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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* linear_allocator.h
*
* @copyright Copyright (C) 2016 Sproute Networks, Inc.
*
* @author Avneesh Sachdev <avneesh@sproute.com>
*/
/*
* Header file for the linear allocator.
*
* An allocator that allocates memory by walking down towards the end
* of a buffer. No attempt is made to reuse blocks that are freed
* subsequently. The assumption is that the buffer is big enough to
* cover allocations for a given purpose.
*/
#include <assert.h>
#include <string.h>
#include <stdint.h>
#include <stddef.h>
/*
* Alignment for block allocated by the allocator. Must be a power of 2.
*/
#define LINEAR_ALLOCATOR_ALIGNMENT 8
#define LINEAR_ALLOCATOR_ALIGN(value) \
(((value) + LINEAR_ALLOCATOR_ALIGNMENT - 1) \
& ~(LINEAR_ALLOCATOR_ALIGNMENT - 1));
/*
* linear_allocator_align_ptr
*/
static inline char *linear_allocator_align_ptr(char *ptr)
{
return (char *)LINEAR_ALLOCATOR_ALIGN((intptr_t)ptr);
}
typedef struct linear_allocator_t_ {
char *buf;
/*
* Current location in the buffer.
*/
char *cur;
/*
* End of buffer.
*/
char *end;
/*
* Version number of the allocator, this is bumped up when the allocator
* is reset and helps identifies bad frees.
*/
uint32_t version;
/*
* The number of blocks that are currently allocated.
*/
int num_allocated;
} linear_allocator_t;
/*
* linear_allocator_block_t
*
* Header structure at the begining of each block.
*/
typedef struct linear_allocator_block_t_ {
uint32_t flags;
/*
* The version of the allocator when this block was allocated.
*/
uint32_t version;
char data[0];
} linear_allocator_block_t;
#define LINEAR_ALLOCATOR_BLOCK_IN_USE 0x01
#define LINEAR_ALLOCATOR_HDR_SIZE (sizeof(linear_allocator_block_t))
/*
* linear_allocator_block_size
*
* The total amount of space a block will take in the buffer,
* including the size of the header.
*/
static inline size_t linear_allocator_block_size(size_t user_size)
{
return LINEAR_ALLOCATOR_ALIGN(LINEAR_ALLOCATOR_HDR_SIZE + user_size);
}
/*
* linear_allocator_ptr_to_block
*/
static inline linear_allocator_block_t *linear_allocator_ptr_to_block(void *ptr)
{
void *block_ptr;
block_ptr = ((char *)ptr) - offsetof(linear_allocator_block_t, data);
return block_ptr;
}
/*
* linear_allocator_init
*/
static inline void linear_allocator_init(linear_allocator_t *allocator,
char *buf, size_t buf_len)
{
memset(allocator, 0, sizeof(*allocator));
assert(linear_allocator_align_ptr(buf) == buf);
allocator->buf = buf;
allocator->cur = buf;
allocator->end = buf + buf_len;
}
/*
* linear_allocator_reset
*
* Prepare an allocator for reuse.
*
* *** NOTE ** This implicitly frees all the blocks in the allocator.
*/
static inline void linear_allocator_reset(linear_allocator_t *allocator)
{
allocator->num_allocated = 0;
allocator->version++;
allocator->cur = allocator->buf;
}
/*
* linear_allocator_alloc
*/
static inline void *linear_allocator_alloc(linear_allocator_t *allocator,
size_t user_size)
{
size_t block_size;
linear_allocator_block_t *block;
block_size = linear_allocator_block_size(user_size);
if (allocator->cur + block_size > allocator->end) {
return NULL;
}
block = (linear_allocator_block_t *)allocator->cur;
allocator->cur += block_size;
block->flags = LINEAR_ALLOCATOR_BLOCK_IN_USE;
block->version = allocator->version;
allocator->num_allocated++;
return block->data;
}
/*
* linear_allocator_free
*/
static inline void linear_allocator_free(linear_allocator_t *allocator,
void *ptr)
{
linear_allocator_block_t *block;
if (((char *)ptr) < allocator->buf || ((char *)ptr) >= allocator->end) {
assert(0);
return;
}
block = linear_allocator_ptr_to_block(ptr);
if (block->version != allocator->version) {
assert(0);
return;
}
block->flags = block->flags & ~LINEAR_ALLOCATOR_BLOCK_IN_USE;
if (--allocator->num_allocated < 0) {
assert(0);
}
}
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