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CharacterIterator Class Reference

Abstract class that defines an API for iteration on text objects. More...

#include <chariter.h>

Class diagram for CharacterIterator:

ForwardCharacterIterator UCharCharacterIterator StringCharacterIterator

List of all members.


Public Members

enum  EOrigin { kStart, kCurrent, kEnd }
Origin enumeration for the move() and move32() functions. More...

virtual CharacterIterator* clone (void) const = 0
Returns a pointer to a new CharacterIterator of the same concrete class as this one, and referring to the same character in the same text-storage object as this one. More...

virtual UChar first (void) = 0
Sets the iterator to refer to the first code unit in its iteration range, and returns that code unit. More...

virtual UChar firstPostInc (void)
Sets the iterator to refer to the first code unit in its iteration range, returns that code unit, and moves the position to the second code unit. More...

virtual UChar32 first32 (void) = 0
Sets the iterator to refer to the first code point in its iteration range, and returns that code unit, This can be used to begin an iteration with next32(). More...

virtual UChar32 first32PostInc (void)
Sets the iterator to refer to the first code point in its iteration range, returns that code point, and moves the position to the second code point. More...

UTextOffset setToStart ()
Sets the iterator to refer to the first code unit or code point in its iteration range. More...

virtual UChar last (void) = 0
Sets the iterator to refer to the last code unit in its iteration range, and returns that code unit. More...

virtual UChar32 last32 (void) = 0
Sets the iterator to refer to the last code point in its iteration range, and returns that code unit. More...

UTextOffset setToEnd ()
Sets the iterator to the end of its iteration range, just behind the last code unit or code point. More...

virtual UChar setIndex (UTextOffset position) = 0
Sets the iterator to refer to the "position"-th code unit in the text-storage object the iterator refers to, and returns that code unit. More...

virtual UChar32 setIndex32 (UTextOffset position) = 0
Sets the iterator to refer to the beginning of the code point that contains the "position"-th code unit in the text-storage object the iterator refers to, and returns that code point. More...

virtual UChar current (void) const = 0
Returns the code unit the iterator currently refers to. More...

virtual UChar32 current32 (void) const = 0
Returns the code point the iterator currently refers to. More...

virtual UChar next (void) = 0
Advances to the next code unit in the iteration range (toward endIndex()), and returns that code unit. More...

virtual UChar32 next32 (void) = 0
Advances to the next code point in the iteration range (toward endIndex()), and returns that code point. More...

virtual UChar previous (void) = 0
Advances to the previous code unit in the iteration rance (toward startIndex()), and returns that code unit. More...

virtual UChar32 previous32 (void) = 0
Advances to the previous code point in the iteration rance (toward startIndex()), and returns that code point. More...

virtual UBool hasPrevious () = 0
Returns FALSE if there are no more code units or code points before the current position in the iteration range. More...

UTextOffset startIndex (void) const
Returns the numeric index in the underlying text-storage object of the character returned by first(). More...

UTextOffset endIndex (void) const
Returns the numeric index in the underlying text-storage object of the position immediately BEYOND the character returned by last(). More...

UTextOffset getIndex (void) const
Returns the numeric index in the underlying text-storage object of the character the iterator currently refers to (i.e., the character returned by current()). More...

int32_t getLength () const
Returns the length of the entire text in the underlying text-storage object.

virtual UTextOffset move (int32_t delta, EOrigin origin) = 0
Moves the current position relative to the start or end of the iteration range, or relative to the current position itself. More...

virtual UTextOffset move32 (int32_t delta, EOrigin origin) = 0
Moves the current position relative to the start or end of the iteration range, or relative to the current position itself. More...

virtual void getText (UnicodeString& result) = 0
Copies the text under iteration into the UnicodeString referred to by "result". More...


Protected Members

 CharacterIterator ()
 CharacterIterator (int32_t length)
 CharacterIterator (int32_t length, UTextOffset position)
 CharacterIterator (int32_t length, UTextOffset begin, UTextOffset end, UTextOffset position)
 CharacterIterator (const CharacterIterator &that)
CharacterIterator& operator= (const CharacterIterator &that)
int32_t textLength
UTextOffset pos
UTextOffset begin
UTextOffset end

Detailed Description

Abstract class that defines an API for iteration on text objects.

This is an interface for forward and backward iteration and random access into a text object.

The API provides backward compatibility to the Java and older ICU CharacterIterator classes but extends them significantly:

  1. CharacterIterator is now a subclass of ForwardCharacterIterator.
  2. While the old API functions provided forward iteration with "pre-increment" semantics, the new one also provides functions with "post-increment" semantics. They are more efficient and should be the preferred iterator functions for new implementations. The backward iteration always had "pre-decrement" semantics, which are efficient.
  3. Just like ForwardCharacterIterator, it provides access to both code units and code points. Code point access versions are available for the old and the new iteration semantics.
  4. There are new functions for setting and moving the current position without returning a character, for efficiency.

