/*  * This file is part of the UCB release of Plan 9. It is subject to the license * terms in the LICENSE file found in the top-level directory of this * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No * part of the UCB release of Plan 9, including this file, may be copied, * modified, propagated, or distributed except according to the terms contained * in the LICENSE file. */ /* * * Stuff that slows the transmission of jobs to PostScript printers. ONLY use it * if you appear to be having trouble with flow control. The idea is simple - only * send a significant amount of data when we're certain the printer is in the * WAITING state. Depends on receiving status messages and only works when the * program is run as a single process. What's done should stop printer generated * XOFFs - provided our input buffer (ie. blocksize) is sufficiently small. Was * originally included in the postio.tmp directory, but can now be requested with * the -S option. Considered eliminating this code, but some printers still depend * on it. In particular Datakit connections made using Datakit PVCs and DACUs seem * to have the most problems. Much of the new stuff that was added can't work when * you use this code and will be automatically disabled. * */ #include <stdio.h> #include "gen.h"#include "postio.h" extern char	*block;extern int	blocksize;extern int	head;extern int	tail;extern char	*line;extern char	mesg[];extern int	ttyo; /*****************************************************************************/ slowsend(fd_in)     int		fd_in;			/* next input file */ { /* * * A slow version of send() that's very careful about when data is sent to the * printer. Should help prevent overflowing the printer's input buffer, provided * blocksize is sufficiently small (1024 should be safe). It's a totally kludged * up routine that should ONLY be used if you have constant transmission problems. * There's really no way it will be able to drive a printer much faster that about * six pages a minute, even for the simplest jobs. Get it by using the -S option. * */     while ( readblock(fd_in) )	switch ( getstatus(0) )  {	    case WAITING:		    writeblock(blocksize);		    break; 	    case BUSY:	    case IDLE:	    case PRINTING:		    writeblock(30);		    break; 	    case NOSTATUS:	    case UNKNOWN:		    break; 	    case PRINTERERROR:		    sleep(30);		    break; 	    case ERROR:		    fprintf(stderr, "%s", mesg);	/* for csw */		    error(FATAL, "PostScript Error");		    break; 	    case FLUSHING:		    error(FATAL, "Flushing Job");		    break; 	    case DISCONNECT:		    error(FATAL, "Disconnected - printer may be offline");		    break; 	    default:		    sleep(2);		    break;	}   /* End switch */ }   /* End of send */ /*****************************************************************************/ static writeblock(num)     int		num;			/* most bytes we'll write */ {     int		count;			/* bytes successfully written */ /* * * Called from send() when it's OK to send the next block to the printer. head * is adjusted after the write, and the number of bytes that were successfully * written is returned to the caller. * */     if ( num > tail - head )	num = tail - head;     if ( (count = write(ttyo, &block[head], num)) == -1 )	error(FATAL, "error writing to %s", line);    else if ( count == 0 )	error(FATAL, "printer appears to be offline");     head += count;    return(count); }   /* End of writeblock */ /*****************************************************************************/