libgloss/sbrk.c

   1 /* sbrk.c -- allocate memory dynamically.
   2  *
   3  * Copyright (c) 1995,1996 Cygnus Support
   4  *
   5  * The authors hereby grant permission to use, copy, modify, distribute,
   6  * and license this software and its documentation for any purpose, provided
   7  * that existing copyright notices are retained in all copies and that this
   8  * notice is included verbatim in any distributions. No written agreement,
   9  * license, or royalty fee is required for any of the authorized uses.
  10  * Modifications to this software may be copyrighted by their authors
  11  * and need not follow the licensing terms described here, provided that
  12  * the new terms are clearly indicated on the first page of each file where
  13  * they apply.
  14  */
  15 #include <errno.h>
  16 #include "glue.h"
  17
  18 /* just in case, most boards have at least some memory */
  19 #ifndef RAMSIZE
  20 #  define RAMSIZE             (caddr_t)0x100000
  21 #endif
  22
  23 char *heap_ptr;
  24
  25 /*
  26  * sbrk -- changes heap size size. Get nbytes more
  27  *         RAM. We just increment a pointer in what's
  28  *         left of memory on the board.
  29  */
  30 char *
  31 sbrk (nbytes)
  32      int nbytes;
  33 {
  34   char        *base;
  35
  36   if (!heap_ptr)
  37     heap_ptr = (char *)&_end;
  38   base = heap_ptr;
  39   heap_ptr += nbytes;
  40
  41   return base;
  42 /* FIXME: We really want to make sure we don't run out of RAM, but this
  43  *       isn't very portable.
  44  */
  45 #if 0
  46   if ((RAMSIZE - heap_ptr - nbytes) >= 0) {
  47     base = heap_ptr;
  48     heap_ptr += nbytes;
  49     return (base);
  50   } else {
  51     errno = ENOMEM;
  52     return ((char *)-1);
  53   }
  54 #endif
  55 }