read.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.
//
//  read.c
//

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

#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <sys/api.h>


size_t read(int fd, void *buf, size_t count)
{
  // Read count bytes from the stream

  int status = 0;

  if (visopsys_in_kernel)
    return (errno = ERR_BUG);

  if (fd == (int) stdin)
    status = textInputStreamReadN(multitaskerGetTextInput(), count, buf);
  else
    status = fileStreamRead((fileStream *) fd, count, buf);

  if (status < 0)
    return (errno = status);

  return (count);
}