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tr(1): rename lookup tables

The lookup tables in tr(1) are called "string1" and "string2".  This is
misleading:

- They aren't C strings, they are lookup tables.

- The names "string1" and "string2" don't hint at what their contents
  actually mean.  The meaning of a given table changes with tr(1)'s
  operating mode.  There are five different modes.

It would be considerably easier to see what is happening at a glance
if the tables were named for their corresponding byte transformation.

So instead of two tables named "string1" and "string2" we'll have
three tables named "delete", "squeeze", and "translate".  In addition,
the "string" passed to the setup() function will be called a "table".

With this patch the code in main() is way easier to understand.
Hopefully this makes subsequent patches easier to review.

Thread: https://marc.info/?l=openbsd-tech&m=164355980600901&w=2

No complaints on tech@ after over a week.

/*	$OpenBSD: tr.c,v 1.21 2022/02/11 16:09:21 cheloha Exp $	*/
/*	$NetBSD: tr.c,v 1.5 1995/08/31 22:13:48 jtc Exp $	*/

/*
 * Copyright (c) 1988, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <err.h>

#include "extern.h"

int delete[NCHARS], squeeze[NCHARS];
int translate[NCHARS] = {
	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,		/* ASCII */
	0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
	0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
	0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
	0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
	0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
	0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
	0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f,
	0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57,
	0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
	0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
	0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
	0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
	0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f,
	0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
	0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
	0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
	0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
	0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
	0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
	0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
	0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
	0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
	0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
	0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
	0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
	0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
	0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
	0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
	0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
};

STR s1 = { STRING1, NORMAL, 0, OOBCH, { 0, OOBCH }, NULL, NULL };
STR s2 = { STRING2, NORMAL, 0, OOBCH, { 0, OOBCH }, NULL, NULL };

static void setup(int *, char *, STR *, int);
static void usage(void);

int
main(int argc, char *argv[])
{
	int ch, cnt, lastch, *p;
	int cflag, dflag, sflag;

	if (pledge("stdio", NULL) == -1)
		err(1, "pledge");

	cflag = dflag = sflag = 0;
	while ((ch = getopt(argc, argv, "Ccds")) != -1)
		switch(ch) {
		case 'C':
		case 'c':
			cflag = 1;
			break;
		case 'd':
			dflag = 1;
			break;
		case 's':
			sflag = 1;
			break;
		case '?':
		default:
			usage();
		}
	argc -= optind;
	argv += optind;

	if (argc < 1 || argc > 2)
		usage();

	/*
	 * tr -ds [-Cc] string1 string2
	 * Delete all characters (or complemented characters) in string1.
	 * Squeeze all characters in string2.
	 */
	if (dflag && sflag) {
		if (argc != 2)
			usage();

		setup(delete, argv[0], &s1, cflag);
		setup(squeeze, argv[1], &s2, 0);

		for (lastch = OOBCH; (ch = getchar()) != EOF;)
			if (!delete[ch] && (!squeeze[ch] || lastch != ch)) {
				lastch = ch;
				(void)putchar(ch);
			}
		exit(0);
	}

	/*
	 * tr -d [-Cc] string1
	 * Delete all characters (or complemented characters) in string1.
	 */
	if (dflag) {
		if (argc != 1)
			usage();

		setup(delete, argv[0], &s1, cflag);

		while ((ch = getchar()) != EOF)
			if (!delete[ch])
				(void)putchar(ch);
		exit(0);
	}

	/*
	 * tr -s [-Cc] string1
	 * Squeeze all characters (or complemented characters) in string1.
	 */
	if (sflag && argc == 1) {
		setup(squeeze, argv[0], &s1, cflag);

		for (lastch = OOBCH; (ch = getchar()) != EOF;)
			if (!squeeze[ch] || lastch != ch) {
				lastch = ch;
				(void)putchar(ch);
			}
		exit(0);
	}

	/*
	 * tr [-Ccs] string1 string2
	 * Replace all characters (or complemented characters) in string1 with
	 * the character in the same position in string2.  If the -s option is
	 * specified, squeeze all the characters in string2.
	 */
	if (argc != 2)
		usage();

	s1.str = (unsigned char *)argv[0];
	s2.str = (unsigned char *)argv[1];

	if (cflag)
		for (cnt = NCHARS, p = translate; cnt--;)
			*p++ = OOBCH;

	if (!next(&s2))
		errx(1, "empty string2");

	/* If string2 runs out of characters, use the last one specified. */
	ch = s2.lastch;
	if (sflag)
		while (next(&s1)) {
			translate[s1.lastch] = ch = s2.lastch;
			squeeze[ch] = 1;
			(void)next(&s2);
		}
	else
		while (next(&s1)) {
			translate[s1.lastch] = ch = s2.lastch;
			(void)next(&s2);
		}

	if (cflag)
		for (cnt = 0, p = translate; cnt < NCHARS; ++p, ++cnt)
			*p = *p == OOBCH ? ch : cnt;

	if (sflag)
		for (lastch = OOBCH; (ch = getchar()) != EOF;) {
			ch = translate[ch];
			if (!squeeze[ch] || lastch != ch) {
				lastch = ch;
				(void)putchar(ch);
			}
		}
	else
		while ((ch = getchar()) != EOF)
			(void)putchar(translate[ch]);
	exit (0);
}

static void
setup(int *table, char *arg, STR *str, int cflag)
{
	int cnt, *p;

	str->str = (unsigned char *)arg;
	bzero(table, NCHARS * sizeof(int));
	while (next(str))
		table[str->lastch] = 1;
	if (cflag)
		for (p = table, cnt = NCHARS; cnt--; ++p)
			*p = !*p;
}

static void
usage(void)
{
	fprintf(stderr,
	    "usage: tr [-Ccs] string1 string2\n"
	    "       tr [-Cc] -d string1\n"
	    "       tr [-Cc] -s string1\n"
	    "       tr [-Cc] -ds string1 string2\n");
	exit(1);
}