/*-
 * Copyright (c) 1989, 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.
 *
 * Defived from FreeBSD head/lib/libc/gen/vis.c 165903, head/include/vis.h
 * 203964.
 */

#include <sys/types.h>
#include <limits.h>
#include <ctype.h>
#include <stdio.h>

/*
 * to select alternate encoding format
 */
#define	VIS_OCTAL	0x01	/* use octal \ddd format */
#define	VIS_CSTYLE	0x02	/* use \[nrft0..] where appropriate */

/*
 * to alter set of characters encoded (default is to encode all
 * non-graphic except space, tab, and newline).
 */
#define	VIS_SP		0x04	/* also encode space */
#define	VIS_TAB		0x08	/* also encode tab */
#define	VIS_NL		0x10	/* also encode newline */
#define	VIS_WHITE	(VIS_SP | VIS_TAB | VIS_NL)
#define	VIS_SAFE	0x20	/* only encode "unsafe" characters */

/*
 * other
 */
#define	VIS_NOSLASH	0x40	/* inhibit printing '\' */
#define	VIS_HTTPSTYLE	0x80	/* http-style escape % HEX HEX */
#define	VIS_GLOB	0x100	/* encode glob(3) magics */

/*
 * unvis return codes
 */
#define	UNVIS_VALID	 1	/* character valid */
#define	UNVIS_VALIDPUSH	 2	/* character valid, push back passed char */
#define	UNVIS_NOCHAR	 3	/* valid sequence, no character produced */
#define	UNVIS_SYNBAD	-1	/* unrecognized escape sequence */
#define	UNVIS_ERROR	-2	/* decoder in unknown state (unrecoverable) */

/*
 * unvis flags
 */
#define	UNVIS_END	1	/* no more characters */

#define	isoctal(c)	(((u_char)(c)) >= '0' && ((u_char)(c)) <= '7')

/*
 * vis - visually encode characters
 */
char *
vis(dst, c, flag, nextc)
	char *dst;
	int c, nextc;
	int flag;
{
	c = (unsigned char)c;

	if (flag & VIS_HTTPSTYLE) {
		/* Described in RFC 1808 */
		if (!(isalnum(c) /* alpha-numeric */
		    /* safe */
		    || c == '$' || c == '-' || c == '_' || c == '.' || c == '+'
		    /* extra */
		    || c == '!' || c == '*' || c == '\'' || c == '('
		    || c == ')' || c == ',')) {
			*dst++ = '%';
			snprintf(dst, 4, (c < 16 ? "0%X" : "%X"), c);
			dst += 2;
			goto done;
		}
	}

	if ((flag & VIS_GLOB) &&
	    (c == '*' || c == '?' || c == '[' || c == '#'))
		;
	else if (isgraph(c) ||
	   ((flag & VIS_SP) == 0 && c == ' ') ||
	   ((flag & VIS_TAB) == 0 && c == '\t') ||
	   ((flag & VIS_NL) == 0 && c == '\n') ||
	   ((flag & VIS_SAFE) && (c == '\b' || c == '\007' || c == '\r'))) {
		*dst++ = c;
		if (c == '\\' && (flag & VIS_NOSLASH) == 0)
			*dst++ = '\\';
		*dst = '\0';
		return (dst);
	}

	if (flag & VIS_CSTYLE) {
		switch(c) {
		case '\n':
			*dst++ = '\\';
			*dst++ = 'n';
			goto done;
		case '\r':
			*dst++ = '\\';
			*dst++ = 'r';
			goto done;
		case '\b':
			*dst++ = '\\';
			*dst++ = 'b';
			goto done;
		case '\a':
			*dst++ = '\\';
			*dst++ = 'a';
			goto done;
		case '\v':
			*dst++ = '\\';
			*dst++ = 'v';
			goto done;
		case '\t':
			*dst++ = '\\';
			*dst++ = 't';
			goto done;
		case '\f':
			*dst++ = '\\';
			*dst++ = 'f';
			goto done;
		case ' ':
			*dst++ = '\\';
			*dst++ = 's';
			goto done;
		case '\0':
			*dst++ = '\\';
			*dst++ = '0';
			if (isoctal(nextc)) {
				*dst++ = '0';
				*dst++ = '0';
			}
			goto done;
		}
	}
	if (((c & 0177) == ' ') || isgraph(c) || (flag & VIS_OCTAL)) {
		*dst++ = '\\';
		*dst++ = ((u_char)c >> 6 & 07) + '0';
		*dst++ = ((u_char)c >> 3 & 07) + '0';
		*dst++ = ((u_char)c & 07) + '0';
		goto done;
	}
	if ((flag & VIS_NOSLASH) == 0)
		*dst++ = '\\';
	if (c & 0200) {
		c &= 0177;
		*dst++ = 'M';
	}
	if (iscntrl(c)) {
		*dst++ = '^';
		if (c == 0177)
			*dst++ = '?';
		else
			*dst++ = c + '@';
	} else {
		*dst++ = '-';
		*dst++ = c;
	}
done:
	*dst = '\0';
	return (dst);
}