neovim

mbyte.c (93849B)

---

/// mbyte.c: Code specifically for handling multi-byte characters.
/// Multibyte extensions partly by Sung-Hoon Baek
///
/// Strings internal to Nvim are always encoded as UTF-8 (thus the legacy
/// 'encoding' option is always "utf-8").
///
/// The cell width on the display needs to be determined from the character
/// value. Recognizing UTF-8 bytes is easy: 0xxx.xxxx is a single-byte char,
/// 10xx.xxxx is a trailing byte, 11xx.xxxx is a leading byte of a multi-byte
/// character. To make things complicated, up to six composing characters
/// are allowed. These are drawn on top of the first char. For most editing
/// the sequence of bytes with composing characters included is considered to
/// be one character.
///
/// UTF-8 is used everywhere in the core. This is in registers, text
/// manipulation, buffers, etc. Nvim core communicates with external plugins
/// and GUIs in this encoding.
///
/// The encoding of a file is specified with 'fileencoding'.  Conversion
/// is to be done when it's different from "utf-8".
///
/// Vim scripts may contain an ":scriptencoding" command. This has an effect
/// for some commands, like ":menutrans".

#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <iconv.h>
#include <limits.h>
#include <locale.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <utf8proc.h>
#include <uv.h>
#include <wctype.h>

#include "auto/config.h"
#include "nvim/arabic.h"
#include "nvim/ascii_defs.h"
#include "nvim/buffer_defs.h"
#include "nvim/charset.h"
#include "nvim/cmdexpand_defs.h"
#include "nvim/cursor.h"
#include "nvim/drawscreen.h"
#include "nvim/errors.h"
#include "nvim/eval/typval.h"
#include "nvim/eval/typval_defs.h"
#include "nvim/getchar.h"
#include "nvim/gettext_defs.h"
#include "nvim/globals.h"
#include "nvim/grid.h"
#include "nvim/iconv_defs.h"
#include "nvim/keycodes.h"
#include "nvim/macros_defs.h"
#include "nvim/mark.h"
#include "nvim/mbyte.h"
#include "nvim/mbyte_defs.h"
#include "nvim/memline.h"
#include "nvim/memory.h"
#include "nvim/message.h"
#include "nvim/move.h"
#include "nvim/option_vars.h"
#include "nvim/optionstr.h"
#include "nvim/os/os.h"
#include "nvim/pos_defs.h"
#include "nvim/strings.h"
#include "nvim/types_defs.h"
#include "nvim/vim_defs.h"

typedef struct {
 int rangeStart;
 int rangeEnd;
 int step;
 int offset;
} convertStruct;

struct interval {
 int first;
 int last;
};

// uncrustify:off
#include "mbyte.c.generated.h"
// uncrustify:on

static const char e_list_item_nr_is_not_list[]
 = N_("E1109: List item %d is not a List");
static const char e_list_item_nr_does_not_contain_3_numbers[]
 = N_("E1110: List item %d does not contain 3 numbers");
static const char e_list_item_nr_range_invalid[]
 = N_("E1111: List item %d range invalid");
static const char e_list_item_nr_cell_width_invalid[]
 = N_("E1112: List item %d cell width invalid");
static const char e_overlapping_ranges_for_nr[]
 = N_("E1113: Overlapping ranges for 0x%lx");
static const char e_only_values_of_0x80_and_higher_supported[]
 = N_("E1114: Only values of 0x80 and higher supported");

// To speed up BYTELEN(); keep a lookup table to quickly get the length in
// bytes of a UTF-8 character from the first byte of a UTF-8 string.  Bytes
// which are illegal when used as the first byte have a 1.  The NUL byte has
// length 1.
const uint8_t utf8len_tab[] = {
 // ?1 ?2 ?3 ?4 ?5 ?6 ?7 ?8 ?9 ?A ?B ?C ?D ?E ?F
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 0?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 1?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 2?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 3?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 4?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 5?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 6?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 7?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 8?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 9?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // A?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // B?
 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,  // C?
 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,  // D?
 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,  // E?
 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 1, 1,  // F?
};

// Like utf8len_tab above, but using a zero for illegal lead bytes.
const uint8_t utf8len_tab_zero[] = {
 // ?1 ?2 ?3 ?4 ?5 ?6 ?7 ?8 ?9 ?A ?B ?C ?D ?E ?F
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 0?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 1?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 2?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 3?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 4?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 5?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 6?
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 7?
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // 8?
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // 9?
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // A?
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // B?
 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,  // C?
 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,  // D?
 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,  // E?
 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 0, 0,  // F?
};

// Canonical encoding names and their properties.
// "iso-8859-n" is handled by enc_canonize() directly.
static struct
{   const char *name;   int prop;              int codepage; }
enc_canon_table[] = {
#define IDX_LATIN_1     0
 { "latin1",          ENC_8BIT + ENC_LATIN1,  1252 },
#define IDX_ISO_2       1
 { "iso-8859-2",      ENC_8BIT,               0 },
#define IDX_ISO_3       2
 { "iso-8859-3",      ENC_8BIT,               0 },
#define IDX_ISO_4       3
 { "iso-8859-4",      ENC_8BIT,               0 },
#define IDX_ISO_5       4
 { "iso-8859-5",      ENC_8BIT,               0 },
#define IDX_ISO_6       5
 { "iso-8859-6",      ENC_8BIT,               0 },
#define IDX_ISO_7       6
 { "iso-8859-7",      ENC_8BIT,               0 },
#define IDX_ISO_8       7
 { "iso-8859-8",      ENC_8BIT,               0 },
#define IDX_ISO_9       8
 { "iso-8859-9",      ENC_8BIT,               0 },
#define IDX_ISO_10      9
 { "iso-8859-10",     ENC_8BIT,               0 },
#define IDX_ISO_11      10
 { "iso-8859-11",     ENC_8BIT,               0 },
#define IDX_ISO_13      11
 { "iso-8859-13",     ENC_8BIT,               0 },
#define IDX_ISO_14      12
 { "iso-8859-14",     ENC_8BIT,               0 },
#define IDX_ISO_15      13
 { "iso-8859-15",     ENC_8BIT + ENC_LATIN9,  0 },
#define IDX_KOI8_R      14
 { "koi8-r",          ENC_8BIT,               0 },
#define IDX_KOI8_U      15
 { "koi8-u",          ENC_8BIT,               0 },
#define IDX_UTF8        16
 { "utf-8",           ENC_UNICODE,            0 },
#define IDX_UCS2        17
 { "ucs-2",           ENC_UNICODE + ENC_ENDIAN_B + ENC_2BYTE, 0 },
#define IDX_UCS2LE      18
 { "ucs-2le",         ENC_UNICODE + ENC_ENDIAN_L + ENC_2BYTE, 0 },
#define IDX_UTF16       19
 { "utf-16",          ENC_UNICODE + ENC_ENDIAN_B + ENC_2WORD, 0 },
#define IDX_UTF16LE     20
 { "utf-16le",        ENC_UNICODE + ENC_ENDIAN_L + ENC_2WORD, 0 },
#define IDX_UCS4        21
 { "ucs-4",           ENC_UNICODE + ENC_ENDIAN_B + ENC_4BYTE, 0 },
#define IDX_UCS4LE      22
 { "ucs-4le",         ENC_UNICODE + ENC_ENDIAN_L + ENC_4BYTE, 0 },

 // For debugging DBCS encoding on Unix.
#define IDX_DEBUG       23
 { "debug",           ENC_DBCS,               DBCS_DEBUG },
#define IDX_EUC_JP      24
 { "euc-jp",          ENC_DBCS,               DBCS_JPNU },
#define IDX_SJIS        25
 { "sjis",            ENC_DBCS,               DBCS_JPN },
#define IDX_EUC_KR      26
 { "euc-kr",          ENC_DBCS,               DBCS_KORU },
#define IDX_EUC_CN      27
 { "euc-cn",          ENC_DBCS,               DBCS_CHSU },
#define IDX_EUC_TW      28
 { "euc-tw",          ENC_DBCS,               DBCS_CHTU },
#define IDX_BIG5        29
 { "big5",            ENC_DBCS,               DBCS_CHT },

 // MS-DOS and MS-Windows codepages are included here, so that they can be
 // used on Unix too.  Most of them are similar to ISO-8859 encodings, but
 // not exactly the same.
#define IDX_CP437       30
 { "cp437",           ENC_8BIT,               437 },   // like iso-8859-1
#define IDX_CP737       31
 { "cp737",           ENC_8BIT,               737 },   // like iso-8859-7
#define IDX_CP775       32
 { "cp775",           ENC_8BIT,               775 },   // Baltic
#define IDX_CP850       33
 { "cp850",           ENC_8BIT,               850 },   // like iso-8859-4
#define IDX_CP852       34
 { "cp852",           ENC_8BIT,               852 },   // like iso-8859-1
#define IDX_CP855       35
 { "cp855",           ENC_8BIT,               855 },   // like iso-8859-2
#define IDX_CP857       36
 { "cp857",           ENC_8BIT,               857 },   // like iso-8859-5
#define IDX_CP860       37
 { "cp860",           ENC_8BIT,               860 },   // like iso-8859-9
#define IDX_CP861       38
 { "cp861",           ENC_8BIT,               861 },   // like iso-8859-1
#define IDX_CP862       39
 { "cp862",           ENC_8BIT,               862 },   // like iso-8859-1
#define IDX_CP863       40
 { "cp863",           ENC_8BIT,               863 },   // like iso-8859-8
#define IDX_CP865       41
 { "cp865",           ENC_8BIT,               865 },   // like iso-8859-1
#define IDX_CP866       42
 { "cp866",           ENC_8BIT,               866 },   // like iso-8859-5
#define IDX_CP869       43
 { "cp869",           ENC_8BIT,               869 },   // like iso-8859-7
#define IDX_CP874       44
 { "cp874",           ENC_8BIT,               874 },   // Thai
#define IDX_CP932       45
 { "cp932",           ENC_DBCS,               DBCS_JPN },
#define IDX_CP936       46
 { "cp936",           ENC_DBCS,               DBCS_CHS },
#define IDX_CP949       47
 { "cp949",           ENC_DBCS,               DBCS_KOR },
#define IDX_CP950       48
 { "cp950",           ENC_DBCS,               DBCS_CHT },
#define IDX_CP1250      49
 { "cp1250",          ENC_8BIT,               1250 },   // Czech, Polish, etc.
#define IDX_CP1251      50
 { "cp1251",          ENC_8BIT,               1251 },   // Cyrillic
 // cp1252 is considered to be equal to latin1
#define IDX_CP1253      51
 { "cp1253",          ENC_8BIT,               1253 },   // Greek
#define IDX_CP1254      52
 { "cp1254",          ENC_8BIT,               1254 },   // Turkish
#define IDX_CP1255      53
 { "cp1255",          ENC_8BIT,               1255 },   // Hebrew
#define IDX_CP1256      54
 { "cp1256",          ENC_8BIT,               1256 },   // Arabic
#define IDX_CP1257      55
 { "cp1257",          ENC_8BIT,               1257 },   // Baltic
#define IDX_CP1258      56
 { "cp1258",          ENC_8BIT,               1258 },   // Vietnamese

#define IDX_MACROMAN    57
 { "macroman",        ENC_8BIT + ENC_MACROMAN, 0 },      // Mac OS
#define IDX_HPROMAN8    58
 { "hp-roman8",       ENC_8BIT,               0 },       // HP Roman8
#define IDX_COUNT       59
};

// Aliases for encoding names.
static struct
{   const char *name; int canon; }
enc_alias_table[] = {
 { "ansi",            IDX_LATIN_1 },
 { "iso-8859-1",      IDX_LATIN_1 },
 { "latin2",          IDX_ISO_2 },
 { "latin3",          IDX_ISO_3 },
 { "latin4",          IDX_ISO_4 },
 { "cyrillic",        IDX_ISO_5 },
 { "arabic",          IDX_ISO_6 },
 { "greek",           IDX_ISO_7 },
 { "hebrew",          IDX_ISO_8 },
 { "latin5",          IDX_ISO_9 },
 { "turkish",         IDX_ISO_9 },   // ?
 { "latin6",          IDX_ISO_10 },
 { "nordic",          IDX_ISO_10 },  // ?
 { "thai",            IDX_ISO_11 },  // ?
 { "latin7",          IDX_ISO_13 },
 { "latin8",          IDX_ISO_14 },
 { "latin9",          IDX_ISO_15 },
 { "utf8",            IDX_UTF8 },
 { "unicode",         IDX_UCS2 },
 { "ucs2",            IDX_UCS2 },
 { "ucs2be",          IDX_UCS2 },
 { "ucs-2be",         IDX_UCS2 },
 { "ucs2le",          IDX_UCS2LE },
 { "utf16",           IDX_UTF16 },
 { "utf16be",         IDX_UTF16 },
 { "utf-16be",        IDX_UTF16 },
 { "utf16le",         IDX_UTF16LE },
 { "ucs4",            IDX_UCS4 },
 { "ucs4be",          IDX_UCS4 },
 { "ucs-4be",         IDX_UCS4 },
 { "ucs4le",          IDX_UCS4LE },
 { "utf32",           IDX_UCS4 },
 { "utf-32",          IDX_UCS4 },
 { "utf32be",         IDX_UCS4 },
 { "utf-32be",        IDX_UCS4 },
 { "utf32le",         IDX_UCS4LE },
 { "utf-32le",        IDX_UCS4LE },
 { "932",             IDX_CP932 },
 { "949",             IDX_CP949 },
 { "936",             IDX_CP936 },
 { "gbk",             IDX_CP936 },
 { "950",             IDX_CP950 },
 { "eucjp",           IDX_EUC_JP },
 { "unix-jis",        IDX_EUC_JP },
 { "ujis",            IDX_EUC_JP },
 { "shift-jis",       IDX_SJIS },
 { "pck",             IDX_SJIS },        // Sun: PCK
 { "euckr",           IDX_EUC_KR },
 { "5601",            IDX_EUC_KR },      // Sun: KS C 5601
 { "euccn",           IDX_EUC_CN },
 { "gb2312",          IDX_EUC_CN },
 { "euctw",           IDX_EUC_TW },
 { "japan",           IDX_EUC_JP },
 { "korea",           IDX_EUC_KR },
 { "prc",             IDX_EUC_CN },
 { "zh-cn",           IDX_EUC_CN },
 { "chinese",         IDX_EUC_CN },
 { "zh-tw",           IDX_EUC_TW },
 { "taiwan",          IDX_EUC_TW },
 { "cp950",           IDX_BIG5 },
 { "950",             IDX_BIG5 },
 { "mac",             IDX_MACROMAN },
 { "mac-roman",       IDX_MACROMAN },
 { NULL,              0 }
};

