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/*
* MIT License
*
* Copyright (c) 2017 Embedded Artistry
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include <stddef.h>
#include <stdint.h>
#include "list.h"
/* align to nearest power of two */
#define ALIGN_SIZE(sz, align) (((sz) + ((align)-1)) & ~((align)-1))
/* free list node*/
typedef struct alloc_node
{
struct list_head node;
size_t size;
char* block;
} alloc_node_t;
/* allocation metadata size */
#define ALLOC_HEADER_SZ __builtin_offsetof(alloc_node_t, block)
/* minimum allocation size of 32 bytes */
#define MIN_ALLOC_SZ ALLOC_HEADER_SZ + 32
/* free list */
static LIST_HEAD(free_list);
static void coalesce_free_list(void)
{
alloc_node_t *b, *lb = NULL, *t;
list_for_each_entry_safe(b, t, &free_list, node)
{
if (lb)
{
/* coalesce adjacent blocks */
if ((((uintptr_t)&lb->block) + lb->size) == (uintptr_t)b)
{
lb->size += sizeof(*b) + b->size;
list_del(&b->node);
continue;
}
}
lb = b;
}
}
void* malloc(size_t size)
{
void* ptr = NULL;
alloc_node_t* blk = NULL;
if (size > 0)
{
/* Align the pointer */
size = ALIGN_SIZE(size, sizeof(void*));
/* try to find a big enough block */
list_for_each_entry(blk, &free_list, node)
{
if (blk->size >= size)
{
ptr = &blk->block;
break;
}
}
if (ptr)
{
/* split block if possible */
if ((blk->size - size) >= MIN_ALLOC_SZ)
{
alloc_node_t* new_blk;
new_blk = (alloc_node_t*)((uintptr_t)(&blk->block) + size);
new_blk->size = blk->size - size - ALLOC_HEADER_SZ;
blk->size = size;
list_add(&new_blk->node, &blk->node);
}
list_del(&blk->node);
}
}
return ptr;
}
void free(void* ptr)
{
alloc_node_t *blk, *free_blk;
if (ptr)
{
blk = container_of(ptr, alloc_node_t, block);
/* add block to free list in ascending order by pointer */
list_for_each_entry(free_blk, &free_list, node)
{
if (free_blk > blk)
{
list_add_tail(&blk->node, &free_blk->node);
goto blockadded;
}
}
list_add_tail(&blk->node, &free_list);
blockadded:
coalesce_free_list();
}
}
void _malloc_addblock(void* addr, size_t size)
{
alloc_node_t* blk;
/* pointer align the block */
blk = (alloc_node_t*)ALIGN_SIZE((uintptr_t)addr, sizeof(void*));
/* calculate usable size */
blk->size = (uintptr_t)addr + size - (uintptr_t)blk - ALLOC_HEADER_SZ;
/* add the block to the free list */
list_add(&blk->node, &free_list);
}
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