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<hr size="2">
<a name="uninorm_002eh"></a>
<a name="SEC42"></a>
<h1 class="chapter"> <a href="libunistring.html#TOC42">12. Normalization forms (composition and decomposition) <code><uninorm.h></code></a> </h1>
<p>This include file defines functions for transforming Unicode strings to one
of the four normal forms, known as NFC, NFD, NKFC, NFKD. These
transformations involve decomposition and — for NFC and NFKC — composition
of Unicode characters.
</p>
<hr size="6">
<a name="Decomposition-of-characters"></a>
<a name="SEC43"></a>
<h2 class="section"> <a href="libunistring.html#TOC43">12.1 Decomposition of Unicode characters</a> </h2>
<p>The following enumerated values are the possible types of decomposition of a
Unicode character.
</p>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_CANONICAL</b>
<a name="IDX646"></a>
</dt>
<dd><p>Denotes canonical decomposition.
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_FONT</b>
<a name="IDX647"></a>
</dt>
<dd><p>UCD marker: <code><font></code>. Denotes a font variant (e.g. a blackletter form).
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_NOBREAK</b>
<a name="IDX648"></a>
</dt>
<dd><p>UCD marker: <code><noBreak></code>.
Denotes a no-break version of a space or hyphen.
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_INITIAL</b>
<a name="IDX649"></a>
</dt>
<dd><p>UCD marker: <code><initial></code>.
Denotes an initial presentation form (Arabic).
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_MEDIAL</b>
<a name="IDX650"></a>
</dt>
<dd><p>UCD marker: <code><medial></code>.
Denotes a medial presentation form (Arabic).
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_FINAL</b>
<a name="IDX651"></a>
</dt>
<dd><p>UCD marker: <code><final></code>.
Denotes a final presentation form (Arabic).
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_ISOLATED</b>
<a name="IDX652"></a>
</dt>
<dd><p>UCD marker: <code><isolated></code>.
Denotes an isolated presentation form (Arabic).
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_CIRCLE</b>
<a name="IDX653"></a>
</dt>
<dd><p>UCD marker: <code><circle></code>.
Denotes an encircled form.
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_SUPER</b>
<a name="IDX654"></a>
</dt>
<dd><p>UCD marker: <code><super></code>.
Denotes a superscript form.
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_SUB</b>
<a name="IDX655"></a>
</dt>
<dd><p>UCD marker: <code><sub></code>.
Denotes a subscript form.
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_VERTICAL</b>
<a name="IDX656"></a>
</dt>
<dd><p>UCD marker: <code><vertical></code>.
Denotes a vertical layout presentation form.
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_WIDE</b>
<a name="IDX657"></a>
</dt>
<dd><p>UCD marker: <code><wide></code>.
Denotes a wide (or zenkaku) compatibility character.
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_NARROW</b>
<a name="IDX658"></a>
</dt>
<dd><p>UCD marker: <code><narrow></code>.
Denotes a narrow (or hankaku) compatibility character.
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_SMALL</b>
<a name="IDX659"></a>
</dt>
<dd><p>UCD marker: <code><small></code>.
Denotes a small variant form (CNS compatibility).
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_SQUARE</b>
<a name="IDX660"></a>
</dt>
<dd><p>UCD marker: <code><square></code>.
Denotes a CJK squared font variant.
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_FRACTION</b>
<a name="IDX661"></a>
</dt>
<dd><p>UCD marker: <code><fraction></code>.
Denotes a vulgar fraction form.
</p></dd></dl>
<dl>
<dt><u>Constant:</u> int <b>UC_DECOMP_COMPAT</b>
<a name="IDX662"></a>
</dt>
<dd><p>UCD marker: <code><compat></code>.
Denotes an otherwise unspecified compatibility character.
</p></dd></dl>
<p>The following constant denotes the maximum size of decomposition of a single
Unicode character.
</p>
<dl>
<dt><u>Macro:</u> unsigned int <b>UC_DECOMPOSITION_MAX_LENGTH</b>
<a name="IDX663"></a>
</dt>
<dd><p>This macro expands to a constant that is the required size of buffer passed to
the <code>uc_decomposition</code> and <code>uc_canonical_decomposition</code> functions.
</p></dd></dl>
<p>The following functions decompose a Unicode character.
</p>
<dl>
<dt><u>Function:</u> int <b>uc_decomposition</b><i> (ucs4_t <var>uc</var>, int *<var>decomp_tag</var>, ucs4_t *<var>decomposition</var>)</i>
<a name="IDX664"></a>
</dt>
<dd><p>Returns the character decomposition mapping of the Unicode character <var>uc</var>.
