C API: Unicode Normalization. More...

#include "unicode/utypes.h"
#include "unicode/uiter.h"
#include "unicode/unorm2.h"

Macros
#define	UNORM_COMPARE_NORM_OPTIONS_SHIFT 20
	Lowest-order bit number of unorm_compare() options bits corresponding to normalization options bits.

Enumerations
enum	UNormalizationMode { UNORM_NONE = 1 , UNORM_NFD = 2 , UNORM_NFKD = 3 , UNORM_NFC = 4 , UNORM_DEFAULT = UNORM_NFC , UNORM_NFKC =5 , UNORM_FCD = 6 , UNORM_MODE_COUNT }
	Constants for normalization modes. More...

enum	{ UNORM_UNICODE_3_2 =0x20 }
	Constants for options flags for normalization. More...

Functions
int32_t	unorm_normalize (const UChar source, int32_t sourceLength, UNormalizationMode mode, int32_t options, UChar result, int32_t resultLength, UErrorCode *status)
	Normalize a string.

UNormalizationCheckResult	unorm_quickCheck (const UChar source, int32_t sourcelength, UNormalizationMode mode, UErrorCode status)
	Performing quick check on a string, to quickly determine if the string is in a particular normalization format.

UNormalizationCheckResult	unorm_quickCheckWithOptions (const UChar src, int32_t srcLength, UNormalizationMode mode, int32_t options, UErrorCode pErrorCode)
	Performing quick check on a string; same as unorm_quickCheck but takes an extra options parameter like most normalization functions.

UBool	unorm_isNormalized (const UChar src, int32_t srcLength, UNormalizationMode mode, UErrorCode pErrorCode)
	Test if a string is in a given normalization form.

UBool	unorm_isNormalizedWithOptions (const UChar src, int32_t srcLength, UNormalizationMode mode, int32_t options, UErrorCode pErrorCode)
	Test if a string is in a given normalization form; same as unorm_isNormalized but takes an extra options parameter like most normalization functions.

int32_t	unorm_next (UCharIterator src, UChar dest, int32_t destCapacity, UNormalizationMode mode, int32_t options, UBool doNormalize, UBool pNeededToNormalize, UErrorCode pErrorCode)
	Iterative normalization forward.

int32_t	unorm_previous (UCharIterator src, UChar dest, int32_t destCapacity, UNormalizationMode mode, int32_t options, UBool doNormalize, UBool pNeededToNormalize, UErrorCode pErrorCode)
	Iterative normalization backward.

int32_t	unorm_concatenate (const UChar left, int32_t leftLength, const UChar right, int32_t rightLength, UChar dest, int32_t destCapacity, UNormalizationMode mode, int32_t options, UErrorCode pErrorCode)
	Concatenate normalized strings, making sure that the result is normalized as well.

Detailed Description

C API: Unicode Normalization.

Old Unicode normalization API.

This API has been replaced by the unorm2.h API and is only available for backward compatibility. The functions here simply delegate to the unorm2.h functions, for example unorm2_getInstance() and unorm2_normalize(). There is one exception: The new API does not provide a replacement for unorm_compare(). Its declaration has been moved to unorm2.h.

unorm_normalize transforms Unicode text into an equivalent composed or decomposed form, allowing for easier sorting and searching of text. unorm_normalize supports the standard normalization forms described in Unicode Standard Annex #15: Unicode Normalization Forms.

Characters with accents or other adornments can be encoded in several different ways in Unicode. For example, take the character A-acute. In Unicode, this can be encoded as a single character (the "composed" form):

00C1 LATIN CAPITAL LETTER A WITH ACUTE

or as two separate characters (the "decomposed" form):

0041 LATIN CAPITAL LETTER A

0301 COMBINING ACUTE ACCENT

To a user of your program, however, both of these sequences should be treated as the same "user-level" character "A with acute accent". When you are searching or comparing text, you must ensure that these two sequences are treated equivalently. In addition, you must handle characters with more than one accent. Sometimes the order of a character's combining accents is significant, while in other cases accent sequences in different orders are really equivalent.

