arcpack.c

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/*
 * $Header: arcpack.c,v 1.9 88/06/02 16:27:36 hyc Locked $
 */

/*  ARC - Archive utility - ARCPACK

    Version 3.49, created on 04/21/87 at 11:26:51

(C) COPYRIGHT 1985-87 by System Enhancement Associates; ALL RIGHTS RESERVED

    By:	 Thom Henderson

    Description:
	 This file contains the routines used to compress a file
	 when placing it in an archive.

    Language:
	 Computer Innovations Optimizing C86
*/
#include <stdio.h>
#include "arc.h"
#if	MTS
#include <ctype.h>
#endif

void	setcode(), sqinit_cm(), sqputc_cm(), init_cm(), putc_cm();
void	filecopy(), abort(), putc_tst();
int	getch(), addcrc();

/* stuff for non-repeat packing */

#define DLE 0x90		/* repeat sequence marker */

static unsigned char state;	/* current packing state */

/* non-repeat packing states */

#define NOHIST  0		/* don't consider previous input */
#define SENTCHAR 1		/* lastchar set, no lookahead yet */
#define SENDNEWC 2		/* run over, send new char next */
#define SENDCNT 3		/* newchar set, send count next */

/* packing results */

static long     stdlen;		/* length for standard packing */
static short    crcval;		/* CRC check value */

void
pack(f, t, hdr)			/* pack file into an archive */
	FILE           *f, *t;	/* source, destination */
	struct heads   *hdr;	/* pointer to header data */
{
	int             c;	/* one character of stream */
	long            ncrlen;	/* length after packing */
	long		huflen;	/* length after squeezing */
	long            lzwlen;	/* length after crunching */
	long		pred_sq(), file_sq();	/* stuff for squeezing */
	long            pred_cm(), sqpred_cm();	/* dynamic crunching cleanup */
	long            tloc, ftell();	/* start of output */
	int		getch();
	int             getc_ncr();
	void            putc_pak();

	/* first pass - see which method is best */

	tloc = ftell(t);	/* note start of output */

	if (!nocomp) {		/* if storage kludge not active */
		if (note) {
			printf(" analyzing, ");
			fflush(stdout);
		}
		state = NOHIST;	/* initialize ncr packing */
		stdlen = ncrlen = 0;	/* reset size counters */
		crcval = 0;	/* initialize CRC check value */
		setcode();	/* initialize encryption */
		init_sq();	/* initialize for squeeze scan */

		if (dosquash) {
			sqinit_cm();
			while ((c = getch(f)) != EOF) {	/* for each byte of file */
				ncrlen++;	/* one more packed byte */
				scan_sq(c);	/* see what squeezing can do */
				sqputc_cm(c, t);	/* see what squashing
							 * can do */
			}
			lzwlen = sqpred_cm(t);
		} else {
			init_cm(t);	/* initialize for crunching */
	
			while ((c = getc_ncr(f)) != EOF) {	/* for each byte of file */
				ncrlen++;	/* one more packed byte */
				scan_sq(c);	/* see what squeezing can do */
				putc_cm(c, t);	/* see what crunching can do */
			}
			lzwlen = pred_cm(t);	/* finish up after crunching */
		}
		huflen = pred_sq();	/* finish up after squeezing */
	} else {		/* else kludge the method */
		stdlen = 0;	/* make standard look best */
		ncrlen = huflen = lzwlen = 1;
	}

	/* standard set-ups common to all methods */

	fseek(f, 0L, 0);	/* rewind input */
	hdr->crc = crcval;	/* note CRC check value */
	hdr->length = stdlen;	/* set actual file length */
	state = NOHIST;		/* reinitialize ncr packing */
	setcode();		/* reinitialize encryption */

