org.apache.pdfbox.filter.ASCIIHexFilter Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of pdfbox Show documentation
The Apache PDFBox library is an open source Java tool for working with PDF documents.
There is a newer version: 3.0.2
/*
 * 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.filter;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.pdfbox.cos.COSDictionary;
import org.apache.pdfbox.util.Hex;

/**
 * Decodes data encoded in an ASCII hexadecimal form, reproducing the original binary data.
 *
 * @author Ben Litchfield
 */
final class ASCIIHexFilter extends Filter
{
    private static final Log LOG = LogFactory.getLog(ASCIIHexFilter.class);

    private static final int[] REVERSE_HEX = {
      /*   0 */  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      /*  10 */  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      /*  20 */  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      /*  30 */  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      /*  40 */  -1, -1, -1, -1, -1, -1, -1, -1,  0,  1,
      /*  50 */   2,  3,  4,  5,  6,  7,  8,  9, -1, -1,
      /*  60 */  -1, -1, -1, -1, -1, 10, 11, 12, 13, 14,
      /*  70 */  15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      /*  80 */  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      /*  90 */  -1, -1, -1, -1, -1, -1, -1, 10, 11, 12,
      /* 100 */  13, 14, 15
    };

    @Override
    public DecodeResult decode(InputStream encoded, OutputStream decoded,
                                         COSDictionary parameters, int index) throws IOException
    {
        int value, firstByte, secondByte;
        while ((firstByte = encoded.read()) != -1)
        {
            // always after first char
            while (isWhitespace(firstByte))
            {
                firstByte = encoded.read();
            }
            if (firstByte == -1 || isEOD(firstByte))
            {
                break;
            }
       
            if (REVERSE_HEX[firstByte] == -1)
            {
                LOG.error("Invalid hex, int: " + firstByte + " char: " + (char)firstByte);
            }
            value = REVERSE_HEX[firstByte] * 16;
            secondByte = encoded.read();
       
            if (secondByte == -1 || isEOD(secondByte)) 
            {
                // second value behaves like 0 in case of EOD
                decoded.write(value);
                break;
            }
            if (secondByte >= 0) 
            {
                if (REVERSE_HEX[secondByte] == -1)
                {
                    LOG.error("Invalid hex, int: " + secondByte + " char: " + (char)secondByte);
                }
                value += REVERSE_HEX[secondByte];
            }
            decoded.write(value);
        }
        decoded.flush();
        return new DecodeResult(parameters);
    }

    // whitespace
    //   0  0x00  Null (NUL)
    //   9  0x09  Tab (HT)
    //  10  0x0A  Line feed (LF)
    //  12  0x0C  Form feed (FF)
    //  13  0x0D  Carriage return (CR)
    //  32  0x20  Space (SP)
    private boolean isWhitespace(int c)
    {
        return c == 0 || c == 9 || c == 10 || c == 12 || c == 13 || c == 32;
    }

    private boolean isEOD(int c)
    {
        return c == '>';
    }

    @Override
    public void encode(InputStream input, OutputStream encoded, COSDictionary parameters)
        throws IOException
    {
        int byteRead;
        while ((byteRead = input.read()) != -1)
        {
            Hex.writeHexByte((byte)byteRead, encoded);
        }
        encoded.flush();
    }
}