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