zfsseek.c

zilog的实时操作系统RZK,可以移植到多种处理器上

/*
 * File       : ZFSSeek.c
 * Description: This file contains the implementation of ZFSSeek API
 * Author     : Mahadev K C
 * Created on : 30-APR-2003
 *
 * Copyright 2004 ZiLOG Inc.  ALL RIGHTS RESERVED.
 *
 * This file contains unpublished confidential and proprietary information
 * of ZiLOG, Inc.
 * NO PART OF THIS WORK MAY BE DUPLICATED, STORED, PUBLISHED OR DISCLOSED 
 * IN ANY FORM WITHOUT THE PRIOR WRITTEN CONSENT OF ZiLOG, INC.
 * This is not a license and no use of any kind of this work is authorized
 * in the absence of a written license granted by ZiLOG, Inc. in ZiLOG's 
 * sole discretion 
 */


#include "ZSysgen.h"
#include "ZTypes.h"
#include "ZThread.h"
#include "ZSemaphore.h"
#include "glextern.h"
extern RZK_SEMAPHOREHANDLE_t hSem_FS;


//Function Name: ZFSSeek
//Description: This API will change the offset in the file
ZFS_STATUS_t ZFSSeek( IN ZFS_HANDLE_t handle, IN INT32 offset, IN INT8 origin )
{
        #define handle ((PZFS_OPEN_REC_t)handle)
	INT32 off ;
	INT32 new_off ;
	ZFS_SEC_ID_t cur_sec_id ;
	INT32 loc_size = 0 ;
	ZFS_SEC_HDR_t sec_hdr ;

	// if ZFS is not initialized, return error
	if( !IsZFSInited() )
		return ZFSERR_NOT_INITIALIZED ;
	
	if( origin != ZFS_FILE_BEGIN && origin != ZFS_FILE_END && origin != ZFS_FILE_CURRENT )
		return ZFSERR_INVALID_ARGUMENTS ;

	// first check whether the handle is valid or not
	if( handle->status != ZFS_OR_MAGIC_NUM )
		return ZFSERR_INVALID_HANDLE ;


	RZKAcquireSemaphore(hSem_FS,INFINITE_SUSPEND);
//	preempt_status = DisablePreemption() ;

	// if mode is APPEND, return error
	if( handle->mode & ZFS_APPEND )
		{
		RZKReleaseSemaphore(hSem_FS);
//		EnablePreemption( preempt_status ) ;
		return ZFSERR_INVALID_OPERATION ;
		}

	if( origin == ZFS_FILE_BEGIN )
		off = 0 ;
	else if( origin == ZFS_FILE_END )
		off = handle->size ;
	else if( origin == ZFS_FILE_CURRENT )
		off = handle->offset ;

	new_off = offset + off ;
	
	if( ( new_off > (INT32) handle->size ) || ( new_off < 0 ) )
		{
		RZKReleaseSemaphore(hSem_FS);
//		EnablePreemption( preempt_status ) ;
		return ZFSERR_INVALID_OFFSET_RANGE ;
		}

	handle->offset = new_off ;

	// now traverse through the nodes to find where current offset lies

	for( cur_sec_id = handle->first_secnum ; cur_sec_id != (ZFS_SEC_ID_t) FREE_SECTOR ; )
		{
		if( ( loc_size + ZFS_SEC_DATA_SIZE ) >= new_off )
			{
			// this is the sec id, just store it in or
			handle->cur_secnum = cur_sec_id ;
			break ;
			}
		// go to next linked sector.
		handle->pvol->pcfg->pfn_drv_read( GetSecAddr( handle->pvol, cur_sec_id), &sec_hdr, sizeof( ZFS_SEC_HDR_t) );
		cur_sec_id = sec_hdr.nxtsecnum ;
		loc_size += ZFS_SEC_DATA_SIZE ;
		}
	
	RZKReleaseSemaphore(hSem_FS);
//	EnablePreemption( preempt_status ) ;
	return ZFSERR_SUCCESS ;
}