<var>decomposition</var> must point to an array of at least
<code>UC_DECOMPOSITION_MAX_LENGTH</code> <code>ucs_t</code> elements.
</p>
<p>When a decomposition exists, <code><var>decomposition</var>[0..<var>n</var>-1]</code> and
<code>*<var>decomp_tag</var></code> are filled and <var>n</var> is returned. Otherwise -1 is
returned.
</p></dd></dl>
<dl>
<dt><u>Function:</u> int <b>uc_canonical_decomposition</b><i> (ucs4_t <var>uc</var>, ucs4_t *<var>decomposition</var>)</i>
<a name="IDX665"></a>
</dt>
<dd><p>Returns the canonical character decomposition mapping of the Unicode character
<var>uc</var>. <var>decomposition</var> must point to an array of at least
<code>UC_DECOMPOSITION_MAX_LENGTH</code> <code>ucs_t</code> elements.
</p>
<p>When a decomposition exists, <code><var>decomposition</var>[0..<var>n</var>-1]</code> is filled
and <var>n</var> is returned. Otherwise -1 is returned.
</p></dd></dl>
<hr size="6">
<a name="Composition-of-characters"></a>
<a name="SEC44"></a>
<h2 class="section"> <a href="libunistring.html#TOC44">12.2 Composition of Unicode characters</a> </h2>
<p>The following function composes a Unicode character from two Unicode
characters.
</p>
<dl>
<dt><u>Function:</u> ucs4_t <b>uc_composition</b><i> (ucs4_t <var>uc1</var>, ucs4_t <var>uc2</var>)</i>
<a name="IDX666"></a>
</dt>
<dd><p>Attempts to combine the Unicode characters <var>uc1</var>, <var>uc2</var>.
<var>uc1</var> is known to have canonical combining class 0.
</p>
<p>Returns the combination of <var>uc1</var> and <var>uc2</var>, if it exists.
Returns 0 otherwise.
</p>
<p>Not all decompositions can be recombined using this function. See the Unicode
file ‘<tt>CompositionExclusions.txt</tt>’ for details.
</p></dd></dl>
<hr size="6">
<a name="Normalization-of-strings"></a>
<a name="SEC45"></a>
<h2 class="section"> <a href="libunistring.html#TOC45">12.3 Normalization of strings</a> </h2>
<p>The Unicode standard defines four normalization forms for Unicode strings.
The following type is used to denote a normalization form.
</p>
<dl>
<dt><u>Type:</u> <b>uninorm_t</b>
<a name="IDX667"></a>
</dt>
<dd><p>An object of type <code>uninorm_t</code> denotes a Unicode normalization form.
This is a scalar type; its values can be compared with <code>==</code>.
</p></dd></dl>
<p>The following constants denote the four normalization forms.
</p>
<dl>
<dt><u>Macro:</u> uninorm_t <b>UNINORM_NFD</b>
<a name="IDX668"></a>
</dt>
<dd><p>Denotes Normalization form D: canonical decomposition.
</p></dd></dl>
<dl>
<dt><u>Macro:</u> uninorm_t <b>UNINORM_NFC</b>
<a name="IDX669"></a>
</dt>
<dd><p>Normalization form C: canonical decomposition, then canonical composition.
</p></dd></dl>
<dl>
<dt><u>Macro:</u> uninorm_t <b>UNINORM_NFKD</b>
<a name="IDX670"></a>
</dt>
<dd><p>Normalization form KD: compatibility decomposition.
</p></dd></dl>
<dl>
<dt><u>Macro:</u> uninorm_t <b>UNINORM_NFKC</b>
<a name="IDX671"></a>
</dt>
<dd><p>Normalization form KC: compatibility decomposition, then canonical composition.
</p></dd></dl>
<p>The following functions operate on <code>uninorm_t</code> objects.
</p>
<dl>
<dt><u>Function:</u> bool <b>uninorm_is_compat_decomposing</b><i> (uninorm_t <var>nf</var>)</i>
<a name="IDX672"></a>
</dt>
<dd><p>Tests whether the normalization form <var>nf</var> does compatibility decomposition.
</p></dd></dl>
<dl>
<dt><u>Function:</u> bool <b>uninorm_is_composing</b><i> (uninorm_t <var>nf</var>)</i>
<a name="IDX673"></a>
</dt>
<dd><p>Tests whether the normalization form <var>nf</var> includes canonical composition.
</p></dd></dl>
<dl>
<dt><u>Function:</u> uninorm_t <b>uninorm_decomposing_form</b><i> (uninorm_t <var>nf</var>)</i>
<a name="IDX674"></a>
</dt>
<dd><p>Returns the decomposing variant of the normalization form <var>nf</var>.