Similarly, the string "ffi" can be encoded as three separate letters:

  LATIN SMALL LETTER F
  LATIN SMALL LETTER F
  LATIN SMALL LETTER I

or as the single character

FB03 LATIN SMALL LIGATURE FFI

The ffi ligature is not a distinct semantic character, and strictly speaking it shouldn't be in Unicode at all, but it was included for compatibility with existing character sets that already provided it. The Unicode standard identifies such characters by giving them "compatibility" decompositions into the corresponding semantic characters. When sorting and searching, you will often want to use these mappings.

unorm_normalize helps solve these problems by transforming text into the canonical composed and decomposed forms as shown in the first example above. In addition, you can have it perform compatibility decompositions so that you can treat compatibility characters the same as their equivalents. Finally, unorm_normalize rearranges accents into the proper canonical order, so that you do not have to worry about accent rearrangement on your own.

Form FCD, "Fast C or D", is also designed for collation. It allows to work on strings that are not necessarily normalized with an algorithm (like in collation) that works under "canonical closure", i.e., it treats precomposed characters and their decomposed equivalents the same.

It is not a normalization form because it does not provide for uniqueness of representation. Multiple strings may be canonically equivalent (their NFDs are identical) and may all conform to FCD without being identical themselves.

The form is defined such that the "raw decomposition", the recursive canonical decomposition of each character, results in a string that is canonically ordered. This means that precomposed characters are allowed for as long as their decompositions do not need canonical reordering.

Its advantage for a process like collation is that all NFD and most NFC texts - and many unnormalized texts - already conform to FCD and do not need to be normalized (NFD) for such a process. The FCD quick check will return UNORM_YES for most strings in practice.

unorm_normalize(UNORM_FCD) may be implemented with UNORM_NFD.

For more details on FCD see the collation design document: https://htmlpreview.github.io/?https://github.com/unicode-org/icu-docs/blob/main/design/collation/ICU_collation_design.htm

ICU collation performs either NFD or FCD normalization automatically if normalization is turned on for the collator object. Beyond collation and string search, normalized strings may be useful for string equivalence comparisons, transliteration/transcription, unique representations, etc.

The W3C generally recommends to exchange texts in NFC. Note also that most legacy character encodings use only precomposed forms and often do not encode any combining marks by themselves. For conversion to such character encodings the Unicode text needs to be normalized to NFC. For more usage examples, see the Unicode Standard Annex.

Definition in file unorm.h.

Macro Definition Documentation

◆ UNORM_COMPARE_NORM_OPTIONS_SHIFT

#define UNORM_COMPARE_NORM_OPTIONS_SHIFT 20

Lowest-order bit number of unorm_compare() options bits corresponding to normalization options bits.

The options parameter for unorm_compare() uses most bits for itself and for various comparison and folding flags. The most significant bits, however, are shifted down and passed on to the normalization implementation. (That is, from unorm_compare(..., options, ...), options>>UNORM_COMPARE_NORM_OPTIONS_SHIFT will be passed on to the internal normalization functions.)

See also: unorm_compare

Deprecated:: ICU 56 Use unorm2.h instead.

Definition at line 196 of file unorm.h.

Enumeration Type Documentation

◆ anonymous enum

anonymous enum

Constants for options flags for normalization.

Use 0 for default options, including normalization according to the Unicode version that is currently supported by ICU (see u_getUnicodeVersion).

Deprecated:: ICU 56 Use unorm2.h instead.

Enumerator

UNORM_UNICODE_3_2

Options bit set value to select Unicode 3.2 normalization (except NormalizationCorrections).

At most one Unicode version can be selected at a time.

Deprecated:: ICU 56 Use unorm2.h instead.

Definition at line 171 of file unorm.h.

◆ UNormalizationMode

enum UNormalizationMode

Constants for normalization modes.

Deprecated:: ICU 56 Use unorm2.h instead.

