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