ICU-3280 initial checkin
X-SVN-Rev: 13188
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Alan Liu
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44e3b8c382
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368
icu4j/src/com/ibm/icu/impl/RuleCharacterIterator.java
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368
icu4j/src/com/ibm/icu/impl/RuleCharacterIterator.java
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/*
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**********************************************************************
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* Copyright (c) 2003, International Business Machines
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* Corporation and others. All Rights Reserved.
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**********************************************************************
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* Author: Alan Liu
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* Created: September 23 2003
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* Since: ICU 2.8
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**********************************************************************
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*/
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package com.ibm.icu.impl;
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import java.text.ParsePosition;
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import com.ibm.icu.text.SymbolTable;
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import com.ibm.icu.text.UTF16;
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/**
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* An iterator that returns 32-bit code points. This class is deliberately
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* <em>not</em> related to any of the JDK or ICU4J character iterator classes
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* in order to minimize complexity.
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* @author Alan Liu
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* @since ICU 2.8
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*/
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public class RuleCharacterIterator {
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// TODO: Ideas for later. (Do not implement if not needed, lest the
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// code coverage numbers go down due to unused methods.)
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// 1. Add a copy constructor, equals() method, clone() method.
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// 2. Add caching of the current code point, so that repeated calls
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// to current() become fast as long as the options do not change.
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// The options bitmask must be cached too.
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// 3. Add caching of the future position, so current() followed by
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// next() becomes fast, as long as the options do not change.
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// 4. Rather than return DONE, throw an exception if the end
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// is reached -- this is an alternate usage model, probably not useful.
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// 5. Return isEscaped from next() and current(). If this happens,
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// don't keep an isEscaped member variable, and getState() and getPos()
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// become the same.
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/**
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* Text being iterated.
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*/
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private String text;
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/**
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* Position of iterator.
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*/
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private ParsePosition pos;
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/**
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* Symbol table used to parse and dereference variables. May be null.
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*/
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private SymbolTable sym;
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/**
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* Current variable expansion, or null if none.
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*/
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private char[] buf;
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/**
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* Position within buf[]. Meaningless if buf == null.
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*/
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private int bufPos;
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/**
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* Flag indicating whether the last character was parsed from an escape.
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*/
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private boolean isEscaped;
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/**
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* Value returned when there are no more characters to iterate.
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*/
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public static final int DONE = -1;
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/**
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* Bitmask option to enable parsing of variable names. If (options &
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* PARSE_VARIABLES) != 0, then an embedded variable will be expanded to
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* its value. Variables are parsed using the SymbolTable API.
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*/
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public static final int PARSE_VARIABLES = 1;
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/**
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* Bitmask option to enable parsing of escape sequences. If (options &
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* PARSE_ESCAPES) != 0, then an embedded escape sequence will be expanded
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* to its value. Escapes are parsed using Utility.unescapeAt().
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*/
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public static final int PARSE_ESCAPES = 2;
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/**
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* Bitmask option to enable skipping of whitespace. If (options &
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* SKIP_WHITESPACE) != 0, then whitespace characters will be silently
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* skipped, as if they were not present in the input. Whitespace
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* characters are defined by UCharacterProperty.isRuleWhiteSpace().
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*/
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public static final int SKIP_WHITESPACE = 4;
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/**
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* Constructs an iterator over the given text, starting at the given
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* position.
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* @param text the text to be iterated
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* @param sym the symbol table, or null if there is none. If sym is null,
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* then variables will not be deferenced, even if the PARSE_VARIABLES
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* option is set.
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* @param pos upon input, the index of the next character to return. If a
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* variable has been dereferenced, then pos will <em>not</em> increment as
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* characters of the variable value are iterated.
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*/
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public RuleCharacterIterator(String text, SymbolTable sym,
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ParsePosition pos) {
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if (text == null || pos.getIndex() > text.length()) {
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throw new IllegalArgumentException();
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}
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this.text = text;
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this.sym = sym;
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this.pos = pos;
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buf = null;
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}
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/**
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* Returns true if this iterator has no more characters to return.
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*/
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public boolean atEnd() {
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return buf == null && pos.getIndex() == text.length();
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}
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/**
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* Returns the next character using the given options, or DONE if there
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* are no more characters, and advance the internal state to the next
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* character.
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* @param options one or more of the following options, bitwise-OR-ed
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* together: PARSE_VARIABLES, PARSE_ESCAPES, SKIP_WHITESPACE.
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* @return the current 32-bit code point, or DONE
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*/
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public int next(int options) {
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int c = DONE;
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isEscaped = false;
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for (;;) {
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c = _current();
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_advance(UTF16.getCharCount(c));
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if (c == SymbolTable.SYMBOL_REF && buf == null &&
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(options & PARSE_VARIABLES) != 0 && sym != null) {
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String name = sym.parseReference(text, pos, text.length());
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// If name == null there was an isolated SYMBOL_REF;
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// return it. Caller must be prepared for this.
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if (name == null) {
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break;
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}
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bufPos = 0;
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buf = sym.lookup(name);
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if (buf == null) {
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throw new IllegalArgumentException(
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"Undefined variable: " + name);
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}
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// Handle empty variable value
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if (buf.length == 0) {
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buf = null;
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}
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continue;
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}
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if ((options & SKIP_WHITESPACE) != 0 &&
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UCharacterProperty.isRuleWhiteSpace(c)) {
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continue;
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}
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if (c == '\\' && (options & PARSE_ESCAPES) != 0) {
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c = Utility.unescapeAt(this);
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isEscaped = true; // unescapeAt() sets isEscaped to false
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if (c < 0) {
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throw new IllegalArgumentException("Invalid escape");
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}
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}
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break;
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}
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return c;
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}
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/**
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* Returns the current character using the given options, or DONE if there
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* are no more characters. NOTE: This method should be avoided if
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* possible; next() is preferred for performance reasons. The
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* implementation of this method is to save the current position, call
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* next(), and restore the position.
