RuleCharacterIterator.java
// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
**********************************************************************
* Copyright (c) 2003-2011, International Business Machines
* Corporation and others. All Rights Reserved.
**********************************************************************
* Author: Alan Liu
* Created: September 23 2003
* Since: ICU 2.8
**********************************************************************
*/
package com.ibm.icu.impl;
import com.ibm.icu.text.SymbolTable;
import com.ibm.icu.text.UTF16;
import java.text.ParsePosition;
/**
* An iterator that returns 32-bit code points. This class is deliberately <em>not</em> related to
* any of the JDK or ICU4J character iterator classes in order to minimize complexity.
*
* @author Alan Liu
* @since ICU 2.8
*/
public class RuleCharacterIterator {
// TODO: Ideas for later. (Do not implement if not needed, lest the
// code coverage numbers go down due to unused methods.)
// 1. Add a copy constructor, equals() method, clone() method.
// 2. Rather than return DONE, throw an exception if the end
// is reached -- this is an alternate usage model, probably not useful.
// 3. Return isEscaped from next(). If this happens,
// don't keep an isEscaped member variable.
/** Text being iterated. */
private String text;
/** Position of iterator. */
private ParsePosition pos;
/** Symbol table used to parse and dereference variables. May be null. */
private SymbolTable sym;
/** Current variable expansion, or null if none. */
private String buf;
/** Position within buf[]. Meaningless if buf == null. */
private int bufPos;
/** Flag indicating whether the last character was parsed from an escape. */
private boolean isEscaped;
/** Value returned when there are no more characters to iterate. */
public static final int DONE = -1;
/**
* Bitmask option to enable parsing of variable names. If (options & PARSE_VARIABLES) != 0, then
* an embedded variable will be expanded to its value. Variables are parsed using the
* SymbolTable API.
*/
public static final int PARSE_VARIABLES = 1;
/**
* Bitmask option to enable parsing of escape sequences. If (options & PARSE_ESCAPES) != 0, then
* an embedded escape sequence will be expanded to its value. Escapes are parsed using
* Utility.unescapeAndLengthAt().
*/
public static final int PARSE_ESCAPES = 2;
/**
* Bitmask option to enable skipping of whitespace. If (options & SKIP_WHITESPACE) != 0, then
* Unicode Pattern_White_Space characters will be silently skipped, as if they were not present
* in the input.
*/
public static final int SKIP_WHITESPACE = 4;
/** For use with {@link #getPos(Position)} & {@link #setPos(Position)}. */
public static final class Position {
private String buf;
private int bufPos;
private int posIndex;
}
;
/**
* Constructs an iterator over the given text, starting at the given position.
*
* @param text the text to be iterated
* @param sym the symbol table, or null if there is none. If sym is null, then variables will
* not be dereferenced, even if the PARSE_VARIABLES option is set.
* @param pos upon input, the index of the next character to return. If a variable has been
* dereferenced, then pos will <em>not</em> increment as characters of the variable value
* are iterated.
*/
public RuleCharacterIterator(String text, SymbolTable sym, ParsePosition pos) {
if (text == null || pos.getIndex() > text.length()) {
throw new IllegalArgumentException();
}
this.text = text;
this.sym = sym;
this.pos = pos;
buf = null;
}
/** Returns true if this iterator has no more characters to return. */
public boolean atEnd() {
return buf == null && pos.getIndex() == text.length();
}
/**
* Returns the next character using the given options, or DONE if there are no more characters,
* and advance the position to the next character.
*
* @param options one or more of the following options, bitwise-OR-ed together: PARSE_VARIABLES,
* PARSE_ESCAPES, SKIP_WHITESPACE.
* @return the current 32-bit code point, or DONE
*/
public int next(int options) {
int c = DONE;
isEscaped = false;
for (; ; ) {
c = _current();
_advance(UTF16.getCharCount(c));
if (c == SymbolTable.SYMBOL_REF
&& buf == null
&& (options & PARSE_VARIABLES) != 0
&& sym != null) {
String name = sym.parseReference(text, pos, text.length());
// If name == null there was an isolated SYMBOL_REF;
// return it. Caller must be prepared for this.
if (name == null) {
break;
}
bufPos = 0;
char[] chars = sym.lookup(name);
if (chars == null) {
buf = null;
throw new IllegalArgumentException("Undefined variable: " + name);
}
// Handle empty variable value
if (chars.length == 0) {
buf = null;
}
buf = new String(chars);
continue;
}
if ((options & SKIP_WHITESPACE) != 0 && PatternProps.isWhiteSpace(c)) {
continue;
}
if (c == '\\' && (options & PARSE_ESCAPES) != 0) {
int cpAndLength =
Utility.unescapeAndLengthAt(getCurrentBuffer(), getCurrentBufferPos());
if (cpAndLength < 0) {
throw new IllegalArgumentException("Invalid escape");
}
c = Utility.cpFromCodePointAndLength(cpAndLength);
jumpahead(Utility.lengthFromCodePointAndLength(cpAndLength));
isEscaped = true;
}
break;
}
return c;
}
/**
* Returns true if the last character returned by next() was escaped. This will only be the case
* if the option passed in to next() included PARSE_ESCAPED and the next character was an escape
* sequence.