/// Find encoding "name" in the list of canonical encoding names.
/// Returns -1 if not found.
static int enc_canon_search(const char *name)
 FUNC_ATTR_PURE
{
 for (int i = 0; i < IDX_COUNT; i++) {
   if (strcmp(name, enc_canon_table[i].name) == 0) {
     return i;
   }
 }
 return -1;
}

// Find canonical encoding "name" in the list and return its properties.
// Returns 0 if not found.
int enc_canon_props(const char *name)
 FUNC_ATTR_PURE
{
 int i = enc_canon_search(name);
 if (i >= 0) {
   return enc_canon_table[i].prop;
 } else if (strncmp(name, "2byte-", 6) == 0) {
   return ENC_DBCS;
 } else if (strncmp(name, "8bit-", 5) == 0 || strncmp(name, "iso-8859-", 9) == 0) {
   return ENC_8BIT;
 }
 return 0;
}

// Return the size of the BOM for the current buffer:
// 0 - no BOM
// 2 - UCS-2 or UTF-16 BOM
// 4 - UCS-4 BOM
// 3 - UTF-8 BOM
int bomb_size(void)
 FUNC_ATTR_PURE
{
 int n = 0;

 if (curbuf->b_p_bomb && !curbuf->b_p_bin) {
   if (*curbuf->b_p_fenc == NUL
       || strcmp(curbuf->b_p_fenc, "utf-8") == 0) {
     n = 3;
   } else if (strncmp(curbuf->b_p_fenc, "ucs-2", 5) == 0
              || strncmp(curbuf->b_p_fenc, "utf-16", 6) == 0) {
     n = 2;
   } else if (strncmp(curbuf->b_p_fenc, "ucs-4", 5) == 0) {
     n = 4;
   }
 }
 return n;
}

// Remove all BOM from "s" by moving remaining text.
void remove_bom(char *s)
{
 char *p = s;

 while ((p = strchr(p, 0xef)) != NULL) {
   if ((uint8_t)p[1] == 0xbb && (uint8_t)p[2] == 0xbf) {
     STRMOVE(p, p + 3);
   } else {
     p++;
   }
 }
}

/// Get class of pointer:
/// 0 for blank or NUL
/// 1 for punctuation
/// 2 for an alphanumeric word character
/// >2 for other word characters, including CJK and emoji
int mb_get_class(const char *p)
 FUNC_ATTR_PURE
{
 return mb_get_class_tab(p, curbuf->b_chartab);
}

int mb_get_class_tab(const char *p, const uint64_t *const chartab)
 FUNC_ATTR_PURE
{
 if (MB_BYTE2LEN((uint8_t)p[0]) == 1) {
   if (p[0] == NUL || ascii_iswhite(p[0])) {
     return 0;
   }
   if (vim_iswordc_tab((uint8_t)p[0], chartab)) {
     return 2;
   }
   return 1;
 }
 return utf_class_tab(utf_ptr2char(p), chartab);
}

static bool prop_is_emojilike(const utf8proc_property_t *prop)
{
 return prop->boundclass == UTF8PROC_BOUNDCLASS_EXTENDED_PICTOGRAPHIC
        || prop->boundclass == UTF8PROC_BOUNDCLASS_REGIONAL_INDICATOR;
}

/// For UTF-8 character "c" return 2 for a double-width character, 1 for others.
/// Returns 4 or 6 for an unprintable character.
/// Is only correct for characters >= 0x80.
/// When p_ambw is "double", return 2 for a character with East Asian Width
/// class 'A'(mbiguous).
int utf_char2cells(int c)
{
 if (c < 0x80) {
   return 1;
 }

 if (!vim_isprintc(c)) {
   assert(c <= 0xFFFF);
   // unprintable is displayed either as <xx> or <xxxx>
   return c > 0xFF ? 6 : 4;
 }

 int n = cw_value(c);
 if (n != 0) {
   return n;
 }

 const utf8proc_property_t *prop = utf8proc_get_property(c);

 if (prop->charwidth == 2) {
   return 2;
 }
 if (*p_ambw == 'd' && prop->ambiguous_width) {
   return 2;
 }

 // Characters below 1F000 may be considered single width traditionally,
 // making them double width causes problems.
 if (p_emoji && c >= 0x1f000 && !prop->ambiguous_width && prop_is_emojilike(prop)) {
   return 2;
 }

 return 1;
}

/// Return the number of display cells character at "*p" occupies.
/// This doesn't take care of unprintable characters, use ptr2cells() for that.
int utf_ptr2cells(const char *p_in)
{
 const uint8_t *p = (const uint8_t *)p_in;
 // Need to convert to a character number.
 if ((*p) >= 0x80) {
   int len = utf8len_tab[*p];
   int32_t c = utf_ptr2CharInfo_impl(p, (uintptr_t)len);
   // An illegal byte is displayed as <xx>.
   if (c <= 0) {
     return 4;
   }
   // If the char is ASCII it must be an overlong sequence.
   if (c < 0x80) {
     return char2cells(c);
   }
   int cells = utf_char2cells(c);
   if (cells == 1 && p_emoji
       && prop_is_emojilike(utf8proc_get_property(c))) {
     int c2 = utf_ptr2char(p_in + len);
     if (c2 == 0xFE0F) {
       return 2;  // emoji presentation
     }
   }
   return cells;
 }
 return 1;
}

/// Convert a UTF-8 byte sequence to a character number.
/// Doesn't handle ascii! only multibyte and illegal sequences. ASCII (including NUL)
/// are treated like illegal sequences.
///
/// @param[in]  p      String to convert.
/// @param[in]  len    Length of the character in bytes, 0 or 1 if illegal.
///
/// @return Unicode codepoint. A negative value when the sequence is illegal (or
///         ASCII, including NUL).
int32_t utf_ptr2CharInfo_impl(uint8_t const *p, uintptr_t const len)
 FUNC_ATTR_PURE FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
{
// uint8_t is a reminder for clang to use smaller cmp
#define CHECK \
 do { \
   if (EXPECT((uint8_t)(cur & 0xC0U) != 0x80U, false)) { \
     return -1; \
   } \
 } while (0)

 static uint32_t const corrections[] = {
   (1U << 31),  // invalid - set invalid bits (safe to add as first 2 bytes
   (1U << 31),  // won't affect highest bit in normal ret)
   -(0x80U + (0xC0U << 6)),  // multibyte - subtract added UTF8 bits (1..10xxx and 10xxx)
   -(0x80U + (0x80U << 6) + (0xE0U << 12)),
   -(0x80U + (0x80U << 6) + (0x80U << 12) + (0xF0U << 18)),
   -(0x80U + (0x80U << 6) + (0x80U << 12) + (0x80U << 18) + (0xF8U << 24)),
   -(0x80U + (0x80U << 6) + (0x80U << 12) + (0x80U << 18) + (0x80U << 24)),  // + (0xFCU << 30)
 };

 // len is 0-6, but declared uintptr_t to avoid zeroing out upper bits
 uint32_t const corr = corrections[len];
 uint8_t cur;

 // reading second byte unconditionally, safe for invalid
 // as it cannot be the last byte, not safe for ascii
 uint32_t code_point = ((uint32_t)p[0] << 6) + (cur = p[1]);
 CHECK;
 if ((uint32_t)len < 3) {
   goto ret;  // len == 0, 1, 2
 }

 code_point = (code_point << 6) + (cur = p[2]);
 CHECK;
 if ((uint32_t)len == 3) {
   goto ret;
 }

 code_point = (code_point << 6) + (cur = p[3]);
 CHECK;
 if ((uint32_t)len == 4) {
   goto ret;
 }

 code_point = (code_point << 6) + (cur = p[4]);
 CHECK;
 if ((uint32_t)len == 5) {
   goto ret;
 }

 code_point = (code_point << 6) + (cur = p[5]);
 CHECK;
 // len == 6

ret:
 return (int32_t)(code_point + corr);

#undef CHECK
}

/// Like utf_ptr2cells(), but limit string length to "size".
/// For an empty string or truncated character returns 1.
int utf_ptr2cells_len(const char *p, int size)
{
 // Need to convert to a wide character.
 if (size > 0 && (uint8_t)(*p) >= 0x80) {
   int len = utf_ptr2len_len(p, size);
   if (len < utf8len_tab[(uint8_t)(*p)]) {
     return 1;        // truncated
   }
   int c = utf_ptr2char(p);
   // An illegal byte is displayed as <xx>.
   if (utf_ptr2len(p) == 1 || c == NUL) {
     return 4;
   }
   // If the char is ASCII it must be an overlong sequence.
   if (c < 0x80) {
     return char2cells(c);
   }
   int cells = utf_char2cells(c);
   if (cells == 1 && p_emoji && size > len
       && prop_is_emojilike(utf8proc_get_property(c))
       && utf_ptr2len_len(p + len, size - len) == utf8len_tab[(uint8_t)p[len]]) {
     int c2 = utf_ptr2char(p + len);
     if (c2 == 0xFE0F) {
       return 2;  // emoji presentation
     }
   }
   return cells;
 }
 return 1;
}

/// Calculate the number of cells occupied by string `str`.
///
/// @param str The source string, may not be NULL, must be a NUL-terminated
///            string.
/// @return The number of cells occupied by string `str`
size_t mb_string2cells(const char *str)
{
 size_t clen = 0;

 for (const char *p = str; *p != NUL; p += utfc_ptr2len(p)) {
   clen += (size_t)utf_ptr2cells(p);
 }

 return clen;
}

/// Get the number of cells occupied by string `str` with maximum length `size`
///
/// @param str The source string, may not be NULL, must be a NUL-terminated
///            string.
/// @param size maximum length of string. It will terminate on earlier NUL.
/// @return The number of cells occupied by string `str`
size_t mb_string2cells_len(const char *str, size_t size)
 FUNC_ATTR_NONNULL_ARG(1)
{
 size_t clen = 0;

 for (const char *p = str; *p != NUL && p < str + size;
      p += utfc_ptr2len_len(p, (int)size - (int)(p - str))) {
   clen += (size_t)utf_ptr2cells_len(p, (int)size - (int)(p - str));
 }

 return clen;
}

/// Convert a UTF-8 byte sequence to a character number.
///
/// If the sequence is illegal or truncated by a NUL then the first byte is
/// returned.
/// For an overlong sequence this may return zero.
/// Does not include composing characters for obvious reasons.
///
/// @param[in]  p_in  String to convert.
///
/// @return Unicode codepoint or byte value.
int utf_ptr2char(const char *const p_in)
 FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
{
 uint8_t *p = (uint8_t *)p_in;

 uint32_t const v0 = p[0];
 if (EXPECT(v0 < 0x80U, true)) {  // Be quick for ASCII.
   return (int)v0;
 }

 const uint8_t len = utf8len_tab[v0];
 if (EXPECT(len < 2, false)) {
   return (int)v0;
 }

#define CHECK(v) \
 do { \
   if (EXPECT((uint8_t)((v) & 0xC0U) != 0x80U, false)) { \
     return (int)v0; \
   } \
 } while (0)
#define LEN_RETURN(len_v, result) \
 do { \
   if (len == (len_v)) { \
     return (int)(result); \
   } \
 } while (0)
#define S(s) ((uint32_t)0x80U << (s))

 uint32_t const v1 = p[1];
 CHECK(v1);
 LEN_RETURN(2, (v0 << 6) + v1 - ((0xC0U << 6) + S(0)));

 uint32_t const v2 = p[2];
 CHECK(v2);
 LEN_RETURN(3, (v0 << 12) + (v1 << 6) + v2 - ((0xE0U << 12) + S(6) + S(0)));

 uint32_t const v3 = p[3];
 CHECK(v3);
 LEN_RETURN(4, (v0 << 18) + (v1 << 12) + (v2 << 6) + v3
            - ((0xF0U << 18) + S(12) + S(6) + S(0)));

 uint32_t const v4 = p[4];
 CHECK(v4);
 LEN_RETURN(5, (v0 << 24) + (v1 << 18) + (v2 << 12) + (v3 << 6) + v4
            - ((0xF8U << 24) + S(18) + S(12) + S(6) + S(0)));

 uint32_t const v5 = p[5];
 CHECK(v5);
 // len == 6
 return (int)((v0 << 30) + (v1 << 24) + (v2 << 18) + (v3 << 12) + (v4 << 6) + v5
              // - (0xFCU << 30)
              - (S(24) + S(18) + S(12) + S(6) + S(0)));

