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BreakIterator Class Reference

The BreakIterator class implements methods for finding the location of boundaries in text. More...

#include <brkiter.h>

Inheritance diagram for BreakIterator:

RuleBasedBreakIterator DictionaryBasedBreakIterator

Public Methods

virtual ~BreakIterator ()
virtual UBool operator== (const BreakIterator &) const=0
 Return true if another object is semantically equal to this one. More...

UBool operator!= (const BreakIterator &rhs) const
 Returns the complement of the result of operator== @stable.

virtual BreakIterator * clone (void) const=0
 Return a polymorphic copy of this object. More...

virtual UClassID getDynamicClassID (void) const=0
 Return a polymorphic class ID for this object. More...

virtual const CharacterIteratorgetText (void) const=0
 Return a CharacterIterator over the text being analyzed. More...

virtual void setText (const UnicodeString &text)=0
 Change the text over which this operates. More...

virtual void adoptText (CharacterIterator *it)=0
 Change the text over which this operates. More...

virtual UTextOffset first (void)=0
 Return the index of the first character in the text being scanned. More...

virtual UTextOffset last (void)=0
 Return the index immediately BEYOND the last character in the text being scanned. More...

virtual UTextOffset previous (void)=0
 Return the boundary preceding the current boundary. More...

virtual UTextOffset next (void)=0
 Return the boundary following the current boundary. More...

virtual UTextOffset current (void) const=0
 Return character index of the text boundary that was most recently returned by next(), previous(), first(), or last(). More...

virtual UTextOffset following (UTextOffset offset)=0
 Return the first boundary following the specified offset. More...

virtual UTextOffset preceding (UTextOffset offset)=0
 Return the first boundary preceding the specified offset. More...

virtual UBool isBoundary (UTextOffset offset)=0
 Return true if the specfied position is a boundary position. More...

virtual UTextOffset next (int32_t n)=0
 Return the nth boundary from the current boundary. More...

virtual BreakIterator * createBufferClone (void *stackBuffer, int32_t &BufferSize, UErrorCode &status)=0
 Thread safe client-buffer-based cloning operation Do NOT call delete on a safeclone, since 'new' is not used to create it. More...

UBool isBufferClone (void)

Static Public Methods

BreakIterator * createWordInstance (const Locale &where, UErrorCode &status)
 Create BreakIterator for word-breaks using the given locale. More...

BreakIterator * createLineInstance (const Locale &where, UErrorCode &status)
 Create BreakIterator for line-breaks using specified locale. More...

BreakIterator * createCharacterInstance (const Locale &where, UErrorCode &status)
 Create BreakIterator for character-breaks using specified locale Returns an instance of a BreakIterator implementing character breaks. More...

BreakIterator * createSentenceInstance (const Locale &where, UErrorCode &status)
 Create BreakIterator for sentence-breaks using specified locale Returns an instance of a BreakIterator implementing sentence breaks. More...

BreakIterator * createTitleInstance (const Locale &where, UErrorCode &status)
 Create BreakIterator for title-casing breaks using the specified locale Returns an instance of a BreakIterator implementing title breaks. More...

const Locale * getAvailableLocales (int32_t &count)
 Get the set of Locales for which TextBoundaries are installed. More...

UnicodeStringgetDisplayName (const Locale &objectLocale, const Locale &displayLocale, UnicodeString &name)
 Get name of the object for the desired Locale, in the desired langauge. More...

UnicodeStringgetDisplayName (const Locale &objectLocale, UnicodeString &name)
 Get name of the object for the desired Locale, in the langauge of the default locale. More...


Static Public Attributes

const UTextOffset DONE
 DONE is returned by previous() and next() after all valid boundaries have been returned. More...


Protected Methods

 BreakIterator ()

Protected Attributes

UBool fBufferClone

Detailed Description

The BreakIterator class implements methods for finding the location of boundaries in text.

BreakIterator is an abstract base class. Instances of BreakIterator maintain a current position and scan over text returning the index of characters where boundaries occur.

Line boundary analysis determines where a text string can be broken when line-wrapping. The mechanism correctly handles punctuation and hyphenated words.

Sentence boundary analysis allows selection with correct interpretation of periods within numbers and abbreviations, and trailing punctuation marks such as quotation marks and parentheses.

Word boundary analysis is used by search and replace functions, as well as within text editing applications that allow the user to select words with a double click. Word selection provides correct interpretation of punctuation marks within and following words. Characters that are not part of a word, such as symbols or punctuation marks, have word-breaks on both sides.