*/
public boolean isEscaped() {
return isEscaped;
}
/** Returns true if this iterator is currently within a variable expansion. */
public boolean inVariable() {
return buf != null;
}
/**
* Returns an object which, when later passed to setPos(), will restore this iterator's
* position. Usage idiom:
*
* <p>RuleCharacterIterator iterator = ...; Position pos = iterator.getPos(null); // allocate
* position object for (;;) { pos = iterator.getPos(pos); // reuse position object int c =
* iterator.next(...); ... } iterator.setPos(pos);
*
* @param p a position object previously returned by {@code getPos()}, or null. If not null, it
* will be updated and returned. If null, a new position object will be allocated and
* returned.
* @return a position object which may be passed to setPos(), either {@code p}, or if {@code p}
* == null, a newly-allocated object
*/
public Position getPos(Position p) {
if (p == null) {
p = new Position();
}
p.buf = buf;
p.bufPos = bufPos;
p.posIndex = pos.getIndex();
return p;
}
/**
* Restores this iterator to the position it had when getPos() returned the given object.
*
* @param p a position object previously returned by getPos()
*/
public void setPos(Position p) {
buf = p.buf;
pos.setIndex(p.posIndex);
bufPos = p.bufPos;
}
/**
* Skips ahead past any ignored characters, as indicated by the given options. This is useful in
* conjunction with the lookahead() method.
*
* <p>Currently, this only has an effect for SKIP_WHITESPACE.
*
* @param options one or more of the following options, bitwise-OR-ed together: PARSE_VARIABLES,
* PARSE_ESCAPES, SKIP_WHITESPACE.
*/
public void skipIgnored(int options) {
if ((options & SKIP_WHITESPACE) != 0) {
for (; ; ) {
int a = _current();
if (!PatternProps.isWhiteSpace(a)) break;
_advance(UTF16.getCharCount(a));
}
}
}
/**
* Returns a string containing the remainder of the characters to be returned by this iterator,
* without any option processing. If the iterator is currently within a variable expansion, this
* will only extend to the end of the variable expansion. This method, together with
* getCurrentBufferPos() (which replace the former lookahead()), is provided so that iterators
* may interoperate with string-based APIs. The typical sequence of calls is to call
* skipIgnored(), then call these methods, then parse that substring, then call jumpahead() to
* resynchronize the iterator.
*
* @return a string containing the characters to be returned by future calls to next()
*/
public String getCurrentBuffer() {
if (buf != null) {
return buf;
} else {
return text;
}
}
public int getCurrentBufferPos() {
if (buf != null) {
return bufPos;
} else {
return pos.getIndex();
}
}
/**
* Advances the position by the given number of 16-bit code units. This is useful in conjunction
* with getCurrentBuffer()+getCurrentBufferPos() (formerly lookahead()).
*
* @param count the number of 16-bit code units to jump over
*/
public void jumpahead(int count) {
if (count < 0) {
throw new IllegalArgumentException();
}
if (buf != null) {
bufPos += count;
if (bufPos > buf.length()) {
throw new IllegalArgumentException();
}
if (bufPos == buf.length()) {
buf = null;
}
} else {
int i = pos.getIndex() + count;
pos.setIndex(i);
if (i > text.length()) {
throw new IllegalArgumentException();
}
}
}
/**
* Returns a string representation of this object, consisting of the characters being iterated,
* with a '|' marking the current position. Position within an expanded variable is <em>not</em>
* indicated.
*
* @return a string representation of this object
*/
@Override
public String toString() {
int b = pos.getIndex();
return text.substring(0, b) + '|' + text.substring(b);
}
/**
* Returns the current 32-bit code point without parsing escapes, parsing variables, or skipping
* whitespace.
*
* @return the current 32-bit code point
*/
private int _current() {
if (buf != null) {
return UTF16.charAt(buf, bufPos);
} else {
int i = pos.getIndex();
return (i < text.length()) ? UTF16.charAt(text, i) : DONE;
}
}
/**
* Advances the position by the given amount.
*
* @param count the number of 16-bit code units to advance past
*/
private void _advance(int count) {
if (buf != null) {
bufPos += count;
if (bufPos == buf.length()) {
buf = null;
}
} else {
pos.setIndex(pos.getIndex() + count);
if (pos.getIndex() > text.length()) {
pos.setIndex(text.length());
}
}
}
}