      See ForwardCharacterIterator for examples for using the new forward iteration functions. For backward iteration, there is also a hasPrevious() function that can be used analogously to hasNext(). The old functions work as before and are shown below.

      Examples for some of the new functions:

      Forward iteration with hasNext(): &#32; void forward1(CharacterIterator &it) { &#32; UChar32 c; &#32; for(it.setToStart(); it.hasNext();) { &#32; c=it.next32PostInc(); &#32; // use c &#32; } &#32; }

      Forward iteration more similar to loops with the old forward iteration, showing a way to convert simple for() loops: &#32; void forward2(CharacterIterator &it) { &#32; UChar c; &#32; for(c=it.firstPostInc(); c!=CharacterIterator::DONE; c=it.nextPostInc()) { &#32; // use c &#32; } &#32; }

      Backward iteration with setToEnd() and hasPrevious(): &#32; void backward1(CharacterIterator &it) { &#32; UChar32 c; &#32; for(it.setToEnd(); it.hasPrevious();) { &#32; c=it.previous32(); &#32; // use c &#32; } &#32; }

      Backward iteration with a more traditional for() loop: &#32; void backward2(CharacterIterator &it) { &#32; UChar c; &#32; for(c=it.last(); c!=CharacterIterator::DONE; c=it.previous()) { &#32; // use c &#32; } &#32; }

      Example for random access: &#32; void random(CharacterIterator &it) { &#32; // set to the third code point from the beginning &#32; it.move32(3, CharacterIterator::kStart); &#32; // get a code point from here without moving the position &#32; UChar32 c=it.current32(); &#32; // get the position &#32; int32_t pos=it.getIndex(); &#32; // get the previous code unit &#32; UChar u=it.previous(); &#32; // move back one more code unit &#32; it.move(-1, CharacterIterator::kCurrent); &#32; // set the position back to where it was &#32; // and read the same code point c and move beyond it &#32; it.setIndex(pos); &#32; if(c!=it.next32PostInc()) { &#32; exit(1); // CharacterIterator inconsistent &#32; } &#32; }

      Examples, especially for the old API:

      Function processing characters, in this example simple output

       &#32; void processChar( UChar c )
       &#32; {
       &#32;     cout &lt;&lt; " " &lt;&lt; c;
       &#32; }
       
      Traverse the text from start to finish
       
       &#32; void traverseForward(CharacterIterator& iter)
       &#32; {
       &#32;     for(UChar c = iter.first(); c != CharacterIterator.DONE; c = iter.next()) {
       &#32;         processChar(c);
       &#32;     }
       &#32; }
       
      Traverse the text backwards, from end to start
       &#32; void traverseBackward(CharacterIterator& iter)
       &#32; {
       &#32;     for(UChar c = iter.last(); c != CharacterIterator.DONE; c = iter.previous()) {
       &#32;         processChar(c);
       &#32;     }
       &#32; }
       
      Traverse both forward and backward from a given position in the text. Calls to notBoundary() in this example represents some additional stopping criteria.
       &#32; void traverseOut(CharacterIterator& iter, UTextOffset pos)
       &#32; {
       &#32;     UChar c;
       &#32;     for (c = iter.setIndex(pos);
       &#32;     c != CharacterIterator.DONE && (Unicode::isLetter(c) || Unicode::isDigit(c));
       &#32;         c = iter.next()) {}
       &#32;     UTextOffset end = iter.getIndex();
       &#32;     for (c = iter.setIndex(pos);
       &#32;         c != CharacterIterator.DONE && (Unicode::isLetter(c) || Unicode::isDigit(c));
       &#32;         c = iter.previous()) {}
       &#32;     UTextOffset start = iter.getIndex() + 1;
       &#32; 
       &#32;     cout &lt;&lt; "start: " &lt;&lt; start &lt;&lt; " end: " &lt;&lt; end &lt;&lt; endl;
       &#32;     for (c = iter.setIndex(start); iter.getIndex() &lt; end; c = iter.next() ) {
       &#32;         processChar(c);
       &#32;     }
       &#32;  }
       