#undef S
#undef CHECK
#undef LEN_RETURN
}

// Convert a UTF-8 byte sequence to a wide character.
// String is assumed to be terminated by NUL or after "n" bytes, whichever
// comes first.
// The function is safe in the sense that it never accesses memory beyond the
// first "n" bytes of "s".
//
// On success, returns decoded codepoint, advances "s" to the beginning of
// next character and decreases "n" accordingly.
//
// If end of string was reached, returns 0 and, if "n" > 0, advances "s" past
// NUL byte.
//
// If byte sequence is illegal or incomplete, returns -1 and does not advance
// "s".
static int utf_safe_read_char_adv(const char **s, size_t *n)
{
 if (*n == 0) {  // end of buffer
   return 0;
 }

 uint8_t k = utf8len_tab_zero[(uint8_t)(**s)];

 if (k == 1) {
   // ASCII character or NUL
   (*n)--;
   return (uint8_t)(*(*s)++);
 }

 if (k <= *n) {
   // We have a multibyte sequence and it isn't truncated by buffer
   // limits so utf_ptr2char() is safe to use. Or the first byte is
   // illegal (k=0), and it's also safe to use utf_ptr2char().
   int c = utf_ptr2char(*s);

   // On failure, utf_ptr2char() returns the first byte, so here we
   // check equality with the first byte. The only non-ASCII character
   // which equals the first byte of its own UTF-8 representation is
   // U+00C3 (UTF-8: 0xC3 0x83), so need to check that special case too.
   // It's safe even if n=1, else we would have k=2 > n.
   if (c != (int)((uint8_t)(**s)) || (c == 0xC3 && (uint8_t)(*s)[1] == 0x83)) {
     // byte sequence was successfully decoded
     *s += k;
     *n -= k;
     return c;
   }
 }

 // byte sequence is incomplete or illegal
 return -1;
}

// Get character at **pp and advance *pp to the next character.
// Note: composing characters are skipped!
int mb_ptr2char_adv(const char **const pp)
{
 int c = utf_ptr2char(*pp);
 *pp += utfc_ptr2len(*pp);
 return c;
}

// Get character at **pp and advance *pp to the next character.
// Note: composing characters are returned as separate characters.
int mb_cptr2char_adv(const char **pp)
{
 int c = utf_ptr2char(*pp);
 *pp += utf_ptr2len(*pp);
 return c;
}

/// When "c" is the first char of a string, determine if it needs to be prefixed
/// by a space byte to be drawn correctly, and not merge with the space left of
/// the string.
bool utf_iscomposing_first(int c)
{
 return c >= 128 && !utf8proc_grapheme_break(' ', c);
}

/// Check if the character pointed to by "p2" is a composing character when it
/// comes after "p1".
///
/// We use the definition in UAX#29 as implemented by utf8proc with the following
/// exceptions:
///
/// - ASCII chars always begin a new cluster. This is a long assumed invariant
///   in the code base and very useful for performance (we can exit early for ASCII
///   all over the place, branch predictor go brrr in ASCII-only text).
///   As of Unicode 15.1 this will only break BOUNDCLASS_UREPEND followed by ASCII,
///   which should be exceedingly rare (these PREPEND chars are expected to be
///   followed by multibyte chars within the same script family)
///
/// - When 'arabicshape' is active, some pairs of arabic letters "ab" is replaced with
///   "c" taking one single cell, which behaves like a cluster.
///
/// @param "state" should be set to GRAPHEME_STATE_INIT before first call
///        it is allowed to be null, but will then not handle some longer
///        sequences, like ZWJ based emoji
bool utf_composinglike(const char *p1, const char *p2, GraphemeState *state)
 FUNC_ATTR_NONNULL_ARG(1, 2)
{
 if ((uint8_t)(*p2) < 128) {
   return false;
 }

 int first = utf_ptr2char(p1);
 int second = utf_ptr2char(p2);

 if (!utf8proc_grapheme_break_stateful(first, second, state)) {
   return true;
 }

 return arabic_combine(first, second);
}

/// same as utf_composinglike but operating on UCS-4 values
bool utf_iscomposing(int c1, int c2, GraphemeState *state)
{
 return (!utf8proc_grapheme_break_stateful(c1, c2, state)
         || arabic_combine(c1, c2));
}

/// Get the screen char at the beginning of a string
///
/// Caller is expected to check for things like unprintable chars etc
/// If first char in string is a composing char, prepend a space to display it correctly.
///
/// If "p" starts with an invalid sequence, zero is returned.
///
/// @param[out] firstc (required) The first codepoint of the screen char,
///                    or the first byte of an invalid sequence
///
/// @return the char
schar_T utfc_ptr2schar(const char *p, int *firstc)
 FUNC_ATTR_NONNULL_ALL
{
 int c = utf_ptr2char(p);
 *firstc = c;  // NOT optional, you are gonna need it
 bool first_compose = utf_iscomposing_first(c);
 size_t maxlen = MAX_SCHAR_SIZE - 1 - first_compose;
 size_t len = (size_t)utfc_ptr2len_len(p, (int)maxlen);

 if (len == 1 && (uint8_t)(*p) >= 0x80) {
   return 0;  // invalid sequence
 }

 return schar_from_buf_first(p, len, first_compose);
}

/// Get the screen char from a char with a known length
///
/// Like utfc_ptr2schar but use no more than p[maxlen].
schar_T utfc_ptrlen2schar(const char *p, int len, int *firstc)
 FUNC_ATTR_NONNULL_ALL
{
 if ((len == 1 && (uint8_t)(*p) >= 0x80) || len == 0) {
   // invalid or truncated sequence
   *firstc = (uint8_t)(*p);
   return 0;
 }

 int c = utf_ptr2char(p);
 *firstc = c;
 bool first_compose = utf_iscomposing_first(c);
 int maxlen = MAX_SCHAR_SIZE - 1 - first_compose;
 if (len > maxlen) {
   len = utfc_ptr2len_len(p, maxlen);
 }

 return schar_from_buf_first(p, (size_t)len, first_compose);
}

/// Caller must ensure there is space for `first_compose`
static schar_T schar_from_buf_first(const char *buf, size_t len, bool first_compose)
{
 if (first_compose) {
   char cbuf[MAX_SCHAR_SIZE];
   cbuf[0] = ' ';
   memcpy(cbuf + 1, buf, len);
   return schar_from_buf(cbuf, len + 1);
 } else {
   return schar_from_buf(buf, len);
 }
}

/// Get the length of a UTF-8 byte sequence representing a single codepoint
///
/// @param[in]  p  UTF-8 string.
///
/// @return Sequence length, 0 for empty string and 1 for non-UTF-8 byte
///         sequence.
int utf_ptr2len(const char *const p_in)
 FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
{
 uint8_t *p = (uint8_t *)p_in;
 if (*p == NUL) {
   return 0;
 }
 const int len = utf8len_tab[*p];
 for (int i = 1; i < len; i++) {
   if ((p[i] & 0xc0) != 0x80) {
     return 1;
   }
 }
 return len;
}

// Return length of UTF-8 character, obtained from the first byte.
// "b" must be between 0 and 255!
// Returns 1 for an invalid first byte value.
int utf_byte2len(int b)
{
 return utf8len_tab[b];
}

// Get the length of UTF-8 byte sequence "p[size]".  Does not include any
// following composing characters.
// Returns 1 for "".
// Returns 1 for an illegal byte sequence (also in incomplete byte seq.).
// Returns number > "size" for an incomplete byte sequence.
// Never returns zero.
int utf_ptr2len_len(const char *p, int size)
{
 int m;

 int len = utf8len_tab[(uint8_t)(*p)];
 if (len == 1) {
   return 1;           // NUL, ascii or illegal lead byte
 }
 if (len > size) {
   m = size;           // incomplete byte sequence.
 } else {
   m = len;
 }
 for (int i = 1; i < m; i++) {
   if ((p[i] & 0xc0) != 0x80) {
     return 1;
   }
 }
 return len;
}

/// Return the number of bytes occupied by a UTF-8 character in a string.
/// This includes following composing characters.
/// Returns zero for NUL.
int utfc_ptr2len(const char *const p)
 FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
{
 uint8_t b0 = (uint8_t)(*p);

 if (b0 == NUL) {
   return 0;
 }
 if (b0 < 0x80 && (uint8_t)p[1] < 0x80) {  // be quick for ASCII
   return 1;
 }

 // Skip over first UTF-8 char, stopping at a NUL byte.
 int len = utf_ptr2len(p);

 // Check for illegal byte.
 if (len == 1 && b0 >= 0x80) {
   return 1;
 }

 // Check for composing characters.
 int prevlen = 0;
 GraphemeState state = GRAPHEME_STATE_INIT;
 while (true) {
   if ((uint8_t)p[len] < 0x80 || !utf_composinglike(p + prevlen, p + len, &state)) {
     return len;
   }

   // Skip over composing char.
   prevlen = len;
   len += utf_ptr2len(p + len);
 }
}

/// Return the number of bytes the UTF-8 encoding of the character at "p[size]"
/// takes.  This includes following composing characters.
/// Returns 0 for an empty string.
/// Returns 1 for an illegal char or an incomplete byte sequence.
int utfc_ptr2len_len(const char *p, int size)
{
 if (size < 1 || *p == NUL) {
   return 0;
 }
 if ((uint8_t)p[0] < 0x80 && (size == 1 || (uint8_t)p[1] < 0x80)) {  // be quick for ASCII
   return 1;
 }

 // Skip over first UTF-8 char, stopping at a NUL byte.
 int len = utf_ptr2len_len(p, size);

 // Check for illegal byte and incomplete byte sequence.
 if ((len == 1 && (uint8_t)p[0] >= 0x80) || len > size) {
   return 1;
 }

 // Check for composing characters.  We can only display a limited amount, but
 // skip all of them (otherwise the cursor would get stuck).
 int prevlen = 0;
 GraphemeState state = GRAPHEME_STATE_INIT;
 while (len < size) {
   if ((uint8_t)p[len] < 0x80) {
     break;
   }

   // Next character length should not go beyond size to ensure that
   // utf_composinglike(...) does not read beyond size.
   int len_next_char = utf_ptr2len_len(p + len, size - len);
   if (len_next_char > size - len) {
     break;
   }

   if (!utf_composinglike(p + prevlen, p + len, &state)) {
     break;
   }

   // Skip over composing char
   prevlen = len;
   len += len_next_char;
 }
 return len;
}

/// Determine how many bytes certain unicode codepoint will occupy
int utf_char2len(const int c)
{
 if (c < 0x80) {
   return 1;
 } else if (c < 0x800) {
   return 2;
 } else if (c < 0x10000) {
   return 3;
 } else if (c < 0x200000) {
   return 4;
 } else if (c < 0x4000000) {
   return 5;
 } else {
   return 6;
 }
}

/// Convert Unicode character to UTF-8 string
///
/// @param c         character to convert to UTF-8 string in \p buf
/// @param[out] buf  UTF-8 string generated from \p c, does not add \0
///                  must have room for at least 6 bytes
/// @return Number of bytes (1-6).
int utf_char2bytes(const int c, char *const buf)
{
 if (c < 0x80) {  // 7 bits
   buf[0] = (char)c;
   return 1;
 } else if (c < 0x800) {  // 11 bits
   buf[0] = (char)(0xc0 + ((unsigned)c >> 6));
   buf[1] = (char)(0x80 + ((unsigned)c & 0x3f));
   return 2;
 } else if (c < 0x10000) {  // 16 bits
   buf[0] = (char)(0xe0 + ((unsigned)c >> 12));
   buf[1] = (char)(0x80 + (((unsigned)c >> 6) & 0x3f));
   buf[2] = (char)(0x80 + ((unsigned)c & 0x3f));
   return 3;
 } else if (c < 0x200000) {  // 21 bits
   buf[0] = (char)(0xf0 + ((unsigned)c >> 18));
   buf[1] = (char)(0x80 + (((unsigned)c >> 12) & 0x3f));
   buf[2] = (char)(0x80 + (((unsigned)c >> 6) & 0x3f));
   buf[3] = (char)(0x80 + ((unsigned)c & 0x3f));
   return 4;
 } else if (c < 0x4000000) {  // 26 bits
   buf[0] = (char)(0xf8 + ((unsigned)c >> 24));
   buf[1] = (char)(0x80 + (((unsigned)c >> 18) & 0x3f));
   buf[2] = (char)(0x80 + (((unsigned)c >> 12) & 0x3f));
   buf[3] = (char)(0x80 + (((unsigned)c >> 6) & 0x3f));
   buf[4] = (char)(0x80 + ((unsigned)c & 0x3f));
   return 5;
 } else {  // 31 bits
   buf[0] = (char)(0xfc + ((unsigned)c >> 30));
   buf[1] = (char)(0x80 + (((unsigned)c >> 24) & 0x3f));
   buf[2] = (char)(0x80 + (((unsigned)c >> 18) & 0x3f));
   buf[3] = (char)(0x80 + (((unsigned)c >> 12) & 0x3f));
   buf[4] = (char)(0x80 + (((unsigned)c >> 6) & 0x3f));
   buf[5] = (char)(0x80 + ((unsigned)c & 0x3f));
   return 6;
 }
}

/// Return true if "c" is a legacy composing UTF-8 character.
///
/// This is deprecated in favour of utf_composinglike() which uses the modern
/// stateful algorithm to determine grapheme clusters. Still available
/// to support some legacy code which hasn't been refactored yet.
///
/// To check if a char would combine with a preceding space, use
/// utf_iscomposing_first() instead.
///
/// Based on code from Markus Kuhn.
/// Returns false for negative values.
bool utf_iscomposing_legacy(int c)
{
 const utf8proc_property_t *prop = utf8proc_get_property(c);
 return prop->category == UTF8PROC_CATEGORY_MN || prop->category == UTF8PROC_CATEGORY_ME;
}

#ifdef __SSE2__

# include <emmintrin.h>

// Return true for characters that can be displayed in a normal way.
// Only for characters of 0x100 and above!
bool utf_printable(int c)
 FUNC_ATTR_CONST
{
 if (c < 0x180B || c > 0xFFFF) {
   return c != 0x70F;
 }

# define L(v) ((int16_t)((v) - 1))  // lower bound (exclusive)
# define H(v) ((int16_t)(v))  // upper bound (inclusive)

 // Boundaries of unprintable characters.
 // Some values are negative when converted to int16_t.
 // Ranges must not wrap around when converted to int16_t.
 __m128i const lo = _mm_setr_epi16(L(0x180b), L(0x200b), L(0x202a), L(0x2060),
                                   L(0xd800), L(0xfeff), L(0xfff9), L(0xfffe));

 __m128i const hi = _mm_setr_epi16(H(0x180e), H(0x200f), H(0x202e), H(0x206f),
                                   H(0xdfff), H(0xfeff), H(0xfffb), H(0xffff));

# undef L
# undef H

 __m128i value = _mm_set1_epi16((int16_t)c);

 // Using _mm_cmplt_epi16() is less optimal, since it would require
 // swapping operands (sse2 only has cmpgt instruction),
 // and only the second operand can be a memory location.

