UCharacterIterator.java
// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
*******************************************************************************
* Copyright (C) 1996-2016, International Business Machines Corporation and
* others. All Rights Reserved.
*******************************************************************************
*/
package com.ibm.icu.text;
import com.ibm.icu.impl.CharacterIteratorWrapper;
import com.ibm.icu.impl.ReplaceableUCharacterIterator;
import com.ibm.icu.impl.UCharArrayIterator;
import com.ibm.icu.impl.UCharacterIteratorWrapper;
import java.text.CharacterIterator;
/**
* 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. Forward iteration is done with
* post-increment and backward iteration is done with pre-decrement semantics, while the <code>
* java.text.CharacterIterator</code> interface methods provided forward iteration with
* "pre-increment" and backward iteration with pre-decrement semantics. This API is more efficient
* for forward iteration over code points. The other major difference is that this API can do both
* code unit and code point iteration, <code>java.text.CharacterIterator</code> can only iterate
* over code units and is limited to BMP (0 - 0xFFFF)
*
* @author Ram
* @stable ICU 2.4
*/
public abstract class UCharacterIterator implements Cloneable, UForwardCharacterIterator {
/**
* Protected default constructor for the subclasses
*
* @stable ICU 2.4
*/
protected UCharacterIterator() {}
// static final methods ----------------------------------------------------
/**
* Returns a <code>UCharacterIterator</code> object given a <code>Replaceable</code> object.
*
* @param source a valid source as a <code>Replaceable</code> object
* @return UCharacterIterator object
* @exception IllegalArgumentException if the argument is null
* @stable ICU 2.4
*/
public static final UCharacterIterator getInstance(Replaceable source) {
return new ReplaceableUCharacterIterator(source);
}
/**
* Returns a <code>UCharacterIterator</code> object given a source string.
*
* @param source a string
* @return UCharacterIterator object
* @exception IllegalArgumentException if the argument is null
* @stable ICU 2.4
*/
public static final UCharacterIterator getInstance(String source) {
return new ReplaceableUCharacterIterator(source);
}
/**
* Returns a <code>UCharacterIterator</code> object given a source character array.
*
* @param source an array of UTF-16 code units
* @return UCharacterIterator object
* @exception IllegalArgumentException if the argument is null
* @stable ICU 2.4
*/
public static final UCharacterIterator getInstance(char[] source) {
return getInstance(source, 0, source.length);
}
/**
* Returns a <code>UCharacterIterator</code> object given a source character array.
*
* @param source an array of UTF-16 code units
* @return UCharacterIterator object
* @exception IllegalArgumentException if the argument is null
* @stable ICU 2.4
*/
public static final UCharacterIterator getInstance(char[] source, int start, int limit) {
return new UCharArrayIterator(source, start, limit);
}
/**
* Returns a <code>UCharacterIterator</code> object given a source StringBuffer.
*
* @param source an string buffer of UTF-16 code units
* @return UCharacterIterator object
* @exception IllegalArgumentException if the argument is null
* @stable ICU 2.4
*/
public static final UCharacterIterator getInstance(StringBuffer source) {
return new ReplaceableUCharacterIterator(source);
}
/**
* Returns a <code>UCharacterIterator</code> object given a CharacterIterator.
*
* @param source a valid CharacterIterator object.
* @return UCharacterIterator object
* @exception IllegalArgumentException if the argument is null
* @stable ICU 2.4
*/
public static final UCharacterIterator getInstance(CharacterIterator source) {
return new CharacterIteratorWrapper(source);
}
// public methods ----------------------------------------------------------
/**
* Returns a <code>java.text.CharacterIterator</code> object for the underlying text of this
* iterator. The returned iterator is independent of this iterator.
*
* @return java.text.CharacterIterator object
* @stable ICU 2.4
*/
public CharacterIterator getCharacterIterator() {
return new UCharacterIteratorWrapper(this);
}
/**
* Returns the code unit at the current index. If index is out of range, returns DONE. Index is
* not changed.
*
* @return current code unit
* @stable ICU 2.4
*/
public abstract int current();
/**
* Returns the codepoint at the current index. If the current index is invalid, DONE is
* returned. If the current index points to a lead surrogate, and there is a following trail
* surrogate, then the code point is returned. Otherwise, the code unit at index is returned.
* Index is not changed.
*
* @return current codepoint
* @stable ICU 2.4
*/
public int currentCodePoint() {
int ch = current();
if (UTF16.isLeadSurrogate(ch)) {
// advance the index to get the
// next code point
next();
// due to post increment semantics
// current() after next() actually
// returns the char we want
int ch2 = current();
// current should never change
// the current index so back off
previous();
if (UTF16.isTrailSurrogate(ch2)) {
// we found a surrogate pair
// return the codepoint
return Character.toCodePoint((char) ch, (char) ch2);
}
}
return ch;
}
/**
* Returns the length of the text
*
* @return length of the text
* @stable ICU 2.4
*/
public abstract int getLength();
/**
* Gets the current index in text.
*
* @return current index in text.
* @stable ICU 2.4
*/
public abstract int getIndex();
/**
* Returns the UTF16 code unit at index, and increments to the next code unit (post-increment
* semantics). If index is out of range, DONE is returned, and the iterator is reset to the
* limit of the text.
*
* @return the next UTF16 code unit, or DONE if the index is at the limit of the text.
* @stable ICU 2.4
*/
@Override
public abstract int next();
/**
* Returns the code point at index, and increments to the next code point (post-increment
* semantics). If index does not point to a valid surrogate pair, the behavior is the same as
* <code>next()</code>. Otherwise the iterator is incremented past the surrogate pair, and the
* code point represented by the pair is returned.