      Creating a StringCharacterIterator and calling the test functions
       &#32;  void CharacterIterator_Example( void )
       &#32;  {
       &#32;      cout &lt;&lt; endl &lt;&lt; "===== CharacterIterator_Example: =====" &lt;&lt; endl;
       &#32;      UnicodeString text("Ein kleiner Satz.");
       &#32;      StringCharacterIterator iterator(text);
       &#32;      cout &lt;&lt; "----- traverseForward: -----------" &lt;&lt; endl;
       &#32;      traverseForward( iterator );
       &#32;      cout &lt;&lt; endl &lt;&lt; endl &lt;&lt; "----- traverseBackward: ----------" &lt;&lt; endl;
       &#32;      traverseBackward( iterator );
       &#32;      cout &lt;&lt; endl &lt;&lt; endl &lt;&lt; "----- traverseOut: ---------------" &lt;&lt; endl;
       &#32;      traverseOut( iterator, 7 );
       &#32;      cout &lt;&lt; endl &lt;&lt; endl &lt;&lt; "-----" &lt;&lt; endl;
       &#32;  }
       

      Definition at line 304 of file chariter.h.


      Member Enumeration Documentation

      enum CharacterIterator::EOrigin

      Origin enumeration for the move() and move32() functions.

      Enumeration values:
      kStart  
      kCurrent  
      kEnd  

      Definition at line 309 of file chariter.h.


      Member Function Documentation

      virtual CharacterIterator * CharacterIterator::clone (void) const [pure virtual]

      Returns a pointer to a new CharacterIterator of the same concrete class as this one, and referring to the same character in the same text-storage object as this one.

      The caller is responsible for deleting the new clone.

      Stable:

      Reimplemented in StringCharacterIterator, and UCharCharacterIterator.

      virtual UChar CharacterIterator::first (void) [pure virtual]

      Sets the iterator to refer to the first code unit in its iteration range, and returns that code unit.

      This can be used to begin an iteration with next().

      Draft:

      Reimplemented in UCharCharacterIterator.

      virtual UChar CharacterIterator::firstPostInc (void) [virtual]

      Sets the iterator to refer to the first code unit in its iteration range, returns that code unit, and moves the position to the second code unit.

      This is an alternative to setToStart() for forward iteration with nextPostInc().

      Draft:

      Reimplemented in UCharCharacterIterator.

      virtual UChar32 CharacterIterator::first32 (void) [pure virtual]

      Sets the iterator to refer to the first code point in its iteration range, and returns that code unit, This can be used to begin an iteration with next32().

      Note that an iteration with next32PostInc(), beginning with, e.g., setToStart() or firstPostInc(), is more efficient.

      Draft:

      Reimplemented in UCharCharacterIterator.

      virtual UChar32 CharacterIterator::first32PostInc (void) [virtual]

      Sets the iterator to refer to the first code point in its iteration range, returns that code point, and moves the position to the second code point.

      This is an alternative to setToStart() for forward iteration with next32PostInc().

      Draft:

      Reimplemented in UCharCharacterIterator.

      UTextOffset CharacterIterator::setToStart () [inline]

      Sets the iterator to refer to the first code unit or code point in its iteration range.

      This can be used to begin a forward iteration with nextPostInc() or next32PostInc().

      Returns:
      the start position of the iteration range
      Draft:

      Definition at line 543 of file chariter.h.

      virtual UChar CharacterIterator::last (void) [pure virtual]

      Sets the iterator to refer to the last code unit in its iteration range, and returns that code unit.

      This can be used to begin an iteration with previous().

      Draft:

      Reimplemented in UCharCharacterIterator.

      virtual UChar32 CharacterIterator::last32 (void) [pure virtual]

      Sets the iterator to refer to the last code point in its iteration range, and returns that code unit.

      This can be used to begin an iteration with previous32().

      Draft:

      Reimplemented in UCharCharacterIterator.

      UTextOffset CharacterIterator::setToEnd () [inline]

      Sets the iterator to the end of its iteration range, just behind the last code unit or code point.

      This can be used to begin a backward iteration with previous() or previous32().

      Returns:
      the end position of the iteration range
      Draft:

      Definition at line 548 of file chariter.h.

      virtual UChar CharacterIterator::setIndex (UTextOffset pos) [pure virtual]

      Sets the iterator to refer to the "position"-th code unit in the text-storage object the iterator refers to, and returns that code unit.

      Draft:

      Reimplemented in UCharCharacterIterator.

      virtual UChar32 CharacterIterator::setIndex32 (UTextOffset pos) [pure virtual]

      Sets the iterator to refer to the beginning of the code point that contains the "position"-th code unit in the text-storage object the iterator refers to, and returns that code point.

      The current position is adjusted to the beginning of the code point (its first code unit).

      Draft:

      Reimplemented in UCharCharacterIterator.

      virtual UChar CharacterIterator::current (void) const [pure virtual]

      Returns the code unit the iterator currently refers to.

      Draft:

      Reimplemented in UCharCharacterIterator.

      virtual UChar32 CharacterIterator::current32 (void) const [pure virtual]

      Returns the code point the iterator currently refers to.