Character boundary analysis allows users to interact with characters as they expect to, for example, when moving the cursor through a text string. Character boundary analysis provides correct navigation of through character strings, regardless of how the character is stored. For example, an accented character might be stored as a base character and a diacritical mark. What users consider to be a character can differ between languages.

This is the interface for all text boundaries.

Examples:

Helper function to output text

 
    void printTextRange( BreakIterator& iterator, UTextOffset start, UTextOffset end )
    {
        UnicodeString textBuffer, temp;
        CharacterIterator *strIter = iterator.createText();
        strIter->getText(temp);
        cout << " " << start << " " << end << " |" 
             << temp.extractBetween(start, end, textBuffer)
             << "|" << endl;
        delete strIter;
    }
Print each element in order:
 
    void printEachForward( BreakIterator& boundary)
    {
       UTextOffset start = boundary.first();
       for (UTextOffset end = boundary.next();
         end != BreakIterator::DONE;
         start = end, end = boundary.next())
         {
             printTextRange( boundary, start, end );
         }
    }
 \code
 </PRE>
 Print each element in reverse order:
 <PRE>
 \code
    void printEachBackward( BreakIterator& boundary)
    {
       UTextOffset end = boundary.last();
       for (UTextOffset start = boundary.previous();
         start != BreakIterator::DONE;
         end = start, start = boundary.previous())
         {
             printTextRange( boundary, start, end );
         }
    }
Print first element
 
    void printFirst(BreakIterator& boundary)
    {
        UTextOffset start = boundary.first();
        UTextOffset end = boundary.next();
        printTextRange( boundary, start, end );
    }
Print last element
  
    void printLast(BreakIterator& boundary)
    {
        UTextOffset end = boundary.last();
        UTextOffset start = boundary.previous();
        printTextRange( boundary, start, end );
    }
Print the element at a specified position
 
    void printAt(BreakIterator &boundary, UTextOffset pos )
    {
        UTextOffset end = boundary.following(pos);
        UTextOffset start = boundary.previous();
        printTextRange( boundary, start, end );
    }
Creating and using text boundaries
 
       void BreakIterator_Example( void )
       {
           BreakIterator* boundary;
           UnicodeString stringToExamine("Aaa bbb ccc. Ddd eee fff.");
           cout << "Examining: " << stringToExamine << endl;
 
           //print each sentence in forward and reverse order
           boundary = BreakIterator::createSentenceInstance( Locale::US );
           boundary->setText(stringToExamine);
           cout << "----- forward: -----------" << endl;
           printEachForward(*boundary);
           cout << "----- backward: ----------" << endl;
           printEachBackward(*boundary);
           delete boundary;
 
           //print each word in order
           boundary = BreakIterator::createWordInstance();
           boundary->setText(stringToExamine);
           cout << "----- forward: -----------" << endl;
           printEachForward(*boundary);
           //print first element
           cout << "----- first: -------------" << endl;
           printFirst(*boundary);
           //print last element
           cout << "----- last: --------------" << endl;
           printLast(*boundary);
           //print word at charpos 10
           cout << "----- at pos 10: ---------" << endl;
           printAt(*boundary, 10 );
 
           delete boundary;
       }


Member Function Documentation

virtual void BreakIterator::adoptText CharacterIterator   it [pure virtual]
 

Change the text over which this operates.

The text boundary is reset to the start. @stable

Implemented in RuleBasedBreakIterator.

virtual BreakIterator* BreakIterator::clone void    const [pure virtual]
 

Return a polymorphic copy of this object.

This is an abstract method which subclasses implement. @stable

Implemented in DictionaryBasedBreakIterator.

virtual BreakIterator* BreakIterator::createBufferClone void *    stackBuffer,
int32_t &    BufferSize,
UErrorCode   status
[pure virtual]
 

Thread safe client-buffer-based cloning operation Do NOT call delete on a safeclone, since 'new' is not used to create it.

Parameters:
stackBuffer  user allocated space for the new clone. If NULL new memory will be allocated. If buffer is not large enough, new memory will be allocated.
BufferSize  reference to size of allocated space. If BufferSize == 0, a sufficient size for use in cloning will be returned ('pre-flighting') If BufferSize is not enough for a stack-based safe clone, new memory will be allocated.
status  to indicate whether the operation went on smoothly or there were errors An informational status value, U_SAFECLONE_ALLOCATED_ERROR, is used if any allocations were necessary.
Returns:
pointer to the new clone
@draft ICU 1.8

Implemented in DictionaryBasedBreakIterator.