 // Character is printable when it is above/below both bounds of each range
 // (corresponding bits in both masks are equal).
 return _mm_movemask_epi8(_mm_cmpgt_epi16(value, lo))
        == _mm_movemask_epi8(_mm_cmpgt_epi16(value, hi));
}

#else

// Return true if "c" is in "table".
static bool intable(const struct interval *table, size_t n_items, int c)
 FUNC_ATTR_CONST
{
 assert(n_items > 0);
 // first quick check for Latin1 etc. characters
 if (c < table[0].first) {
   return false;
 }

 assert(n_items <= SIZE_MAX / 2);
 // binary search in table
 size_t bot = 0;
 size_t top = n_items;
 do {
   size_t mid = (bot + top) >> 1;
   if (table[mid].last < c) {
     bot = mid + 1;
   } else if (table[mid].first > c) {
     top = mid;
   } else {
     return true;
   }
 } while (top > bot);
 return false;
}

// Return true for characters that can be displayed in a normal way.
// Only for characters of 0x100 and above!
bool utf_printable(int c)
 FUNC_ATTR_CONST
{
 // Sorted list of non-overlapping intervals.
 // 0xd800-0xdfff is reserved for UTF-16, actually illegal.
 static const struct interval nonprint[] = {
   { 0x070f, 0x070f }, { 0x180b, 0x180e }, { 0x200b, 0x200f }, { 0x202a, 0x202e },
   { 0x2060, 0x206f }, { 0xd800, 0xdfff }, { 0xfeff, 0xfeff }, { 0xfff9, 0xfffb },
   { 0xfffe, 0xffff }
 };

 return !intable(nonprint, ARRAY_SIZE(nonprint), c);
}

#endif

// Get class of a Unicode character.
// 0: white space
// 1: punctuation
// 2 or bigger: some class of word character.
int utf_class(const int c)
{
 return utf_class_tab(c, curbuf->b_chartab);
}

int utf_class_tab(const int c, const uint64_t *const chartab)
 FUNC_ATTR_PURE
{
 // sorted list of non-overlapping intervals
 static struct clinterval {
   unsigned first;
   unsigned last;
   unsigned cls;
 } classes[] = {
   { 0x037e, 0x037e, 1 },              // Greek question mark
   { 0x0387, 0x0387, 1 },              // Greek ano teleia
   { 0x055a, 0x055f, 1 },              // Armenian punctuation
   { 0x0589, 0x0589, 1 },              // Armenian full stop
   { 0x05be, 0x05be, 1 },
   { 0x05c0, 0x05c0, 1 },
   { 0x05c3, 0x05c3, 1 },
   { 0x05f3, 0x05f4, 1 },
   { 0x060c, 0x060c, 1 },
   { 0x061b, 0x061b, 1 },
   { 0x061f, 0x061f, 1 },
   { 0x066a, 0x066d, 1 },
   { 0x06d4, 0x06d4, 1 },
   { 0x0700, 0x070d, 1 },              // Syriac punctuation
   { 0x0964, 0x0965, 1 },
   { 0x0970, 0x0970, 1 },
   { 0x0df4, 0x0df4, 1 },
   { 0x0e4f, 0x0e4f, 1 },
   { 0x0e5a, 0x0e5b, 1 },
   { 0x0f04, 0x0f12, 1 },
   { 0x0f3a, 0x0f3d, 1 },
   { 0x0f85, 0x0f85, 1 },
   { 0x104a, 0x104f, 1 },              // Myanmar punctuation
   { 0x10fb, 0x10fb, 1 },              // Georgian punctuation
   { 0x1361, 0x1368, 1 },              // Ethiopic punctuation
   { 0x166d, 0x166e, 1 },              // Canadian Syl. punctuation
   { 0x1680, 0x1680, 0 },
   { 0x169b, 0x169c, 1 },
   { 0x16eb, 0x16ed, 1 },
   { 0x1735, 0x1736, 1 },
   { 0x17d4, 0x17dc, 1 },              // Khmer punctuation
   { 0x1800, 0x180a, 1 },              // Mongolian punctuation
   { 0x2000, 0x200b, 0 },              // spaces
   { 0x200c, 0x2027, 1 },              // punctuation and symbols
   { 0x2028, 0x2029, 0 },
   { 0x202a, 0x202e, 1 },              // punctuation and symbols
   { 0x202f, 0x202f, 0 },
   { 0x2030, 0x205e, 1 },              // punctuation and symbols
   { 0x205f, 0x205f, 0 },
   { 0x2060, 0x206f, 1 },              // punctuation and symbols
   { 0x2070, 0x207f, 0x2070 },         // superscript
   { 0x2080, 0x2094, 0x2080 },         // subscript
   { 0x20a0, 0x27ff, 1 },              // all kinds of symbols
   { 0x2800, 0x28ff, 0x2800 },         // braille
   { 0x2900, 0x2998, 1 },              // arrows, brackets, etc.
   { 0x29d8, 0x29db, 1 },
   { 0x29fc, 0x29fd, 1 },
   { 0x2e00, 0x2e7f, 1 },              // supplemental punctuation
   { 0x3000, 0x3000, 0 },              // ideographic space
   { 0x3001, 0x3020, 1 },              // ideographic punctuation
   { 0x3030, 0x3030, 1 },
   { 0x303d, 0x303d, 1 },
   { 0x3040, 0x309f, 0x3040 },         // Hiragana
   { 0x30a0, 0x30ff, 0x30a0 },         // Katakana
   { 0x3300, 0x9fff, 0x4e00 },         // CJK Ideographs
   { 0xac00, 0xd7a3, 0xac00 },         // Hangul Syllables
   { 0xf900, 0xfaff, 0x4e00 },         // CJK Ideographs
   { 0xfd3e, 0xfd3f, 1 },
   { 0xfe30, 0xfe6b, 1 },              // punctuation forms
   { 0xff00, 0xff0f, 1 },              // half/fullwidth ASCII
   { 0xff1a, 0xff20, 1 },              // half/fullwidth ASCII
   { 0xff3b, 0xff40, 1 },              // half/fullwidth ASCII
   { 0xff5b, 0xff65, 1 },              // half/fullwidth ASCII
   { 0x1d000, 0x1d24f, 1 },            // Musical notation
   { 0x1d400, 0x1d7ff, 1 },            // Mathematical Alphanumeric Symbols
   { 0x1f000, 0x1f2ff, 1 },            // Game pieces; enclosed characters
   { 0x1f300, 0x1f9ff, 1 },            // Many symbol blocks
   { 0x20000, 0x2a6df, 0x4e00 },       // CJK Ideographs
   { 0x2a700, 0x2b73f, 0x4e00 },       // CJK Ideographs
   { 0x2b740, 0x2b81f, 0x4e00 },       // CJK Ideographs
   { 0x2f800, 0x2fa1f, 0x4e00 },       // CJK Ideographs
 };
 int bot = 0;
 int top = ARRAY_SIZE(classes) - 1;

 // First quick check for Latin1 characters, use 'iskeyword'.
 if (c < 0x100) {
   if (c == ' ' || c == '\t' || c == NUL || c == 0xa0) {
     return 0;             // blank
   }
   if (vim_iswordc_tab(c, chartab)) {
     return 2;             // word character
   }
   return 1;               // punctuation
 }

 const utf8proc_property_t *prop = utf8proc_get_property(c);
 // emoji
 if (prop_is_emojilike(prop)) {
   return 3;
 }

 // binary search in table
 while (top >= bot) {
   int mid = (bot + top) / 2;
   if (classes[mid].last < (unsigned)c) {
     bot = mid + 1;
   } else if (classes[mid].first > (unsigned)c) {
     top = mid - 1;
   } else {
     return (int)classes[mid].cls;
   }
 }

 // most other characters are "word" characters
 return 2;
}

bool utf_ambiguous_width(const char *p)
{
 // be quick if there is nothing to print or ASCII-only
 if (p[0] == NUL || p[1] == NUL) {
   return false;
 }

 CharInfo info = utf_ptr2CharInfo(p);
 if (info.value >= 0x80) {
   const utf8proc_property_t *prop = utf8proc_get_property(info.value);
   if (prop->ambiguous_width || prop_is_emojilike(prop)) {
     return true;
   }
 }

 // check if second sequence is 0xFE0F VS-16 which can turn things into emoji,
 // safe with NUL (no second sequence)
 return memcmp(p + info.len, "\xef\xb8\x8f", 3) == 0;
}

// Return the folded-case equivalent of "a", which is a UCS-4 character.  Uses
// full case folding.
int utf_fold(int a)
{
 if (a < 0x80) {
   // be fast for ASCII
   return a >= 0x41 && a <= 0x5a ? a + 32 : a;
 }

 // TODO(dundargoc): utf8proc only does full case folding, which breaks some tests. This is a
 // temporary workaround to circumvent failing tests.
 //
 // (0xdf) ß == ss in full casefolding. Using this however breaks the vim spell tests and the error
 // E763 is thrown. This is due to the test spells relying on the vim spell files.
 //
 // (0x130) İ == i̇ in full casefolding.
 if (a == 0xdf || a == 0x130) {
   return a;
 }

 utf8proc_int32_t result[1];

 utf8proc_ssize_t res = utf8proc_decompose_char(a, result, 1, UTF8PROC_CASEFOLD, NULL);

 return (res == 1) ? result[0] : a;
}

// Vim's own character class functions.  These exist because many library
// islower()/toupper() etc. do not work properly: they crash when used with
// invalid values or can't handle latin1 when the locale is C.
// Speed is most important here.

