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/*
* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
/** \file
* \ingroup bli
*
* \brief A generic structure queue
* (a queue for fixed length generally small) structures.
*/
#include <string.h>
#include "MEM_guardedalloc.h"
#include "BLI_gsqueue.h"
#include "BLI_strict_flags.h"
#include "BLI_utildefines.h"
/* target chunk size: 64kb */
#define CHUNK_SIZE_DEFAULT (1 << 16)
/* ensure we get at least this many elems per chunk */
#define CHUNK_ELEM_MIN 32
struct QueueChunk {
struct QueueChunk *next;
char data[0];
};
struct _GSQueue {
struct QueueChunk *chunk_first; /* first active chunk to pop from */
struct QueueChunk *chunk_last; /* last active chunk to push onto */
struct QueueChunk *chunk_free; /* free chunks to reuse */
size_t chunk_first_index; /* index into 'chunk_first' */
size_t chunk_last_index; /* index into 'chunk_last' */
size_t chunk_elem_max; /* number of elements per chunk */
size_t elem_size; /* memory size of elements */
size_t totelem; /* total number of elements */
};
static void *queue_get_first_elem(GSQueue *queue)
{
return ((char *)(queue)->chunk_first->data) + ((queue)->elem_size * (queue)->chunk_first_index);
}
static void *queue_get_last_elem(GSQueue *queue)
{
return ((char *)(queue)->chunk_last->data) + ((queue)->elem_size * (queue)->chunk_last_index);
}
/**
* \return number of elements per chunk, optimized for slop-space.
*/
static size_t queue_chunk_elem_max_calc(const size_t elem_size, size_t chunk_size)
{
/* get at least this number of elems per chunk */
const size_t elem_size_min = elem_size * CHUNK_ELEM_MIN;
BLI_assert((elem_size != 0) && (chunk_size != 0));
while (UNLIKELY(chunk_size <= elem_size_min)) {
chunk_size <<= 1;
}
/* account for slop-space */
chunk_size -= (sizeof(struct QueueChunk) + MEM_SIZE_OVERHEAD);
return chunk_size / elem_size;
}
GSQueue *BLI_gsqueue_new(const size_t elem_size)
{
GSQueue *queue = MEM_callocN(sizeof(*queue), "BLI_gsqueue_new");
queue->chunk_elem_max = queue_chunk_elem_max_calc(elem_size, CHUNK_SIZE_DEFAULT);
queue->elem_size = elem_size;
/* force init */
queue->chunk_last_index = queue->chunk_elem_max - 1;
return queue;
}
static void queue_free_chunk(struct QueueChunk *data)
{
while (data) {
struct QueueChunk *data_next = data->next;
MEM_freeN(data);
data = data_next;
}
}
/**
* Free the queue's data and the queue itself
*/
void BLI_gsqueue_free(GSQueue *queue)
{
queue_free_chunk(queue->chunk_first);
queue_free_chunk(queue->chunk_free);
MEM_freeN(queue);
}
/**
* Copies the source value onto the end of the queue
*
* \note This copies #GSQueue.elem_size bytes from \a item,
* (the pointer itself is not stored).
*
* \param item: source data to be copied to the queue.
*/
void BLI_gsqueue_push(GSQueue *queue, const void *item)
{
queue->chunk_last_index++;
queue->totelem++;
if (UNLIKELY(queue->chunk_last_index == queue->chunk_elem_max)) {
struct QueueChunk *chunk;
if (queue->chunk_free) {
chunk = queue->chunk_free;
queue->chunk_free = chunk->next;
}
else {
chunk = MEM_mallocN(sizeof(*chunk) + (queue->elem_size * queue->chunk_elem_max), __func__);
}
chunk->next = NULL;
if (queue->chunk_last == NULL) {
queue->chunk_first = chunk;
}
else {
queue->chunk_last->next = chunk;
}
queue->chunk_last = chunk;
queue->chunk_last_index = 0;
}
BLI_assert(queue->chunk_last_index < queue->chunk_elem_max);
/* Return last of queue */
memcpy(queue_get_last_elem(queue), item, queue->elem_size);
}
/**
* Retrieves and removes the first element from the queue.
* The value is copies to \a r_item, which must be at least \a elem_size bytes.
*
* Does not reduce amount of allocated memory.
*/
void BLI_gsqueue_pop(GSQueue *queue, void *r_item)
{
BLI_assert(BLI_gsqueue_is_empty(queue) == false);
memcpy(r_item, queue_get_first_elem(queue), queue->elem_size);
queue->chunk_first_index++;
queue->totelem--;
if (UNLIKELY(queue->chunk_first_index == queue->chunk_elem_max || queue->totelem == 0)) {
struct QueueChunk *chunk_free = queue->chunk_first;
queue->chunk_first = queue->chunk_first->next;
queue->chunk_first_index = 0;
if (queue->chunk_first == NULL) {
queue->chunk_last = NULL;
queue->chunk_last_index = queue->chunk_elem_max - 1;
}
chunk_free->next = queue->chunk_free;
queue->chunk_free = chunk_free;
}
}
size_t BLI_gsqueue_len(const GSQueue *queue)
{
return queue->totelem;
}
/**
* Returns true if the queue is empty, false otherwise
*/
bool BLI_gsqueue_is_empty(const GSQueue *queue)
{
return (queue->chunk_first == NULL);
}
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