Enumerator
UNORM_NONE	No decomposition/composition. Deprecated: ICU 56 Use unorm2.h instead.
UNORM_NFD	Canonical decomposition. Deprecated: ICU 56 Use unorm2.h instead.
UNORM_NFKD	Compatibility decomposition. Deprecated: ICU 56 Use unorm2.h instead.
UNORM_NFC	Canonical decomposition followed by canonical composition. Deprecated: ICU 56 Use unorm2.h instead.
UNORM_DEFAULT	Default normalization. Deprecated: ICU 56 Use unorm2.h instead.
UNORM_NFKC	Compatibility decomposition followed by canonical composition. Deprecated: ICU 56 Use unorm2.h instead.
UNORM_FCD	"Fast C or D" form. Deprecated: ICU 56 Use unorm2.h instead.
UNORM_MODE_COUNT	One more than the highest normalization mode constant. Deprecated: ICU 56 Use unorm2.h instead.

Definition at line 140 of file unorm.h.

Function Documentation

◆ unorm_concatenate()

int32_t unorm_concatenate	(	const UChar *	left,
		int32_t	leftLength,
		const UChar *	right,
		int32_t	rightLength,
		UChar *	dest,
		int32_t	destCapacity,
		UNormalizationMode	mode,
		int32_t	options,
		UErrorCode *	pErrorCode
	)

Concatenate normalized strings, making sure that the result is normalized as well.

If both the left and the right strings are in the normalization form according to "mode/options", then the result will be

dest=normalize(left+right, mode, options)

With the input strings already being normalized, this function will use unorm_next() and unorm_previous() to find the adjacent end pieces of the input strings. Only the concatenation of these end pieces will be normalized and then concatenated with the remaining parts of the input strings.

It is allowed to have dest==left to avoid copying the entire left string.

Parameters

left	Left source string, may be same as dest.
leftLength	Length of left source string, or -1 if NUL-terminated.
right	Right source string. Must not be the same as dest, nor overlap.
rightLength	Length of right source string, or -1 if NUL-terminated.
dest	The output buffer; can be NULL if destCapacity==0 for pure preflighting.
destCapacity	The number of UChars that fit into dest.
mode	The normalization mode.
options	The normalization options, ORed together (0 for no options).
pErrorCode	ICU error code in/out parameter. Must fulfill U_SUCCESS before the function call.

Returns: Length of output (number of UChars) when successful or buffer overflow.

See also: unorm_normalize; unorm_next; unorm_previous

Deprecated:: ICU 56 Use unorm2.h instead.

◆ unorm_isNormalized()

UBool unorm_isNormalized	(	const UChar *	src,
		int32_t	srcLength,
		UNormalizationMode	mode,
		UErrorCode *	pErrorCode
	)

Test if a string is in a given normalization form.

This is semantically equivalent to source.equals(normalize(source, mode)) .

Unlike unorm_quickCheck(), this function returns a definitive result, never a "maybe". For NFD, NFKD, and FCD, both functions work exactly the same. For NFC and NFKC where quickCheck may return "maybe", this function will perform further tests to arrive at a true/false result.

Parameters

src	String that is to be tested if it is in a normalization format.
srcLength	Length of source to test, or -1 if NUL-terminated.
mode	Which normalization form to test for.
pErrorCode	ICU error code in/out parameter. Must fulfill U_SUCCESS before the function call.

Returns: Boolean value indicating whether the source string is in the "mode" normalization form.

See also: unorm_quickCheck

Deprecated:: ICU 56 Use unorm2.h instead.

◆ unorm_isNormalizedWithOptions()

UBool unorm_isNormalizedWithOptions	(	const UChar *	src,
		int32_t	srcLength,
		UNormalizationMode	mode,
		int32_t	options,
		UErrorCode *	pErrorCode
	)

Test if a string is in a given normalization form; same as unorm_isNormalized but takes an extra options parameter like most normalization functions.

Parameters

src	String that is to be tested if it is in a normalization format.
srcLength	Length of source to test, or -1 if NUL-terminated.
mode	Which normalization form to test for.
options	The normalization options, ORed together (0 for no options).
pErrorCode	ICU error code in/out parameter. Must fulfill U_SUCCESS before the function call.

