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Change UTF-8 combining to inspect the previous character at the cursor
position rather than keeping the last character from the input stream,
this is how most terminals work and fixes problems with displaying these
characters in vim. GitHub issue 3600.

/* $OpenBSD: utf8.c,v 1.64 2023/09/15 15:49:05 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 <ctype.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <vis.h>

#include "tmux.h"

static const wchar_t utf8_force_wide[] = {
	0x0261D,
	0x026F9,
	0x0270A,
	0x0270B,
	0x0270C,
	0x0270D,
	0x1F1E6,
	0x1F1E7,
	0x1F1E8,
	0x1F1E9,
	0x1F1EA,
	0x1F1EB,
	0x1F1EC,
	0x1F1ED,
	0x1F1EE,
	0x1F1EF,
	0x1F1F0,
	0x1F1F1,
	0x1F1F2,
	0x1F1F3,
	0x1F1F4,
	0x1F1F5,
	0x1F1F6,
	0x1F1F7,
	0x1F1F8,
	0x1F1F9,
	0x1F1FA,
	0x1F1FB,
	0x1F1FC,
	0x1F1FD,
	0x1F1FE,
	0x1F1FF,
	0x1F385,
	0x1F3C2,
	0x1F3C3,
	0x1F3C4,
	0x1F3C7,
	0x1F3CA,
	0x1F3CB,
	0x1F3CC,
	0x1F3FB,
	0x1F3FC,
	0x1F3FD,
	0x1F3FE,
	0x1F3FF,
	0x1F442,
	0x1F443,
	0x1F446,
	0x1F447,
	0x1F448,
	0x1F449,
	0x1F44A,
	0x1F44B,
	0x1F44C,
	0x1F44D,
	0x1F44E,
	0x1F44F,
	0x1F450,
	0x1F466,
	0x1F467,
	0x1F468,
	0x1F469,
	0x1F46B,
	0x1F46C,
	0x1F46D,
	0x1F46E,
	0x1F470,
	0x1F471,
	0x1F472,
	0x1F473,
	0x1F474,
	0x1F475,
	0x1F476,
	0x1F477,
	0x1F478,
	0x1F47C,
	0x1F481,
	0x1F482,
	0x1F483,
	0x1F485,
	0x1F486,
	0x1F487,
	0x1F48F,
	0x1F491,
	0x1F4AA,
	0x1F574,
	0x1F575,
	0x1F57A,
	0x1F590,
	0x1F595,
	0x1F596,
	0x1F645,
	0x1F646,
	0x1F647,
	0x1F64B,
	0x1F64C,
	0x1F64D,
	0x1F64E,
	0x1F64F,
	0x1F6A3,
	0x1F6B4,
	0x1F6B5,
	0x1F6B6,
	0x1F6C0,
	0x1F6CC,
	0x1F90C,
	0x1F90F,
	0x1F918,
	0x1F919,
	0x1F91A,
	0x1F91B,
	0x1F91C,
	0x1F91D,
	0x1F91E,
	0x1F91F,
	0x1F926,
	0x1F930,
	0x1F931,
	0x1F932,
	0x1F933,
	0x1F934,
	0x1F935,
	0x1F936,
	0x1F937,
	0x1F938,
	0x1F939,
	0x1F93D,
	0x1F93E,
	0x1F977,
	0x1F9B5,
	0x1F9B6,
	0x1F9B8,
	0x1F9B9,
	0x1F9BB,
	0x1F9CD,
	0x1F9CE,
	0x1F9CF,
	0x1F9D1,
	0x1F9D2,
	0x1F9D3,
	0x1F9D4,
	0x1F9D5,
	0x1F9D6,
	0x1F9D7,
	0x1F9D8,
	0x1F9D9,
	0x1F9DA,
	0x1F9DB,
	0x1F9DC,
	0x1F9DD,
	0x1FAC3,
	0x1FAC4,
	0x1FAC5,
	0x1FAF0,
	0x1FAF1,
	0x1FAF2,
	0x1FAF3,
	0x1FAF4,
	0x1FAF5,
	0x1FAF6,
	0x1FAF7,
	0x1FAF8
};

struct utf8_item {
	RB_ENTRY(utf8_item)	index_entry;
	u_int			index;

	RB_ENTRY(utf8_item)	data_entry;
	char			data[UTF8_SIZE];
	u_char			size;
};

static int
utf8_data_cmp(struct utf8_item *ui1, struct utf8_item *ui2)
{
	if (ui1->size < ui2->size)
		return (-1);
	if (ui1->size > ui2->size)
		return (1);
	return (memcmp(ui1->data, ui2->data, ui1->size));
}
RB_HEAD(utf8_data_tree, utf8_item);
RB_GENERATE_STATIC(utf8_data_tree, utf8_item, data_entry, utf8_data_cmp);
static struct utf8_data_tree utf8_data_tree = RB_INITIALIZER(utf8_data_tree);

static int
utf8_index_cmp(struct utf8_item *ui1, struct utf8_item *ui2)
{
	if (ui1->index < ui2->index)
		return (-1);
	if (ui1->index > ui2->index)
		return (1);
	return (0);
}
RB_HEAD(utf8_index_tree, utf8_item);
RB_GENERATE_STATIC(utf8_index_tree, utf8_item, index_entry, utf8_index_cmp);
static struct utf8_index_tree utf8_index_tree = RB_INITIALIZER(utf8_index_tree);

static u_int utf8_next_index;

