heap::avail_len, ast_heap::cmp_fn, ast_heap::heap, ast_heap::index_offset, ast_heap::lock, and LOG_ERROR.

Referenced by ast_timing_init(), load_resource_list(), and sched_context_create().

00121 {
00122    struct ast_heap *h;
00123 
00124    if (!cmp_fn) {
00125       ast_log(LOG_ERROR, "A comparison function must be provided\n");
00126       return NULL;
00127    }
00128 
00129    if (!init_height) {
00130       init_height = 8;
00131    }
00132 
00133    if (!(h =
00134 #ifdef MALLOC_DEBUG
00135          __ast_calloc(1, sizeof(*h), file, lineno, func)
00136 #else
00137          ast_calloc(1, sizeof(*h))
00138 #endif
00139       )) {
00140       return NULL;
00141    }
00142 
00143    h->cmp_fn = cmp_fn;
00144    h->index_offset = index_offset;
00145    h->avail_len = (1 << init_height) - 1;
00146 
00147    if (!(h->heap =
00148 #ifdef MALLOC_DEBUG
00149          __ast_calloc(1, h->avail_len * sizeof(void *), file, lineno, func)
00150 #else
00151          ast_calloc(1, h->avail_len * sizeof(void *))
00152 #endif
00153       )) {
00154       ast_free(h);
00155       return NULL;
00156    }
00157 
00158    ast_rwlock_init(&h->lock);
00159 
00160    return h;
00161 }

struct ast_heap* ast_heap_destroy ( struct ast_heap h  )  [read]

Destroy a max heap.

Parameters:
h the heap to destroy
Returns:
NULL for convenience
Since:
1.6.1

Definition at line 163 of file heap.c.

References ast_free, ast_rwlock_destroy, ast_heap::heap, and ast_heap::lock.

Referenced by load_resource_list(), sched_context_destroy(), and timing_shutdown().

00164 {
00165    ast_free(h->heap);
00166    h->heap = NULL;
00167 
00168    ast_rwlock_destroy(&h->lock);
00169 
00170    ast_free(h);
00171 
00172    return NULL;
00173 }

void* ast_heap_peek ( struct ast_heap h,
unsigned int  index 
)

Peek at an element on a heap.

Parameters:
h the heap
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.
Returns:
an element at the specified index on the heap. This element will 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.

Example code for a traversal:

 struct ast_heap *h;

 ...

 size_t size, i;
 void *cur_obj;

 ast_heap_rdlock(h);

 size = ast_heap_size(h);

 for (i = 1; i <= size && (cur_obj = ast_heap_peek(h, i)); i++) {
     ... Do stuff with cur_obj ...
 }

 ast_heap_unlock(h);
Since:
1.6.1

Definition at line 300 of file heap.c.

References ast_heap::cur_len, and heap_get().

Referenced by ast_sched_dump(), ast_sched_report(), ast_sched_runq(), ast_sched_wait(), and ast_timer_open().

00301 {
00302    if (!h->cur_len || !index || index > h->cur_len) {
00303       return NULL;
00304    }
00305 
00306    return heap_get(h, index);
00307 }

void* ast_heap_pop ( struct ast_heap h  ) 

Pop the max element off of the heap.

Parameters:
h the heap
Returns:
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.
Since:
1.6.1

Definition at line 295 of file heap.c.

References _ast_heap_remove().

Referenced by ast_sched_runq(), load_resource_list(), and sched_context_destroy().

00296 {
00297    return _ast_heap_remove(h, 1);
00298 }

int ast_heap_push ( struct ast_heap h,
void *  elm 
)

Push an element on to a heap.

Parameters:
h the heap being added to
elm the element being put on the heap
Return values:
0 success
non-zero failure
Since:
1.6.1

Definition at line 250 of file heap.c.

References ast_heap::avail_len, bubble_up(), ast_heap::cur_len, grow_heap(), and heap_set().

Referenced by _ast_register_timing_interface(), load_resource(), and schedule().

00252 {
00253    if (h->cur_len == h->avail_len && grow_heap(h
00254 #ifdef MALLOC_DEBUG
00255       , file, lineno, func
00256 #endif
00257       )) {
00258       return -1;
00259    }
00260 
00261    heap_set(h, ++(h->cur_len), elm);
00262 
00263    bubble_up(h, h->cur_len);
00264 
00265    return 0;
00266 }

void* ast_heap_remove ( struct ast_heap h,
void *  elm 
)

Remove a specific element from a heap.

Parameters:
h the heap to remove from
elm the element to remove
Returns:
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.
Since:
1.6.1

Definition at line 284 of file heap.c.

References _ast_heap_remove(), and get_index().

Referenced by ast_sched_del(), and ast_unregister_timing_interface().

00285 {
00286    ssize_t i = get_index(h, elm);
00287 
00288    if (i == -1) {
00289       return NULL;
00290    }
00291 
00292    return _ast_heap_remove(h, i);
00293 }

size_t ast_heap_size ( struct ast_heap h  ) 

Get the current size of a heap.

Parameters:
h the heap
Returns:
the number of elements currently in the heap
Since:
1.6.1

Definition at line 309 of file heap.c.

References ast_heap::cur_len.

Referenced by ast_sched_dump(), and ast_sched_report().

00310 {
00311    return h->cur_len;
00312 }

int ast_heap_verify ( struct ast_heap h  ) 

Verify that a heap has been properly constructed.

Parameters:
h a heap
Return values:
0 success
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.
Since:
1.6.1

Definition at line 90 of file heap.c.

References ast_heap::cmp_fn, ast_heap::cur_len, heap_get(), left_node(), and right_node().

00091 {
00092    unsigned int i;
00093 
00094    for (i = 1; i <= (h->cur_len / 2); i++) {
00095       int l = left_node(i);
00096       int r = right_node(i);
00097 
00098       if (l <= h->cur_len) {
00099          if (h->cmp_fn(heap_get(h, i), heap_get(h, l)) < 0) {
00100             return -1;
00101          }
00102       }
00103 
00104       if (r <= h->cur_len) {
00105          if (h->cmp_fn(heap_get(h, i), heap_get(h, r)) < 0) {
00106             return -1;
00107          }
00108       }
00109    }
00110 
00111    return 0;
00112 }


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