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Apache Commons Text is a library focused on algorithms working on strings.
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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.commons.text.translate;
import java.io.IOException;
import java.io.Writer;
/**
* Translate escaped octal Strings back to their octal values.
*
* For example, "\45" should go back to being the specific value (a %).
*
* Note that this currently only supports the viable range of octal for Java; namely
* 1 to 377. This is because parsing Java is the main use case.
*
* @since 1.0
*/
public class OctalUnescaper extends CharSequenceTranslator {
/**
* Tests if the given char is an octal digit. Octal digits are the character representations of the digits 0 to 7.
*
* @param ch the char to check
* @return true if the given char is the character representation of one of the digits from 0 to 7
*/
private boolean isOctalDigit(final char ch) {
return ch >= '0' && ch <= '7';
}
/**
* Tests if the given char is the character representation of one of the digit from 0 to 3.
*
* @param ch the char to check
* @return true if the given char is the character representation of one of the digits from 0 to 3
*/
private boolean isZeroToThree(final char ch) {
return ch >= '0' && ch <= '3';
}
/**
* {@inheritDoc}
*/
@Override
public int translate(final CharSequence input, final int index, final Writer writer) throws IOException {
final int remaining = input.length() - index - 1; // how many characters left, ignoring the first \
final StringBuilder builder = new StringBuilder();
if (input.charAt(index) == '\\' && remaining > 0 && isOctalDigit(input.charAt(index + 1))) {
final int next = index + 1;
final int next2 = index + 2;
final int next3 = index + 3;
// we know this is good as we checked it in the if block above
builder.append(input.charAt(next));
if (remaining > 1 && isOctalDigit(input.charAt(next2))) {
builder.append(input.charAt(next2));
if (remaining > 2 && isZeroToThree(input.charAt(next)) && isOctalDigit(input.charAt(next3))) {
builder.append(input.charAt(next3));
}
}
writer.write(Integer.parseInt(builder.toString(), 8));
return 1 + builder.length();
}
return 0;
}
}
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