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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;

}