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/*
* Copyright (c) 2020 Cisco and/or its affiliates.
* 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.
*/
/**
* \file pool.c
* \brief Implementation of fixed-size pool allocator.
*
* NOTE:
* - Ideally, we should have a single realloc per resize, that would encompass
* both the free indices vector and bitmap, by nesting data structures. Because
* of the added complexity, and by lack of evidence of the need for this, we
* currently rely on a simpler implementation.
*/
#include <assert.h>
#include <stdlib.h> // calloc
#include "common.h"
#include "pool.h"
void
_pool_init(void ** pool_ptr, size_t elt_size, size_t max_size)
{
assert(pool_ptr);
assert(elt_size);
pool_hdr_t * ph = calloc(POOL_HDRLEN + elt_size * max_size, 1);
if (!ph) {
*pool_ptr = NULL;
return;
}
ph->elt_size = elt_size;
ph->max_size = max_size;
/* Free indices */
off_t * free_indices;
vector_init(free_indices, max_size);
for(unsigned i = 0; i < max_size; i++)
free_indices[i] = (max_size - 1) - i;
vector_len(free_indices) = max_size;
ph->free_indices = free_indices;
/* Free bitmap */
uint_fast32_t * fb = ph->free_bitmap;
bitmap_init(fb, max_size);
bitmap_set_to(fb, max_size);
ph->free_bitmap = fb;
*pool_ptr = (uint8_t*)ph + POOL_HDRLEN;
}
void
_pool_free(void ** pool_ptr)
{
free(pool_hdr(*pool_ptr));
*pool_ptr = NULL;
}
void
_pool_resize(void ** pool_ptr, size_t elt_size)
{
pool_hdr_t * ph = pool_hdr(*pool_ptr);
size_t old_elts = ph->max_size;
size_t new_elts = old_elts * 2;
/* Double pool storage */
ph = realloc(ph, POOL_HDRLEN + new_elts * elt_size);
if (!ph) {
*pool_ptr = NULL;
return;
}
ph->elt_size = elt_size;
ph->max_size = new_elts;
/*
* After resize, the pool will have old_elts free indices, ranging from
* old_elts to (new_elts - 1)
*/
off_t * free_indices = ph->free_indices;
vector_ensure_pos(free_indices, old_elts);
for (unsigned i = 0; i < old_elts; i++)
free_indices[i] = new_elts - 1 - i;
/* Reassign pool pointer */
*pool_ptr = (uint8_t*)ph + POOL_HDRLEN;
}
void
_pool_get(void ** pool_ptr, void ** elt, size_t elt_size)
{
pool_hdr_t * ph = pool_hdr(*pool_ptr);
uint64_t l = vector_len(ph->free_indices);
if (l == 0)
_pool_resize(pool_ptr, elt_size);
off_t free_id = ph->free_indices[l - 1];
vector_len(ph->free_indices)--;
*elt = *pool_ptr + free_id;
memset(*elt, 0, sizeof(elt));
}
void
_pool_put(void ** pool_ptr, void ** elt, size_t elt_size)
{
pool_hdr_t * ph = pool_hdr(*pool_ptr);
uint64_t l = vector_len(ph->free_indices);
vector_ensure_pos(ph->free_indices, l);
ph->free_indices[l] = *elt - *pool_ptr;
vector_len(ph->free_indices)++;
bitmap_set(ph->free_bitmap, l);
}
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