fopen.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.
//
//  fopen.c
//

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

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


FILE *fopen(const char *fileName, const char *mode)
{
  // Excerpted from the GNU man page:
  //
  // The fopen() function opens the file whose name is the string pointed to
  // by fileName and associates a stream with it.
  //
  // The argument mode points to a string beginning with one of the
  // following sequences (Additional characters may follow these sequences.):
  //
  // r      Open text file for reading.  The stream is positioned at the
  //        beginning of the file.
  //
  // r+     Open for reading and writing.  The stream is positioned at the
  //        beginning of the file.
  //
  // w      Truncate file to zero length or create text file for writing.
  //        The stream is positioned at the beginning of the file.
  //
  // w+     Open for reading and writing.  The file is created if it does
  //        not exist, otherwise it is truncated.  The stream is positioned
  //        at the beginning of the file.
  //
  // a      Open for appending (writing at end of file).  The file is created
  //        if it does not exist.  The stream is positioned at the end
  //        of the file.
  //
  // a+     Open for reading and appending (writing at end of file).  The
  //        file is created if it does not exist.  The initial file position
  //        for reading is at the beginning of the file, but output is
  //        always appended to the end of the file.
  //
  // N.B.:  The a+ argument will always be broken in Visopsys.  Reading from
  //        the start of the file and writing to the end of the file are silly
  //        IMO and have no equivalent in Visopsys.

  int status = 0;
  fileStream *theStream = NULL;
  int flags = 0;
  int append = 0;

  if (visopsys_in_kernel)
    {
      errno = ERR_BUG;
      return (theStream = NULL);
    }

  // Check params
  if ((fileName == NULL) || (mode == NULL))
    {
      errno = ERR_NULLPARAMETER;
      return (theStream = NULL);
    }

  // We have to convert the text string mode arguments to our flags

  if (strstr(mode, "r+"))
    flags |= OPENMODE_READWRITE;
  else if (strchr(mode, 'r'))
    flags |= OPENMODE_READ;
  if (strstr(mode, "w+"))
    flags |= (OPENMODE_READWRITE | OPENMODE_CREATE | OPENMODE_TRUNCATE);
  else if (strchr(mode, 'w'))
    flags |= (OPENMODE_WRITE | OPENMODE_CREATE | OPENMODE_TRUNCATE);
  if (strstr(mode, "a+"))
    {
      flags |= (OPENMODE_READWRITE | OPENMODE_CREATE);
      append = 1;
    }
  else if (strchr(mode, 'a'))
    {
      flags |= (OPENMODE_WRITE | OPENMODE_CREATE);
      append = 1;
    }

  // Get memory for the file stream
  theStream = malloc(sizeof(fileStream));
  if (theStream == NULL)
    {
      errno = ERR_MEMORY;
      return (theStream);
    }

  bzero(theStream, sizeof(fileStream));
  status = fileStreamOpen(fileName, flags, theStream);
  if (status < 0)
    {
      errno = status;
      free(theStream);
      return (theStream = NULL);
    }

  // If we're not appending, seek to the beginning of the file, since the
  // fileStreamOpen() call is automatically in 'append' mode
  if (!append)
    {
      status = fileStreamSeek(theStream, 0);
      if (status < 0)
	{
	  errno = status;
	  fileStreamClose(theStream);
	  free(theStream);
	  return (theStream = NULL);
	}
    }

  return ((FILE *) theStream);
}