This maps NFC,NFD → NFD and NFKC,NFKD → NFKD.
</p></dd></dl>
<p>The following functions apply a Unicode normalization form to a Unicode string.
</p>
<dl>
<dt><u>Function:</u> uint8_t * <b>u8_normalize</b><i> (uninorm_t <var>nf</var>, const uint8_t *<var>s</var>, size_t <var>n</var>, uint8_t *<var>resultbuf</var>, size_t *<var>lengthp</var>)</i>
<a name="IDX675"></a>
</dt>
<dt><u>Function:</u> uint16_t * <b>u16_normalize</b><i> (uninorm_t <var>nf</var>, const uint16_t *<var>s</var>, size_t <var>n</var>, uint16_t *<var>resultbuf</var>, size_t *<var>lengthp</var>)</i>
<a name="IDX676"></a>
</dt>
<dt><u>Function:</u> uint32_t * <b>u32_normalize</b><i> (uninorm_t <var>nf</var>, const uint32_t *<var>s</var>, size_t <var>n</var>, uint32_t *<var>resultbuf</var>, size_t *<var>lengthp</var>)</i>
<a name="IDX677"></a>
</dt>
<dd><p>Returns the specified normalization form of a string.
</p></dd></dl>
<hr size="6">
<a name="Normalizing-comparisons"></a>
<a name="SEC46"></a>
<h2 class="section"> <a href="libunistring.html#TOC46">12.4 Normalizing comparisons</a> </h2>
<p>The following functions compare Unicode string, ignoring differences in
normalization.
</p>
<dl>
<dt><u>Function:</u> int <b>u8_normcmp</b><i> (const uint8_t *<var>s1</var>, size_t <var>n1</var>, const uint8_t *<var>s2</var>, size_t <var>n2</var>, uninorm_t <var>nf</var>, int *<var>resultp</var>)</i>
<a name="IDX678"></a>
</dt>
<dt><u>Function:</u> int <b>u16_normcmp</b><i> (const uint16_t *<var>s1</var>, size_t <var>n1</var>, const uint16_t *<var>s2</var>, size_t <var>n2</var>, uninorm_t <var>nf</var>, int *<var>resultp</var>)</i>
<a name="IDX679"></a>
</dt>
<dt><u>Function:</u> int <b>u32_normcmp</b><i> (const uint32_t *<var>s1</var>, size_t <var>n1</var>, const uint32_t *<var>s2</var>, size_t <var>n2</var>, uninorm_t <var>nf</var>, int *<var>resultp</var>)</i>
<a name="IDX680"></a>
</dt>
<dd><p>Compares <var>s1</var> and <var>s2</var>, ignoring differences in normalization.
</p>
<p><var>nf</var> must be either <code>UNINORM_NFD</code> or <code>UNINORM_NFKD</code>.
</p>
<p>If successful, sets <code>*<var>resultp</var></code> to -1 if <var>s1</var> < <var>s2</var>,
0 if <var>s1</var> = <var>s2</var>, 1 if <var>s1</var> > <var>s2</var>, and returns 0.
Upon failure, returns -1 with <code>errno</code> set.
</p></dd></dl>
<a name="IDX681"></a>
<a name="IDX682"></a>
<dl>
<dt><u>Function:</u> char * <b>u8_normxfrm</b><i> (const uint8_t *<var>s</var>, size_t <var>n</var>, uninorm_t <var>nf</var>, char *<var>resultbuf</var>, size_t *<var>lengthp</var>)</i>
<a name="IDX683"></a>
</dt>
<dt><u>Function:</u> char * <b>u16_normxfrm</b><i> (const uint16_t *<var>s</var>, size_t <var>n</var>, uninorm_t <var>nf</var>, char *<var>resultbuf</var>, size_t *<var>lengthp</var>)</i>
<a name="IDX684"></a>
</dt>
<dt><u>Function:</u> char * <b>u32_normxfrm</b><i> (const uint32_t *<var>s</var>, size_t <var>n</var>, uninorm_t <var>nf</var>, char *<var>resultbuf</var>, size_t *<var>lengthp</var>)</i>
<a name="IDX685"></a>
</dt>
<dd><p>Converts the string <var>s</var> of length <var>n</var> to a NUL-terminated byte
sequence, in such a way that comparing <code>u8_normxfrm (<var>s1</var>)</code> and
<code>u8_normxfrm (<var>s2</var>)</code> with the <code>u8_cmp2</code> function is equivalent to
comparing <var>s1</var> and <var>s2</var> with the <code>u8_normcoll</code> function.
</p>
<p><var>nf</var> must be either <code>UNINORM_NFC</code> or <code>UNINORM_NFKC</code>.
