realloc.c

上一个上传的有问题,这个是好的。visopsys包括系统内核和GUI的全部SOURCE code ,还包括一些基本的docs文档。里面src子目录对应所有SOURCE code.对于想研究操作系统的朋

// 
//  Visopsys
//  Copyright (C) 1998-2007 J. Andrew McLaughlin
//  
//  This library is free software; you can redistribute it and/or modify it
//  under the terms of the GNU Lesser General Public License as published by
//  the Free Software Foundation; either version 2.1 of the License, or (at
//  your option) any later version.
//
//  This library is distributed in the hope that it will be useful, but
//  WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
//  General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public License
//  along with this library; if not, write to the Free Software Foundation,
//  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
//  realloc.c
//

// This is the standard "realloc" function, as found in standard C libraries

#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/api.h>


void *_realloc(void *oldMemory, size_t size, const char *function)
{
  // This is what the linux man page says about this function:
  // realloc() changes the size of the memory block pointed to by ptr to
  // size bytes.  The contents will be unchanged to the minimum of the old
  // and new sizes; newly allocated memory will be uninitialized.  If ptr is
  // NULL, the call is equivalent to malloc(size); if size is equal to zero,
  // the call is equivalent to free(ptr).  Unless ptr is NULL, it must have
  // been returned by an earlier call to malloc(), calloc() or realloc().
  // If the area pointed to was moved, a free(ptr) is done.

  int status = 0;
  memoryBlock oldBlock;
  void *memoryPointer = NULL;

  if (oldMemory == NULL)
    return (memoryPointer = _malloc(size, function));

  else if (!size)
    {
      _free(oldMemory, function);
      return (memoryPointer = NULL);
    }

  // Get stats about the old memory
  status = _mallocBlockInfo(oldMemory, &oldBlock);
  if (status < 0)
    {
      errno = status;
      return (memoryPointer = NULL);
    }
  
  memoryPointer = _malloc(size, function);

  if (memoryPointer)
    {
      size = min(size, ((oldBlock.endLocation - oldBlock.startLocation) + 1));
      bcopy(oldMemory, memoryPointer, size);
      _free(oldMemory, function);
    }

  // Return this value, whether or not we were successful
  return (memoryPointer);
}