newlib-cygwin/newlib/libc/string/wcwidth.c

242 lines
7.9 KiB
C

/*
FUNCTION
<<wcwidth>>---number of column positions of a wide-character code
INDEX
wcwidth
SYNOPSIS
#include <wchar.h>
int wcwidth(const wint_t <[wc]>);
DESCRIPTION
The <<wcwidth>> function shall determine the number of column
positions required for the wide character <[wc]>. The application
shall ensure that the value of <[wc]> is a character representable
as a wint_t (combining Unicode surrogate pairs into single 21-bit
Unicode code points), and is a wide-character code corresponding to a
valid character in the current locale.
RETURNS
The <<wcwidth>> function shall either return 0 (if <[wc]> is a null
wide-character code), or return the number of column positions to
be occupied by the wide-character code <[wc]>, or return -1 (if <[wc]>
does not correspond to a printable wide-character code).
PORTABILITY
<<wcwidth>> has been introduced in the Single UNIX Specification Volume 2.
<<wcwidth>> has been marked as an extension in the Single UNIX Specification Volume 3.
*/
/*
* This is an implementation of wcwidth() (defined in
* IEEE Std 1002.1-2001) for Unicode.
*
* http://www.opengroup.org/onlinepubs/007904975/functions/wcwidth.html
*
* In fixed-width output devices, Latin characters all occupy a single
* "cell" position of equal width, whereas ideographic CJK characters
* occupy two such cells. Interoperability between terminal-line
* applications and (teletype-style) character terminals using the
* UTF-8 encoding requires agreement on which character should advance
* the cursor by how many cell positions. No established formal
* standards exist at present on which Unicode character shall occupy
* how many cell positions on character terminals. These routines are
* a first attempt of defining such behavior based on simple rules
* applied to data provided by the Unicode Consortium.
*
* For some graphical characters, the Unicode standard explicitly
* defines a character-cell width via the definition of the East Asian
* FullWidth (F), Wide (W), Half-width (H), and Narrow (Na) classes.
* In all these cases, there is no ambiguity about which width a
* terminal shall use. For characters in the East Asian Ambiguous (A)
* class, the width choice depends purely on a preference of backward
* compatibility with either historic CJK or Western practice.
* Choosing single-width for these characters is easy to justify as
* the appropriate long-term solution, as the CJK practice of
* displaying these characters as double-width comes from historic
* implementation simplicity (8-bit encoded characters were displayed
* single-width and 16-bit ones double-width, even for Greek,
* Cyrillic, etc.) and not any typographic considerations.
*
* Much less clear is the choice of width for the Not East Asian
* (Neutral) class. Existing practice does not dictate a width for any
* of these characters. It would nevertheless make sense
* typographically to allocate two character cells to characters such
* as for instance EM SPACE or VOLUME INTEGRAL, which cannot be
* represented adequately with a single-width glyph. The following
* routines at present merely assign a single-cell width to all
* neutral characters, in the interest of simplicity. This is not
* entirely satisfactory and should be reconsidered before
* establishing a formal standard in this area. At the moment, the
* decision which Not East Asian (Neutral) characters should be
* represented by double-width glyphs cannot yet be answered by
* applying a simple rule from the Unicode database content. Setting
* up a proper standard for the behavior of UTF-8 character terminals
* will require a careful analysis not only of each Unicode character,
* but also of each presentation form, something the author of these
* routines has avoided to do so far.
*
* http://www.unicode.org/unicode/reports/tr11/
*
* Markus Kuhn -- 2007-05-26 (Unicode 5.0)
*
* Permission to use, copy, modify, and distribute this software
* for any purpose and without fee is hereby granted. The author
* disclaims all warranties with regard to this software.
