path: root/doc/unicase.texi

@node unicase.h
@chapter Case mappings @code{<unicase.h>}

This include file defines functions for case mapping for Unicode strings and
case insensitive comparison of Unicode strings and C strings.

These string functions fix the problems that were mentioned in
@ref{char * strings}, namely, they handle the Croatian
@sc{LETTER DZ WITH CARON}, the German @sc{LATIN SMALL LETTER SHARP S}, the
Greek sigma and the Lithuanian i correctly.

@menu
* Case mappings of characters::
* Case mappings of strings::
* Case insensitive comparison::
* Case detection::
@end menu

@node Case mappings of characters
@section Case mappings of characters

@cindex Unicode character, case mappings
The following functions implement case mappings on Unicode characters ---
for those cases only where the result of the mapping is a again a single
Unicode character.

These mappings are locale and context independent.

@cartouche
@strong{WARNING!} These functions are not sufficient for languages such as
German, Greek and Lithuanian.  Better use the functions below that treat an
entire string at once and are language aware.
@end cartouche

@deftypefun ucs4_t uc_toupper (ucs4_t @var{uc})
Returns the uppercase mapping of the Unicode character @var{uc}.
@end deftypefun

@deftypefun ucs4_t uc_tolower (ucs4_t @var{uc})
Returns the lowercase mapping of the Unicode character @var{uc}.
@end deftypefun

@deftypefun ucs4_t uc_totitle (ucs4_t @var{uc})
Returns the titlecase mapping of the Unicode character @var{uc}.

The titlecase mapping of a character is to be used when the character should
look like upper case and the following characters are lower cased.

For most characters, this is the same as the uppercase mapping.  There are
only few characters where the title case variant and the uuper case variant
are different.  These characters occur in the Latin writing of the Croatian,
Bosnian, and Serbian languages.

@c Normally we would use .33 space for each column, but this is too much in
@c TeX mode, see
@c <http://lists.gnu.org/archive/html/bug-texinfo/2009-05/msg00016.html>.
@multitable @columnfractions .31 .31 .31
@headitem Lower case @tab Title case @tab Upper case
@item LATIN SMALL LETTER LJ
 @tab LATIN CAPITAL LETTER L WITH SMALL LETTER J
 @tab LATIN CAPITAL LETTER LJ
@item LATIN SMALL LETTER NJ
 @tab LATIN CAPITAL LETTER N WITH SMALL LETTER J
 @tab LATIN CAPITAL LETTER NJ
@item LATIN SMALL LETTER DZ
 @tab LATIN CAPITAL LETTER D WITH SMALL LETTER Z
 @tab LATIN CAPITAL LETTER DZ
@item LATIN SMALL LETTER DZ WITH CARON
 @tab LATIN CAPITAL LETTER D WITH SMALL LETTER Z WITH CARON
 @tab LATIN CAPITAL LETTER DZ WITH CARON
@end multitable
@end deftypefun

@node Case mappings of strings
@section Case mappings of strings

@cindex case mappings
@cindex uppercasing
@cindex lowercasing
@cindex titlecasing
Case mapping should always be performed on entire strings, not on individual
characters.  The functions in this sections do so.

These functions allow to apply a normalization after the case mapping.  The
reason is that if you want to treat @samp{@"{a}} and @samp{@"{A}} the same,
you most often also want to treat the composed and decomposed forms of such
a character, U+00C4 @sc{LATIN CAPITAL LETTER A WITH DIAERESIS} and
U+0041 @sc{LATIN CAPITAL LETTER A} U+0308 @sc{COMBINING DIAERESIS} the same.
The @var{nf} argument designates the normalization.

@cindex locale language
These functions are locale dependent.  The @var{iso639_language} argument
identifies the language (e.g. @code{"tr"} for Turkish).  NULL means to use
locale independent case mappings.

@deftypefun {const char *} uc_locale_language ()
Returns the ISO 639 language code of the current locale.
Returns @code{""} if it is unknown, or in the "C" locale.
@end deftypefun

@deftypefun {uint8_t *} u8_toupper (const uint8_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, uint8_t *@var{resultbuf}, size_t *@var{lengthp})
@deftypefunx {uint16_t *} u16_toupper (const uint16_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, uint16_t *@var{resultbuf}, size_t *@var{lengthp})
@deftypefunx {uint32_t *} u32_toupper (const uint32_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, uint32_t *@var{resultbuf}, size_t *@var{lengthp})
Returns the uppercase mapping of a string.

