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Loads of platforms appear to have old or broken Unicode character type
information and are missing widths for relatively common Unicode
characters (so mbtowc() works, but wcwidth() fails). So if wcwidth()
returns -1, assume a width of 1 instead of ignoring the character.

/* $OpenBSD: utf8.c,v 1.31 2016/04/27 09:36:25 nicm Exp $ */

/*
 * Copyright (c) 2008 Nicholas Marriott <nicholas.marriott@gmail.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <vis.h>
#include <wchar.h>

#include "tmux.h"

static int	utf8_width(wchar_t);

/* Set a single character. */
void
utf8_set(struct utf8_data *ud, u_char ch)
{
	u_int	i;

	*ud->data = ch;
	ud->have = 1;
	ud->size = 1;

	ud->width = 1;

	for (i = ud->size; i < sizeof ud->data; i++)
		ud->data[i] = '\0';
}

/* Copy UTF-8 character. */
void
utf8_copy(struct utf8_data *to, const struct utf8_data *from)
{
	u_int	i;

	memcpy(to, from, sizeof *to);

	for (i = to->size; i < sizeof to->data; i++)
		to->data[i] = '\0';
}

/*
 * Open UTF-8 sequence.
 *
 * 11000010-11011111 C2-DF start of 2-byte sequence
 * 11100000-11101111 E0-EF start of 3-byte sequence
 * 11110000-11110100 F0-F4 start of 4-byte sequence
 */
enum utf8_state
utf8_open(struct utf8_data *ud, u_char ch)
{
	memset(ud, 0, sizeof *ud);
	if (ch >= 0xc2 && ch <= 0xdf)
		ud->size = 2;
	else if (ch >= 0xe0 && ch <= 0xef)
		ud->size = 3;
	else if (ch >= 0xf0 && ch <= 0xf4)
		ud->size = 4;
	else
		return (UTF8_ERROR);
	utf8_append(ud, ch);
	return (UTF8_MORE);
}

/* Append character to UTF-8, closing if finished. */
enum utf8_state
utf8_append(struct utf8_data *ud, u_char ch)
{
	wchar_t	wc;
	int	width;

	if (ud->have >= ud->size)
		fatalx("UTF-8 character overflow");
	if (ud->size > sizeof ud->data)
		fatalx("UTF-8 character size too large");

	if (ud->have != 0 && (ch & 0xc0) != 0x80)
		ud->width = 0xff;

	ud->data[ud->have++] = ch;
	if (ud->have != ud->size)
		return (UTF8_MORE);

	if (ud->width == 0xff)
		return (UTF8_ERROR);

	if (utf8_combine(ud, &wc) != UTF8_DONE)
		return (UTF8_ERROR);
	if ((width = utf8_width(wc)) < 0)
		return (UTF8_ERROR);
	ud->width = width;

	return (UTF8_DONE);
}

/* Get width of Unicode character. */
static int
utf8_width(wchar_t wc)
{
	int	width;

	width = wcwidth(wc);
	if (width < 0 || width > 0xff) {
		log_debug("Unicode %04x, wcwidth() %d", wc, width);

		/*
		 * Many platforms have no width for relatively common
		 * characters (wcwidth() returns -1); assume width 1 in this
		 * case and hope for the best.
		 */
		if (width < 0)
			return (1);
		return (-1);
	}
	return (width);
}

/* Combine UTF-8 into Unicode. */
enum utf8_state
utf8_combine(const struct utf8_data *ud, wchar_t *wc)
{
	switch (mbtowc(wc, ud->data, ud->size)) {
	case -1:
		log_debug("UTF-8 %.*s, mbtowc() %d", (int)ud->size, ud->data,
		    errno);
		mbtowc(NULL, NULL, MB_CUR_MAX);
		return (UTF8_ERROR);
	case 0:
		return (UTF8_ERROR);
	default:
		return (UTF8_DONE);
	}
}

/* Split Unicode into UTF-8. */
enum utf8_state
utf8_split(wchar_t wc, struct utf8_data *ud)
{
	char	s[MB_LEN_MAX];
	int	slen;

	slen = wctomb(s, wc);
	if (slen <= 0 || slen > (int)sizeof ud->data)
		return (UTF8_ERROR);

	memcpy(ud->data, s, slen);
	ud->size = slen;

	ud->width = utf8_width(wc);
	return (UTF8_DONE);
}

/*
 * Encode len characters from src into dst, which is guaranteed to have four
 * bytes available for each character from src (for \abc or UTF-8) plus space
 * for \0.
 */
int
utf8_strvis(char *dst, const char *src, size_t len, int flag)
{
	struct utf8_data	 ud;
	const char		*start, *end;
	enum utf8_state		 more;
	size_t			 i;

	start = dst;
	end = src + len;

	while (src < end) {
		if ((more = utf8_open(&ud, *src)) == UTF8_MORE) {
			while (++src < end && more == UTF8_MORE)
				more = utf8_append(&ud, *src);
			if (more == UTF8_DONE) {
				/* UTF-8 character finished. */
				for (i = 0; i < ud.size; i++)
					*dst++ = ud.data[i];
				continue;
			}
			/* Not a complete, valid UTF-8 character. */
			src -= ud.have;
		}
		if (src < end - 1)
			dst = vis(dst, src[0], flag, src[1]);
		else if (src < end)
			dst = vis(dst, src[0], flag, '\0');
		src++;
	}