*
* Latest version: http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
*/
#include <_ansi.h>
#include <wchar.h>
#ifndef _MB_CAPABLE
#include <wctype.h> /* iswprint, iswcntrl */
#endif
#include "local.h"
#ifdef _MB_CAPABLE
struct interval
{
int first;
int last;
};
/* auxiliary function for binary search in interval table */
static int
bisearch(wint_t ucs, const struct interval *table, int max)
{
int min = 0;
int mid;
if (ucs < table[0].first || ucs > table[max].last)
return 0;
while (max >= min)
{
mid = (min + max) / 2;
if (ucs > table[mid].last)
min = mid + 1;
else if (ucs < table[mid].first)
max = mid - 1;
else
return 1;
}
return 0;
}
#endif /* _MB_CAPABLE */
/* The following function defines the column width of an ISO 10646
* character as follows:
*
* - The null character (U+0000) has a column width of 0.
*
* - Other C0/C1 control characters and DEL will lead to a return
* value of -1.
*
* - If the current language is recognized as a language usually using
* CJK fonts, spacing characters in the East Asian Ambiguous (A)
* category as defined in Unicode Technical Report #11 have a column
* width of 2.
*
* - Non-spacing and enclosing combining characters (general
* category code Mn or Me in the Unicode database) have a
* column width of 0.
*
* - SOFT HYPHEN (U+00AD) has a column width of 1.
*
* - Other format characters (general category code Cf in the Unicode
* database) and ZERO WIDTH SPACE (U+200B) have a column width of 0.
*
* - Hangul Jamo medial vowels and final consonants (U+1160-U+11FF)
* have a column width of 0.
*
* - Spacing characters in the East Asian Wide (W) or East Asian
* Full-width (F) category as defined in Unicode Technical
* Report #11 have a column width of 2.
*
* - All remaining characters (including all printable
* ISO 8859-1 and WGL4 characters, Unicode control characters,
* etc.) have a column width of 1.
*
* This implementation assumes that wint_t characters are encoded
* in ISO 10646.
*/
int
__wcwidth (const wint_t ucs)
{
#ifdef _MB_CAPABLE
/* sorted list of non-overlapping intervals of East Asian Ambiguous chars */
static const struct interval ambiguous[] =
#include "ambiguous.t"
/* sorted list of non-overlapping intervals of non-spacing characters */
static const struct interval combining[] =
#include "combining.t"
/* sorted list of non-overlapping intervals of wide characters,
ranges extended to Blocks where possible
*/
static const struct interval wide[] =
#include "wide.t"
/* Test for NUL character */
if (ucs == 0)
return 0;
/* Test for printable ASCII characters */
if (ucs >= 0x20 && ucs < 0x7f)
return 1;
/* Test for control characters */
if (ucs < 0xa0)
return -1;
/* Test for surrogate pair values. */
if (ucs >= 0xd800 && ucs <= 0xdfff)
return -1;
/* check CJK width mode (1: ambiguous-wide, 0: normal, -1: disabled) */
int cjk_lang = __locale_cjk_lang ();
/* binary search in table of ambiguous characters */
if (cjk_lang > 0
&& bisearch(ucs, ambiguous,
sizeof(ambiguous) / sizeof(struct interval) - 1))
return 2;
/* binary search in table of non-spacing characters */
if (bisearch(ucs, combining,
sizeof(combining) / sizeof(struct interval) - 1))
return 0;
/* if we arrive here, ucs is not a combining or C0/C1 control character */
/* binary search in table of wide character codes */
if (cjk_lang >= 0
&& bisearch(ucs, wide,
sizeof(wide) / sizeof(struct interval) - 1))
return 2;
else
return 1;
#else /* !_MB_CAPABLE */
if (iswprint (ucs))
return 1;
if (iswcntrl (ucs) || ucs == L'\0')
return 0;
return -1;
#endif /* _MB_CAPABLE */
}
int
wcwidth (const wint_t wc)
{
wint_t wi = wc;
#ifdef _MB_CAPABLE
wi = _jp2uc (wi);
#endif /* _MB_CAPABLE */
return __wcwidth (wi);
}