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The Apache PDFBox library is an open source Java tool for working with PDF documents.

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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.pdfbox.pdfparser;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.apache.pdfbox.cos.COSBase;
import org.apache.pdfbox.cos.COSBoolean;
import org.apache.pdfbox.cos.COSDictionary;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.cos.COSNull;
import org.apache.pdfbox.cos.COSNumber;
import org.apache.pdfbox.cos.COSObject;
import org.apache.pdfbox.cos.COSStream;
import org.apache.pdfbox.io.RandomAccess;
import org.apache.pdfbox.pdmodel.common.PDStream;
import org.apache.pdfbox.util.ImageParameters;
import org.apache.pdfbox.util.PDFOperator;

/**
 * This will parse a PDF byte stream and extract operands and such.
 *
 * @author Ben Litchfield
 * @version $Revision$
 */
public class PDFStreamParser extends BaseParser
{
    /**
     * Log instance.
     */
    private static final Log LOG = LogFactory.getLog(PDFStreamParser.class);
    
    private List streamObjects = new ArrayList( 100 );
    private final RandomAccess file;
    private final int    maxBinCharTestLength = 10;
    private final byte[] binCharTestArr = new byte[maxBinCharTestLength];

    /**
     * Constructor that takes a stream to parse.
     *
     * @since Apache PDFBox 1.3.0
     * @param stream The stream to read data from.
     * @param raf The random access file.
     * @param forceParsing flag to skip malformed or otherwise unparseable
     *                     input where possible
     * @throws IOException If there is an error reading from the stream.
     */
    public PDFStreamParser(
            InputStream stream, RandomAccess raf, boolean forceParsing)
            throws IOException 
    {
        super(stream, forceParsing);
        file = raf;
    }

    /**
     * Constructor that takes a stream to parse.
     *
     * @param stream The stream to read data from.
     * @param raf The random access file.
     *
     * @throws IOException If there is an error reading from the stream.
     */
    public PDFStreamParser(InputStream stream, RandomAccess raf)
            throws IOException 
    {
        this(stream, raf, FORCE_PARSING);
    }

    /**
     * Constructor.
     *
     * @param stream The stream to parse.
     *
     * @throws IOException If there is an error initializing the stream.
     */
    public PDFStreamParser( PDStream stream ) throws IOException
    {
       this( stream.createInputStream(), stream.getStream().getScratchFile() );
    }

    /**
     * Constructor.
     *
     * @since Apache PDFBox 1.3.0
     * @param stream The stream to parse.
     * @param forceParsing flag to skip malformed or otherwise unparseable
     *                     input where possible
     * @throws IOException If there is an error initializing the stream.
     */
    public PDFStreamParser(COSStream stream, boolean forceParsing)
            throws IOException 
    {
       this(stream.getUnfilteredStream(), stream.getScratchFile(), forceParsing);
    }

    /**
     * Constructor.
     *
     * @param stream The stream to parse.
     *
     * @throws IOException If there is an error initializing the stream.
     */
    public PDFStreamParser( COSStream stream ) throws IOException
    {
       this( stream.getUnfilteredStream(), stream.getScratchFile() );
    }

    /**
     * This will parse the tokens in the stream.  This will close the
     * stream when it is finished parsing.
     *
     * @throws IOException If there is an error while parsing the stream.
     */
    public void parse() throws IOException
    {
        try
        {
            Object token;
            while( (token = parseNextToken()) != null )
            {
                streamObjects.add( token );
                //logger().fine( "parsed=" + token );
            }
        }
        finally
        {
            pdfSource.close();
        }
    }

    /**
     * This will get the tokens that were parsed from the stream.
     *
     * @return All of the tokens in the stream.
     */
    public List getTokens()
    {
        return streamObjects;
    }

    /**
     * This will close the underlying pdfSource object.
     * 
     * @throws IOException If there is an error releasing resources.
     */
    public void close() throws IOException
    {
        pdfSource.close();
    }

    /**
     * This will get an iterator which can be used to parse the stream
     * one token after the other.
     *
     * @return an iterator to get one token after the other
     */
    public Iterator getTokenIterator()
    {
        return new Iterator()
        {
            private Object token;

            private void tryNext()
            {
                try
                {
                    if (token == null)
                    {
                        token = parseNextToken();
                    }
                }
                catch (IOException e)
                {
                    throw new RuntimeException(e);
                }
            }

            /** {@inheritDoc} */
            public boolean hasNext()
            {
                tryNext();
                return token != null;
            }

            /** {@inheritDoc} */
            public Object next() 
            {
                tryNext();
                Object tmp = token;
                if (tmp == null)
                {
                    throw new NoSuchElementException();
                }
                token = null;
                return tmp;
            }

            /** {@inheritDoc} */
            public void remove()
            {
                throw new UnsupportedOperationException();
            }
        };
    }