	/* choose and use the shortest method */

	if (kludge && note)
		printf("\n\tS:%ld  P:%ld  S:%ld  C:%ld,\t ",
			stdlen, ncrlen, huflen, lzwlen);

	if (stdlen <= ncrlen && stdlen <= huflen && stdlen <= lzwlen) {
		if (note) {
			printf("storing, ");	/* store without compression */
			fflush(stdout);
		}
		hdrver = 2;	/* note packing method */
		fseek(t, tloc, 0);	/* reset output for new method */
		stdlen = crcval = 0;	/* recalc these for kludge */
		while ((c = getch(f)) != EOF)	/* store it straight */
			putc_pak(c, t);
		hdr->crc = crcval;
		hdr->length = hdr->size = stdlen;
	} else if (ncrlen < lzwlen && ncrlen < huflen) {
		if (note) {
			printf("packing, ");	/* pack with repeat
			fflush(stdout);		 * suppression */
		}
		hdrver = 3;	/* note packing method */
		hdr->size = ncrlen;	/* set data length */
		fseek(t, tloc, 0);	/* reset output for new method */
		while ((c = getc_ncr(f)) != EOF)
			putc_pak(c, t);
	} else if (huflen < lzwlen) {
		if (note) {
			printf("squeezing, ");
			fflush(stdout);
		}
		hdrver = 4;	/* note packing method */
		fseek(t, tloc, 0);	/* reset output for new method */
		hdr->size = file_sq(f, t);	/* note final size */
	} else {
		if (note)
			printf(dosquash ? "squashed, " : "crunched, ");
		hdrver = dosquash ? 9 : 8;
		hdr->size = lzwlen;	/* size should not change */
	}

	/* standard cleanups common to all methods */

	if (note)
		printf("done. (%ld%%)\n",100L - (100L*hdr->size)/hdr->length);
}

/*
 * Non-repeat compression - text is passed through normally, except that a
 * run of more than two is encoded as:
 * 
 * <char> <DLE> <count>
 * 
 * Special case: a count of zero indicates that the DLE is really a DLE, not a
 * repeat marker.
 */

int
getc_ncr(f)			/* get bytes with collapsed runs */
	FILE           *f;	/* file to get from */
{
	static int      lastc;	/* value returned on last call */
	static int      repcnt;	/* repetition counter */
	static int      c;	/* latest value seen */

	switch (state) {	/* depends on our state */
	case NOHIST:		/* no relevant history */
		state = SENTCHAR;
		return lastc = getch(f);	/* remember the value next
						 * time */

	case SENTCHAR:		/* char was sent. look ahead */
		switch (lastc) {/* action depends on char */
		case DLE:	/* if we sent a real DLE */
			state = NOHIST;	/* then start over again */
			return 0;	/* but note that the DLE was real */

		case EOF:	/* EOF is always a special case */
			return EOF;

		default:	/* else test for a repeat */
			for (repcnt = 1; (c = getch(f)) == lastc && repcnt < 255; repcnt++);
			/* find end of run */

			switch (repcnt) {	/* action depends on run size */
			case 1:/* not a repeat */
				return lastc = c;	/* but remember value
							 * next time */

			case 2:/* a repeat, but too short */
				state = SENDNEWC;	/* send the second one
							 * next time */
				return lastc;

			default:	/* a run - compress it */
				state = SENDCNT;	/* send repeat count
							 * next time */
				return DLE;	/* send repeat marker this
						 * time */
			}
		}

	case SENDNEWC:		/* send second char of short run */
		state = SENTCHAR;
		return lastc = c;

	case SENDCNT:		/* sent DLE, now send count */
		state = SENDNEWC;
		return repcnt;

	default:
		abort("Bug - bad ncr state\n");
	}
}

int
getch(f)			/* special get char for packing */
	FILE           *f;	/* file to get from */
{
	int		c;	/* a char from the file */
#if	!DOS
	static int      cr = 0;	/* add \r before \n ? */

	if (cr) {
		c = '\n';
#if	MTS
		c = toascii(c);
#endif
		crcval = addcrc(crcval, c);
		stdlen++;
		cr = 0;
		return (c);
	}
#endif

	if ((c = fgetc(f)) != EOF) {	/* if not the end of file */
#if	!DOS
		if (!image && (c == '\n')) {
			c = '\r';
			cr = 1;
		}
#endif
#if	MTS
		if (!image)
			c = toascii(c);
#endif
		crcval = addcrc(crcval, c);	/* then update CRC check
						 * value */
		stdlen++;	/* and bump length counter */
	}
	return c;
}

void
putc_pak(c, f)			/* put a packed byte into archive */
	char            c;	/* byte to put */
	FILE           *f;	/* archive to put it in */
{
	unsigned char		code();
	putc_tst(code(c), f);	/* put encoded byte, with checks */
}