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/*
* Copyright (c) 2022 EdgeImpulse Inc.
*
* 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.
*
* SPDX-License-Identifier: Apache-2.0
*/
#ifndef _EDGE_IMPULSE_ALIGNED_MALLOC_H_
#define _EDGE_IMPULSE_ALIGNED_MALLOC_H_
#include <assert.h>
#include "../porting/ei_classifier_porting.h"
#ifdef __cplusplus
namespace {
#endif // __cplusplus
/**
* Based on https://github.com/embeddedartistry/embedded-resources/blob/master/examples/c/malloc_aligned.c
*/
/**
* Simple macro for making sure memory addresses are aligned
* to the nearest power of two
*/
#ifndef align_up
#define align_up(num, align) \
(((num) + ((align) - 1)) & ~((align) - 1))
#endif
//Number of bytes we're using for storing the aligned pointer offset
typedef uint16_t offset_t;
#define PTR_OFFSET_SZ sizeof(offset_t)
/**
* aligned_malloc takes in the requested alignment and size
* We will call malloc with extra bytes for our header and the offset
* required to guarantee the desired alignment.
*/
__attribute__((unused)) void * ei_aligned_calloc(size_t align, size_t size)
{
void * ptr = NULL;
//We want it to be a power of two since align_up operates on powers of two
assert((align & (align - 1)) == 0);
if(align && size)
{
/*
* We know we have to fit an offset value
* We also allocate extra bytes to ensure we can meet the alignment
*/
uint32_t hdr_size = PTR_OFFSET_SZ + (align - 1);
void * p = ei_calloc(size + hdr_size, 1);
if(p)
{
/*
* Add the offset size to malloc's pointer (we will always store that)
* Then align the resulting value to the arget alignment
*/
ptr = (void *) align_up(((uintptr_t)p + PTR_OFFSET_SZ), align);
//Calculate the offset and store it behind our aligned pointer
*((offset_t *)ptr - 1) = (offset_t)((uintptr_t)ptr - (uintptr_t)p);
} // else NULL, could not malloc
} //else NULL, invalid arguments
return ptr;
}
/**
* aligned_free works like free(), but we work backwards from the returned
* pointer to find the correct offset and pointer location to return to free()
* Note that it is VERY BAD to call free() on an aligned_malloc() pointer.
*/
__attribute__((unused)) void ei_aligned_free(void * ptr)
{
assert(ptr);
/*
* Walk backwards from the passed-in pointer to get the pointer offset
* We convert to an offset_t pointer and rely on pointer math to get the data
*/
offset_t offset = *((offset_t *)ptr - 1);
/*
* Once we have the offset, we can get our original pointer and call free
*/
void * p = (void *)((uint8_t *)ptr - offset);
ei_free(p);
}
#ifdef __cplusplus
}
#endif // __cplusplus
#endif // _EDGE_IMPULSE_ALIGNED_MALLOC_H_
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