ICU 68.2: icu::CharacterIterator Class Reference

ICU 68.2 68.2

Public Types | Public Member Functions | Protected Member Functions | Protected Attributes
icu::CharacterIterator Class Referenceabstract

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

`#include <chariter.h>`

Inheritance diagram for icu::CharacterIterator:

## Public Types
enum | EOrigin { kStart, kCurrent, kEnd }
| Origin enumeration for the move() and move32() functions. More...
Public Types inherited from icu::ForwardCharacterIterator
enum | { DONE = 0xffff }
| Value returned by most of ForwardCharacterIterator's functions when the iterator has reached the limits of its iteration. More...

## Public Member Functions
virtual | ~CharacterIterator ()
| Destructor. More...
virtual CharacterIterator * | clone () 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 char16_t | first (void)=0
| Sets the iterator to refer to the first code unit in its iteration range, and returns that code unit. More...
virtual char16_t | 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...
int32_t | setToStart ()
| Sets the iterator to refer to the first code unit or code point in its iteration range. More...
virtual char16_t | 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...
int32_t | setToEnd ()
| Sets the iterator to the end of its iteration range, just behind the last code unit or code point. More...
virtual char16_t | setIndex (int32_t 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 (int32_t 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 char16_t | 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 char16_t | 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 char16_t | previous (void)=0
| Advances to the previous code unit in the iteration range (toward startIndex()), and returns that code unit. More...
virtual UChar32 | previous32 (void)=0
| Advances to the previous code point in the iteration range (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...
int32_t | startIndex (void) const
| Returns the numeric index in the underlying text-storage object of the character returned by first(). More...
int32_t | endIndex (void) const
| Returns the numeric index in the underlying text-storage object of the position immediately BEYOND the character returned by last(). More...
int32_t | 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. More...
virtual int32_t | 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 int32_t | 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...
Public Member Functions inherited from icu::ForwardCharacterIterator
virtual | ~ForwardCharacterIterator ()
| Destructor. More...
virtual UBool | operator== (const ForwardCharacterIterator &that) const =0
| Returns true when both iterators refer to the same character in the same character-storage object. More...
UBool | operator!= (const ForwardCharacterIterator &that) const
| Returns true when the iterators refer to different text-storage objects, or to different characters in the same text-storage object. More...
virtual int32_t | hashCode (void) const =0
| Generates a hash code for this iterator. More...
virtual UClassID | getDynamicClassID (void) const =0
| Returns a UClassID for this ForwardCharacterIterator ("poor man's RTTI"). More...
virtual char16_t | nextPostInc (void)=0
| Gets the current code unit for returning and advances to the next code unit in the iteration range (toward endIndex()). More...
virtual UChar32 | next32PostInc (void)=0
| Gets the current code point for returning and advances to the next code point in the iteration range (toward endIndex()). More...
virtual UBool | hasNext ()=0
| Returns false if there are no more code units or code points at or after the current position in the iteration range. More...
Public Member Functions inherited from icu::UObject
virtual | ~UObject ()
| Destructor. More...

## Protected Member Functions
| CharacterIterator ()
| Empty constructor. More...
| CharacterIterator (int32_t length)
| Constructor, just setting the length field in this base class. More...
| CharacterIterator (int32_t length, int32_t position)
| Constructor, just setting the length and position fields in this base class. More...
| CharacterIterator (int32_t length, int32_t textBegin, int32_t textEnd, int32_t position)
| Constructor, just setting the length, start, end, and position fields in this base class. More...
| CharacterIterator (const CharacterIterator &that)
| Copy constructor. More...
CharacterIterator & | operator= (const CharacterIterator &that)
| Assignment operator. More...
Protected Member Functions inherited from icu::ForwardCharacterIterator
| ForwardCharacterIterator ()
| Default constructor to be overridden in the implementing class. More...
| ForwardCharacterIterator (const ForwardCharacterIterator &other)
| Copy constructor to be overridden in the implementing class. More...
ForwardCharacterIterator & | operator= (const ForwardCharacterIterator &)
| Assignment operator to be overridden in the implementing class. More...

## Protected Attributes
int32_t | textLength
| Base class text length field. More...
int32_t | pos
| Base class field for the current position. More...
int32_t | begin
| Base class field for the start of the iteration range. More...
int32_t | end
| Base class field for the end of the iteration range. More...

## 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():

void forward1(CharacterIterator &it) {
UChar32 c;
for(it.setToStart(); it.hasNext();) {
c=it.next32PostInc();
// use c
}
}

Forward iteration more similar to loops with the old forward iteration, showing a way to convert simple for() loops:

void forward2(CharacterIterator &it) {
char16_t c;
for(c=it.firstPostInc(); c!=CharacterIterator::DONE; c=it.nextPostInc()) {
// use c
}
}

Backward iteration with setToEnd() and hasPrevious():

void backward1(CharacterIterator &it) {
UChar32 c;
for(it.setToEnd(); it.hasPrevious();) {
c=it.previous32();
// use c
}
}