Returns: Boolean value indicating whether the source string is in the "mode/options" normalization form.

See also: unorm_quickCheck; unorm_isNormalized

Deprecated:: ICU 56 Use unorm2.h instead.

◆ unorm_next()

int32_t unorm_next	(	UCharIterator *	src,
		UChar *	dest,
		int32_t	destCapacity,
		UNormalizationMode	mode,
		int32_t	options,
		UBool	doNormalize,
		UBool *	pNeededToNormalize,
		UErrorCode *	pErrorCode
	)

Iterative normalization forward.

This function (together with unorm_previous) is somewhat similar to the C++ Normalizer class (see its non-static functions).

Iterative normalization is useful when only a small portion of a longer string/text needs to be processed.

For example, the likelihood may be high that processing the first 10% of some text will be sufficient to find certain data. Another example: When one wants to concatenate two normalized strings and get a normalized result, it is much more efficient to normalize just a small part of the result around the concatenation place instead of re-normalizing everything.

The input text is an instance of the C character iteration API UCharIterator. It may wrap around a simple string, a CharacterIterator, a Replaceable, or any other kind of text object.

If a buffer overflow occurs, then the caller needs to reset the iterator to the old index and call the function again with a larger buffer - if the caller cares for the actual output. Regardless of the output buffer, the iterator will always be moved to the next normalization boundary.

This function (like unorm_previous) serves two purposes:

1) To find the next boundary so that the normalization of the part of the text from the current position to that boundary does not affect and is not affected by the part of the text beyond that boundary.

2) To normalize the text up to the boundary.

The second step is optional, per the doNormalize parameter. It is omitted for operations like string concatenation, where the two adjacent string ends need to be normalized together. In such a case, the output buffer will just contain a copy of the text up to the boundary.

pNeededToNormalize is an output-only parameter. Its output value is only defined if normalization was requested (doNormalize) and successful (especially, no buffer overflow). It is useful for operations like a normalizing transliterator, where one would not want to replace a piece of text if it is not modified.

If doNormalize==true and pNeededToNormalize!=NULL then *pNeeded... is set true if the normalization was necessary.

If doNormalize==false then *pNeededToNormalize will be set to false.

If the buffer overflows, then *pNeededToNormalize will be undefined; essentially, whenever U_FAILURE is true (like in buffer overflows), this result will be undefined.

Parameters

src	The input text in the form of a C character iterator.
dest	The output buffer; can be NULL if destCapacity==0 for pure preflighting.
destCapacity	The number of UChars that fit into dest.
mode	The normalization mode.
options	The normalization options, ORed together (0 for no options).
doNormalize	Indicates if the source text up to the next boundary is to be normalized (true) or just copied (false).
pNeededToNormalize	Output flag indicating if the normalization resulted in different text from the input. Not defined if an error occurs including buffer overflow. Always false if !doNormalize.
pErrorCode	ICU error code in/out parameter. Must fulfill U_SUCCESS before the function call.

Returns: Length of output (number of UChars) when successful or buffer overflow.

See also: unorm_previous; unorm_normalize

Deprecated:: ICU 56 Use unorm2.h instead.

◆ unorm_normalize()

int32_t unorm_normalize	(	const UChar *	source,
		int32_t	sourceLength,
		UNormalizationMode	mode,
		int32_t	options,
		UChar *	result,
		int32_t	resultLength,
		UErrorCode *	status
	)

Normalize a string.

The string will be normalized according the specified normalization mode and options. The source and result buffers must not be the same, nor overlap.

Parameters

source	The string to normalize.
sourceLength	The length of source, or -1 if NUL-terminated.
mode	The normalization mode; one of UNORM_NONE, UNORM_NFD, UNORM_NFC, UNORM_NFKC, UNORM_NFKD, UNORM_DEFAULT.
options	The normalization options, ORed together (0 for no options).
result	A pointer to a buffer to receive the result string. The result string is NUL-terminated if possible.
resultLength	The maximum size of result.
status	A pointer to a UErrorCode to receive any errors.