/// Return the upper-case equivalent of "a", which is a UCS-4 character.  Use
/// simple case folding.
int mb_toupper(int a)
{
 // If 'casemap' contains "keepascii" use ASCII style toupper().
 if (a < 128 && (cmp_flags & kOptCmpFlagKeepascii)) {
   return TOUPPER_ASC(a);
 }

 if (!(cmp_flags & kOptCmpFlagInternal)) {
   return (int)towupper((wint_t)a);
 }

 // For characters below 128 use locale sensitive toupper().
 if (a < 128) {
   return TOUPPER_LOC(a);
 }

 return utf8proc_toupper(a);
}

bool mb_islower(int a)
{
 return mb_toupper(a) != a;
}

/// Return the lower-case equivalent of "a", which is a UCS-4 character.  Use
/// simple case folding.
int mb_tolower(int a)
{
 // If 'casemap' contains "keepascii" use ASCII style tolower().
 if (a < 128 && (cmp_flags & kOptCmpFlagKeepascii)) {
   return TOLOWER_ASC(a);
 }

 if (!(cmp_flags & kOptCmpFlagInternal)) {
   return (int)towlower((wint_t)a);
 }

 // For characters below 128 use locale sensitive tolower().
 if (a < 128) {
   return TOLOWER_LOC(a);
 }

 return utf8proc_tolower(a);
}

bool mb_isupper(int a)
{
 return mb_tolower(a) != a;
}

bool mb_isalpha(int a)
 FUNC_ATTR_WARN_UNUSED_RESULT
{
 return mb_islower(a) || mb_isupper(a);
}

int utf_strnicmp(const char *s1, const char *s2, size_t n1, size_t n2)
{
 int c1, c2;
 char buffer[6];

 while (true) {
   c1 = utf_safe_read_char_adv(&s1, &n1);
   c2 = utf_safe_read_char_adv(&s2, &n2);

   if (c1 <= 0 || c2 <= 0) {
     break;
   }

   if (c1 == c2) {
     continue;
   }

   int cdiff = utf_fold(c1) - utf_fold(c2);
   if (cdiff != 0) {
     return cdiff;
   }
 }

 // some string ended or has an incomplete/illegal character sequence

 if (c1 == 0 || c2 == 0) {
   // some string ended. shorter string is smaller
   if (c1 == 0 && c2 == 0) {
     return 0;
   }
   return c1 == 0 ? -1 : 1;
 }

 // Continue with bytewise comparison to produce some result that
 // would make comparison operations involving this function transitive.
 //
 // If only one string had an error, comparison should be made with
 // folded version of the other string. In this case it is enough
 // to fold just one character to determine the result of comparison.

 if (c1 != -1 && c2 == -1) {
   n1 = (size_t)utf_char2bytes(utf_fold(c1), buffer);
   s1 = buffer;
 } else if (c2 != -1 && c1 == -1) {
   n2 = (size_t)utf_char2bytes(utf_fold(c2), buffer);
   s2 = buffer;
 }

 while (n1 > 0 && n2 > 0 && *s1 != NUL && *s2 != NUL) {
   int cdiff = (int)((uint8_t)(*s1)) - (int)((uint8_t)(*s2));
   if (cdiff != 0) {
     return cdiff;
   }

   s1++;
   s2++;
   n1--;
   n2--;
 }

 if (n1 > 0 && *s1 == NUL) {
   n1 = 0;
 }
 if (n2 > 0 && *s2 == NUL) {
   n2 = 0;
 }

 if (n1 == 0 && n2 == 0) {
   return 0;
 }
 return n1 == 0 ? -1 : 1;
}

#ifdef MSWIN
# ifndef CP_UTF8
#  define CP_UTF8 65001  // magic number from winnls.h
# endif

/// Converts string from UTF-8 to UTF-16.
///
/// @param utf8  UTF-8 string.
/// @param utf8len  Length of `utf8`. May be -1 if `utf8` is NUL-terminated.
/// @param utf16[out,allocated]  NUL-terminated UTF-16 string, or NULL on error
/// @return 0 on success, or libuv error code
int utf8_to_utf16(const char *utf8, int utf8len, wchar_t **utf16)
 FUNC_ATTR_NONNULL_ALL
{
 // Compute the length needed for the converted UTF-16 string.
 int bufsize = MultiByteToWideChar(CP_UTF8,
                                   0,     // dwFlags: must be 0 for UTF-8
                                   utf8,  // -1: process up to NUL
                                   utf8len,
                                   NULL,
                                   0);    // 0: get length, don't convert
 if (bufsize == 0) {
   *utf16 = NULL;
   return uv_translate_sys_error(GetLastError());
 }

 // Allocate the destination buffer adding an extra byte for the terminating
 // NULL. If `utf8len` is not -1 MultiByteToWideChar will not add it, so
 // we do it ourselves always, just in case.
 *utf16 = xmalloc(sizeof(wchar_t) * (bufsize + 1));

 // Convert to UTF-16.
 bufsize = MultiByteToWideChar(CP_UTF8, 0, utf8, utf8len, *utf16, bufsize);
 if (bufsize == 0) {
   XFREE_CLEAR(*utf16);
   return uv_translate_sys_error(GetLastError());
 }

 (*utf16)[bufsize] = L'\0';
 return 0;
}

/// Converts string from UTF-16 to UTF-8.
///
/// @param utf16  UTF-16 string.
/// @param utf16len  Length of `utf16`. May be -1 if `utf16` is NUL-terminated.
/// @param utf8[out,allocated]  NUL-terminated UTF-8 string, or NULL on error
/// @return 0 on success, or libuv error code
int utf16_to_utf8(const wchar_t *utf16, int utf16len, char **utf8)
 FUNC_ATTR_NONNULL_ALL
{
 // Compute the space needed for the converted UTF-8 string.
 DWORD bufsize = WideCharToMultiByte(CP_UTF8,
                                     0,
                                     utf16,
                                     utf16len,
                                     NULL,
                                     0,
                                     NULL,
                                     NULL);
 if (bufsize == 0) {
   *utf8 = NULL;
   return uv_translate_sys_error(GetLastError());
 }

 // Allocate the destination buffer adding an extra byte for the terminating
 // NULL. If `utf16len` is not -1 WideCharToMultiByte will not add it, so
 // we do it ourselves always, just in case.
 *utf8 = xmalloc(bufsize + 1);

 // Convert to UTF-8.
 bufsize = WideCharToMultiByte(CP_UTF8,
                               0,
                               utf16,
                               utf16len,
                               *utf8,
                               bufsize,
                               NULL,
                               NULL);
 if (bufsize == 0) {
   XFREE_CLEAR(*utf8);
   return uv_translate_sys_error(GetLastError());
 }

 (*utf8)[bufsize] = NUL;
 return 0;
}

#endif

/// Measure the length of a string in corresponding UTF-32 and UTF-16 units.
///
/// Invalid UTF-8 bytes, or embedded surrogates, count as one code point/unit
/// each.
///
/// The out parameters are incremented. This is used to measure the size of
/// a buffer region consisting of multiple line segments.
///
/// @param s the string
/// @param len maximum length (an earlier NUL terminates)
/// @param[out] codepoints incremented with UTF-32 code point size
/// @param[out] codeunits incremented with UTF-16 code unit size
void mb_utflen(const char *s, size_t len, size_t *codepoints, size_t *codeunits)
 FUNC_ATTR_NONNULL_ALL
{
 size_t count = 0;
 size_t extra = 0;
 size_t clen;
 for (size_t i = 0; i < len; i += clen) {
   clen = (size_t)utf_ptr2len_len(s + i, (int)(len - i));
   // NB: gets the byte value of invalid sequence bytes.
   // we only care whether the char fits in the BMP or not
   int c = (clen > 1) ? utf_ptr2char(s + i) : (uint8_t)s[i];
   count++;
   if (c > 0xFFFF) {
     extra++;
   }
 }
 *codepoints += count;
 *codeunits += count + extra;
}

ssize_t mb_utf_index_to_bytes(const char *s, size_t len, size_t index, bool use_utf16_units)
 FUNC_ATTR_NONNULL_ALL
{
 size_t count = 0;
 size_t clen;
 if (index == 0) {
   return 0;
 }
 for (size_t i = 0; i < len; i += clen) {
   clen = (size_t)utf_ptr2len_len(s + i, (int)(len - i));
   // NB: gets the byte value of invalid sequence bytes.
   // we only care whether the char fits in the BMP or not
   int c = (clen > 1) ? utf_ptr2char(s + i) : (uint8_t)s[i];
   count++;
   if (use_utf16_units && c > 0xFFFF) {
     count++;
   }
   if (count >= index) {
     return (ssize_t)(i + clen);
   }
 }
 return -1;
}

/// Version of strnicmp() that handles multi-byte characters.
/// Needed for Big5, Shift-JIS and UTF-8 encoding.  Other DBCS encodings can
/// probably use strnicmp(), because there are no ASCII characters in the
/// second byte.
///
/// @return  zero if s1 and s2 are equal (ignoring case), the difference between
///          two characters otherwise.
int mb_strnicmp(const char *s1, const char *s2, const size_t nn)
{
 return utf_strnicmp(s1, s2, nn, nn);
}

/// Compare strings case-insensitively
///
/// @note We need to call mb_stricmp() even when we aren't dealing with
///       a multi-byte encoding because mb_stricmp() takes care of all ASCII and
///       non-ascii encodings, including characters with umlauts in latin1,
///       etc., while STRICMP() only handles the system locale version, which
///       often does not handle non-ascii properly.
///
/// @param[in]  s1  First string to compare, not more then #MAXCOL characters.
/// @param[in]  s2  Second string to compare, not more then #MAXCOL characters.
///
/// @return 0 if strings are equal, <0 if s1 < s2, >0 if s1 > s2.
int mb_stricmp(const char *s1, const char *s2)
{
 return mb_strnicmp(s1, s2, MAXCOL);
}

// "g8": show bytes of the UTF-8 char under the cursor.  Doesn't matter what
// 'encoding' has been set to.
void show_utf8(void)
{
 // Get the byte length of the char under the cursor, including composing
 // characters.
 char *line = get_cursor_pos_ptr();
 int len = utfc_ptr2len(line);
 if (len == 0) {
   msg("NUL", 0);
   return;
 }

 size_t rlen = 0;
 int clen = 0;
 for (int i = 0; i < len; i++) {
   if (clen == 0) {
     // start of (composing) character, get its length
     if (i > 0) {
       STRCPY(IObuff + rlen, "+ ");
       rlen += 2;
     }
     clen = utf_ptr2len(line + i);
   }
   assert(IOSIZE > rlen);
   snprintf(IObuff + rlen, IOSIZE - rlen, "%02x ",
            (line[i] == NL) ? NUL : (uint8_t)line[i]);  // NUL is stored as NL
   clen--;
   rlen += strlen(IObuff + rlen);
   if (rlen > IOSIZE - 20) {
     break;
   }
 }

 msg(IObuff, 0);
}

/// @return true if boundclass bc always starts a new cluster regardless of what's before
/// false negatives are allowed (perf cost, not correctness)
static bool always_break(int bc)
{
 return (bc == UTF8PROC_BOUNDCLASS_CONTROL);
}

/// @return true if bc2 always starts a cluster after bc1
/// false negatives are allowed (perf cost, not correctness)
static bool always_break_two(int bc1, int bc2)
{
 // don't check for UTF8PROC_BOUNDCLASS_CONTROL for bc2 as it either has been checked by
 // "always_break" on first iteration or when it was bc1 in the previous iteration
 return ((bc1 != UTF8PROC_BOUNDCLASS_PREPEND && bc2 == UTF8PROC_BOUNDCLASS_OTHER)
         || (bc1 >= UTF8PROC_BOUNDCLASS_CR && bc1 <= UTF8PROC_BOUNDCLASS_CONTROL)
         || (bc2 == UTF8PROC_BOUNDCLASS_EXTENDED_PICTOGRAPHIC
             && (bc1 == UTF8PROC_BOUNDCLASS_OTHER
                 || bc1 == UTF8PROC_BOUNDCLASS_EXTENDED_PICTOGRAPHIC)));
}

/// Return offset from "p" to the start of a character, including composing characters.
/// "base" must be the start of the string, which must be NUL terminated.
/// If "p" points to the NUL at the end of the string return 0.
/// Returns 0 when already at the first byte of a character.
int utf_head_off(const char *base_in, const char *p_in)
{
 if ((uint8_t)(*p_in) < 0x80) {              // be quick for ASCII
   return 0;
 }

 const uint8_t *base = (uint8_t *)base_in;
 const uint8_t *p = (uint8_t *)p_in;

 const uint8_t *start = p;

 // move start to the first byte of this codepoint
 // might stop on a continuation byte if overlong, handled by utf_ptr2CharInfo_impl
 while (start > base && (*start & 0xc0) == 0x80 && (p - start) < 6) {
   start--;
 }

 const uint8_t last_len = utf8len_tab[*start];
 int32_t cur_code = utf_ptr2CharInfo_impl(start, (uintptr_t)last_len);
 if (cur_code < 0 || p - start >= last_len) {
   return 0;  // p must be part of an illegal sequence
 }
 const uint8_t * const safe_end = start + last_len;

 int cur_bc = utf8proc_get_property(cur_code)->boundclass;
 if (always_break(cur_bc) || start == base) {
   return (int)(p - start);
 }

 // backtrack to find the start of a cluster. we might go too far, checked in the next loop
 const uint8_t *cur_pos = start;
 const uint8_t *const p_start = start;

 while (true) {
   if (start[-1] == NUL) {
     break;
   }

   start--;
   if (*start < 0x80) {  // stop on ascii, we are done
     break;
   }

   while (start > base && (*start & 0xc0) == 0x80 && (cur_pos - start) < 6) {
     start--;
   }

   int prev_len = utf8len_tab[*start];
   int32_t prev_code = utf_ptr2CharInfo_impl(start, (uintptr_t)prev_len);
   if (prev_code < 0 || prev_len < cur_pos - start) {
     start = cur_pos;  // start at valid sequence after invalid bytes
     break;
   }

   int prev_bc = utf8proc_get_property(prev_code)->boundclass;
   if (always_break_two(prev_bc, cur_bc) && !arabic_combine(prev_code, cur_code)) {
     start = cur_pos;  // prev_code cannot be a part of this cluster
     break;
   } else if (start == base) {
     break;
   }
   cur_pos = start;
   cur_bc = prev_bc;
   cur_code = prev_code;
 }

 // hot path: we are already on the first codepoint of a sequence
 if (start == p_start && last_len > p - start) {
   return (int)(p - start);
 }

 const uint8_t *q = start;
 while (q < p) {
   // don't need to find end of cluster. once we reached the codepoint of p, we are done
   int len = utfc_ptr2len_len((const char *)q, (int)(safe_end - q));

   if (q + len > p) {
     return (int)(p - q);
   }

   q += len;
 }

 return 0;
}

/// Assumes caller already handles ascii. see `utfc_next`
StrCharInfo utfc_next_impl(StrCharInfo cur)
{
 int32_t prev_code = cur.chr.value;
 uint8_t *next = (uint8_t *)(cur.ptr + cur.chr.len);
 GraphemeState state = GRAPHEME_STATE_INIT;
 assert(*next >= 0x80);

 while (true) {
   uint8_t const next_len = utf8len_tab[*next];
   int32_t const next_code = utf_ptr2CharInfo_impl(next, (uintptr_t)next_len);
   if (!utf_iscomposing(prev_code, next_code, &state)) {
     return (StrCharInfo){
       .ptr = (char *)next,
       .chr = (CharInfo){ .value = next_code, .len = (next_code < 0 ? 1 : next_len) },
     };
   }

   prev_code = next_code;
   next += next_len;
   if (EXPECT(*next < 0x80U, true)) {
     return (StrCharInfo){
       .ptr = (char *)next,
       .chr = (CharInfo){ .value = *next, .len = 1 },
     };
   }
 }
}

