//-------------------------------------------------------------------
//	xmitajay.cpp
//
//	This program is for testing our 'ajfschar.c' device-driver's 
//	'write()' method if an amount of transfer-data is specified.
//
//		to compile:  $ g++ xmitajay.cpp -o ajayxmit
//		to execute:  $ ./amitajay <byte-count>
//
//	NOTE: Installing our 'ajfschar.c' device-driver is required.
//
//	programmer: ALLAN CRUSE
//	written on: 01 JUN 2010
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for write() 

char devname[] = "/dev/ajay";

char txbuf[ 41000 ];

int main( int argc, char **argv )
{
	// override default byte-count with a command-line argument
	int	n = (argc > 1) ? atoi( argv[1] ) : 100;
	if ( n > 41000 ) { fprintf( stderr, "too big\n" ); exit(1); }
	printf( "\n Writing %d bytes to \'%s\' \n", n, devname );

	// open the device-file for writing
	int	fd = open( devname, O_WRONLY );
	if ( fd < 0 ) { perror( devname ); exit(1); }

	// initialize the userspace data-buffer with ascii codes
	for (int i = 0; i < 41000; i++)
		{
		int	q = i / 64;
		int	r = i % 64;
		int	ch = 'A' + (q % 32);
		if (( ch < 0x20 )||( ch > 0x7E )) ch = ',';
		if ( (r % 8) == 7 ) ch = ' ';
		if ( r == 63 ) ch = '\n';
		txbuf[i] = ch;
		}

	// display the data to be transferred 
	printf( "\n" );
	for (int i = 0; i < n; i++) printf( "%c", txbuf[i] );
	printf( "\n\n" );

	// write the specified amount of data to the device-file 
	int	txbytes = write( fd, txbuf, n ); 
	if ( txbytes < 0 ) { perror( "write" ); exit(1); }

	// report the amount of data that our driver has transferred
	printf( "\n OK, sent %d bytes to \'%s\' \n", txbytes, devname );
}