Returns: The total buffer size needed; if greater than resultLength, the output was truncated, and the error code is set to U_BUFFER_OVERFLOW_ERROR.

Deprecated:: ICU 56 Use unorm2.h instead.

◆ unorm_previous()

int32_t unorm_previous	(	UCharIterator *	src,
		UChar *	dest,
		int32_t	destCapacity,
		UNormalizationMode	mode,
		int32_t	options,
		UBool	doNormalize,
		UBool *	pNeededToNormalize,
		UErrorCode *	pErrorCode
	)

Iterative normalization backward.

This function (together with unorm_next) is somewhat similar to the C++ Normalizer class (see its non-static functions). For all details see unorm_next.

Parameters

src	The input text in the form of a C character iterator.
dest	The output buffer; can be NULL if destCapacity==0 for pure preflighting.
destCapacity	The number of UChars that fit into dest.
mode	The normalization mode.
options	The normalization options, ORed together (0 for no options).
doNormalize	Indicates if the source text up to the next boundary is to be normalized (true) or just copied (false).
pNeededToNormalize	Output flag indicating if the normalization resulted in different text from the input. Not defined if an error occurs including buffer overflow. Always false if !doNormalize.
pErrorCode	ICU error code in/out parameter. Must fulfill U_SUCCESS before the function call.

Returns: Length of output (number of UChars) when successful or buffer overflow.

See also: unorm_next; unorm_normalize

Deprecated:: ICU 56 Use unorm2.h instead.

◆ unorm_quickCheck()

UNormalizationCheckResult unorm_quickCheck	(	const UChar *	source,
		int32_t	sourcelength,
		UNormalizationMode	mode,
		UErrorCode *	status
	)

Performing quick check on a string, to quickly determine if the string is in a particular normalization format.

Three types of result can be returned UNORM_YES, UNORM_NO or UNORM_MAYBE. Result UNORM_YES indicates that the argument string is in the desired normalized format, UNORM_NO determines that argument string is not in the desired normalized format. A UNORM_MAYBE result indicates that a more thorough check is required, the user may have to put the string in its normalized form and compare the results.

Parameters

source	string for determining if it is in a normalized format
sourcelength	length of source to test, or -1 if NUL-terminated
mode	which normalization form to test for
status	a pointer to a UErrorCode to receive any errors

Returns: UNORM_YES, UNORM_NO or UNORM_MAYBE

See also: unorm_isNormalized

Deprecated:: ICU 56 Use unorm2.h instead.

◆ unorm_quickCheckWithOptions()

UNormalizationCheckResult unorm_quickCheckWithOptions	(	const UChar *	src,
		int32_t	srcLength,
		UNormalizationMode	mode,
		int32_t	options,
		UErrorCode *	pErrorCode
	)

Performing quick check on a string; same as unorm_quickCheck but takes an extra options parameter like most normalization functions.

Parameters

src	String that is to be tested if it is in a normalization format.
srcLength	Length of source to test, or -1 if NUL-terminated.
mode	Which normalization form to test for.
options	The normalization options, ORed together (0 for no options).
pErrorCode	ICU error code in/out parameter. Must fulfill U_SUCCESS before the function call.

Returns: UNORM_YES, UNORM_NO or UNORM_MAYBE

See also: unorm_quickCheck; unorm_isNormalized

Deprecated:: ICU 56 Use unorm2.h instead.

Macros

Enumerations

Functions

Detailed Description

Macro Definition Documentation

◆ UNORM_COMPARE_NORM_OPTIONS_SHIFT

Enumeration Type Documentation

◆ anonymous enum

◆ UNormalizationMode

Function Documentation

◆ unorm_concatenate()

◆ unorm_isNormalized()

◆ unorm_isNormalizedWithOptions()

◆ unorm_next()

◆ unorm_normalize()

◆ unorm_previous()

◆ unorm_quickCheck()

◆ unorm_quickCheckWithOptions()