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/* SPDX-License-Identifier: LGPL-3.0-or-later */
/*
* mempool.c
*
* Copyright (C) 2021 David Oberhollenzer <goliath@infraroot.at>
*/
#include "mempool.h"
#include <stdlib.h>
#include <limits.h>
#include <string.h>
#include <assert.h>
#if defined(_WIN32) || defined(__WINDOWS__)
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#else
#include <sys/mman.h>
#endif
#define DEF_POOL_SIZE (65536)
#define MEM_ALIGN (8)
typedef struct pool_t {
struct pool_t *next;
unsigned char *data;
unsigned char *limit;
unsigned int *bitmap;
size_t obj_free;
unsigned int blob[];
} pool_t;
struct mem_pool_t {
size_t obj_size;
size_t pool_size;
size_t bitmap_count;
pool_t *pool_list;
};
static size_t pool_size_from_bitmap_count(size_t count, size_t obj_size)
{
size_t size, byte_count, bit_count;
size = sizeof(pool_t);
if (size % sizeof(unsigned int))
size += sizeof(unsigned int) - size % sizeof(unsigned int);
byte_count = count * sizeof(unsigned int);
bit_count = byte_count * CHAR_BIT;
size += byte_count;
if (size % obj_size)
size += obj_size - size % obj_size;
size += bit_count * obj_size;
return size;
}
static pool_t *create_pool(const mem_pool_t *mem)
{
unsigned char *ptr;
pool_t *pool;
#if defined(_WIN32) || defined(__WINDOWS__)
pool = VirtualAlloc(NULL, mem->pool_size, MEM_RESERVE | MEM_COMMIT,
PAGE_READWRITE);
if (pool == NULL)
return NULL;
#else
pool = mmap(NULL, mem->pool_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (pool == MAP_FAILED)
return NULL;
#endif
pool->bitmap = pool->blob;
pool->obj_free = mem->bitmap_count * sizeof(unsigned int) * CHAR_BIT;
ptr = (unsigned char *)(pool->bitmap + mem->bitmap_count);
if (((uintptr_t)ptr) % mem->obj_size) {
ptr += mem->obj_size;
ptr -= ((uintptr_t)ptr) % mem->obj_size;
}
pool->data = ptr;
pool->limit = pool->data + pool->obj_free * mem->obj_size - 1;
memset(pool->bitmap, 0, mem->bitmap_count * sizeof(unsigned int));
return pool;
}
mem_pool_t *mem_pool_create(size_t obj_size)
{
mem_pool_t *mem = calloc(1, sizeof(*mem));
size_t count = 1, total;
if (mem == NULL)
return NULL;
if (obj_size % MEM_ALIGN)
obj_size += MEM_ALIGN - obj_size % MEM_ALIGN;
for (;;) {
total = pool_size_from_bitmap_count(count, obj_size);
if (total > DEF_POOL_SIZE)
break;
++count;
}
--count;
mem->obj_size = obj_size;
mem->pool_size = DEF_POOL_SIZE;
mem->bitmap_count = count;
return mem;
}
void mem_pool_destroy(mem_pool_t *mem)
{
while (mem->pool_list != NULL) {
pool_t *pool = mem->pool_list;
mem->pool_list = pool->next;
#if defined(_WIN32) || defined(__WINDOWS__)
VirtualFree(pool, mem->pool_size, MEM_RELEASE);
#else
munmap(pool, mem->pool_size);
#endif
}
free(mem);
}
void *mem_pool_allocate(mem_pool_t *mem)
{
size_t idx, i, j;
void *ptr = NULL;
pool_t *it;
retry_pool:
for (it = mem->pool_list; it != NULL; it = it->next) {
if (it->obj_free > 0)
break;
}
if (it == NULL) {
it = create_pool(mem);
if (it == NULL)
return NULL;
it->next = mem->pool_list;
mem->pool_list = it;
}
for (i = 0; i < mem->bitmap_count; ++i) {
if (it->bitmap[i] < UINT_MAX)
break;
}
if (i == mem->bitmap_count) {
it->obj_free = 0;
goto retry_pool;
}
for (j = 0; j < (sizeof(it->bitmap[i]) * CHAR_BIT); ++j) {
if (!(it->bitmap[i] & (1UL << j)))
break;
}
if (j == (sizeof(it->bitmap[i]) * CHAR_BIT)) {
it->obj_free = 0;
goto retry_pool;
}
idx = i * sizeof(unsigned int) * CHAR_BIT + j;
ptr = it->data + idx * mem->obj_size;
it->bitmap[i] |= (1UL << j);
it->obj_free -= 1;
memset(ptr, 0, mem->obj_size);
return ptr;
}
void mem_pool_free(mem_pool_t *mem, void *ptr)
{
size_t idx, i, j;
pool_t *it;
for (it = mem->pool_list; it != NULL; it = it->next) {
if ((unsigned char *)ptr >= it->data &&
(unsigned char *)ptr < it->limit) {
break;
}
}
assert(it != NULL);
idx = (size_t)((unsigned char *)ptr - it->data);
assert((idx % mem->obj_size) == 0);
idx /= mem->obj_size;
i = idx / (sizeof(unsigned int) * CHAR_BIT);
j = idx % (sizeof(unsigned int) * CHAR_BIT);
assert((it->bitmap[i] & (1 << j)) != 0);
it->bitmap[i] &= ~(1 << j);
}
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