Backward iteration with a more traditional for() loop:

void backward2(CharacterIterator &it) {
char16_t c;
for(c=it.last(); c!=CharacterIterator::DONE; c=it.previous()) {
// use c
}
}

Example for random access:

void random(CharacterIterator &it) {
// set to the third code point from the beginning
it.move32(3, CharacterIterator::kStart);
// get a code point from here without moving the position
UChar32 c=it.current32();
// get the position
int32_t pos=it.getIndex();
// get the previous code unit
char16_t u=it.previous();
// move back one more code unit
it.move(-1, CharacterIterator::kCurrent);
// set the position back to where it was
// and read the same code point c and move beyond it
it.setIndex(pos);
if(c!=it.next32PostInc()) {
exit(1); // CharacterIterator inconsistent
}
}

Examples, especially for the old API:

Function processing characters, in this example simple output

    void processChar( char16_t c )
    {
        cout << " " << c;
    }

Traverse the text from start to finish

    void traverseForward(CharacterIterator& iter)
    {
        for(char16_t c = iter.first(); c != CharacterIterator.DONE; c = iter.next()) {
            processChar(c);
        }
    }

Traverse the text backwards, from end to start

    void traverseBackward(CharacterIterator& iter)
    {
        for(char16_t c = iter.last(); c != CharacterIterator.DONE; c = iter.previous()) {
            processChar(c);
        }
    }

Traverse both forward and backward from a given position in the text. Calls to notBoundary() in this example represents some additional stopping criteria.

    void traverseOut(CharacterIterator& iter, int32_t pos)
    {
         char16_t c;
         for (c = iter.setIndex(pos);
         c != CharacterIterator.DONE && (Unicode::isLetter(c) || Unicode::isDigit(c));
             c = iter.next()) {}
         int32_t end = iter.getIndex();
         for (c = iter.setIndex(pos);
             c != CharacterIterator.DONE && (Unicode::isLetter(c) || Unicode::isDigit(c));
             c = iter.previous()) {}
         int32_t start = iter.getIndex() + 1;

         cout << "start: " << start << " end: " << end << endl;
         for (c = iter.setIndex(start); iter.getIndex() < end; c = iter.next() ) {
             processChar(c);
        }
     }

Creating a StringCharacterIterator and calling the test functions

    void CharacterIterator_Example( void )
     {
         cout << endl << "===== CharacterIterator_Example: =====" << endl;
         UnicodeString text("Ein kleiner Satz.");
         StringCharacterIterator iterator(text);
         cout << "----- traverseForward: -----------" << endl;
         traverseForward( iterator );
         cout << endl << endl << "----- traverseBackward: ----------" << endl;
         traverseBackward( iterator );
         cout << endl << endl << "----- traverseOut: ---------------" << endl;
         traverseOut( iterator, 7 );
         cout << endl << endl << "-----" << endl;
     }

Stable:
  ICU 2.0

Definition at line 361 of file chariter.h.

## Member Enumeration Documentation

## ◆ EOrigin

enum icu::CharacterIterator::EOrigin

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

Stable:
  ICU 2.0

Definition at line 367 of file chariter.h.

## Constructor & Destructor Documentation

## ◆ ~CharacterIterator()

virtual icu::CharacterIterator::~CharacterIterator | ( |  | ) |
| virtual

Destructor.

Stable:
  ICU 2.0

## ◆ CharacterIterator() [1/5]

icu::CharacterIterator::CharacterIterator | ( |  | ) |
| protected

Empty constructor.

Stable:
  ICU 2.0

## ◆ CharacterIterator() [2/5]

icu::CharacterIterator::CharacterIterator | ( | int32_t | length | ) |
| protected

Constructor, just setting the length field in this base class.

Stable:
  ICU 2.0

## ◆ CharacterIterator() [3/5]

icu::CharacterIterator::CharacterIterator | ( | int32_t | length,
|  | int32_t | position
| ) |  |
| protected

Constructor, just setting the length and position fields in this base class.

Stable:
  ICU 2.0

## ◆ CharacterIterator() [4/5]

icu::CharacterIterator::CharacterIterator | ( | int32_t | length,
|  | int32_t | textBegin,
|  | int32_t | textEnd,
|  | int32_t | position
| ) |  |
| protected

Constructor, just setting the length, start, end, and position fields in this base class.

Stable:
  ICU 2.0

## ◆ CharacterIterator() [5/5]

icu::CharacterIterator::CharacterIterator | ( | const CharacterIterator & | that | ) |
| protected

Copy constructor.

Parameters

  that | The CharacterIterator to be copied

Stable:
  ICU 2.0

## Member Function Documentation

## ◆ clone()

virtual CharacterIterator* icu::CharacterIterator::clone | ( |  | ) | 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.

Returns
  a pointer to a new CharacterIterator

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator, and icu::StringCharacterIterator.

## ◆ current()

virtual char16_t icu::CharacterIterator::current | ( | void |  | ) | const
| pure virtual

Returns the code unit the iterator currently refers to.

Returns
  the current code unit.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ current32()

virtual UChar32 icu::CharacterIterator::current32 | ( | void |  | ) | const
| pure virtual

Returns the code point the iterator currently refers to.

