sbrk.c

基于Xilinx-XUPV2P开发平台的嵌入式系统实验例程：实验4编写基本的应用程序

/*-----------------------------------------------------------------------------
//     $Date: 2004/07/31 23:46:47 $
//     $RCSfile: sbrk.c,v $
//-----------------------------------------------------------------------------
//
// Copyright (c) 2004 Xilinx, Inc.  All rights reserved. 
// 
// Xilinx, Inc. 
// XILINX IS PROVIDING THIS DESIGN, CODE, OR INFORMATION "AS IS" AS A 
// COURTESY TO YOU.  BY PROVIDING THIS DESIGN, CODE, OR INFORMATION AS 
// ONE POSSIBLE   IMPLEMENTATION OF THIS FEATURE, APPLICATION OR 
// STANDARD, XILINX IS MAKING NO REPRESENTATION THAT THIS IMPLEMENTATION 
// IS FREE FROM ANY CLAIMS OF INFRINGEMENT, AND YOU ARE RESPONSIBLE 
// FOR OBTAINING ANY RIGHTS YOU MAY REQUIRE FOR YOUR IMPLEMENTATION. 
// XILINX EXPRESSLY DISCLAIMS ANY WARRANTY WHATSOEVER WITH RESPECT TO 
// THE ADEQUACY OF THE IMPLEMENTATION, INCLUDING BUT NOT LIMITED TO 
// ANY WARRANTIES OR REPRESENTATIONS THAT THIS IMPLEMENTATION IS FREE 
// FROM CLAIMS OF INFRINGEMENT, IMPLIED WARRANTIES OF MERCHANTABILITY 
// AND FITNESS FOR A PARTICULAR PURPOSE.
//
//---------------------------------------------------------------------------*/

#include <errno.h>

extern char _heap_start[];
extern char _heap_end[];

static char *heap_ptr;

char *sbrk (int nbytes)
{
  char *base;

  if (!heap_ptr)
    heap_ptr = (char *)&_heap_start;
  base = heap_ptr;
  heap_ptr += nbytes;

  if (heap_ptr <= (char *)&_heap_end)
    return base;
  else
  {
    errno = ENOMEM;
    return ((char *)-1);
  }
}