</p></dd></dl>
<dl>
<dt><u>Function:</u> int <b>u8_normcoll</b><i> (const uint8_t *<var>s1</var>, size_t <var>n1</var>, const uint8_t *<var>s2</var>, size_t <var>n2</var>, uninorm_t <var>nf</var>, int *<var>resultp</var>)</i>
<a name="IDX686"></a>
</dt>
<dt><u>Function:</u> int <b>u16_normcoll</b><i> (const uint16_t *<var>s1</var>, size_t <var>n1</var>, const uint16_t *<var>s2</var>, size_t <var>n2</var>, uninorm_t <var>nf</var>, int *<var>resultp</var>)</i>
<a name="IDX687"></a>
</dt>
<dt><u>Function:</u> int <b>u32_normcoll</b><i> (const uint32_t *<var>s1</var>, size_t <var>n1</var>, const uint32_t *<var>s2</var>, size_t <var>n2</var>, uninorm_t <var>nf</var>, int *<var>resultp</var>)</i>
<a name="IDX688"></a>
</dt>
<dd><p>Compares <var>s1</var> and <var>s2</var>, ignoring differences in normalization, using
the collation rules of the current locale.
</p>
<p><var>nf</var> must be either <code>UNINORM_NFC</code> or <code>UNINORM_NFKC</code>.
</p>
<p>If successful, sets <code>*<var>resultp</var></code> to -1 if <var>s1</var> < <var>s2</var>,
0 if <var>s1</var> = <var>s2</var>, 1 if <var>s1</var> > <var>s2</var>, and returns 0.
Upon failure, returns -1 with <code>errno</code> set.
</p></dd></dl>
<hr size="6">
<a name="Normalization-of-streams"></a>
<a name="SEC47"></a>
<h2 class="section"> <a href="libunistring.html#TOC47">12.5 Normalization of streams of Unicode characters</a> </h2>
<p>A “stream of Unicode characters” is essentially a function that accepts an
<code>ucs4_t</code> argument repeatedly, optionally combined with a function that
“flushes” the stream.
</p>
<dl>
<dt><u>Type:</u> <b>struct uninorm_filter</b>
<a name="IDX689"></a>
</dt>
<dd><p>This is the data type of a stream of Unicode characters that normalizes its
input according to a given normalization form and passes the normalized
character sequence to the encapsulated stream of Unicode characters.
</p></dd></dl>
<dl>
<dt><u>Function:</u> struct uninorm_filter * <b>uninorm_filter_create</b><i> (uninorm_t <var>nf</var>, int (*<var>stream_func</var>) (void *<var>stream_data</var>, ucs4_t <var>uc</var>), void *<var>stream_data</var>)</i>
<a name="IDX690"></a>
</dt>
<dd><p>Creates and returns a normalization filter for Unicode characters.
</p>
<p>The pair (<var>stream_func</var>, <var>stream_data</var>) is the encapsulated stream.
<code><var>stream_func</var> (<var>stream_data</var>, <var>uc</var>)</code> receives the Unicode
character <var>uc</var> and returns 0 if successful, or -1 with <code>errno</code> set
upon failure.
</p>
<p>Returns the new filter, or NULL with <code>errno</code> set upon failure.
</p></dd></dl>
<dl>
<dt><u>Function:</u> int <b>uninorm_filter_write</b><i> (struct uninorm_filter *<var>filter</var>, ucs4_t <var>uc</var>)</i>
<a name="IDX691"></a>
</dt>
<dd><p>Stuffs a Unicode character into a normalizing filter.
Returns 0 if successful, or -1 with <code>errno</code> set upon failure.
</p></dd></dl>
<dl>
<dt><u>Function:</u> int <b>uninorm_filter_flush</b><i> (struct uninorm_filter *<var>filter</var>)</i>
<a name="IDX692"></a>
</dt>
<dd><p>Brings data buffered in the filter to its destination, the encapsulated stream.
</p>
<p>Returns 0 if successful, or -1 with <code>errno</code> set upon failure.
</p>
<p>Note! If after calling this function, additional characters are written
into the filter, the resulting character sequence in the encapsulated stream
will not necessarily be normalized.
</p></dd></dl>
<dl>
<dt><u>Function:</u> int <b>uninorm_filter_free</b><i> (struct uninorm_filter *<var>filter</var>)</i>
<a name="IDX693"></a>
</dt>
<dd><p>Brings data buffered in the filter to its destination, the encapsulated stream,
then closes and frees the filter.
</p>
<p>Returns 0 if successful, or -1 with <code>errno</code> set upon failure.
</p></dd></dl>
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