Returns
  the current code point.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ endIndex()

int32_t icu::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().

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

Stable:
  ICU 2.0

Definition at line 716 of file chariter.h.

## ◆ first()

virtual char16_t icu::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().

Returns
  the first code unit in its iteration range.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ first32()

virtual UChar32 icu::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.

Returns
  the first code point in its iteration range.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ first32PostInc()

virtual UChar32 icu::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().

Returns
  the first code point in its iteration range.

Stable:
  ICU 2.0

Reimplemented in icu::UCharCharacterIterator.

## ◆ firstPostInc()

virtual char16_t icu::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().

Returns
  the first code unit in its iteration range.

Stable:
  ICU 2.0

Reimplemented in icu::UCharCharacterIterator.

## ◆ getIndex()

int32_t icu::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()).

Returns
  the numeric index in the text-storage object of the character the iterator currently refers to

Stable:
  ICU 2.0

Definition at line 721 of file chariter.h.

## ◆ getLength()

int32_t icu::CharacterIterator::getLength | ( | void |  | ) | const
| inline

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

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

Stable:
  ICU 2.0

Definition at line 726 of file chariter.h.

## ◆ getText()

virtual void icu::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:
  ICU 2.0

Implemented in icu::UCharCharacterIterator, and icu::StringCharacterIterator.

## ◆ hasPrevious()

virtual UBool icu::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.

Returns
  false if there are no more code units or code points before the current position in the iteration range, return true otherwise.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ last()

virtual char16_t icu::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().

Returns
  the last code unit.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ last32()

virtual UChar32 icu::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().

Returns
  the last code point.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ move()

virtual int32_t icu::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.

Parameters

  delta | the position relative to origin. A positive delta means forward; a negative delta means backward.
  origin | Origin enumeration {kStart, kCurrent, kEnd}

Returns
  the new position

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ move32()

virtual int32_t icu::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.

Parameters

  delta | the position relative to origin. A positive delta means forward; a negative delta means backward.
  origin | Origin enumeration {kStart, kCurrent, kEnd}

Returns
  the new position

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ next()

virtual char16_t icu::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.

Returns
  the next code unit.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ next32()

virtual UChar32 icu::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().

Returns
  the next code point.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ operator=()

CharacterIterator& icu::CharacterIterator::operator= | ( | const CharacterIterator & | that | ) |
| protected

Assignment operator.

Sets this CharacterIterator to have the same behavior, as the one passed in.

Parameters

  that | The CharacterIterator passed in.

Returns
  the newly set CharacterIterator.

Stable:
  ICU 2.0

## ◆ previous()

virtual char16_t icu::CharacterIterator::previous | ( | void |  | ) |
| pure virtual

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

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

Returns
  the previous code unit.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ previous32()

virtual UChar32 icu::CharacterIterator::previous32 | ( | void |  | ) |
| pure virtual

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

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

Returns
  the previous code point.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ setIndex()

virtual char16_t icu::CharacterIterator::setIndex | ( | int32_t | position | ) |
| 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.

Parameters

  position | the "position"-th code unit in the text-storage object

Returns
  the "position"-th code unit.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ setIndex32()

virtual UChar32 icu::CharacterIterator::setIndex32 | ( | int32_t | position | ) |
| 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).

Parameters

  position | the "position"-th code unit in the text-storage object

Returns
  the "position"-th code point.

Stable:
  ICU 2.0

Implemented in icu::UCharCharacterIterator.

## ◆ setToEnd()

int32_t icu::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

Stable:
  ICU 2.0

Definition at line 706 of file chariter.h.

## ◆ setToStart()

int32_t icu::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

Stable:
  ICU 2.0

Definition at line 701 of file chariter.h.

## ◆ startIndex()

int32_t icu::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.

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

Stable:
  ICU 2.0

Definition at line 711 of file chariter.h.

## Field Documentation

## ◆ begin

int32_t icu::CharacterIterator::begin
| protected

Base class field for the start of the iteration range.

Stable:
  ICU 2.0

Definition at line 686 of file chariter.h.

## ◆ end

int32_t icu::CharacterIterator::end
| protected

Base class field for the end of the iteration range.

Stable:
  ICU 2.0

Definition at line 692 of file chariter.h.

## ◆ pos

int32_t icu::CharacterIterator::pos
| protected

Base class field for the current position.

Stable:
  ICU 2.0

Definition at line 680 of file chariter.h.

## ◆ textLength

int32_t icu::CharacterIterator::textLength
| protected

Base class text length field.

Necessary this for correct getText() and hashCode().

Stable:
  ICU 2.0

Definition at line 674 of file chariter.h.

The documentation for this class was generated from the following file:

- chariter.h

icu::CharacterIterator::pos
int32_t pos
Base class field for the current position.
Definition: chariter.h:680
UChar32
int32_t UChar32
Define UChar32 as a type for single Unicode code points.
Definition: umachine.h:467
icu::CharacterIterator::CharacterIterator
CharacterIterator()
Empty constructor.
icu::CharacterIterator::end
int32_t end
Base class field for the end of the iteration range.
Definition: chariter.h:692