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/* sbrk.c -- Implementation of the low-level sbrk() routine
*
* Copyright (c) 2004 National Semiconductor Corporation
*
* The authors hereby grant permission to use, copy, modify, distribute,
* and license this software and its documentation for any purpose, provided
* that existing copyright notices are retained in all copies and that this
* notice is included verbatim in any distributions. No written agreement,
* license, or royalty fee is required for any of the authorized uses.
* Modifications to this software may be copyrighted by their authors
* and need not follow the licensing terms described here, provided that
* the new terms are clearly indicated on the first page of each file where
* they apply.
*/
#include <errno.h>
#include <stddef.h> /* where ptrdiff_t is defined */
#include <stdlib.h>
/* Extend heap space by size bytes.
Return start of new space allocated, or -1 for errors
Error cases:
1. Allocation is not within heap range */
void * sbrk (ptrdiff_t size)
{
/*
* The following two memory locations should be defined in the linker script file
*/
extern const char _HEAP_START; /* start of heap */
extern const char _HEAP_MAX; /* end of heap (maximum value of heap_ptr) */
static const char * heap_ptr; /* pointer to head of heap */
const char * old_heap_ptr;
static unsigned char init_sbrk = 0;
/* heap_ptr is initialized to HEAP_START */
if (init_sbrk == 0)
{
heap_ptr = &_HEAP_START;
init_sbrk = 1;
}
old_heap_ptr = heap_ptr;
if ((heap_ptr + size) > &_HEAP_MAX)
{
/* top of heap is bigger than _HEAP_MAX */
errno = ENOMEM;
return (void *) -1;
}
/* success: update heap_ptr and return previous value */
heap_ptr += size;
return (void *)old_heap_ptr;
}
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