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* @param options one or more of the following options, bitwise-OR-ed
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* together: PARSE_VARIABLES, PARSE_ESCAPES, SKIP_WHITESPACE.
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* @return the current 32-bit code point, or DONE
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*/
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public int current(int options) {
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Object start = getPos();
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int c = next(options);
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setPos(start);
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return c;
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}
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/**
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* Returns true if the last character returned by next() or current() was
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* escaped. This will only be the case if the option passed in to next()
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* or current() included PARSE_ESCAPED and the next character was an
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* escape sequence.
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*/
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public boolean isEscaped() {
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return isEscaped;
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}
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/**
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* Returns true if this iterator is currently within a variable expansion.
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*/
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public boolean inVariable() {
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return buf != null;
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}
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/**
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* Returns an object which, when later passed to setState(), will restore
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* this iterator's state.
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* @return a state object which may be passed to setState().
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*/
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public Object getState() {
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return new Object[] { buf, new int[] { pos.getIndex(), bufPos,
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isEscaped?1:0 } };
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}
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/**
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* Restores this iterator's state to its value when getState() was
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* previously called, returning the given object.
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* @param save a state object previously returned by getState().
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*/
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public void setState(Object save) {
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Object[] a = (Object[]) save;
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buf = (char[]) a[0];
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int[] v = (int[]) a[1];
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pos.setIndex(v[0]);
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bufPos = v[1];
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isEscaped = (v[2] != 0);
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}
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/**
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* Returns an object which, when later passed to setPos(), will restore
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* this iterator's position.
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* @return a position object which may be passed to setPos().
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*/
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private Object getPos() {
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return new Object[] { buf, new int[] { pos.getIndex(), bufPos } };
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}
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/**
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* Restores this iterator's position to its value when getPos() was
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* previously called, returning the given object.
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* @param save a position object previously returned by getPos().
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*/
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private void setPos(Object save) {
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Object[] a = (Object[]) save;
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buf = (char[]) a[0];
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int[] v = (int[]) a[1];
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pos.setIndex(v[0]);
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bufPos = v[1];
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}
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/**
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* Skips ahead past any ignored characters, as indicated by the given
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* options. This is useful in conjunction with the lookahead() method.
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*
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* Currently, this only has an effect for SKIP_WHITESPACE.
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* @param options one or more of the following options, bitwise-OR-ed
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* together: PARSE_VARIABLES, PARSE_ESCAPES, SKIP_WHITESPACE.
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*/
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public void skipIgnored(int options) {
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if ((options & SKIP_WHITESPACE) != 0) {
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for (;;) {
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int a = _current();
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if (!UCharacterProperty.isRuleWhiteSpace(a)) break;
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_advance(UTF16.getCharCount(a));
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}
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}
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}
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/**
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* Returns a string containing the remainder of the characters to be
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* returned by this iterator, without any option processing. If the
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* iterator is currently within a variable expansion, this will only
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* extend to the end of the variable expansion. This method is provided
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* so that iterators may interoperate with string-based APIs. The typical
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* sequence of calls is to call skipIgnored(), then call lookahead(), then
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* parse the string returned by lookahead(), then call jumpahead() to
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* resynchronize the iterator.
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* @return a string containing the characters to be returned by future
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* calls to next() or current()
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*/
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public String lookahead() {
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if (buf != null) {
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return new String(buf, bufPos, buf.length - bufPos);
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} else {
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return text.substring(pos.getIndex());
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}
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}
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/**
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* Advances the position by the given number of 16-bit code units.
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* This is useful in conjunction with the lookahead() method.
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* @param count the number of 16-bit code units to jump over
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*/
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public void jumpahead(int count) {
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if (count < 0) {
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throw new IllegalArgumentException();
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}
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if (buf != null) {
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bufPos += count;
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if (bufPos > buf.length) {
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throw new IllegalArgumentException();
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}
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if (bufPos == buf.length) {
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buf = null;
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}
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} else {
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int i = pos.getIndex() + count;
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pos.setIndex(i);
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if (i > text.length()) {
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throw new IllegalArgumentException();
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}
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}
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}
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/**
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* Returns a string representation of this object, consisting of the
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* characters being iterated, with a '|' marking the current position.
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* Position within an expanded variable is <em>not</em> indicated.
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* @return a string representation of this object
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*/
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public String toString() {
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int b = pos.getIndex();
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return text.substring(0, b) + '|' + text.substring(b);
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}
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/**
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* Returns the current 32-bit code point without parsing escapes, parsing
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* variables, or skipping whitespace.
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* @return the current 32-bit code point
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*/
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private int _current() {
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if (buf != null) {
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return UTF16.charAt(buf, 0, buf.length, bufPos);
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} else {
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int i = pos.getIndex();
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return (i < text.length()) ? UTF16.charAt(text, i) : DONE;
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}
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}
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/**
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* Advances the position by the given amount.
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* @param count the number of 16-bit code units to advance past
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*/
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private void _advance(int count) {
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if (buf != null) {
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bufPos += count;
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if (bufPos == buf.length) {
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buf = null;
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}
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} else {
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pos.setIndex(pos.getIndex() + count);
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if (pos.getIndex() > text.length()) {
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pos.setIndex(text.length());
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}
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}
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}
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}
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