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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package org.apache.tools.ant.filters;
import java.io.IOException;
import java.io.Reader;
/**
* This is a Java comment and string stripper reader that filters
* those lexical tokens out for purposes of simple Java parsing.
* (if you have more complex Java parsing needs, use a real lexer).
* Since this class heavily relies on the single char read function,
* you are recommended to make it work on top of a buffered reader.
*
*/
public final class StripJavaComments
extends BaseFilterReader
implements ChainableReader {
/**
* The read-ahead character, used for effectively pushing a single
* character back. A value of -1 indicates that no character is in the
* buffer.
*/
private int readAheadCh = -1;
/**
* Whether or not the parser is currently in the middle of a string
* literal.
*/
private boolean inString = false;
/**
* Whether or not the last char has been a backslash.
*/
private boolean quoted = false;
/**
* Constructor for "dummy" instances.
*
* @see BaseFilterReader#BaseFilterReader()
*/
public StripJavaComments() {
super();
}
/**
* Creates a new filtered reader.
*
* @param in A Reader object providing the underlying stream.
* Must not be <code>null</code>.
*/
public StripJavaComments(final Reader in) {
super(in);
}
/**
* Returns the next character in the filtered stream, not including
* Java comments.
*
* @return the next character in the resulting stream, or -1
* if the end of the resulting stream has been reached
*
* @exception IOException if the underlying stream throws an IOException
* during reading
*/
public int read() throws IOException {
int ch = -1;
if (readAheadCh != -1) {
ch = readAheadCh;
readAheadCh = -1;
} else {
ch = in.read();
if (ch == '"' && !quoted) {
inString = !inString;
quoted = false;
} else if (ch == '\\') {
quoted = !quoted;
} else {
quoted = false;
if (!inString) {
if (ch == '/') {
ch = in.read();
if (ch == '/') {
while (ch != '\n' && ch != -1 && ch != '\r') {
ch = in.read();
}
} else if (ch == '*') {
while (ch != -1) {
ch = in.read();
if (ch == '*') {
ch = in.read();
while (ch == '*') {
ch = in.read();
}
if (ch == '/') {
ch = read();
break;
}
}
}
} else {
readAheadCh = ch;
ch = '/';
}
}
}
}
}
return ch;
}
/**
* Creates a new StripJavaComments using the passed in
* Reader for instantiation.
*
* @param rdr A Reader object providing the underlying stream.
* Must not be <code>null</code>.
*
* @return a new filter based on this configuration, but filtering
* the specified reader
*/
public Reader chain(final Reader rdr) {
StripJavaComments newFilter = new StripJavaComments(rdr);
return newFilter;
}
}
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