/*
 * compress HP PCL-format bit image data
 * usage: pcl_pack input output
 * copyright 1990 Digital Insight
 */
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>

#define MAX_RUN 128		/* max compressed run length */

char inbuf[4096];		/* image input buffer */
char pbuf[4096];		/* packed output buffer */
char esbuf[100];		/* escape sequence buffer */

char rawbuf[8192];		/* raw input buffer */
char *rawptr = rawbuf;		/* current position in buffer */
int rawbytes;			/* bytes left in buffer */

FILE *in_fp;
FILE *out_fp;

/*
 * Abort program with error message
 */
void fail(char *msg)
{
	puts(msg);
	exit(1);
}

/*
 * Buffered input from in_fp. Used in place of fread() to speed things up
 * (depending on the stream I/O library's own buffer size)
 */
int bfread(char *buf, int nbytes)
{
	int bytes_read = 0;		/* bytes read so far */
	register int partial;		/* partial transfer count */

	while (nbytes > 0) {
		if (rawbytes == 0) {	/* buffer empty, get some more */
			rawbytes = fread(rawptr=rawbuf, 1, sizeof(rawbuf), 
					 in_fp);
			if (rawbytes == 0)
				break;
		}

		partial = nbytes;	/* transfer data from buffer */
		if (partial > rawbytes)
			partial = rawbytes;
		memcpy(buf, rawptr, partial);
		bytes_read += partial;
		rawptr     += partial;
		buf        += partial;
		nbytes     -= partial;
		rawbytes   -= partial;
	}

	return bytes_read;
}

/*
 * Buffered input from in_fp. Used in place of fgetc() to speed things up
 * (depending on the stream I/O library's own buffer size)
 */
int bfgetc(void)
{
	if (rawbytes == 0) {	/* buffer empty, get some more */
		rawbytes = fread(rawptr=rawbuf, 1, sizeof(rawbuf), in_fp);
		if (rawbytes == 0)
			return EOF;
	}

	rawbytes--;
	return *rawptr++;
}

/*
 * Copy input to output up to next escape sequence;
 * save sequence in esbuf[]. Return sequence length.
 */
int read_seq(void)
{
	int c;
	char *seq = esbuf;

	do {				/* read up to escape char */
		if ((c = bfgetc()) == EOF)
			exit(0);	/* done! */
		fputc(c, out_fp);
	} while (c != 0x1B);

	do {				/* read seq thru uppercase char */
		*seq++ = c = bfgetc();
		if (c == EOF)
			fail("unexpected end of input");
	} while (!isupper(c));

	*seq = 0;			/* terminate sequence */
	return seq-esbuf;
}

/*
 * Read line of image data into inbuf; return length.
 * Any other data (text, escape sequences) are sent directly to output.
 */
int read_line(void)
{
	register int n;
	char *pos;

	for (;;) {			/* look for [esc]*b...W/M */
		n = read_seq();
		
		if (n < 3 || esbuf[0] != '*' || esbuf[1] != 'b') {
			/* some other seq, send out */
			fwrite(esbuf, 1, n, out_fp);	
			continue;
		}

		for (pos=esbuf+2; *pos; pos++) {	
			/* get #<func> */
			n = (int)strtol(pos, &pos, 10);
			switch (*pos) {
			case 'W':	/* found image data */
				goto got_image;
			case 'm':	/* compression mode */
			case 'M':
				if (n != 0) 
					fail("Input is already compressed");
				break;
			default:	/* some other sequence */
				/* split off and output */
				if (islower(*pos))
					*pos = toupper(*pos);
				fprintf(out_fp, "*b%d%c\1xB", n, *pos++);
			}
		}
	}

  got_image:
	if (bfread(inbuf, n) != n) 
		fail("Unexpected end of input");

	while (n>1 && inbuf[n-1] == 0)	/* remove trailing zero bytes */
		n--;

  	return n;
}

/*
 * Pack image data lines
 */
void pack(void)
{
	static int first=1;		/* first time? */
	register char *rptr;		/* repeat pointer */
	register char *bptr;		/* input buffer position */
	char *bend;			/* end of input */
	char *pptr;			/* pack buffer position */
	int  n, cnt;

	for (;;) {
		n = read_line();	/* (last output was [esc]) */
		bend = inbuf+n;

		for (bptr=inbuf, pptr=pbuf; bptr<bend;) {

			/* find number of repeated bytes */
			for (rptr=bptr+1; rptr<bend && *rptr==*bptr; rptr++)
				;
			cnt = rptr - bptr;
			while (cnt > 1) {
				n = (cnt < MAX_RUN) ? cnt : MAX_RUN;
				*pptr++ = 1 - n;
				*pptr++ = *bptr;
				cnt     -= n;
				bptr    += n;
			}

			/* finished with repeat run? */
			if (rptr >= bend)
				break;

			/* find number of non-repeated bytes */
			for (rptr=bptr+1; rptr<bend && *rptr != *(rptr-1); rptr++)
				;
			cnt = rptr - bptr - 1;
			if (rptr >= bend)
				cnt++;
			while (cnt > 0) {
				n = (cnt < MAX_RUN) ? cnt : MAX_RUN;
				*pptr++ = n - 1;
				memcpy(pptr, bptr, n);
				cnt -= n;
				bptr += n;
				pptr += n;
			}
		}

		n = pptr - pbuf;
		if (first) {		/* set compaction mode */
			first = 0;	/* (note: ESC already output) */
			fwrite("*b2M\x1B", 5, 1, out_fp);
		}

		/* output compressed image data */
		fprintf(out_fp, "*b%dW", n);
		if (fwrite(pbuf, 1, n, out_fp) != n)
			fail("can't write output");
	}
}

main(int argc, char **argv)
{
	if (argc != 3) {
		puts("Compress HP PCL-format graphics file");
		puts("(c) Copyright 1990 Digital Insight");
		puts("Usage: pcl_pack <infile> <outfile>");
		exit(1);
	}

	if ((in_fp = fopen(argv[1], "rb")) == NULL) {
		perror(argv[1]);
		exit(1);
	}

	if ((out_fp = fopen(argv[2], "wb")) == NULL) {
		perror(argv[2]);
		exit(1);
	}

	pack();
}