	*dst = '\0';
	return (dst - start);
}

/*
 * Sanitize a string, changing any UTF-8 characters to '_'. Caller should free
 * the returned string. Anything not valid printable ASCII or UTF-8 is
 * stripped.
 */
char *
utf8_sanitize(const char *src)
{
	char			*dst;
	size_t			 n;
	enum utf8_state		 more;
	struct utf8_data	 ud;
	u_int			 i;

	dst = NULL;

	n = 0;
	while (*src != '\0') {
		dst = xreallocarray(dst, n + 1, sizeof *dst);
		if ((more = utf8_open(&ud, *src)) == UTF8_MORE) {
			while (*++src != '\0' && more == UTF8_MORE)
				more = utf8_append(&ud, *src);
			if (more == UTF8_DONE) {
				dst = xreallocarray(dst, n + ud.width,
				    sizeof *dst);
				for (i = 0; i < ud.width; i++)
					dst[n++] = '_';
				continue;
			}
			src -= ud.have;
		}
		if (*src > 0x1f && *src < 0x7f)
			dst[n++] = *src;
		else
			dst[n++] = '_';
		src++;
	}

	dst = xreallocarray(dst, n + 1, sizeof *dst);
	dst[n] = '\0';
	return (dst);
}

/*
 * Convert a string into a buffer of UTF-8 characters. Terminated by size == 0.
 * Caller frees.
 */
struct utf8_data *
utf8_fromcstr(const char *src)
{
	struct utf8_data	*dst;
	size_t			 n;
	enum utf8_state		 more;

	dst = NULL;

	n = 0;
	while (*src != '\0') {
		dst = xreallocarray(dst, n + 1, sizeof *dst);
		if ((more = utf8_open(&dst[n], *src)) == UTF8_MORE) {
			while (*++src != '\0' && more == UTF8_MORE)
				more = utf8_append(&dst[n], *src);
			if (more == UTF8_DONE) {
				n++;
				continue;
			}
			src -= dst[n].have;
		}
		utf8_set(&dst[n], *src);
		n++;
		src++;
	}

	dst = xreallocarray(dst, n + 1, sizeof *dst);
	dst[n].size = 0;
	return (dst);
}

/* Convert from a buffer of UTF-8 characters into a string. Caller frees. */
char *
utf8_tocstr(struct utf8_data *src)
{
	char	*dst;
	size_t	 n;

	dst = NULL;

	n = 0;
	for(; src->size != 0; src++) {
		dst = xreallocarray(dst, n + src->size, 1);
		memcpy(dst + n, src->data, src->size);
		n += src->size;
	}

	dst = xreallocarray(dst, n + 1, 1);
	dst[n] = '\0';
	return (dst);
}

/* Get width of UTF-8 string. */
u_int
utf8_cstrwidth(const char *s)
{
	struct utf8_data	tmp;
	u_int			width;
	enum utf8_state		more;

	width = 0;
	while (*s != '\0') {
		if ((more = utf8_open(&tmp, *s)) == UTF8_MORE) {
			while (*++s != '\0' && more == UTF8_MORE)
				more = utf8_append(&tmp, *s);
			if (more == UTF8_DONE) {
				width += tmp.width;
				continue;
			}
			s -= tmp.have;
		}
		if (*s > 0x1f && *s != 0x7f)
			width++;
		s++;
	}
	return (width);
}

/* Trim UTF-8 string to width. Caller frees. */
char *
utf8_trimcstr(const char *s, u_int width)
{
	struct utf8_data	*tmp, *next;
	char			*out;
	u_int			 at;

	tmp = utf8_fromcstr(s);

	at = 0;
	for (next = tmp; next->size != 0; next++) {
		if (at + next->width > width) {
			next->size = 0;
			break;
		}
		at += next->width;
	}

	out = utf8_tocstr(tmp);
	free(tmp);
	return (out);
}

/* Trim UTF-8 string to width. Caller frees. */
char *
utf8_rtrimcstr(const char *s, u_int width)
{
	struct utf8_data	*tmp, *next, *end;
	char			*out;
	u_int			 at;

	tmp = utf8_fromcstr(s);

	for (end = tmp; end->size != 0; end++)
		/* nothing */;
	if (end == tmp) {
		free(tmp);
		return (xstrdup(""));
	}
	next = end - 1;

	at = 0;
	for (;;)
	{
		if (at + next->width > width) {
			next++;
			break;
		}
		at += next->width;

		if (next == tmp)
			break;
		next--;
	}

	out = utf8_tocstr(next);
	free(tmp);
	return (out);
}

/* Pad UTF-8 string to width. Caller frees. */
char *
utf8_padcstr(const char *s, u_int width)
{
	size_t	 slen;
	char	*out;
	u_int	  n, i;

	n = utf8_cstrwidth(s);
	if (n >= width)
		return (xstrdup(s));

	slen = strlen(s);
	out = xmalloc(slen + 1 + (width - n));
	memcpy(out, s, slen);
	for (i = n; i < width; i++)
		out[slen++] = ' ';
	out[slen] = '\0';
	return (out);
}