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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 Member Functions

virtual UBool operator== (const BreakIterator &) const =0
 Return true if another object is semantically equal to this one.
UBool operator!= (const BreakIterator &rhs) const
 Returns the complement of the result of operator== .
virtual BreakIteratorclone (void) const =0
 Return a polymorphic copy of this object.
virtual UClassID getDynamicClassID (void) const =0
 Return a polymorphic class ID for this object.
virtual const CharacterIteratorgetText (void) const =0
 Return a CharacterIterator over the text being analyzed.
virtual void setText (const UnicodeString &text)=0
 Change the text over which this operates.
virtual void adoptText (CharacterIterator *it)=0
 Change the text over which this operates.
virtual int32_t first (void)=0
 Return the index of the first character in the text being scanned.
virtual int32_t last (void)=0
 Return the index immediately BEYOND the last character in the text being scanned.
virtual int32_t previous (void)=0
 Return the boundary preceding the current boundary.
virtual int32_t next (void)=0
 Return the boundary following the current boundary.
virtual int32_t current (void) const =0
 Return character index of the text boundary that was most recently returned by next(), previous(), first(), or last().
virtual int32_t following (int32_t offset)=0
 Return the first boundary following the specified offset.
virtual int32_t preceding (int32_t offset)=0
 Return the first boundary preceding the specified offset.
virtual UBool isBoundary (int32_t offset)=0
 Return true if the specfied position is a boundary position.
virtual int32_t next (int32_t n)=0
 Return the nth boundary from the current boundary.
virtual BreakIteratorcreateBufferClone (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.
UBool isBufferClone (void)

Static Public Member Functions

static BreakIteratorcreateWordInstance (const Locale &where, UErrorCode &status)
 Create BreakIterator for word-breaks using the given locale.
static BreakIteratorcreateLineInstance (const Locale &where, UErrorCode &status)
 Create BreakIterator for line-breaks using specified locale.
static BreakIteratorcreateCharacterInstance (const Locale &where, UErrorCode &status)
 Create BreakIterator for character-breaks using specified locale Returns an instance of a BreakIterator implementing character breaks.
static BreakIteratorcreateSentenceInstance (const Locale &where, UErrorCode &status)
 Create BreakIterator for sentence-breaks using specified locale Returns an instance of a BreakIterator implementing sentence breaks.
static BreakIteratorcreateTitleInstance (const Locale &where, UErrorCode &status)
 Create BreakIterator for title-casing breaks using the specified locale Returns an instance of a BreakIterator implementing title breaks.
static const Locale * getAvailableLocales (int32_t &count)
 Get the set of Locales for which TextBoundaries are installed.
static UnicodeStringgetDisplayName (const Locale &objectLocale, const Locale &displayLocale, UnicodeString &name)
 Get name of the object for the desired Locale, in the desired langauge.
static UnicodeStringgetDisplayName (const Locale &objectLocale, UnicodeString &name)
 Get name of the object for the desired Locale, in the langauge of the default locale.

Static Public Attributes

static const int32_t DONE
 DONE is returned by previous() and next() after all valid boundaries have been returned.

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, int32_t start, int32_t 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)
    {
       int32_t start = boundary.first();
       for (int32_t 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)
    {
       int32_t end = boundary.last();
       for (int32_t start = boundary.previous();
         start != BreakIterator::DONE;
         end = start, start = boundary.previous())
         {
             printTextRange( boundary, start, end );
         }
    }
Print first element
 
    void printFirst(BreakIterator& boundary)
    {
        int32_t start = boundary.first();
        int32_t end = boundary.next();
        printTextRange( boundary, start, end );
    }
Print last element
  
    void printLast(BreakIterator& boundary)
    {
        int32_t end = boundary.last();
        int32_t start = boundary.previous();
        printTextRange( boundary, start, end );
    }
Print the element at a specified position
 
    void printAt(BreakIterator &boundary, int32_t pos )
    {
        int32_t end = boundary.following(pos);
        int32_t 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.

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.

Implemented in DictionaryBasedBreakIterator, and RuleBasedBreakIterator.

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
ICU 1.8

Implemented in DictionaryBasedBreakIterator, and RuleBasedBreakIterator.

static 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.

static 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.

static 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.

static 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.

static 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.

virtual int32_t 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.

Implemented in RuleBasedBreakIterator.

virtual int32_t BreakIterator::first void   )  [pure virtual]
 

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

Implemented in RuleBasedBreakIterator.

virtual int32_t BreakIterator::following int32_t  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.

Implemented in DictionaryBasedBreakIterator, and RuleBasedBreakIterator.

static 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

static 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

static 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

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

Return a polymorphic class ID for this object.

Different subclasses will return distinct unequal values.

Implemented in DictionaryBasedBreakIterator, and RuleBasedBreakIterator.

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

Return a CharacterIterator over the text being analyzed.

Implemented in RuleBasedBreakIterator.

virtual UBool BreakIterator::isBoundary int32_t  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.

Implemented in RuleBasedBreakIterator.

virtual int32_t BreakIterator::last void   )  [pure virtual]
 

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

Implemented in RuleBasedBreakIterator.

virtual int32_t 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.

Implemented in RuleBasedBreakIterator.

virtual int32_t 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.

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.

Implemented in RuleBasedBreakIterator.

virtual int32_t BreakIterator::preceding int32_t  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.

Implemented in DictionaryBasedBreakIterator, and RuleBasedBreakIterator.

virtual int32_t 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.

Implemented in DictionaryBasedBreakIterator, and RuleBasedBreakIterator.

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

Change the text over which this operates.

The text boundary is reset to the start.

Implemented in RuleBasedBreakIterator.


Field Documentation

const int32_t BreakIterator::DONE [static]
 

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


The documentation for this class was generated from the following file:
Generated on Sun May 22 18:49:39 2005 for ICU 2.1 by  doxygen 1.4.2