/*
 * $Header: arcsvc.c,v 1.8 88/06/13 00:42:59 hyc Locked $
 */

/*  ARC - Archive utility - ARCSVC

    Version 2.23, created on 04/22/87 at 13:10:10

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

    By:	 Thom Henderson

    Description:
	 This file contains service routines needed to maintain an archive.

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

void	abort(), setstamp();
int	unlink();

void
openarc(chg)			/* open archive */
	int             chg;	/* true to open for changes */
{
	FILE           *fopen();/* file opener */

	if (!(arc = fopen(arcname, "rb"))) {
		if (chg) {
			if (note)
				printf("Creating new archive: %s\n", arcname);
		}
		else
			abort("Archive not found: %s", arcname);
	}
#if	MTS	/* allow reading archives of max MTS record length */
	else {
		char *buffer, *malloc();
		int inlen;
		struct GDDSECT *region;

		region=gdinfo(arc->_fd);
		inlen=region->GDINLEN;
		buffer=malloc(inlen);
		setbuf(arc, buffer);
		arc->_bufsiz=inlen;
	}
#endif
	if (chg) {		/* if opening for changes */
		if (!(new = fopen(newname, "wb")))
			abort("Cannot create archive copy: %s", newname);

	changing = chg;		/* note if open for changes */
	}
}

void
closearc(chg)			/* close an archive */
	int             chg;	/* true if archive was changed */
{
	if (arc) {		/* if we had an initial archive */
		fclose(arc);
		if (kludge)	/* kludge to update timestamp */
#if	!MTS
			setstamp(arcname, olddate, oldtime);
#endif
	}
	if (chg) {		/* if things have changed */
		fclose(new);	/* close the new copy */
		if (arc) {	/* if we had an original archive */
			if (keepbak) {	/* if a backup is wanted */
				unlink(bakname);	/* erase any old copies */
				if (move(arcname, bakname))
					abort("Cannot rename %s to %s", arcname, bakname);
				printf("Keeping backup archive: %s\n", bakname);
			} else if (unlink(arcname))
				abort("Cannot delete old archive: %s", arcname);
		}
		if (move(newname, arcname))
			abort("Cannot move %s to %s", newname, arcname);
#if	!MTS
		setstamp(arcname, arcdate, arctime);
#endif
	}
}

/*
 * CRC computation logic
 * 
 * The logic for this method of calculating the CRC 16 bit polynomial is taken
 * from an article by David Schwaderer in the April 1985 issue of PC Tech
 * Journal.
 */

static short      crctab[] =	/* CRC lookup table */
{
 0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
 0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
 0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
 0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
 0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
 0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
 0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
 0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
 0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
 0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
 0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
 0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
 0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
 0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
 0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
 0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
 0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
 0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
 0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
 0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
 0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
 0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
 0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
 0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
 0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
 0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
 0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
 0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
 0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
 0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
 0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
 0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040
};

int
addcrc(crc, c)			/* update a CRC check */
	int             crc;	/* running CRC value */
	unsigned char   c;	/* character to add */
{
	return ((crc >> 8) & 0x00ff) ^ crctab[(crc ^ c) & 0x00ff];
}