BreakIterator* BreakIterator::createCharacterInstance const Locale &    where,
UErrorCode   status
[static]
 

Create BreakIterator for character-breaks using specified locale Returns an instance of a BreakIterator implementing character breaks.

Character breaks are boundaries of combining character sequences.

Parameters:
where  the locale.
Returns:
A BreakIterator for character-breaks. The UErrorCode& status parameter is used to return status information to the user. To check whether the construction succeeded or not, you should check the value of U_SUCCESS(err). If you wish more detailed information, you can check for informational error results which still indicate success. U_USING_FALLBACK_ERROR indicates that a fall back locale was used. For example, 'de_CH' was requested, but nothing was found there, so 'de' was used. U_USING_DEFAULT_ERROR indicates that the default locale data was used; neither the requested locale nor any of its fall back locales could be found. The caller owns the returned object and is responsible for deleting it. @stable

BreakIterator* BreakIterator::createLineInstance const Locale &    where,
UErrorCode   status
[static]
 

Create BreakIterator for line-breaks using specified locale.

Returns an instance of a BreakIterator implementing line breaks. Line breaks are logically possible line breaks, actual line breaks are usually determined based on display width. LineBreak is useful for word wrapping text.

Parameters:
where  the locale. .
Returns:
A BreakIterator for line-breaks. The UErrorCode& status parameter is used to return status information to the user. To check whether the construction succeeded or not, you should check the value of U_SUCCESS(err). If you wish more detailed information, you can check for informational error results which still indicate success. U_USING_FALLBACK_ERROR indicates that a fall back locale was used. For example, 'de_CH' was requested, but nothing was found there, so 'de' was used. U_USING_DEFAULT_ERROR indicates that the default locale data was used; neither the requested locale nor any of its fall back locales could be found. The caller owns the returned object and is responsible for deleting it. @stable

BreakIterator* BreakIterator::createSentenceInstance const Locale &    where,
UErrorCode   status
[static]
 

Create BreakIterator for sentence-breaks using specified locale Returns an instance of a BreakIterator implementing sentence breaks.

Parameters:
where  the locale.
Returns:
A BreakIterator for sentence-breaks. The UErrorCode& status parameter is used to return status information to the user. To check whether the construction succeeded or not, you should check the value of U_SUCCESS(err). If you wish more detailed information, you can check for informational error results which still indicate success. U_USING_FALLBACK_ERROR indicates that a fall back locale was used. For example, 'de_CH' was requested, but nothing was found there, so 'de' was used. U_USING_DEFAULT_ERROR indicates that the default locale data was used; neither the requested locale nor any of its fall back locales could be found. The caller owns the returned object and is responsible for deleting it. @stable

BreakIterator* BreakIterator::createTitleInstance const Locale &    where,
UErrorCode   status
[static]
 

Create BreakIterator for title-casing breaks using the specified locale Returns an instance of a BreakIterator implementing title breaks.

Parameters:
where  the locale.
Returns:
A BreakIterator for title-breaks. The UErrorCode& status parameter is used to return status information to the user. To check whether the construction succeeded or not, you should check the value of U_SUCCESS(err). If you wish more detailed information, you can check for informational error results which still indicate success. U_USING_FALLBACK_ERROR indicates that a fall back locale was used. For example, 'de_CH' was requested, but nothing was found there, so 'de' was used. U_USING_DEFAULT_ERROR indicates that the default locale data was used; neither the requested locale nor any of its fall back locales could be found. The caller owns the returned object and is responsible for deleting it. @stable

BreakIterator* BreakIterator::createWordInstance const Locale &    where,
UErrorCode   status
[static]
 

Create BreakIterator for word-breaks using the given locale.

Returns an instance of a BreakIterator implementing word breaks. WordBreak is useful for word selection (ex. double click)

Parameters:
where  the locale.
status  the error code
Returns:
A BreakIterator for word-breaks. The UErrorCode& status parameter is used to return status information to the user. To check whether the construction succeeded or not, you should check the value of U_SUCCESS(err). If you wish more detailed information, you can check for informational error results which still indicate success. U_USING_FALLBACK_ERROR indicates that a fall back locale was used. For example, 'de_CH' was requested, but nothing was found there, so 'de' was used. U_USING_DEFAULT_ERROR indicates that the default locale data was used; neither the requested locale nor any of its fall back locales could be found. The caller owns the returned object and is responsible for deleting it. @stable

virtual UTextOffset BreakIterator::current void    const [pure virtual]
 

Return character index of the text boundary that was most recently returned by next(), previous(), first(), or last().

