lseek.c

嵌入式实验uC-OS-II相关程序用例与参考资料

/* $id:dmLseek.c  V1.0 2002/01/15 */

/******************************************************************************
 *  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: Lseek.c
 *
 *  MODULE: RLT
 *
 *  PURPOSE: lseek() - POSIX 1003.1b 6.4.2 - Reposition read/write file offset
 *
 *  AUTHOR(S):Zhang Yumin
 *
 *  GROUP:TOOL_GROUP
 *
 *  DATE CREATED:2002/01/15
 *
 *  REFERENCE DOCUMENT ID:
 *
 *  MODIFICATIONS:
 *  Date          user Name       Description
 *  2002/01/15    Zhang Yumin    Create this file
 *
 *********************************************************************************/

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


off_t  sys_lseek(int fd, off_t offset, int whence)
{
	
}

/********************************************************************
 *  FUNCTION: lseek
 *
 *  PURPOSE:  Reposition read/write file offset.
 *  PARAMETERS:
 *
 *    Input   fd -file descriptor of target file.
 *			  offset&whence
 *				-If whence is SEEK_SET,the offset is set to offset bytes.
 *				-If whence is SEEK_CUR,the offset is set to its current
 *					location plusoffset bytes.
 *				-If whence isSEEK_END,the offset is set to the size of the
 *					file plusoffset bytes.
 *    Output: None
 *    InOut:  None
 *
 *  Return value: Upon successful completion,lseek() returns the resulting
 *				  offset location as measured in bytes from the beginning
 *				  of the file. Otherwise, a value of -1 is returned and
 *				  errno is set to indicate the error.
 *  Reentrant: No
 ********************************************************************/
off_t _lseek_r(struct _reent *ptr,int fd, off_t offset,int whence)
{
	int rc = sys_lseek(fd,offset,whence);
	if(rc < 0)
	{
		ptr->_errno = -rc;
		return -1;
	}
	return rc;
}


#ifndef _REENT_ONLY

off_t lseek(int fd, off_t offset,int whence)
{
  	return _lseek_r(_REENT,fd,offset,whence);
}

#endif