      Draft:

      Reimplemented in UCharCharacterIterator.

      virtual UChar CharacterIterator::next (void) [pure virtual]

      Advances to the next code unit in the iteration range (toward endIndex()), and returns that code unit.

      If there are no more code units to return, returns DONE.

      Draft:

      Reimplemented in UCharCharacterIterator.

      virtual UChar32 CharacterIterator::next32 (void) [pure virtual]

      Advances to the next code point in the iteration range (toward endIndex()), and returns that code point.

      If there are no more code points to return, returns DONE. Note that iteration with "pre-increment" semantics is less efficient than iteration with "post-increment" semantics that is provided by next32PostInc().

      Draft:

      Reimplemented in UCharCharacterIterator.

      virtual UChar CharacterIterator::previous (void) [pure virtual]

      Advances to the previous code unit in the iteration rance (toward startIndex()), and returns that code unit.

      If there are no more code units to return, returns DONE.

      Draft:

      Reimplemented in UCharCharacterIterator.

      virtual UChar32 CharacterIterator::previous32 (void) [pure virtual]

      Advances to the previous code point in the iteration rance (toward startIndex()), and returns that code point.

      If there are no more code points to return, returns DONE.

      Draft:

      Reimplemented in UCharCharacterIterator.

      virtual UBool CharacterIterator::hasPrevious () [pure virtual]

      Returns FALSE if there are no more code units or code points before the current position in the iteration range.

      This is used with previous() or previous32() in backward iteration.

      Reimplemented in UCharCharacterIterator.

      UTextOffset CharacterIterator::startIndex (void) const [inline]

      Returns the numeric index in the underlying text-storage object of the character returned by first().

      Since it's possible to create an iterator that iterates across only part of a text-storage object, this number isn't necessarily 0.

      Stable:

      Definition at line 553 of file chariter.h.

      UTextOffset CharacterIterator::endIndex (void) const [inline]

      Returns the numeric index in the underlying text-storage object of the position immediately BEYOND the character returned by last().

      Stable:

      Definition at line 558 of file chariter.h.

      UTextOffset CharacterIterator::getIndex (void) const [inline]

      Returns the numeric index in the underlying text-storage object of the character the iterator currently refers to (i.e., the character returned by current()).

      Stable:

      Definition at line 563 of file chariter.h.

      int32_t CharacterIterator::getLength (void) const [inline]

      Returns the length of the entire text in the underlying text-storage object.

      Definition at line 568 of file chariter.h.

      virtual UTextOffset CharacterIterator::move (int32_t delta, EOrigin origin) [pure virtual]

      Moves the current position relative to the start or end of the iteration range, or relative to the current position itself.

      The movement is expressed in numbers of code units forward or backward by specifying a positive or negative delta.

      Returns:
      the new position

      Reimplemented in UCharCharacterIterator.

      virtual UTextOffset CharacterIterator::move32 (int32_t delta, EOrigin origin) [pure virtual]

      Moves the current position relative to the start or end of the iteration range, or relative to the current position itself.

      The movement is expressed in numbers of code points forward or backward by specifying a positive or negative delta.

      Returns:
      the new position

      Reimplemented in UCharCharacterIterator.

      virtual void CharacterIterator::getText (UnicodeString & result) [pure virtual]

      Copies the text under iteration into the UnicodeString referred to by "result".

      Parameters:
      result   Receives a copy of the text under iteration.
      Stable:

      Reimplemented in StringCharacterIterator, and UCharCharacterIterator.

      CharacterIterator::CharacterIterator () [inline, protected]

      Definition at line 523 of file chariter.h.

      CharacterIterator::CharacterIterator (int32_t length) [protected]

      CharacterIterator::CharacterIterator (int32_t length, UTextOffset position) [protected]

      CharacterIterator::CharacterIterator (int32_t length, UTextOffset begin, UTextOffset end, UTextOffset position) [protected]

      CharacterIterator::CharacterIterator (const CharacterIterator & that) [protected]

      CharacterIterator& CharacterIterator::operator= (const CharacterIterator & that) [protected]


      Member Data Documentation

      int32_t CharacterIterator::textLength [protected]

      Definition at line 531 of file chariter.h.

      UTextOffset CharacterIterator::pos [protected]

      Definition at line 532 of file chariter.h.

      UTextOffset CharacterIterator::begin [protected]

      Definition at line 533 of file chariter.h.

      UTextOffset CharacterIterator::end [protected]

      Definition at line 534 of file chariter.h.


      The documentation for this class was generated from the following file:
      Generated at Mon Jun 5 12:53:11 2000 for ICU1.5 by doxygen 1.0.0 written by Dimitri van Heesch, © 1997-1999