Returns:
The boundary most recently returned. @stable

Implemented in RuleBasedBreakIterator.

virtual UTextOffset BreakIterator::first void    [pure virtual]
 

Return the index of the first character in the text being scanned.

@stable

Implemented in RuleBasedBreakIterator.

virtual UTextOffset BreakIterator::following UTextOffset    offset [pure virtual]
 

Return the first boundary following the specified offset.

The value returned is always greater than the offset or the value BreakIterator.DONE

Parameters:
offset  the offset to begin scanning.
Returns:
The first boundary after the specified offset. @stable

const Locale* BreakIterator::getAvailableLocales int32_t &    count [static]
 

Get the set of Locales for which TextBoundaries are installed.

Parameters:
count  the output parameter of number of elements in the locale list
Returns:
available locales @stable

UnicodeString& BreakIterator::getDisplayName const Locale &    objectLocale,
UnicodeString   name
[static]
 

Get name of the object for the desired Locale, in the langauge of the default locale.

Parameters:
objectLocale  must be from getMatchingLocales
name  the fill-in parameter of the return value
Returns:
user-displayable name @stable

UnicodeString& BreakIterator::getDisplayName const Locale &    objectLocale,
const Locale &    displayLocale,
UnicodeString   name
[static]
 

Get name of the object for the desired Locale, in the desired langauge.

Parameters:
objectLocale  must be from getAvailableLocales.
displayLocale  specifies the desired locale for output.
name  the fill-in parameter of the return value Uses best match.
Returns:
user-displayable name @stable

virtual UClassID BreakIterator::getDynamicClassID void    const [pure virtual]
 

Return a polymorphic class ID for this object.

Different subclasses will return distinct unequal values. @stable

Implemented in DictionaryBasedBreakIterator.

virtual const CharacterIterator& BreakIterator::getText void    const [pure virtual]
 

Return a CharacterIterator over the text being analyzed.

@stable

Implemented in RuleBasedBreakIterator.

virtual UBool BreakIterator::isBoundary UTextOffset    offset [pure virtual]
 

Return true if the specfied position is a boundary position.

Parameters:
offset  the offset to check.
Returns:
True if "offset" is a boundary position. @stable

virtual UTextOffset BreakIterator::last void    [pure virtual]
 

Return the index immediately BEYOND the last character in the text being scanned.

@stable

Implemented in RuleBasedBreakIterator.

virtual UTextOffset BreakIterator::next int32_t    n [pure virtual]
 

Return the nth boundary from the current boundary.

Parameters:
n  which boundary to return. A value of 0 does nothing. Negative values move to previous boundaries and positive values move to later boundaries.
Returns:
The index of the nth boundary from the current position, or DONE if there are fewer than |n| boundaries in the specfied direction. @stable

Implemented in RuleBasedBreakIterator.

virtual UTextOffset BreakIterator::next void    [pure virtual]
 

Return the boundary following the current boundary.

Returns:
The character index of the next text boundary or DONE if all boundaries have been returned. @stable

Implemented in RuleBasedBreakIterator.

virtual UBool BreakIterator::operator== const BreakIterator &    const [pure virtual]
 

Return true if another object is semantically equal to this one.

The other object should be an instance of the same subclass of BreakIterator. Objects of different subclasses are considered unequal.

Return true if this BreakIterator is at the same position in the same text, and is the same class and type (word, line, etc.) of BreakIterator, as the argument. Text is considered the same if it contains the same characters, it need not be the same object, and styles are not considered. @stable

Implemented in RuleBasedBreakIterator.

virtual UTextOffset BreakIterator::preceding UTextOffset    offset [pure virtual]
 

Return the first boundary preceding the specified offset.

The value returned is always smaller than the offset or the value BreakIterator.DONE

Parameters:
offset  the offset to begin scanning.
Returns:
The first boundary before the specified offset. @stable

virtual UTextOffset BreakIterator::previous void    [pure virtual]
 

Return the boundary preceding the current boundary.

Returns:
The character index of the previous text boundary or DONE if all boundaries have been returned. @stable

Implemented in DictionaryBasedBreakIterator.

virtual void BreakIterator::setText const UnicodeString   text [pure virtual]
 

Change the text over which this operates.

The text boundary is reset to the start. @stable

Implemented in RuleBasedBreakIterator.


Field Documentation

const UTextOffset BreakIterator::DONE [static]
 

DONE is returned by previous() and next() after all valid boundaries have been returned.

@stable


The documentation for this class was generated from the following file:
Generated on Mon Mar 4 20:07:17 2002 for ICU 2.0 by doxygen1.2.14 written by Dimitri van Heesch, © 1997-2002