#define UTF8_GET_SIZE(uc) (((uc) >> 24) & 0x1f)
#define UTF8_GET_WIDTH(uc) (((uc) >> 29) - 1)

#define UTF8_SET_SIZE(size) (((utf8_char)(size)) << 24)
#define UTF8_SET_WIDTH(width) ((((utf8_char)(width)) + 1) << 29)

/* Get a UTF-8 item from data. */
static struct utf8_item *
utf8_item_by_data(const u_char *data, size_t size)
{
	struct utf8_item	ui;

	memcpy(ui.data, data, size);
	ui.size = size;

	return (RB_FIND(utf8_data_tree, &utf8_data_tree, &ui));
}

/* Get a UTF-8 item from data. */
static struct utf8_item *
utf8_item_by_index(u_int index)
{
	struct utf8_item	ui;

	ui.index = index;

	return (RB_FIND(utf8_index_tree, &utf8_index_tree, &ui));
}

/* Add a UTF-8 item. */
static int
utf8_put_item(const u_char *data, size_t size, u_int *index)
{
	struct utf8_item	*ui;

	ui = utf8_item_by_data(data, size);
	if (ui != NULL) {
		*index = ui->index;
		log_debug("%s: found %.*s = %u", __func__, (int)size, data,
		    *index);
		return (0);
	}

	if (utf8_next_index == 0xffffff + 1)
		return (-1);

	ui = xcalloc(1, sizeof *ui);
	ui->index = utf8_next_index++;
	RB_INSERT(utf8_index_tree, &utf8_index_tree, ui);

	memcpy(ui->data, data, size);
	ui->size = size;
	RB_INSERT(utf8_data_tree, &utf8_data_tree, ui);

	*index = ui->index;
	log_debug("%s: added %.*s = %u", __func__, (int)size, data, *index);
	return (0);
}

static int
utf8_table_cmp(const void *vp1, const void *vp2)
{
	const wchar_t	*wc1 = vp1, *wc2 = vp2;

	if (*wc1 < *wc2)
		return (-1);
	if (*wc1 > *wc2)
		return (1);
	return (0);
}

/* Check if character in table. */
int
utf8_in_table(wchar_t find, const wchar_t *table, u_int count)
{
	wchar_t	*found;

	found = bsearch(&find, table, count, sizeof *table, utf8_table_cmp);
	return (found != NULL);
}

/* Get UTF-8 character from data. */
enum utf8_state
utf8_from_data(const struct utf8_data *ud, utf8_char *uc)
{
	u_int	index;

	if (ud->width > 2)
		fatalx("invalid UTF-8 width: %u", ud->width);

	if (ud->size > UTF8_SIZE)
		goto fail;
	if (ud->size <= 3) {
		index = (((utf8_char)ud->data[2] << 16)|
			  ((utf8_char)ud->data[1] << 8)|
			  ((utf8_char)ud->data[0]));
	} else if (utf8_put_item(ud->data, ud->size, &index) != 0)
		goto fail;
	*uc = UTF8_SET_SIZE(ud->size)|UTF8_SET_WIDTH(ud->width)|index;
	log_debug("%s: (%d %d %.*s) -> %08x", __func__, ud->width, ud->size,
	    (int)ud->size, ud->data, *uc);
	return (UTF8_DONE);

fail:
	if (ud->width == 0)
		*uc = UTF8_SET_SIZE(0)|UTF8_SET_WIDTH(0);
	else if (ud->width == 1)
		*uc = UTF8_SET_SIZE(1)|UTF8_SET_WIDTH(1)|0x20;
	else
		*uc = UTF8_SET_SIZE(1)|UTF8_SET_WIDTH(1)|0x2020;
	return (UTF8_ERROR);
}

/* Get UTF-8 data from character. */
void
utf8_to_data(utf8_char uc, struct utf8_data *ud)
{
	struct utf8_item	*ui;
	u_int			 index;

	memset(ud, 0, sizeof *ud);
	ud->size = ud->have = UTF8_GET_SIZE(uc);
	ud->width = UTF8_GET_WIDTH(uc);

	if (ud->size <= 3) {
		ud->data[2] = (uc >> 16);
		ud->data[1] = ((uc >> 8) & 0xff);
		ud->data[0] = (uc & 0xff);
	} else {
		index = (uc & 0xffffff);
		if ((ui = utf8_item_by_index(index)) == NULL)
			memset(ud->data, ' ', ud->size);
		else
			memcpy(ud->data, ui->data, ud->size);
	}

	log_debug("%s: %08x -> (%d %d %.*s)", __func__, uc, ud->width, ud->size,
	    (int)ud->size, ud->data);
}