// Whether space is NOT allowed before/after 'c'.
bool utf_eat_space(int cc)
 FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
{
 return (cc >= 0x2000 && cc <= 0x206F)   // General punctuations
        || (cc >= 0x2e00 && cc <= 0x2e7f)   // Supplemental punctuations
        || (cc >= 0x3000 && cc <= 0x303f)   // CJK symbols and punctuations
        || (cc >= 0xff01 && cc <= 0xff0f)   // Full width ASCII punctuations
        || (cc >= 0xff1a && cc <= 0xff20)   // ..
        || (cc >= 0xff3b && cc <= 0xff40)   // ..
        || (cc >= 0xff5b && cc <= 0xff65);  // ..
}

// Whether line break is allowed before "cc".
bool utf_allow_break_before(int cc)
 FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
{
 static const int BOL_prohibition_punct[] = {
   '!',
   '%',
   ')',
   ',',
   ':',
   ';',
   '>',
   '?',
   ']',
   '}',
   0x2019,  // ’ right single quotation mark
   0x201d,  // ” right double quotation mark
   0x2020,  // † dagger
   0x2021,  // ‡ double dagger
   0x2026,  // … horizontal ellipsis
   0x2030,  // ‰ per mille sign
   0x2031,  // ‱ per the thousand sign
   0x203c,  // ‼ double exclamation mark
   0x2047,  // ⁇ double question mark
   0x2048,  // ⁈ question exclamation mark
   0x2049,  // ⁉ exclamation question mark
   0x2103,  // ℃ degree celsius
   0x2109,  // ℉ degree fahrenheit
   0x3001,  // 、 ideographic comma
   0x3002,  // 。 ideographic full stop
   0x3009,  // 〉 right angle bracket
   0x300b,  // 》 right double angle bracket
   0x300d,  // 」 right corner bracket
   0x300f,  // 』 right white corner bracket
   0x3011,  // 】 right black lenticular bracket
   0x3015,  // 〕 right tortoise shell bracket
   0x3017,  // 〗 right white lenticular bracket
   0x3019,  // 〙 right white tortoise shell bracket
   0x301b,  // 〛 right white square bracket
   0xff01,  // ！ fullwidth exclamation mark
   0xff09,  // ） fullwidth right parenthesis
   0xff0c,  // ， fullwidth comma
   0xff0e,  // ． fullwidth full stop
   0xff1a,  // ： fullwidth colon
   0xff1b,  // ； fullwidth semicolon
   0xff1f,  // ？ fullwidth question mark
   0xff3d,  // ］ fullwidth right square bracket
   0xff5d,  // ｝ fullwidth right curly bracket
 };

 int first = 0;
 int last = ARRAY_SIZE(BOL_prohibition_punct) - 1;

 while (first < last) {
   const int mid = (first + last) / 2;

   if (cc == BOL_prohibition_punct[mid]) {
     return false;
   } else if (cc > BOL_prohibition_punct[mid]) {
     first = mid + 1;
   } else {
     last = mid - 1;
   }
 }

 return cc != BOL_prohibition_punct[first];
}

// Whether line break is allowed after "cc".
bool utf_allow_break_after(int cc)
 FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
{
 static const int EOL_prohibition_punct[] = {
   '(',
   '<',
   '[',
   '`',
   '{',
   // 0x2014,  // — em dash
   0x2018,     // ‘ left single quotation mark
   0x201c,     // “ left double quotation mark
   // 0x2053,  // ～ swung dash
   0x3008,     // 〈 left angle bracket
   0x300a,     // 《 left double angle bracket
   0x300c,     // 「 left corner bracket
   0x300e,     // 『 left white corner bracket
   0x3010,     // 【 left black lenticular bracket
   0x3014,     // 〔 left tortoise shell bracket
   0x3016,     // 〖 left white lenticular bracket
   0x3018,     // 〘 left white tortoise shell bracket
   0x301a,     // 〚 left white square bracket
   0xff08,     // （ fullwidth left parenthesis
   0xff3b,     // ［ fullwidth left square bracket
   0xff5b,     // ｛ fullwidth left curly bracket
 };

 int first = 0;
 int last = ARRAY_SIZE(EOL_prohibition_punct) - 1;

 while (first < last) {
   const int mid = (first + last)/2;

   if (cc == EOL_prohibition_punct[mid]) {
     return false;
   } else if (cc > EOL_prohibition_punct[mid]) {
     first = mid + 1;
   } else {
     last = mid - 1;
   }
 }

 return cc != EOL_prohibition_punct[first];
}

// Whether line break is allowed between "cc" and "ncc".
bool utf_allow_break(int cc, int ncc)
 FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
{
 // don't break between two-letter punctuations
 if (cc == ncc
     && (cc == 0x2014         // em dash
         || cc == 0x2026)) {  // horizontal ellipsis
   return false;
 }
 return utf_allow_break_after(cc) && utf_allow_break_before(ncc);
}

/// Copy a character, advancing the pointers
///
/// @param[in,out]  fp  Source of the character to copy.
/// @param[in,out]  tp  Destination to copy to.
void mb_copy_char(const char **const fp, char **const tp)
{
 const size_t l = (size_t)utfc_ptr2len(*fp);

 memmove(*tp, *fp, l);
 *tp += l;
 *fp += l;
}

/// Return the offset from "p" to the first byte of a character.  When "p" is
/// at the start of a character 0 is returned, otherwise the offset to the next
/// character.  Can start anywhere in a stream of bytes.
int mb_off_next(const char *base, const char *p)
{
 int head_off = utf_head_off(base, p);

 if (head_off == 0) {
   return 0;
 }

 return utfc_ptr2len(p - head_off) - head_off;
}

/// Returns the offset in bytes from "p_in" to the first and one-past-end bytes
/// of the codepoint it points to.
/// "p_in" can point anywhere in a stream of bytes.
/// "p_len" limits number of bytes after "p_in".
/// Note: Counts individual codepoints of composed characters separately.
CharBoundsOff utf_cp_bounds_len(char const *base, char const *p_in, int p_len)
 FUNC_ATTR_PURE FUNC_ATTR_NONNULL_ALL
{
 assert(base <= p_in && p_len > 0);
 uint8_t const *const b = (uint8_t *)base;
 uint8_t const *const p = (uint8_t *)p_in;
 if (*p < 0x80U) {  // be quick for ASCII
   return (CharBoundsOff){ 0, 1 };
 }

 int const max_first_off = -MIN((int)(p - b), MB_MAXCHAR - 1);
 int first_off = 0;
 for (; utf_is_trail_byte(p[first_off]); first_off--) {
   if (first_off == max_first_off) {  // failed to find first byte
     return (CharBoundsOff){ 0, 1 };
   }
 }

 int const max_end_off = utf8len_tab[p[first_off]] + first_off;
 if (max_end_off <= 0 || max_end_off > p_len) {  // illegal or incomplete sequence
   return (CharBoundsOff){ 0, 1 };
 }

 for (int end_off = 1; end_off < max_end_off; end_off++) {
   if (!utf_is_trail_byte(p[end_off])) {  // not enough trail bytes
     return (CharBoundsOff){ 0, 1 };
   }
 }

 return (CharBoundsOff){ .begin_off = (int8_t)-first_off, .end_off = (int8_t)max_end_off };
}

/// Returns the offset in bytes from "p_in" to the first and one-past-end bytes
/// of the codepoint it points to.
/// "p_in" can point anywhere in a stream of bytes.
/// Stream must be NUL-terminated.
/// Note: Counts individual codepoints of composed characters separately.
CharBoundsOff utf_cp_bounds(char const *base, char const *p_in)
 FUNC_ATTR_PURE FUNC_ATTR_NONNULL_ALL
{
 return utf_cp_bounds_len(base, p_in, INT_MAX);
}

// Find the next illegal byte sequence.
void utf_find_illegal(void)
{
 pos_T pos = curwin->w_cursor;
 vimconv_T vimconv;
 char *tofree = NULL;

 vimconv.vc_type = CONV_NONE;
 if (enc_canon_props(curbuf->b_p_fenc) & ENC_8BIT) {
   // 'encoding' is "utf-8" but we are editing a 8-bit encoded file,
   // possibly a utf-8 file with illegal bytes.  Setup for conversion
   // from utf-8 to 'fileencoding'.
   convert_setup(&vimconv, p_enc, curbuf->b_p_fenc);
 }

 curwin->w_cursor.coladd = 0;
 while (true) {
   char *p = get_cursor_pos_ptr();
   if (vimconv.vc_type != CONV_NONE) {
     xfree(tofree);
     tofree = string_convert(&vimconv, p, NULL);
     if (tofree == NULL) {
       break;
     }
     p = tofree;
   }

   while (*p != NUL) {
     // Illegal means that there are not enough trail bytes (checked by
     // utf_ptr2len()) or too many of them (overlong sequence).
     int len = utf_ptr2len(p);
     if ((uint8_t)(*p) >= 0x80 && (len == 1 || utf_char2len(utf_ptr2char(p)) != len)) {
       if (vimconv.vc_type == CONV_NONE) {
         curwin->w_cursor.col += (colnr_T)(p - get_cursor_pos_ptr());
       } else {
         int l;

         len = (int)(p - tofree);
         for (p = get_cursor_pos_ptr(); *p != NUL && len-- > 0; p += l) {
           l = utf_ptr2len(p);
           curwin->w_cursor.col += l;
         }
       }
       goto theend;
     }
     p += len;
   }
   if (curwin->w_cursor.lnum == curbuf->b_ml.ml_line_count) {
     break;
   }
   curwin->w_cursor.lnum++;
   curwin->w_cursor.col = 0;
 }

 // didn't find it: don't move and beep
 curwin->w_cursor = pos;
 beep_flush();

theend:
 xfree(tofree);
 convert_setup(&vimconv, NULL, NULL);
}

/// @return  true if string "s" is a valid utf-8 string.
/// When "end" is NULL stop at the first NUL.  Otherwise stop at "end".
bool utf_valid_string(const char *s, const char *end)
{
 const uint8_t *p = (uint8_t *)s;

 while (end == NULL ? *p != NUL : p < (uint8_t *)end) {
   int l = utf8len_tab_zero[*p];
   if (l == 0) {
     return false;  // invalid lead byte
   }
   if (end != NULL && p + l > (uint8_t *)end) {
     return false;  // incomplete byte sequence
   }
   p++;
   while (--l > 0) {
     if ((*p++ & 0xc0) != 0x80) {
       return false;  // invalid trail byte
     }
   }
 }
 return true;
}

// If the cursor moves on an trail byte, set the cursor on the lead byte.
// Thus it moves left if necessary.
void mb_adjust_cursor(void)
{
 mark_mb_adjustpos(curbuf, &curwin->w_cursor);
}

/// Checks and adjusts cursor column. Not mode-dependent.
/// @see check_cursor_col
///
/// @param  win_  Places cursor on a valid column for this window.
void mb_check_adjust_col(void *win_)
{
 win_T *win = (win_T *)win_;
 colnr_T oldcol = win->w_cursor.col;

 // Column 0 is always valid.
 if (oldcol != 0) {
   char *p = ml_get_buf(win->w_buffer, win->w_cursor.lnum);
   colnr_T len = (colnr_T)strlen(p);

   // Empty line or invalid column?
   if (len == 0 || oldcol < 0) {
     win->w_cursor.col = 0;
   } else {
     // Cursor column too big for line?
     if (oldcol > len) {
       win->w_cursor.col = len - 1;
     }
     // Move the cursor to the head byte.
     win->w_cursor.col -= utf_head_off(p, p + win->w_cursor.col);
   }

   // Reset `coladd` when the cursor would be on the right half of a
   // double-wide character.
   if (win->w_cursor.coladd == 1 && p[win->w_cursor.col] != TAB
       && vim_isprintc(utf_ptr2char(p + win->w_cursor.col))
       && ptr2cells(p + win->w_cursor.col) > 1) {
     win->w_cursor.coladd = 0;
   }
 }
}

/// @param line  start of the string
///
/// @return      a pointer to the character before "*p", if there is one.
char *mb_prevptr(char *line, char *p)
{
 if (p > line) {
   MB_PTR_BACK(line, p);
 }
 return p;
}

/// Return the character length of "str".  Each multi-byte character (with
/// following composing characters) counts as one.
int mb_charlen(const char *str)
{
 const char *p = str;
 int count;

 if (p == NULL) {
   return 0;
 }

 for (count = 0; *p != NUL; count++) {
   p += utfc_ptr2len(p);
 }

 return count;
}

/// Like mb_charlen() but for a string with specified length.
int mb_charlen_len(const char *str, int len)
{
 const char *p = str;
 int count;

 for (count = 0; *p != NUL && p < str + len; count++) {
   p += utfc_ptr2len(p);
 }

 return count;
}

/// Try to unescape a multibyte character
///
/// Used for the rhs and lhs of the mappings.
///
/// @param[in,out]  pp  String to unescape. Is advanced to just after the bytes
///                     that form a multibyte character.
///
/// @return Unescaped string if it is a multibyte character, NULL if no
///         multibyte character was found. Returns a static buffer, always one
///         and the same.
const char *mb_unescape(const char **const pp)
 FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
{
 static char buf[6];
 size_t buf_idx = 0;
 uint8_t *str = (uint8_t *)(*pp);