*
* @return the next codepoint in text, or DONE if the index is at the limit of the text.
* @stable ICU 2.4
*/
@Override
public int nextCodePoint() {
int ch1 = next();
if (UTF16.isLeadSurrogate(ch1)) {
int ch2 = next();
if (UTF16.isTrailSurrogate(ch2)) {
return Character.toCodePoint((char) ch1, (char) ch2);
} else if (ch2 != DONE) {
// unmatched surrogate so back out
previous();
}
}
return ch1;
}
/**
* Decrement to the position of the previous code unit in the text, and return it (pre-decrement
* semantics). If the resulting index is less than 0, the index is reset to 0 and DONE is
* returned.
*
* @return the previous code unit in the text, or DONE if the new index is before the start of
* the text.
* @stable ICU 2.4
*/
public abstract int previous();
/**
* Retreat to the start of the previous code point in the text, and return it (pre-decrement
* semantics). If the index is not preceded by a valid surrogate pair, the behavior is the same
* as <code>previous()</code>. Otherwise the iterator is decremented to the start of the
* surrogate pair, and the code point represented by the pair is returned.
*
* @return the previous code point in the text, or DONE if the new index is before the start of
* the text.
* @stable ICU 2.4
*/
public int previousCodePoint() {
int ch1 = previous();
if (UTF16.isTrailSurrogate(ch1)) {
int ch2 = previous();
if (UTF16.isLeadSurrogate(ch2)) {
return Character.toCodePoint((char) ch2, (char) ch1);
} else if (ch2 != DONE) {
// unmatched trail surrogate so back out
next();
}
}
return ch1;
}
/**
* Sets the index to the specified index in the text.
*
* @param index the index within the text.
* @exception IndexOutOfBoundsException is thrown if an invalid index is supplied
* @stable ICU 2.4
*/
public abstract void setIndex(int index);
/**
* Sets the current index to the limit.
*
* @stable ICU 2.4
*/
public void setToLimit() {
setIndex(getLength());
}
/**
* Sets the current index to the start.
*
* @stable ICU 2.4
*/
public void setToStart() {
setIndex(0);
}
/**
* Fills the buffer with the underlying text storage of the iterator If the buffer capacity is
* not enough a exception is thrown. The capacity of the fill in buffer should at least be equal
* to length of text in the iterator obtained by calling <code>getLength()</code>).
* <b>Usage:</b>
*
* <pre>
* UChacterIterator iter = new UCharacterIterator.getInstance(text);
* char[] buf = new char[iter.getLength()];
* iter.getText(buf);
*
* OR
* char[] buf= new char[1];
* int len = 0;
* for(;;){
* try{
* len = iter.getText(buf);
* break;
* }catch(IndexOutOfBoundsException e){
* buf = new char[iter.getLength()];
* }
* }
* </pre>
*
* @param fillIn an array of chars to fill with the underlying UTF-16 code units.
* @param offset the position within the array to start putting the data.
* @return the number of code units added to fillIn, as a convenience
* @exception IndexOutOfBoundsException exception if there is not enough room after offset in
* the array, or if offset < 0.
* @stable ICU 2.4
*/
public abstract int getText(char[] fillIn, int offset);
/**
* Convenience override for <code>getText(char[], int)</code> that provides an offset of 0.
*
* @param fillIn an array of chars to fill with the underlying UTF-16 code units.
* @return the number of code units added to fillIn, as a convenience
* @exception IndexOutOfBoundsException exception if there is not enough room in the array.
* @stable ICU 2.4
*/
public final int getText(char[] fillIn) {
return getText(fillIn, 0);
}
/**
* Convenience method for returning the underlying text storage as as string
*
* @return the underlying text storage in the iterator as a string
* @stable ICU 2.4
*/
public String getText() {
char[] text = new char[getLength()];
getText(text);
return new String(text);
}
/**
* Moves the current position by the number of code units specified, either forward or backward
* depending on the sign of delta (positive or negative respectively). If the resulting index
* would be less than zero, the index is set to zero, and if the resulting index would be
* greater than limit, the index is set to limit.
*
* @param delta the number of code units to move the current index.
* @return the new index.
* @exception IndexOutOfBoundsException is thrown if an invalid index is supplied
* @stable ICU 2.4
*/
public int moveIndex(int delta) {
int x = Math.max(0, Math.min(getIndex() + delta, getLength()));
setIndex(x);
return x;
}
/**
* Moves the current position by the number of code points specified, either forward or backward
* depending on the sign of delta (positive or negative respectively). If the current index is
* at a trail surrogate then the first adjustment is by code unit, and the remaining adjustments
* are by code points. If the resulting index would be less than zero, the index is set to zero,
* and if the resulting index would be greater than limit, the index is set to limit.
*
* @param delta the number of code units to move the current index.
* @return the new index
* @exception IndexOutOfBoundsException is thrown if an invalid delta is supplied
* @stable ICU 2.4
*/
public int moveCodePointIndex(int delta) {
if (delta > 0) {
while (delta > 0 && nextCodePoint() != DONE) {
delta--;
}
} else {
while (delta < 0 && previousCodePoint() != DONE) {
delta++;
}
}
if (delta != 0) {
throw new IndexOutOfBoundsException();
}
return getIndex();
}
/**
* Creates a copy of this iterator, independent from other iterators. If it is not possible to
* clone the iterator, returns null.
*
* @return copy of this iterator
* @stable ICU 2.4
*/
@Override
public UCharacterIterator clone() throws CloneNotSupportedException {
return (UCharacterIterator) super.clone();
}
}