The @var{nf} argument identifies the normalization form to apply after the
case-mapping.  It can also be NULL, for no normalization.
@end deftypefun

@deftypefun {uint8_t *} u8_tolower (const uint8_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, uint8_t *@var{resultbuf}, size_t *@var{lengthp})
@deftypefunx {uint16_t *} u16_tolower (const uint16_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, uint16_t *@var{resultbuf}, size_t *@var{lengthp})
@deftypefunx {uint32_t *} u32_tolower (const uint32_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, uint32_t *@var{resultbuf}, size_t *@var{lengthp})
Returns the lowercase mapping of a string.

The @var{nf} argument identifies the normalization form to apply after the
case-mapping.  It can also be NULL, for no normalization.
@end deftypefun

@deftypefun {uint8_t *} u8_totitle (const uint8_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, uint8_t *@var{resultbuf}, size_t *@var{lengthp})
@deftypefunx {uint16_t *} u16_totitle (const uint16_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, uint16_t *@var{resultbuf}, size_t *@var{lengthp})
@deftypefunx {uint32_t *} u32_totitle (const uint32_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, uint32_t *@var{resultbuf}, size_t *@var{lengthp})
Returns the titlecase mapping of a string.

Mapping to title case means that, in each word, the first cased character
is being mapped to title case and the remaining characters of the word
are being mapped to lower case.

The @var{nf} argument identifies the normalization form to apply after the
case-mapping.  It can also be NULL, for no normalization.
@end deftypefun

@node Case insensitive comparison
@section Case insensitive comparison

@cindex comparing, ignoring case
@cindex comparing, ignoring normalization and case
The following functions implement comparison that ignores differences in case
and normalization.

@deftypefun {uint8_t *} u8_casefold (const uint8_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, uint8_t *@var{resultbuf}, size_t *@var{lengthp})
@deftypefunx {uint16_t *} u16_casefold (const uint16_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, uint16_t *@var{resultbuf}, size_t *@var{lengthp})
@deftypefunx {uint32_t *} u32_casefold (const uint32_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, uint32_t *@var{resultbuf}, size_t *@var{lengthp})
Returns the case folded string.

Comparing @code{u8_casefold (@var{s1})} and @code{u8_casefold (@var{s2})}
with the @code{u8_cmp2} function is equivalent to comparing @var{s1} and
@var{s2} with @code{u8_casecmp}.

The @var{nf} argument identifies the normalization form to apply after the
case-mapping.  It can also be NULL, for no normalization.
@end deftypefun

@deftypefun int u8_casecmp (const uint8_t *@var{s1}, size_t @var{n1}, const uint8_t *@var{s2}, size_t @var{n2}, const char *@var{iso639_language}, uninorm_t @var{nf}, int *@var{resultp})
@deftypefunx int u16_casecmp (const uint16_t *@var{s1}, size_t @var{n1}, const uint16_t *@var{s2}, size_t @var{n2}, const char *@var{iso639_language}, uninorm_t @var{nf}, int *@var{resultp})
@deftypefunx int u32_casecmp (const uint32_t *@var{s1}, size_t @var{n1}, const uint32_t *@var{s2}, size_t @var{n2}, const char *@var{iso639_language}, uninorm_t @var{nf}, int *@var{resultp})
@deftypefunx int ulc_casecmp (const char *@var{s1}, size_t @var{n1}, const char *@var{s2}, size_t @var{n2}, const char *@var{iso639_language}, uninorm_t @var{nf}, int *@var{resultp})
Compares @var{s1} and @var{s2}, ignoring differences in case and normalization.

The @var{nf} argument identifies the normalization form to apply after the
case-mapping.  It can also be NULL, for no normalization.

If successful, sets @code{*@var{resultp}} to -1 if @var{s1} < @var{s2},
0 if @var{s1} = @var{s2}, 1 if @var{s1} > @var{s2}, and returns 0.
Upon failure, returns -1 with @code{errno} set.
@end deftypefun

@cindex comparing, ignoring case, with collation rules
@cindex comparing, with collation rules, ignoring case
@cindex comparing, ignoring normalization and case, with collation rules
@cindex comparing, with collation rules, ignoring normalization and case
The following functions additionally take into account the sorting rules of the
current locale.

@deftypefun {char *} u8_casexfrm (const uint8_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, char *@var{resultbuf}, size_t *@var{lengthp})
@deftypefunx {char *} u16_casexfrm (const uint16_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, char *@var{resultbuf}, size_t *@var{lengthp})
@deftypefunx {char *} u32_casexfrm (const uint32_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, char *@var{resultbuf}, size_t *@var{lengthp})
@deftypefunx {char *} ulc_casexfrm (const char *@var{s}, size_t @var{n}, const char *@var{iso639_language}, uninorm_t @var{nf}, char *@var{resultbuf}, size_t *@var{lengthp})
Converts the string @var{s} of length @var{n} to a NUL-terminated byte
sequence, in such a way that comparing @code{u8_casexfrm (@var{s1})} and
@code{u8_casexfrm (@var{s2})} with the gnulib function @code{memcmp2} is
equivalent to comparing @var{s1} and @var{s2} with @code{u8_casecoll}.

