ref: 1ccd0cd04d75840861e26f6c5f6ac73396d43d8a
dir: /sys/src/cmd/postscript/postio/slowsend.c/
/* * * 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 */ /*****************************************************************************/