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@prasadwrites
Created December 6, 2014 05:11
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n byte aligned malloc implementation
/*
* nMalloc.cpp
*
* Created on: Dec 5, 2014
* Author: prasadnair
*/
#include <stdlib.h>
#include <stdio.h>
void * aligned_malloc(size_t size, int align) {
/* alignment could not be less then zero */
if (align < 0) {
return NULL;
}
/* Allocate necessary memory area client request - size parameter -
* plus area to store the address of the memory returned by standard
* malloc().
*/
void *ptr;
/* accomodating atleast one aligned memory area by adding align-1
/ size of (void *) is added since we intent to keep the below address
/ in p. This will be retrieved later during free
*/
void *p = malloc(size + align - 1 + sizeof(void*));
if (p != NULL) {
/* Address of the aligned memory according to the align parameter*/
ptr = (void*) (((size_t)p + sizeof(void*) + align -1) & ~(align-1));
/* store the address of the malloc() above the beginning of our total memory area.
*/
*((void**)((size_t)ptr - sizeof(void*))) = p;
/* Return the address of aligned memory */
return ptr;
}
return NULL;
}
void aligned_free(void *p) {
/* Get the address of the memory, stored at the
* start of our total memory area.
*/
void *ptr = *((void**)((size_t)p - sizeof(void*)));
free(ptr);
return;
}
int main ()
{
int align;
for (align = 2; align < 5000000; align= align*2)
{
int *p = (int *) aligned_malloc (1024, align);
// trying to see if its aligned properly by finding mode with align
// mode operator should always return zero if memory is aligned to align
printf (" %p %d \n", p, ((long int)p)%align);
aligned_free (p);
}
return 0;
}
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