/* Get UTF-8 character from a single ASCII character. */
u_int
utf8_build_one(u_char ch)
{
	return (UTF8_SET_SIZE(1)|UTF8_SET_WIDTH(1)|ch);
}

/* Set a single character. */
void
utf8_set(struct utf8_data *ud, u_char ch)
{
	static const struct utf8_data empty = { { 0 }, 1, 1, 1 };

	memcpy(ud, &empty, sizeof *ud);
	*ud->data = ch;
}

/* 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';
}

/* Get width of Unicode character. */
static enum utf8_state
utf8_width(struct utf8_data *ud, int *width)
{
	wchar_t	wc;

	if (utf8_towc(ud, &wc) != UTF8_DONE)
		return (UTF8_ERROR);
	if (utf8_in_table(wc, utf8_force_wide, nitems(utf8_force_wide))) {
		*width = 2;
		return (UTF8_DONE);
	}

	*width = wcwidth(wc);
	log_debug("wcwidth(%05X) returned %d", (u_int)wc, *width);
	if (*width < 0) {
		/*
		 * C1 control characters are nonprintable, so they are always
		 * zero width.
		 */
		*width = (wc >= 0x80 && wc <= 0x9f) ? 0 : 1;
	}
	if (*width >= 0 && *width <= 0xff)
		return (UTF8_DONE);
	return (UTF8_ERROR);
}

/* Convert UTF-8 character to wide character. */
enum utf8_state
utf8_towc(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);
	}
	log_debug("UTF-8 %.*s is %05X", (int)ud->size, ud->data, (u_int)*wc);
	return (UTF8_DONE);
}

/*
 * 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)
{
	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_width(ud, &width) != UTF8_DONE)
		return (UTF8_ERROR);
	ud->width = width;

	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 = dst, *end = src + len;
	enum utf8_state		 more;
	size_t			 i;

	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[0] == '$' && src < end - 1) {
			if (isalpha((u_char)src[1]) ||
			    src[1] == '_' ||
			    src[1] == '{')
				*dst++ = '\\';
			*dst++ = '$';
		} else 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);
}

/* Same as utf8_strvis but allocate the buffer. */
int
utf8_stravis(char **dst, const char *src, int flag)
{
	char	*buf;
	int	 len;

	buf = xreallocarray(NULL, 4, strlen(src) + 1);
	len = utf8_strvis(buf, src, strlen(src), flag);

	*dst = xrealloc(buf, len + 1);
	return (len);
}

/* Same as utf8_strvis but allocate the buffer. */
int
utf8_stravisx(char **dst, const char *src, size_t srclen, int flag)
{
	char	*buf;
	int	 len;

	buf = xreallocarray(NULL, 4, srclen + 1);
	len = utf8_strvis(buf, src, srclen, flag);

	*dst = xrealloc(buf, len + 1);
	return (len);
}

/* Does this string contain anything that isn't valid UTF-8? */
int
utf8_isvalid(const char *s)
{
	struct utf8_data ud;
	const char	*end;
	enum utf8_state	 more;

	end = s + strlen(s);
	while (s < end) {
		if ((more = utf8_open(&ud, *s)) == UTF8_MORE) {
			while (++s < end && more == UTF8_MORE)
				more = utf8_append(&ud, *s);
			if (more == UTF8_DONE)
				continue;
			return (0);
		}
		if (*s < 0x20 || *s > 0x7e)
			return (0);
		s++;
	}
	return (1);
}

/*
 * 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 = NULL;
	size_t		 n = 0;
	enum utf8_state	 more;
	struct utf8_data ud;
	u_int		 i;

	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);
}

/* Get UTF-8 buffer length. */
size_t
utf8_strlen(const struct utf8_data *s)
{
	size_t	i;

	for (i = 0; s[i].size != 0; i++)
		/* nothing */;
	return (i);
}

/* Get UTF-8 string width. */
u_int
utf8_strwidth(const struct utf8_data *s, ssize_t n)
{
	ssize_t	i;
	u_int	width = 0;

	for (i = 0; s[i].size != 0; i++) {
		if (n != -1 && n == i)
			break;
		width += s[i].width;
	}
	return (width);
}

/*
 * 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 = NULL;
	size_t			 n = 0;
	enum utf8_state		 more;

	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 = NULL;
	size_t	 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);
}

/* Pad UTF-8 string to width on the left. 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);
}

/* Pad UTF-8 string to width on the right. Caller frees. */
char *
utf8_rpadcstr(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));
	for (i = 0; i < width - n; i++)
		out[i] = ' ';
	memcpy(out + i, s, slen);
	out[i + slen] = '\0';
	return (out);
}

int
utf8_cstrhas(const char *s, const struct utf8_data *ud)
{
	struct utf8_data	*copy, *loop;
	int			 found = 0;

	copy = utf8_fromcstr(s);
	for (loop = copy; loop->size != 0; loop++) {
		if (loop->size != ud->size)
			continue;
		if (memcmp(loop->data, ud->data, loop->size) == 0) {
			found = 1;
			break;
		}
	}
	free(copy);

	return (found);
}