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To simplify the upcoming UTF-8 cleanup in less(1), delete support
for ANSI escape sequences introduced by an 8-bit CSI (e.g. "\23343m")
because these are neither compatible with UTF-8 nor strictly
compatible with pure ASCII and for those introduced by an UTF-8 CSI
(e.g. "\302\23343m") because not even xterm(1) supports them at
all, not even with a non-default configuration, because both forms
are very rarely used, if at all, and because the current code trying
to support them doesn't even appear to work according to my tests.
Full support for the ESC-[ CSI (e.g. "\033[43m") remains.

Tweaks and OK millert@, OK nicm@,
and sthen@ agrees with the general direction.

/*
 * Copyright (C) 1984-2012  Mark Nudelman
 * Modified for use with illumos by Garrett D'Amore.
 * Copyright 2014 Garrett D'Amore <garrett@damore.org>
 *
 * You may distribute under the terms of either the GNU General Public
 * License or the Less License, as specified in the README file.
 *
 * For more information, see the README file.
 */

/*
 * Routines to convert text in various ways.  Used by search.
 */

#include "charset.h"
#include "less.h"

extern int utf_mode;

/*
 * Get the length of a buffer needed to convert a string.
 */
int
cvt_length(int len)
{
	if (utf_mode)
		/*
		 * Just copying a string in UTF-8 mode can cause it to grow
		 * in length.
		 * Four output bytes for one input byte is the worst case.
		 */
		len *= 4;
	return (len + 1);
}

/*
 * Allocate a chpos array for use by cvt_text.
 */
int *
cvt_alloc_chpos(int len)
{
	int i;
	int *chpos = ecalloc(sizeof (int), len);
	/* Initialize all entries to an invalid position. */
	for (i = 0; i < len; i++)
		chpos[i] = -1;
	return (chpos);
}

/*
 * Convert text.  Perform the transformations specified by ops.
 * Returns converted text in odst.  The original offset of each
 * odst character (when it was in osrc) is returned in the chpos array.
 */
void
cvt_text(char *odst, char *osrc, int *chpos, int *lenp, int ops)
{
	char *dst;
	char *edst = odst;
	char *src;
	char *src_end;
	LWCHAR ch;

	if (lenp != NULL)
		src_end = osrc + *lenp;
	else
		src_end = osrc + strlen(osrc);

	for (src = osrc, dst = odst; src < src_end; ) {
		int src_pos = src - osrc;
		int dst_pos = dst - odst;
		ch = step_char(&src, +1, src_end);
		if ((ops & CVT_BS) && ch == '\b' && dst > odst) {
			/* Delete backspace and preceding char. */
			do {
				dst--;
			} while (dst > odst &&
			    !IS_ASCII_OCTET(*dst) && !IS_UTF8_LEAD(*dst));
		} else if ((ops & CVT_ANSI) && ch == ESC) {
			/* Skip to end of ANSI escape sequence. */
			src++;	/* skip the CSI start char */
			while (src < src_end)
				if (!is_ansi_middle(*src++))
					break;
		} else {
			/* Just copy the char to the destination buffer. */
			if ((ops & CVT_TO_LC) && iswupper(ch))
				ch = towlower(ch);
			put_wchar(&dst, ch);
			/* Record the original position of the char. */
			if (chpos != NULL)
				chpos[dst_pos] = src_pos;
		}
		if (dst > edst)
			edst = dst;
	}
	if ((ops & CVT_CRLF) && edst > odst && edst[-1] == '\r')
		edst--;
	*edst = '\0';
	if (lenp != NULL)
		*lenp = edst - odst;
}