@var{nf} must be either @code{UNINORM_NFC}, @code{UNINORM_NFKC}, or NULL for
no normalization.
@end deftypefun

@deftypefun int u8_casecoll (const uint8_t *@var{s1}, size_t @var{n1}, const uint8_t *@var{s2}, size_t @var{n2}, const char *@var{iso639_language}, uninorm_t @var{nf}, int *@var{resultp})
@deftypefunx int u16_casecoll (const uint16_t *@var{s1}, size_t @var{n1}, const uint16_t *@var{s2}, size_t @var{n2}, const char *@var{iso639_language}, uninorm_t @var{nf}, int *@var{resultp})
@deftypefunx int u32_casecoll (const uint32_t *@var{s1}, size_t @var{n1}, const uint32_t *@var{s2}, size_t @var{n2}, const char *@var{iso639_language}, uninorm_t @var{nf}, int *@var{resultp})
@deftypefunx int ulc_casecoll (const char *@var{s1}, size_t @var{n1}, const char *@var{s2}, size_t @var{n2}, const char *@var{iso639_language}, uninorm_t @var{nf}, int *@var{resultp})
Compares @var{s1} and @var{s2}, ignoring differences in case and normalization,
using the collation rules of the current locale.

The @var{nf} argument identifies the normalization form to apply after the
case-mapping.  It must be either @code{UNINORM_NFC} or @code{UNINORM_NFKC}.
It can also be NULL, for no normalization.

If successful, sets @code{*@var{resultp}} to -1 if @var{s1} < @var{s2},
0 if @var{s1} = @var{s2}, 1 if @var{s1} > @var{s2}, and returns 0.
Upon failure, returns -1 with @code{errno} set.
@end deftypefun

@node Case detection
@section Case detection

@cindex case detection
@cindex detecting case
The following functions determine whether a Unicode string is entirely in
upper case. or entirely in lower case, or entirely in title case, or already
case-folded.

@deftypefun int u8_is_uppercase (const uint8_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
@deftypefunx int u16_is_uppercase (const uint16_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
@deftypefunx int u32_is_uppercase (const uint32_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
Sets @code{*@var{resultp}} to true if mapping NFD(@var{s}) to upper case is
a no-op, or to false otherwise, and returns 0.  Upon failure, returns -1 with
@code{errno} set.
@end deftypefun

@deftypefun int u8_is_lowercase (const uint8_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
@deftypefunx int u16_is_lowercase (const uint16_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
@deftypefunx int u32_is_lowercase (const uint32_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
Sets @code{*@var{resultp}} to true if mapping NFD(@var{s}) to lower case is
a no-op, or to false otherwise, and returns 0.  Upon failure, returns -1 with
@code{errno} set.
@end deftypefun

@deftypefun int u8_is_titlecase (const uint8_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
@deftypefunx int u16_is_titlecase (const uint16_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
@deftypefunx int u32_is_titlecase (const uint32_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
Sets @code{*@var{resultp}} to true if mapping NFD(@var{s}) to title case is
a no-op, or to false otherwise, and returns 0.  Upon failure, returns -1 with
@code{errno} set.
@end deftypefun

@deftypefun int u8_is_casefolded (const uint8_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
@deftypefunx int u16_is_casefolded (const uint16_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
@deftypefunx int u32_is_casefolded (const uint32_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
Sets @code{*@var{resultp}} to true if applying case folding to NFD(@var{S}) is
a no-op, or to false otherwise, and returns 0.  Upon failure, returns -1 with
@code{errno} set.
@end deftypefun

The following functions determine whether case mappings have any effect on a
Unicode string.

@deftypefun int u8_is_cased (const uint8_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
@deftypefunx int u16_is_cased (const uint16_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
@deftypefunx int u32_is_cased (const uint32_t *@var{s}, size_t @var{n}, const char *@var{iso639_language}, bool *@var{resultp})
Sets @code{*@var{resultp}} to true if case matters for @var{s}, that is, if
mapping NFD(@var{s}) to either upper case or lower case or title case is not
a no-op.  Set @code{*@var{resultp}} to false if NFD(@var{s}) maps to itself
under the upper case mapping, under the lower case mapping, and under the title
case mapping; in other words, when NFD(@var{s}) consists entirely of caseless
characters. Upon failure, returns -1 with @code{errno} set.
@end deftypefun