 // Must translate K_SPECIAL KS_SPECIAL KE_FILLER to K_SPECIAL.
 // Maximum length of a utf-8 character is 4 bytes.
 for (size_t str_idx = 0; str[str_idx] != NUL && buf_idx < 4; str_idx++) {
   if (str[str_idx] == K_SPECIAL
       && str[str_idx + 1] == KS_SPECIAL
       && str[str_idx + 2] == KE_FILLER) {
     buf[buf_idx++] = (char)K_SPECIAL;
     str_idx += 2;
   } else if (str[str_idx] == K_SPECIAL) {
     break;  // A special key can't be a multibyte char.
   } else {
     buf[buf_idx++] = (char)str[str_idx];
   }
   buf[buf_idx] = NUL;

   // Return a multi-byte character if it's found.  An illegal sequence
   // will result in a 1 here.
   if (utf_ptr2len(buf) > 1) {
     *pp = (const char *)str + str_idx + 1;
     return buf;
   }

   // Bail out quickly for ASCII.
   if ((uint8_t)buf[0] < 128) {
     break;
   }
 }
 return NULL;
}

/// Skip the Vim specific head of a 'encoding' name.
char *enc_skip(char *p)
{
 if (strncmp(p, "2byte-", 6) == 0) {
   return p + 6;
 }
 if (strncmp(p, "8bit-", 5) == 0) {
   return p + 5;
 }
 return p;
}

/// Find the canonical name for encoding "enc".
/// When the name isn't recognized, returns "enc" itself, but with all lower
/// case characters and '_' replaced with '-'.
///
/// @return  an allocated string.
char *enc_canonize(char *enc)
 FUNC_ATTR_NONNULL_RET
{
 if (strcmp(enc, "default") == 0) {
   // Use the default encoding as found by set_init_1().
   return xstrdup(fenc_default);
 }

 // copy "enc" to allocated memory, with room for two '-'
 char *r = xmalloc(strlen(enc) + 3);
 // Make it all lower case and replace '_' with '-'.
 char *p = r;
 for (char *s = enc; *s != NUL; s++) {
   if (*s == '_') {
     *p++ = '-';
   } else {
     *p++ = (char)TOLOWER_ASC(*s);
   }
 }
 *p = NUL;

 // Skip "2byte-" and "8bit-".
 p = enc_skip(r);

 // Change "microsoft-cp" to "cp".  Used in some spell files.
 if (strncmp(p, "microsoft-cp", 12) == 0) {
   STRMOVE(p, p + 10);
 }

 // "iso8859" -> "iso-8859"
 if (strncmp(p, "iso8859", 7) == 0) {
   STRMOVE(p + 4, p + 3);
   p[3] = '-';
 }

 // "iso-8859n" -> "iso-8859-n"
 if (strncmp(p, "iso-8859", 8) == 0 && p[8] != '-') {
   STRMOVE(p + 9, p + 8);
   p[8] = '-';
 }

 // "latin-N" -> "latinN"
 if (strncmp(p, "latin-", 6) == 0) {
   STRMOVE(p + 5, p + 6);
 }

 int i;
 if (enc_canon_search(p) >= 0) {
   // canonical name can be used unmodified
   if (p != r) {
     STRMOVE(r, p);
   }
 } else if ((i = enc_alias_search(p)) >= 0) {
   // alias recognized, get canonical name
   xfree(r);
   r = xstrdup(enc_canon_table[i].name);
 }
 return r;
}

/// Search for an encoding alias of "name".
/// Returns -1 when not found.
static int enc_alias_search(const char *name)
{
 for (int i = 0; enc_alias_table[i].name != NULL; i++) {
   if (strcmp(name, enc_alias_table[i].name) == 0) {
     return enc_alias_table[i].canon;
   }
 }
 return -1;
}

#ifdef HAVE_LANGINFO_H
# include <langinfo.h>
#endif

// Get the canonicalized encoding of the current locale.
// Returns an allocated string when successful, NULL when not.
char *enc_locale(void)
{
 int i;
 char buf[50];

 const char *s;

#ifdef HAVE_NL_LANGINFO_CODESET
 if (!(s = nl_langinfo(CODESET)) || *s == NUL)
#endif
 {
   if (!(s = setlocale(LC_CTYPE, NULL)) || *s == NUL) {
     if ((s = os_getenv_noalloc("LC_ALL"))) {
       if ((s = os_getenv_noalloc("LC_CTYPE"))) {
         s = os_getenv_noalloc("LANG");
       }
     }
   }
 }

 if (!s) {
   return NULL;
 }

 // The most generic locale format is:
 // language[_territory][.codeset][@modifier][+special][,[sponsor][_revision]]
 // If there is a '.' remove the part before it.
 // if there is something after the codeset, remove it.
 // Make the name lowercase and replace '_' with '-'.
 // Exception: "ja_JP.EUC" == "euc-jp", "zh_CN.EUC" = "euc-cn",
 // "ko_KR.EUC" == "euc-kr"
 const char *p = vim_strchr(s, '.');
 if (p != NULL) {
   if (p > s + 2 && !STRNICMP(p + 1, "EUC", 3)
       && !isalnum((uint8_t)p[4]) && p[4] != '-' && p[-3] == '_') {
     // Copy "XY.EUC" to "euc-XY" to buf[10].
     memmove(buf, "euc-", 4);
     buf[4] = (char)(ASCII_ISALNUM(p[-2]) ? TOLOWER_ASC(p[-2]) : 0);
     buf[5] = (char)(ASCII_ISALNUM(p[-1]) ? TOLOWER_ASC(p[-1]) : 0);
     buf[6] = NUL;
   } else {
     s = p + 1;
     goto enc_locale_copy_enc;
   }
 } else {
enc_locale_copy_enc:
   for (i = 0; i < (int)sizeof(buf) - 1 && s[i] != NUL; i++) {
     if (s[i] == '_' || s[i] == '-') {
       buf[i] = '-';
     } else if (ASCII_ISALNUM((uint8_t)s[i])) {
       buf[i] = (char)TOLOWER_ASC(s[i]);
     } else {
       break;
     }
   }
   buf[i] = NUL;
 }

 return enc_canonize(buf);
}

// Call iconv_open() with a check if iconv() works properly (there are broken
// versions).
// Returns (void *)-1 if failed.
// (should return iconv_t, but that causes problems with prototypes).
void *my_iconv_open(char *to, char *from)
{
#define ICONV_TESTLEN 400
 char tobuf[ICONV_TESTLEN];
 static WorkingStatus iconv_working = kUnknown;

 if (iconv_working == kBroken) {
   return (void *)-1;          // detected a broken iconv() previously
 }
 iconv_t fd = iconv_open(enc_skip(to), enc_skip(from));

 if (fd != (iconv_t)-1 && iconv_working == kUnknown) {
   // Do a dummy iconv() call to check if it actually works.  There is a
   // version of iconv() on Linux that is broken.  We can't ignore it,
   // because it's wide-spread.  The symptoms are that after outputting
   // the initial shift state the "to" pointer is NULL and conversion
   // stops for no apparent reason after about 8160 characters.
   char *p = tobuf;
   size_t tolen = ICONV_TESTLEN;
   iconv(fd, NULL, NULL, &p, &tolen);
   if (p == NULL) {
     iconv_working = kBroken;
     iconv_close(fd);
     fd = (iconv_t)-1;
   } else {
     iconv_working = kWorking;
   }
 }

 return (void *)fd;
}

// Convert the string "str[slen]" with iconv().
// If "unconvlenp" is not NULL handle the string ending in an incomplete
// sequence and set "*unconvlenp" to the length of it.
// Returns the converted string in allocated memory.  NULL for an error.
// If resultlenp is not NULL, sets it to the result length in bytes.
static char *iconv_string(const vimconv_T *const vcp, const char *str, size_t slen,
                         size_t *unconvlenp, size_t *resultlenp)
{
 char *to;
 size_t len = 0;
 size_t done = 0;
 char *result = NULL;

 const char *from = str;
 size_t fromlen = slen;
 while (true) {
   if (len == 0 || ICONV_ERRNO == ICONV_E2BIG) {
     // Allocate enough room for most conversions.  When re-allocating
     // increase the buffer size.
     len = len + fromlen * 2 + 40;
     char *p = xmalloc(len);
     if (done > 0) {
       memmove(p, result, done);
     }
     xfree(result);
     result = p;
   }

   to = result + done;
   size_t tolen = len - done - 2;
   // Avoid a warning for systems with a wrong iconv() prototype by
   // casting the second argument to void *.
   if (iconv(vcp->vc_fd, (void *)&from, &fromlen, &to, &tolen) != SIZE_MAX) {
     // Finished, append a NUL.
     *to = NUL;
     break;
   }

   // Check both ICONV_EINVAL and EINVAL, because the dynamically loaded
   // iconv library may use one of them.
   if (!vcp->vc_fail && unconvlenp != NULL
       && (ICONV_ERRNO == ICONV_EINVAL || ICONV_ERRNO == EINVAL)) {
     // Handle an incomplete sequence at the end.
     *to = NUL;
     *unconvlenp = fromlen;
     break;
   } else if (!vcp->vc_fail
              && (ICONV_ERRNO == ICONV_EILSEQ || ICONV_ERRNO == EILSEQ
                  || ICONV_ERRNO == ICONV_EINVAL || ICONV_ERRNO == EINVAL)) {
     // Check both ICONV_EILSEQ and EILSEQ, because the dynamically loaded
     // iconv library may use one of them.

     // Can't convert: insert a '?' and skip a character.  This assumes
     // conversion from 'encoding' to something else.  In other
     // situations we don't know what to skip anyway.
     *to++ = '?';
     if (utf_ptr2cells(from) > 1) {
       *to++ = '?';
     }
     int l = utfc_ptr2len_len(from, (int)fromlen);
     from += l;
     fromlen -= (size_t)l;
   } else if (ICONV_ERRNO != ICONV_E2BIG) {
     // conversion failed
     XFREE_CLEAR(result);
     break;
   }
   // Not enough room or skipping illegal sequence.
   done = (size_t)(to - result);
 }

 if (resultlenp != NULL && result != NULL) {
   *resultlenp = (size_t)(to - result);
 }
 return result;
}

/// iconv() function
void f_iconv(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
{
 vimconv_T vimconv;

 rettv->v_type = VAR_STRING;
 rettv->vval.v_string = NULL;

 const char *const str = tv_get_string(&argvars[0]);
 char buf1[NUMBUFLEN];
 char *const from = enc_canonize(enc_skip((char *)tv_get_string_buf(&argvars[1], buf1)));
 char buf2[NUMBUFLEN];
 char *const to = enc_canonize(enc_skip((char *)tv_get_string_buf(&argvars[2], buf2)));
 vimconv.vc_type = CONV_NONE;
 convert_setup(&vimconv, from, to);

 // If the encodings are equal, no conversion needed.
 if (vimconv.vc_type == CONV_NONE) {
   rettv->vval.v_string = xstrdup(str);
 } else {
   rettv->vval.v_string = string_convert(&vimconv, (char *)str, NULL);
 }

 convert_setup(&vimconv, NULL, NULL);
 xfree(from);
 xfree(to);
}

/// Setup "vcp" for conversion from "from" to "to".
/// The names must have been made canonical with enc_canonize().
/// vcp->vc_type must have been initialized to CONV_NONE.
/// Note: cannot be used for conversion from/to ucs-2 and ucs-4 (will use utf-8
/// instead).
/// Afterwards invoke with "from" and "to" equal to NULL to cleanup.
///
/// @return  FAIL when conversion is not supported, OK otherwise.
int convert_setup(vimconv_T *vcp, char *from, char *to)
{
 return convert_setup_ext(vcp, from, true, to, true);
}

/// As convert_setup(), but only when from_unicode_is_utf8 is true will all
/// "from" unicode charsets be considered utf-8.  Same for "to".
int convert_setup_ext(vimconv_T *vcp, char *from, bool from_unicode_is_utf8, char *to,
                     bool to_unicode_is_utf8)
{
 int from_is_utf8;
 int to_is_utf8;

 // Reset to no conversion.
 if (vcp->vc_type == CONV_ICONV && vcp->vc_fd != (iconv_t)-1) {
   iconv_close(vcp->vc_fd);
 }
 *vcp = (vimconv_T)MBYTE_NONE_CONV;

