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The Apache PDFBox library is an open source Java tool for working with PDF documents.
/*
* 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.pdfbox.pdmodel.common.function.type4;
import java.util.Stack;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* Basic parser for Type 4 functions which is used to build up instruction sequences.
*
*/
public final class InstructionSequenceBuilder extends Parser.AbstractSyntaxHandler
{
private final InstructionSequence mainSequence = new InstructionSequence();
private final Stack seqStack = new Stack();
private InstructionSequenceBuilder()
{
this.seqStack.push(this.mainSequence);
}
/**
* Returns the instruction sequence that has been build from the syntactic elements.
* @return the instruction sequence
*/
public InstructionSequence getInstructionSequence()
{
return this.mainSequence;
}
/**
* Parses the given text into an instruction sequence representing a Type 4 function
* that can be executed.
* @param text the Type 4 function text
* @return the instruction sequence
*/
public static InstructionSequence parse(CharSequence text)
{
InstructionSequenceBuilder builder = new InstructionSequenceBuilder();
Parser.parse(text, builder);
return builder.getInstructionSequence();
}
private InstructionSequence getCurrentSequence()
{
return this.seqStack.peek();
}
private static final Pattern INTEGER_PATTERN = Pattern.compile("[\\+\\-]?\\d+");
private static final Pattern REAL_PATTERN = Pattern.compile("[\\-]?\\d*\\.\\d*([Ee]\\-?\\d+)?");
/** {@inheritDoc} */
@Override
public void token(CharSequence text)
{
String token = text.toString();
token(token);
}
private void token(String token)
{
if ("{".equals(token))
{
InstructionSequence child = new InstructionSequence();
getCurrentSequence().addProc(child);
this.seqStack.push(child);
}
else if ("}".equals(token))
{
this.seqStack.pop();
}
else
{
Matcher m = INTEGER_PATTERN.matcher(token);
if (m.matches())
{
getCurrentSequence().addInteger(parseInt(token));
return;
}
m = REAL_PATTERN.matcher(token);
if (m.matches())
{
getCurrentSequence().addReal(parseReal(token));
return;
}
//TODO Maybe implement radix numbers, such as 8#1777 or 16#FFFE
getCurrentSequence().addName(token);
}
}
/**
* Parses a value of type "int".
* @param token the token to be parsed
* @return the parsed value
*/
public static int parseInt(String token)
{
if (token.startsWith("+"))
{
token = token.substring(1);
}
return Integer.parseInt(token);
}
/**
* Parses a value of type "real".
* @param token the token to be parsed
* @return the parsed value
*/
public static float parseReal(String token)
{
return Float.parseFloat(token);
}
}