character input on the VAX

[revans at voodoo.ucsb.edu]

-Message-Text-Follows-
In article <2176 at rodan.acs.syr.edu>, tpschar at rodan.acs.syr.edu (Thomas Pschar) writes...

>Hi.  I need to write a kind of editor in C on the VAX.  Since it is to be
>a fullscreen editor, I need to grab one character at a time as it is typed
>without waiting for a carriage return.  Does anyone know of a (relatively)
>painless way to do this?

Short answer : No

Long answer : We met this problem a few months ago, whilst porting some
RT-11 applications written in DECUS C to VMS.  This was the best solution
we came up with ... enjoy!

Russ Evans		e_gs18 at va.nmh.ac.uk / j.r.evans at edinburgh.ac.uk
British Geological Survey, West Mains Road, Edinburgh EH9 3LA UK

/***************************************************************************/
/*
 * 	Author		Phil Wild
 *	Date		24 July 1989
 *	Function	macro definitions etc. particularly overridding those
 *			DECUS_C ones that are not VAX C
 *	Modified	Russ Evans 6 Nov 1989
 *			EOS & min definitions moved to vt.c
 *			becomes vtvms.c as independent module
 *			Did not appear to work .. added SYS$ASSIGN code !
 *			Fixed kbinr to work as in RT-11 implementation
 *	Copyright	Edinburgh Anisotropy Project,
 *			British Geological Survey, Edinburgh, UK
 */

/***************************************************************************/

#include <iodef>
#include <ssdef>
#include <descrip>

static int qioch_in = 0;

$DESCRIPTOR (input_stream, "SYS$INPUT");

typedef struct {
	short 	cond_code;
	short 	count;
	int     info;
	} io_status_block;

typedef struct {
	int	type;
	int	mask;
	} io_mask;

/***************************************************************************/

int kbin( )

/*
 *	Returns code for next character struck at keyboard .. WITHOUT
 *	waiting for a <return>.
 */

{
        char	c;
	int	stat_in;
        io_mask	mask = {0, 0};
        io_status_block iosb;


	if (qioch_in == 0) { 
		if ((stat_in = SYS$ASSIGN(&input_stream, 
			        	  &qioch_in, 
					  0, 
					  0)) 	
				!= SS$_NORMAL) {
			printf("Can't open connection\n");
			LIB$STOP(stat_in);
			}
		}

        if ((stat_in = SYS$QIOW(0,
		                qioch_in,
        			IO$_READVBLK | IO$M_NOECHO | IO$M_TRMNOECHO
					| IO$M_NOFILTR,
	        	        &iosb,
	                	0,
		                0,
		                &c,
		                1,
		                0,
		                &mask,
		                0,
	                	0))	
			!= SS$_NORMAL) {
		LIB$SIGNAL(stat_in);
		}

        return ((int)c);
}	

/***************************************************************************/

int kbinr( )

/*
 *	Returns code for next character struck at keyboard .. WITHOUT
 *	waiting for a <return>.  Returns (-1) if no character is available.
 */

{
        char	c;
        int	stat_in;
        io_status_block iosb;
        io_mask	mask = {0, 0};


	if (qioch_in == 0) { 
		if ((stat_in = SYS$ASSIGN(&input_stream, 
			        	  &qioch_in, 
					  0, 
					  0)) 	
				!= SS$_NORMAL) {
			printf("Can't open connection\n");
			LIB$STOP(stat_in);
			}
		}

        if ((stat_in = SYS$QIOW(0,
	                	qioch_in,
        			IO$_READVBLK | IO$M_NOECHO | IO$M_TRMNOECHO |
					IO$M_NOFILTR | IO$M_TIMED,
	                	&iosb,
	                	0,
	                	0,
	                	&c,
	                	1,
	                	1,
	                	&mask,
	                	0,
                		0))	
			!= SS$_NORMAL) {
 		LIB$SIGNAL(stat_in);
		}

        return ((iosb.count == 0) ? -1 : (int)c);
}	

/***************************************************************************/
End of vtvms.c