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unorm.h File Reference

C API: Unicode Normalization. More...

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

Go to the source code of this file.

Defines

#define u_normalize   unorm_normalize
 The function u_normalize() has been renamed to unorm_normalize() for consistency. More...


Typedefs

typedef enum UNormalizationCheckResult UNormalizationCheckResult
 Result values for unorm_quickCheck(). More...


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,
  UCOL_NO_NORMALIZATION = 1, UCOL_DECOMP_CAN = 2, UCOL_DECOMP_COMPAT = 3, UCOL_DEFAULT_NORMALIZATION = UCOL_DECOMP_COMPAT,
  UCOL_DECOMP_CAN_COMP_COMPAT = 4, UCOL_DECOMP_COMPAT_COMP_CAN = 5, UCOL_IGNORE_HANGUL = 16, UNORM_IGNORE_HANGUL = 16
}
 Constants for normalization modes. More...

enum  UNormalizationCheckResult { UNORM_NO, UNORM_YES, UNORM_MAYBE }
 Result values for unorm_quickCheck(). More...


Functions

U_CAPI int32_t U_EXPORT2 unorm_normalize (const UChar *source, int32_t sourceLength, UNormalizationMode mode, int32_t options, UChar *result, int32_t resultLength, UErrorCode *status)
 Normalize a string. More...

U_CAPI UNormalizationCheckResult
U_EXPORT2 
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. More...

U_CAPI int32_t U_EXPORT2 unorm_next (UCharIterator *src, UChar *dest, int32_t destCapacity, UNormalizationMode mode, int32_t options, UBool doNormalize, UBool *pNeededToNormalize, UErrorCode *pErrorCode)
 Iterative normalization forward. More...

U_CAPI int32_t U_EXPORT2 unorm_previous (UCharIterator *src, UChar *dest, int32_t destCapacity, UNormalizationMode mode, int32_t options, UBool doNormalize, UBool *pNeededToNormalize, UErrorCode *pErrorCode)
 Iterative normalization backward. More...

U_CAPI int32_t U_EXPORT2 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)


Detailed Description

C API: Unicode Normalization.

Unicode normalization API

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:

      0066    LATIN SMALL LETTER F
      0066    LATIN SMALL LETTER F
      0069    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: http://oss.software.ibm.com/cvs/icu/~checkout~/icuhtml/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.


Define Documentation

#define u_normalize   unorm_normalize
 

The function u_normalize() has been renamed to unorm_normalize() for consistency.

The old name is deprecated.

Deprecated:
To be removed after 2002-mar-31.


Typedef Documentation

typedef enum UNormalizationCheckResult UNormalizationCheckResult
 

Result values for unorm_quickCheck().

For details see Unicode Technical Report 15. @stable


Enumeration Type Documentation

enum UNormalizationCheckResult
 

Result values for unorm_quickCheck().

For details see Unicode Technical Report 15. @stable

Enumeration values:
UNORM_NO  Indicates that string is not in the normalized format.
UNORM_YES  Indicates that string is in the normalized format.
UNORM_MAYBE  Indicates that string cannot be determined if it is in the normalized format without further thorough checks.

enum UNormalizationMode
 

Constants for normalization modes.

@stable except for deprecated constants

Enumeration values:
UNORM_NONE  No decomposition/composition.

@stable

UNORM_NFD  Canonical decomposition.

@stable

UNORM_NFKD  Compatibility decomposition.

@stable

UNORM_NFC  Canonical decomposition followed by canonical composition.

@stable

UNORM_DEFAULT  Default normalization.

@stable

UNORM_NFKC  Compatibility decomposition followed by canonical composition.

@stable

UNORM_FCD  "Fast C or D" form.

@draft ICU 2.0

UNORM_MODE_COUNT  One more than the highest normalization mode constant.

@stable

UCOL_NO_NORMALIZATION  No decomposition/composition.

Deprecated:
To be removed after 2002-sep-30, use UNORM_NONE.
UCOL_DECOMP_CAN  Canonical decomposition.

Deprecated:
To be removed after 2002-sep-30, use UNORM_NFD.
UCOL_DECOMP_COMPAT  Compatibility decomposition.

Deprecated:
To be removed after 2002-sep-30, use UNORM_NFKD.
UCOL_DEFAULT_NORMALIZATION  Default normalization.

Deprecated:
To be removed after 2002-sep-30, use UNORM_NFKD or UNORM_DEFAULT.
UCOL_DECOMP_CAN_COMP_COMPAT  Canonical decomposition followed by canonical composition.

Deprecated:
To be removed after 2002-sep-30, use UNORM_NFC.
UCOL_DECOMP_COMPAT_COMP_CAN  Compatibility decomposition followed by canonical composition.

Deprecated:
To be removed after 2002-sep-30, use UNORM_NFKC.
UCOL_IGNORE_HANGUL  Do not normalize Hangul.

Deprecated:
To be removed without replacement after 2002-mar-31.
UNORM_IGNORE_HANGUL  Do not normalize Hangul.

Deprecated:
To be removed without replacement after 2002-mar-31.


Function Documentation

U_CAPI int32_t U_EXPORT2 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  A bit set of normalization 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
@draft ICU 2.1

U_CAPI int32_t U_EXPORT2 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 (there are currently no options defined).

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); currently there is no option defined.
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. @stable

U_CAPI int32_t U_EXPORT2 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  A bit set of normalization 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
@draft ICU 2.1

U_CAPI UNormalizationCheckResult U_EXPORT2 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
an mode which normalization form to test for
Parameters:
status  a pointer to a UErrorCode to receive any errors
Returns:
UNORM_YES, UNORM_NO or UNORM_MAYBE @stable


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