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ICU 77.1: icu::CharacterIterator Class Reference

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

#include <chariter.h>

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():

for(it.setToStart(); it.hasNext();) {

c=it.next32PostInc();

}

}

CharacterIterator()

Empty constructor.

int32_t UChar32

Define UChar32 as a type for single Unicode code points.

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

char16_t c;

for(c=it.firstPostInc(); c!=CharacterIterator::DONE; c=it.nextPostInc()) {

}

}

Backward iteration with setToEnd() and hasPrevious():

for(it.setToEnd(); it.hasPrevious();) {

c=it.previous32();

}

}

Backward iteration with a more traditional for() loop:

char16_t c;

for(c=it.last(); c!=CharacterIterator::DONE; c=it.previous()) {

}

}

Example for random access:

it.move32(3, CharacterIterator::kStart);

int32_t

=it.getIndex();

char16_t u=it.previous();

it.move(-1, CharacterIterator::kCurrent);

if(c!=it.next32PostInc()) {

exit(1);

}

}

int32_t pos

Base class field for the current position.

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

 

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

Traverse the text backwards, from end to start

{
    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.

{
     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);
    }
 }
int32_t end
Base class field for the end of the iteration range.

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.

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

Stable:

ICU 2.0

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

Stable:

ICU 2.0

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

Stable:

ICU 2.0

Copy constructor.

Parameters

Stable:

ICU 2.0

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Base class field for the start of the iteration range.

Stable:

ICU 2.0

Definition at line 686 of file chariter.h.

Base class field for the end of the iteration range.

Stable:

ICU 2.0

Definition at line 692 of file chariter.h.

Base class field for the current position.

Stable:

ICU 2.0

Definition at line 680 of file chariter.h.

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

• common/unicode/chariter.h

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