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<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 ‘char *’ strings, namely, they handle the Croatian LETTER DZ WITH CARON, the German LATIN SMALL LETTER SHARP S, the Greek sigma and the Lithuanian i correctly.
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.
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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. |
Returns the uppercase mapping of the Unicode character uc.
Returns the lowercase mapping of the Unicode character uc.
Returns the titlecase mapping of the Unicode character 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.
Lower case | Title case | Upper case |
|---|---|---|
LATIN SMALL LETTER LJ | LATIN CAPITAL LETTER L WITH SMALL LETTER J | LATIN CAPITAL LETTER LJ |
LATIN SMALL LETTER NJ | LATIN CAPITAL LETTER N WITH SMALL LETTER J | LATIN CAPITAL LETTER NJ |
LATIN SMALL LETTER DZ | LATIN CAPITAL LETTER D WITH SMALL LETTER Z | LATIN CAPITAL LETTER DZ |
LATIN SMALL LETTER DZ WITH CARON | LATIN CAPITAL LETTER D WITH SMALL LETTER Z WITH CARON | LATIN CAPITAL LETTER DZ WITH CARON |
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 ‘ä’ and ‘Ä’ the same, you most often also want to treat the composed and decomposed forms of such a character, U+00C4 LATIN CAPITAL LETTER A WITH DIAERESIS and U+0041 LATIN CAPITAL LETTER A U+0308 COMBINING DIAERESIS the same. The nf argument designates the normalization.
These functions are locale dependent. The iso639_language argument
identifies the language (e.g. "tr" for Turkish). NULL means to use
locale independent case mappings.
Returns the ISO 639 language code of the current locale.
Returns "" if it is unknown, or in the "C" locale.
Returns the uppercase mapping of a string.
The nf argument identifies the normalization form to apply after the case-mapping. It can also be NULL, for no normalization.
The resultbuf and lengthp arguments are as described in chapter Conventions.
Returns the lowercase mapping of a string.
The nf argument identifies the normalization form to apply after the case-mapping. It can also be NULL, for no normalization.
The resultbuf and lengthp arguments are as described in chapter Conventions.
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 nf argument identifies the normalization form to apply after the case-mapping. It can also be NULL, for no normalization.
The resultbuf and lengthp arguments are as described in chapter Conventions.
Case mapping of a substring cannot simply be performed by extracting the substring and then applying the case mapping function to it. This does not work because case mapping requires some information about the surrounding characters. The following functions allow to apply case mappings to substrings of a given string, while taking into account the characters that precede it (the “prefix”) and the characters that follow it (the “suffix”).
This data type denotes the case-mapping context that is given by a prefix string. It is an immediate type that can be copied by simple assignment, without involving memory allocation. It is not an array type.
This constant is the case-mapping context that corresponds to an empty prefix string.
The following functions return casing_prefix_context_t objects:
Returns the case-mapping context of a given prefix string.
Returns the case-mapping context of the prefix concat(a, s), given the case-mapping context of the prefix a.
This data type denotes the case-mapping context that is given by a suffix string. It is an immediate type that can be copied by simple assignment, without involving memory allocation. It is not an array type.
This constant is the case-mapping context that corresponds to an empty suffix string.
The following functions return casing_suffix_context_t objects:
Returns the case-mapping context of a given suffix string.
Returns the case-mapping context of the suffix concat(s, a), given the case-mapping context of the suffix a.
The following functions perform a case mapping, considering the prefix context and the suffix context.
Returns the uppercase mapping of a string that is surrounded by a prefix and a suffix.
The resultbuf and lengthp arguments are as described in chapter Conventions.
Returns the lowercase mapping of a string that is surrounded by a prefix and a suffix.
The resultbuf and lengthp arguments are as described in chapter Conventions.
Returns the titlecase mapping of a string that is surrounded by a prefix and a suffix.
The resultbuf and lengthp arguments are as described in chapter Conventions.
For example, to uppercase the UTF-8 substring between s + start_index
and s + end_index of a string that extends from s to
s + u8_strlen (s), you can use the statements
size_t result_length;
uint8_t result =
u8_ct_toupper (s + start_index, end_index - start_index,
u8_casing_prefix_context (s, start_index),
u8_casing_suffix_context (s + end_index,
u8_strlen (s) - end_index),
iso639_language, NULL, NULL, &result_length);
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The following functions implement comparison that ignores differences in case and normalization.
Returns the case folded string.
Comparing u8_casefold (s1) and u8_casefold (s2)
with the u8_cmp2 function is equivalent to comparing s1 and
s2 with u8_casecmp.
The nf argument identifies the normalization form to apply after the case-mapping. It can also be NULL, for no normalization.
The resultbuf and lengthp arguments are as described in chapter Conventions.
Returns the case folded string. The case folding takes into account the case mapping contexts of the prefix and suffix strings.
The resultbuf and lengthp arguments are as described in chapter Conventions.
Compares s1 and s2, ignoring differences in case and normalization.
The nf argument identifies the normalization form to apply after the case-mapping. It can also be NULL, for no normalization.
If successful, sets *resultp to -1 if s1 < s2,
0 if s1 = s2, 1 if s1 > s2, and returns 0.
Upon failure, returns -1 with errno set.
The following functions additionally take into account the sorting rules of the current locale.
Converts the string s of length n to a NUL-terminated byte
sequence, in such a way that comparing u8_casexfrm (s1) and
u8_casexfrm (s2) with the gnulib function memcmp2 is
equivalent to comparing s1 and s2 with u8_casecoll.
nf must be either UNINORM_NFC, UNINORM_NFKC, or NULL for
no normalization.
The resultbuf and lengthp arguments are as described in chapter Conventions.
Compares s1 and s2, ignoring differences in case and normalization, using the collation rules of the current locale.
The nf argument identifies the normalization form to apply after the
case-mapping. It must be either UNINORM_NFC or UNINORM_NFKC.
It can also be NULL, for no normalization.
If successful, sets *resultp to -1 if s1 < s2,
0 if s1 = s2, 1 if s1 > s2, and returns 0.
Upon failure, returns -1 with errno set.
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.
Sets *resultp to true if mapping NFD(s) to upper case is
a no-op, or to false otherwise, and returns 0. Upon failure, returns -1 with
errno set.
Sets *resultp to true if mapping NFD(s) to lower case is
a no-op, or to false otherwise, and returns 0. Upon failure, returns -1 with
errno set.
Sets *resultp to true if mapping NFD(s) to title case is
a no-op, or to false otherwise, and returns 0. Upon failure, returns -1 with
errno set.
Sets *resultp to true if applying case folding to NFD(S) is
a no-op, or to false otherwise, and returns 0. Upon failure, returns -1 with
errno set.
The following functions determine whether case mappings have any effect on a Unicode string.
Sets *resultp to true if case matters for s, that is, if
mapping NFD(s) to either upper case or lower case or title case is not
a no-op. Set *resultp to false if NFD(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(s) consists entirely of caseless
characters. Upon failure, returns -1 with errno set.
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