read.c

嵌入式实验uC-OS-II相关程序用例与参考资料

/* $id:dmRead.c  V1.0 2001/09/5 */

/******************************************************************************
 *  This source code has been made available to you by CORETEK  on
 *  AS-IS.Anyone receiving this source is licensed under
 *  CORETEK copyrights to use it in any way he or she deems fit,including
 *  copying it,modifying it,compiling it,and redistributing it either with
 *  or without modifictions.
 *
 *
 *  Any person who transfers this source code or any derivative work must
 *  include the CORETEK copyright notice, this paragraph,and the preceding
 *  two paragraphs in the transferred software.
 *
 *
 *       COPYRIGHT CORETEK CORPORATION 2001
 *     LICENSED MATERIAL - PROGRAM PROPERTY OF CORETEK
 *****************************************************************************/


/******************************************************************************
 *
 *  FILE: Read.c
 *
 *  MODULE: RTL
 *
 *  PURPOSE: read() - POSIX 1003.1b 6.4.1 - Read From a File
 *
 *  AUTHOR(S):Zhang Yumin
 *
 *  GROUP:TOOL_GROUP
 *
 *  DATE CREATED:2001/09/05
 *
 *  REFERENCE DOCUMENT ID:
 *
 *  MODIFICATIONS:
 *  Date          user Name       Description
 *  2001/09/05    Zhang Yumin    Create this file
 *
 *********************************************************************************/

#include <sys/types.h>
#include <sys/reent.h>


ssize_t sys_read(int fd, void* buffer, size_t count)
{
	//实现read系统调用方法	
}

/********************************************************************
 *  FUNCTION: read
 *
 *  PURPOSE:  Read() attempts to read nbytes of data from the object
 *		      referenced by the descriptor fd into the buffer
 *  PARAMETERS:
 *
 *    Input:  fd	-file descriptor of target file.
 *			  count	-the number of data in bytes.
 *    Output: buffer-data buffer.
 *    InOut:  None
 *
 *  Return value: If successful, the number of bytes actually read is returned.
 *		          Upon reading end-of-file, zero is returned.Otherwise, a -1 is
 *		          returned and the global variable errno is set to indicate the.
 *				  error.
 *  Reentrant: Yes
 ********************************************************************/
ssize_t _read_r(
  struct _reent *ptr,
  int         fd,
  void        *buffer,
  size_t         count
)
{
	int rc = sys_read(fd,buffer,count);
	if(rc < 0)
	{
		ptr->_errno = -rc;
		return -1;
	}
	return rc;
}

#ifndef _REENT_ONLY

ssize_t read(
  int         fd,
  void        *buffer,
  size_t         count
)
{
  	return _read_r(_REENT,fd,buffer,count);
}

#endif