dx_fileseek( )

Description | Cautions | Example | Errors | See Also

Name:	long dx_fileseek(handle, offset, origin)
Inputs:	int handle	handle returned from dx_fileopen( )
	long offset	number of bytes from the origin
	int origin	initial position
Returns:	number of bytes read if success
	-1 if failure
Category:	File Management

Description

The dx_fileseek( ) function moves a file pointer associated with the file handle to a new location that is offset bytes from origin. The function returns the offset, in bytes, of the new position from the beginning of the file. See the _lseek function in the Microsoft Visual C++ Run-Time Library Reference for more information.

Cautions

Use dx_fileseek( ) instead of _lseek to ensure the compatibility of applications with the libraries across various versions of Visual C++.

Example

#include <stdio.h>  
#include <srllib.h>  
#include <dxxxlib.h>  
#include <windows.h>  
int cd;                 /* channel descriptor */  
DX_UIO myio;            /* user definable I/O structure */  
/*  
 * User defined I/O functions  
 */  
int my_read(fd,ptr,cnt)  
int fd;  
char * ptr;  
unsigned cnt;  
{  
   printf("My read\n");  
   return(dx_fileread(fd,ptr,cnt));  
}  
/*  
 * my write function  
 */  
int my_write(fd,ptr,cnt)  
int fd;  
char * ptr;  
unsigned cnt;  
{  
printf("My write \n");  
   return(dx_filewrite(fd,ptr,cnt));  
}  
/*  
 * my seek function  
 */  
long my_seek(fd,offset,whence)  
int fd;  
long offset;  
int whence;  
{  
   printf("My seek\n");  
   return(dx_fileseek(fd,offset,whence));  
}  
void main(argc,argv)  
int argc;  
char *argv[];  
{  
   .  
   . /* Other initialization */  
   .  
   DX_UIO uioblk;  
/* Initialize the UIO structure */  
uioblk.u_read=my_read;  
uioblk.u_write=my_write;  
uioblk.u_seek=my_seek;  
/* Install my I/O routines */  
dx_setuio(uioblk);  
vodat_fd = dx_fileopen("JUNK.VOX",O_RDWR|O_BINARY);  
/*This block uses standard I/O functions */  
iott->io_type = IO_DEV|IO_CONT  
iott->io_fhandle = vodat_fd;  
iott->io_offset = 0;  
iott->io_length = 20000;  
/*This block uses my I/O functions */  
iottp++;  
iottp->io_type = IO_DEV|IO_UIO|IO_CONT  
iottp->io_fhandle = vodat_fd;  
iott->io_offset = 20001;  
iott->io_length = 20000;  
/*This block uses standard I/O functions */  
iottp++  
iott->io_type = IO_DEV|IO_CONT  
iott->io_fhandle = vodat_fd;  
iott->io_offset = 20002;  
iott->io_length = 20000;  
/*This block uses my I/O functions */  
iott->io_type = IO_DEV|IO_UIO|IO_EOT  
iott->io_fhandle = vodat_fd;  
iott->io_offset = 10003;  
iott->io_length = 20000;  
devhandle = dx_open("dxxxB1C1", NULL);  
dx_sethook(devhandle, DX-ONHOOK,EV_SYNC)  
dx_wtring(devhandle,1,DX_OFFHOOK,EV_SYNC);  
dx_clrdigbuf;  
   if(dx_rec(devhandle,iott,(DX_TPT*)NULL,RM_TONE|EV_SYNC) == -1) {  
  perror("");  
  exit(1);  
}  
dx_clrdigbuf(devhandle);  
   if(dx_play(devhandle,iott,(DX_TPT*)EV_SYNC) == -1 {  
   perror("");  
   exit(1);  
   }  
   dx_close(devhandle);

Errors

If this function returns -1 to indicate failure, a system error has occurred; use dx_fileerrno( ) to obtain the system error value. Refer to the dx_fileerrno( ) function for a list of the possible system error values.

See Also

• dx_fileopen( )
• dx_fileclose( )
• dx_fileread( )
• dx_filewrite( )

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