 // No conversion when one of the names is empty or they are equal.
 if (from == NULL || *from == NUL || to == NULL || *to == NUL
     || strcmp(from, to) == 0) {
   return OK;
 }

 int from_prop = enc_canon_props(from);
 int to_prop = enc_canon_props(to);
 if (from_unicode_is_utf8) {
   from_is_utf8 = from_prop & ENC_UNICODE;
 } else {
   from_is_utf8 = from_prop == ENC_UNICODE;
 }
 if (to_unicode_is_utf8) {
   to_is_utf8 = to_prop & ENC_UNICODE;
 } else {
   to_is_utf8 = to_prop == ENC_UNICODE;
 }

 if ((from_prop & ENC_LATIN1) && to_is_utf8) {
   // Internal latin1 -> utf-8 conversion.
   vcp->vc_type = CONV_TO_UTF8;
   vcp->vc_factor = 2;         // up to twice as long
 } else if ((from_prop & ENC_LATIN9) && to_is_utf8) {
   // Internal latin9 -> utf-8 conversion.
   vcp->vc_type = CONV_9_TO_UTF8;
   vcp->vc_factor = 3;         // up to three as long (euro sign)
 } else if (from_is_utf8 && (to_prop & ENC_LATIN1)) {
   // Internal utf-8 -> latin1 conversion.
   vcp->vc_type = CONV_TO_LATIN1;
 } else if (from_is_utf8 && (to_prop & ENC_LATIN9)) {
   // Internal utf-8 -> latin9 conversion.
   vcp->vc_type = CONV_TO_LATIN9;
 } else {
   // Use iconv() for conversion.
   vcp->vc_fd = (iconv_t)my_iconv_open(to_is_utf8 ? "utf-8" : to,
                                       from_is_utf8 ? "utf-8" : from);
   if (vcp->vc_fd != (iconv_t)-1) {
     vcp->vc_type = CONV_ICONV;
     vcp->vc_factor = 4;       // could be longer too...
   }
 }
 if (vcp->vc_type == CONV_NONE) {
   return FAIL;
 }

 return OK;
}

/// Convert text "ptr[*lenp]" according to "vcp".
/// Returns the result in allocated memory and sets "*lenp".
/// When "lenp" is NULL, use NUL terminated strings.
/// Illegal chars are often changed to "?", unless vcp->vc_fail is set.
/// When something goes wrong, NULL is returned and "*lenp" is unchanged.
char *string_convert(const vimconv_T *const vcp, char *ptr, size_t *lenp)
{
 return string_convert_ext(vcp, ptr, lenp, NULL);
}

// Like string_convert(), but when "unconvlenp" is not NULL and there are is
// an incomplete sequence at the end it is not converted and "*unconvlenp" is
// set to the number of remaining bytes.
char *string_convert_ext(const vimconv_T *const vcp, char *ptr, size_t *lenp, size_t *unconvlenp)
{
 uint8_t *retval = NULL;
 uint8_t *d;
 int c;

 size_t len;
 if (lenp == NULL) {
   len = strlen(ptr);
 } else {
   len = *lenp;
 }
 if (len == 0) {
   return xstrdup("");
 }

 switch (vcp->vc_type) {
 case CONV_TO_UTF8:            // latin1 to utf-8 conversion
   retval = xmalloc(len * 2 + 1);
   d = retval;
   for (size_t i = 0; i < len; i++) {
     c = (uint8_t)ptr[i];
     if (c < 0x80) {
       *d++ = (uint8_t)c;
     } else {
       *d++ = (uint8_t)(0xc0 + (uint8_t)((unsigned)c >> 6));
       *d++ = (uint8_t)(0x80 + (c & 0x3f));
     }
   }
   *d = NUL;
   if (lenp != NULL) {
     *lenp = (size_t)(d - retval);
   }
   break;

 case CONV_9_TO_UTF8:          // latin9 to utf-8 conversion
   retval = xmalloc(len * 3 + 1);
   d = retval;
   for (size_t i = 0; i < len; i++) {
     c = (uint8_t)ptr[i];
     switch (c) {
     case 0xa4:
       c = 0x20ac; break;                 // euro
     case 0xa6:
       c = 0x0160; break;                 // S hat
     case 0xa8:
       c = 0x0161; break;                 // S -hat
     case 0xb4:
       c = 0x017d; break;                 // Z hat
     case 0xb8:
       c = 0x017e; break;                 // Z -hat
     case 0xbc:
       c = 0x0152; break;                 // OE
     case 0xbd:
       c = 0x0153; break;                 // oe
     case 0xbe:
       c = 0x0178; break;                 // Y
     }
     d += utf_char2bytes(c, (char *)d);
   }
   *d = NUL;
   if (lenp != NULL) {
     *lenp = (size_t)(d - retval);
   }
   break;

 case CONV_TO_LATIN1:          // utf-8 to latin1 conversion
 case CONV_TO_LATIN9:          // utf-8 to latin9 conversion
   retval = xmalloc(len + 1);
   d = retval;
   for (size_t i = 0; i < len; i++) {
     int l = utf_ptr2len_len(ptr + i, (int)(len - i));
     if (l == 0) {
       *d++ = NUL;
     } else if (l == 1) {
       uint8_t l_w = utf8len_tab_zero[(uint8_t)ptr[i]];

       if (l_w == 0) {
         // Illegal utf-8 byte cannot be converted
         xfree(retval);
         return NULL;
       }
       if (unconvlenp != NULL && l_w > len - i) {
         // Incomplete sequence at the end.
         *unconvlenp = len - i;
         break;
       }
       *d++ = (uint8_t)ptr[i];
     } else {
       c = utf_ptr2char(ptr + i);
       if (vcp->vc_type == CONV_TO_LATIN9) {
         switch (c) {
         case 0x20ac:
           c = 0xa4; break;                     // euro
         case 0x0160:
           c = 0xa6; break;                     // S hat
         case 0x0161:
           c = 0xa8; break;                     // S -hat
         case 0x017d:
           c = 0xb4; break;                     // Z hat
         case 0x017e:
           c = 0xb8; break;                     // Z -hat
         case 0x0152:
           c = 0xbc; break;                     // OE
         case 0x0153:
           c = 0xbd; break;                     // oe
         case 0x0178:
           c = 0xbe; break;                     // Y
         case 0xa4:
         case 0xa6:
         case 0xa8:
         case 0xb4:
         case 0xb8:
         case 0xbc:
         case 0xbd:
         case 0xbe:
           c = 0x100; break;                   // not in latin9
         }
       }
       if (!utf_iscomposing_legacy(c)) {  // skip composing chars
         if (c < 0x100) {
           *d++ = (uint8_t)c;
         } else if (vcp->vc_fail) {
           xfree(retval);
           return NULL;
         } else {
           *d++ = 0xbf;
           if (utf_char2cells(c) > 1) {
             *d++ = '?';
           }
         }
       }
       i += (size_t)l - 1;
     }
   }
   *d = NUL;
   if (lenp != NULL) {
     *lenp = (size_t)(d - retval);
   }
   break;

 case CONV_ICONV:  // conversion with vcp->vc_fd
   retval = (uint8_t *)iconv_string(vcp, ptr, len, unconvlenp, lenp);
   break;
 }

 return (char *)retval;
}

/// Table set by setcellwidths().
typedef struct {
 int64_t first;
 int64_t last;
 char width;
} cw_interval_T;

static cw_interval_T *cw_table = NULL;
static size_t cw_table_size = 0;

/// Return the value of the cellwidth table for the character `c`.
///
/// @param c The source character.
/// @return 1 or 2 when `c` is in the cellwidth table, 0 if not.
static int cw_value(int c)
{
 if (cw_table == NULL) {
   return 0;
 }

 // first quick check for Latin1 etc. characters
 if (c < cw_table[0].first) {
   return 0;
 }

 // binary search in table
 int bot = 0;
 int top = (int)cw_table_size - 1;
 while (top >= bot) {
   int mid = (bot + top) / 2;
   if (cw_table[mid].last < c) {
     bot = mid + 1;
   } else if (cw_table[mid].first > c) {
     top = mid - 1;
   } else {
     return cw_table[mid].width;
   }
 }
 return 0;
}

static int tv_nr_compare(const void *a1, const void *a2)
{
 const listitem_T *const li1 = tv_list_first(*(const list_T **)a1);
 const listitem_T *const li2 = tv_list_first(*(const list_T **)a2);
 const varnumber_T n1 = TV_LIST_ITEM_TV(li1)->vval.v_number;
 const varnumber_T n2 = TV_LIST_ITEM_TV(li2)->vval.v_number;

 return n1 == n2 ? 0 : n1 > n2 ? 1 : -1;
}

/// "setcellwidths()" function
void f_setcellwidths(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
{
 if (argvars[0].v_type != VAR_LIST || argvars[0].vval.v_list == NULL) {
   emsg(_(e_listreq));
   return;
 }

 const list_T *const l = argvars[0].vval.v_list;
 cw_interval_T *table = NULL;
 const size_t table_size = (size_t)tv_list_len(l);
 if (table_size == 0) {
   // Clearing the table.
   goto update;
 }

 // Note: use list_T instead of listitem_T so that TV_LIST_ITEM_NEXT can be used properly below.
 const list_T **ptrs = xmalloc(sizeof(const list_T *) * table_size);

 // Check that all entries are a list with three numbers, the range is
 // valid and the cell width is valid.
 int item = 0;
 TV_LIST_ITER_CONST(l, li, {
   const typval_T *const li_tv = TV_LIST_ITEM_TV(li);

   if (li_tv->v_type != VAR_LIST || li_tv->vval.v_list == NULL) {
     semsg(_(e_list_item_nr_is_not_list), item);
     xfree((void *)ptrs);
     return;
   }

   const list_T *const li_l = li_tv->vval.v_list;
   ptrs[item] = li_l;
   const listitem_T *lili = tv_list_first(li_l);
   int i;
   varnumber_T n1;
   for (i = 0; lili != NULL; lili = TV_LIST_ITEM_NEXT(li_l, lili), i++) {
     const typval_T *const lili_tv = TV_LIST_ITEM_TV(lili);
     if (lili_tv->v_type != VAR_NUMBER) {
       break;
     }
     if (i == 0) {
       n1 = lili_tv->vval.v_number;
       if (n1 < 0x80) {
         emsg(_(e_only_values_of_0x80_and_higher_supported));
         xfree((void *)ptrs);
         return;
       }
     } else if (i == 1 && lili_tv->vval.v_number < n1) {
       semsg(_(e_list_item_nr_range_invalid), item);
       xfree((void *)ptrs);
       return;
     } else if (i == 2 && (lili_tv->vval.v_number < 1 || lili_tv->vval.v_number > 2)) {
       semsg(_(e_list_item_nr_cell_width_invalid), item);
       xfree((void *)ptrs);
       return;
     }
   }

   if (i != 3) {
     semsg(_(e_list_item_nr_does_not_contain_3_numbers), item);
     xfree((void *)ptrs);
     return;
   }

   item++;
 });

 // Sort the list on the first number.
 qsort((void *)ptrs, table_size, sizeof(const list_T *), tv_nr_compare);

 table = xmalloc(sizeof(cw_interval_T) * table_size);

 // Store the items in the new table.
 for (item = 0; (size_t)item < table_size; item++) {
   const list_T *const li_l = ptrs[item];
   const listitem_T *lili = tv_list_first(li_l);
   const varnumber_T n1 = TV_LIST_ITEM_TV(lili)->vval.v_number;
   if (item > 0 && n1 <= table[item - 1].last) {
     semsg(_(e_overlapping_ranges_for_nr), (size_t)n1);
     xfree((void *)ptrs);
     xfree(table);
     return;
   }
   table[item].first = n1;
   lili = TV_LIST_ITEM_NEXT(li_l, lili);
   table[item].last = TV_LIST_ITEM_TV(lili)->vval.v_number;
   lili = TV_LIST_ITEM_NEXT(li_l, lili);
   table[item].width = (char)TV_LIST_ITEM_TV(lili)->vval.v_number;
 }

 xfree((void *)ptrs);

update:
 ;
 cw_interval_T *const cw_table_save = cw_table;
 const size_t cw_table_size_save = cw_table_size;
 cw_table = table;
 cw_table_size = table_size;

 // Check that the new value does not conflict with 'listchars' or
 // 'fillchars'.
 const char *const error = check_chars_options();
 if (error != NULL) {
   emsg(_(error));
   cw_table = cw_table_save;
   cw_table_size = cw_table_size_save;
   xfree(table);
   return;
 }

 xfree(cw_table_save);
 changed_window_setting_all();
 redraw_all_later(UPD_NOT_VALID);
}

/// "getcellwidths()" function
void f_getcellwidths(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
{
 tv_list_alloc_ret(rettv, (ptrdiff_t)cw_table_size);

 for (size_t i = 0; i < cw_table_size; i++) {
   list_T *entry = tv_list_alloc(3);
   tv_list_append_number(entry, (varnumber_T)cw_table[i].first);
   tv_list_append_number(entry, (varnumber_T)cw_table[i].last);
   tv_list_append_number(entry, (varnumber_T)cw_table[i].width);

   tv_list_append_list(rettv->vval.v_list, entry);
 }
}

void f_charclass(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
{
 if (tv_check_for_string_arg(argvars, 0) == FAIL
     || argvars[0].vval.v_string == NULL) {
   return;
 }
 rettv->vval.v_number = mb_get_class(argvars[0].vval.v_string);
}

/// Function given to ExpandGeneric() to obtain the possible arguments of the
/// encoding options.
char *get_encoding_name(expand_T *xp FUNC_ATTR_UNUSED, int idx)
{
 if (idx >= (int)ARRAY_SIZE(enc_canon_table)) {
   return NULL;
 }

 return (char *)enc_canon_table[idx].name;
}

/// Compare strings
///
/// @param[in]  ic  True if case is to be ignored.
///
/// @return 0 if s1 == s2, <0 if s1 < s2, >0 if s1 > s2.
int mb_strcmp_ic(bool ic, const char *s1, const char *s2)
 FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
{
 return (ic ? mb_stricmp(s1, s2) : strcmp(s1, s2));
}