lib/libstand/sbrk.c

   1 /*-
   2  * Copyright (c) 1998 Michael Smith
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  *
  26  * $FreeBSD: src/lib/libstand/sbrk.c,v 1.2.2.1 2000/05/18 08:00:57 ps Exp $
  27  * $DragonFly: src/lib/libstand/sbrk.c,v 1.2 2003/06/17 04:26:51 dillon Exp $
  28  */
  29
  30 /*
  31  * Minimal sbrk() emulation required for malloc support.
  32  */
  33
  34 #include <string.h>
  35 #include "stand.h"
  36
  37 static size_t   maxheap, heapsize = 0;
  38 static void     *heapbase;
  39
  40 void
  41 setheap(void *base, void *top)
  42 {
  43     /* Align start address to 16 bytes for the malloc code. Sigh. */
  44     heapbase = (void *)(((uintptr_t)base + 15) & ~15);
  45     maxheap = top - heapbase;
  46 }
  47
  48 char *
  49 sbrk(int incr)
  50 {
  51     char        *ret;
  52
  53     if ((heapsize + incr) <= maxheap) {
  54         ret = heapbase + heapsize;
  55         bzero(ret, incr);
  56         heapsize += incr;
  57         return(ret);
  58     }
  59     errno = ENOMEM;
  60     return((char *)-1);
  61 }
  62