    /**
     * This will parse the next token in the stream.
     *
     * @return The next token in the stream or null if there are no more tokens in the stream.
     *
     * @throws IOException If an io error occurs while parsing the stream.
     */
    private Object parseNextToken() throws IOException
    {
        Object retval;

        skipSpaces();
        int nextByte = pdfSource.peek();
        if( ((byte)nextByte) == -1 )
        {
            return null;
        }
        char c = (char)nextByte;
        switch(c)
        {
            case '<':
            {
                int leftBracket = pdfSource.read();//pull off first left bracket
                c = (char)pdfSource.peek(); //check for second left bracket
                pdfSource.unread( leftBracket ); //put back first bracket
                if(c == '<')
                {
                    COSDictionary pod = parseCOSDictionary();
                    skipSpaces();
                    if((char)pdfSource.peek() == 's')
                    {
                        retval = parseCOSStream( pod, file );
                    }
                    else
                    {
                        retval = pod;
                    }
                }
                else
                {
                    retval = parseCOSString();
                }
                break;
            }
            case '[': // array
            {
                retval = parseCOSArray();
                break;
            }
            case '(': // string
                retval = parseCOSString();
                break;
            case '/':   // name
                retval = parseCOSName();
                break;
            case 'n':   // null
            {
                String nullString = readString();
                if( nullString.equals( "null") )
                {
                    retval = COSNull.NULL;
                }
                else
                {
                    retval = PDFOperator.getOperator( nullString );
                }
                break;
            }
            case 't':
            case 'f':
            {
                String next = readString();
                if( next.equals( "true" ) )
                {
                    retval = COSBoolean.TRUE;
                    break;
                }
                else if( next.equals( "false" ) )
                {
                    retval = COSBoolean.FALSE;
                }
                else
                {
                    retval = PDFOperator.getOperator( next );
                }
                break;
            }
            case 'R':
            {
                String line = readString();
                if( line.equals( "R" ) )
                {
                    retval = new COSObject( null );
                }
                else
                {
                    retval = PDFOperator.getOperator( line );
                }
                break;
            }
            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
            case '-':
            case '+':
            case '.':
            {
                /* We will be filling buf with the rest of the number.  Only
                 * allow 1 "." and "-" and "+" at start of number. */
                StringBuffer buf = new StringBuffer();
                buf.append( c );
                pdfSource.read();

                boolean dotNotRead = (c != '.');
                while (Character.isDigit((c = (char) pdfSource.peek())) || (dotNotRead && (c == '.')) || c == '-')
                {
                    if (c != '-')
                    {
                        // PDFBOX-4064: ignore "-" in the middle of a number
                        buf.append(c);
                    }
                    pdfSource.read();

                    if (dotNotRead && (c == '.'))
                    {
                        dotNotRead = false;
                    }
                }
                retval = COSNumber.get( buf.toString() );
                break;
            }
            case 'B':
            {
                String next = readString();
                retval = PDFOperator.getOperator( next );
                if( next.equals( "BI" ) )
                {
                    PDFOperator beginImageOP = (PDFOperator)retval;
                    COSDictionary imageParams = new COSDictionary();
                    beginImageOP.setImageParameters( new ImageParameters( imageParams ) );
                    Object nextToken = null;
                    while( (nextToken = parseNextToken()) instanceof COSName )
                    {
                        Object value = parseNextToken();
                        imageParams.setItem( (COSName)nextToken, (COSBase)value );
                    }
                    //final token will be the image data, maybe??
                    PDFOperator imageData = (PDFOperator)nextToken;
                    beginImageOP.setImageData( imageData.getImageData() );
                }
                break;
            }
            case 'I':
            {
                //Special case for ID operator
                String id = "" + (char)pdfSource.read() + (char)pdfSource.read();
                if( !id.equals( "ID" ) )
                {
                    throw new IOException( "Error: Expected operator 'ID' actual='" + id + "'" );
                }
                ByteArrayOutputStream imageData = new ByteArrayOutputStream();
                if( isWhitespace() )
                {
                    //pull off the whitespace character
                    pdfSource.read();
                }
                int lastByte = pdfSource.read();
                int currentByte = pdfSource.read();
                // PDF spec is kinda unclear about this. Should a whitespace
                // always appear before EI? Not sure, so that we just read
                // until EI.
                // Be aware not all kind of whitespaces are allowed here. see PDFBOX-1561
                while( !(lastByte == 'E' &&
                         currentByte == 'I' &&
                         hasNextSpaceOrReturn() &&
                         hasNoFollowingBinData( pdfSource )) &&
                       !pdfSource.isEOF() )
                {
                    imageData.write( lastByte );
                    lastByte = currentByte;
                    currentByte = pdfSource.read();
                }
                // the EI operator isn't unread, as it won't be processed anyway
                retval = PDFOperator.getOperator( "ID" );
                // save the image data to the operator, so that it can be accessed later
                ((PDFOperator)retval).setImageData( imageData.toByteArray() );
                break;
            }
            case ']':
            {
                // some ']' around without its previous '['
                // this means a PDF is somewhat corrupt but we will continue to parse.
                pdfSource.read();
                retval = COSNull.NULL;  // must be a better solution than null...
                break;
            }
            default:
            {
                //we must be an operator
                String operator = readOperator();
                if( operator.trim().length() == 0 )
                {
                    //we have a corrupt stream, stop reading here
                    retval = null;
                }
                else
                {
                    retval = PDFOperator.getOperator( operator );
                }
            }
        }
        return retval;
    }

    /**
     * Looks up an amount of bytes if they contain only ASCII characters (no
     * control sequences etc.), and that these ASCII characters begin with a
     * sequence of 1-3 non-blank characters between blanks
     *
     * @return true if next bytes are probably printable ASCII
     * characters starting with a PDF operator, otherwise false
     */
    private boolean hasNoFollowingBinData(final PushbackInputStream pdfSource) 
            throws IOException
    {
        // as suggested in PDFBOX-1164
        final int readBytes = pdfSource.read(binCharTestArr, 0, maxBinCharTestLength);
        boolean noBinData = true;
        int startOpIdx = -1;
        int endOpIdx = -1;
        
        if (readBytes > 0)
        {
            for (int bIdx = 0; bIdx < readBytes; bIdx++)
            {
                final byte b = binCharTestArr[bIdx];
                if (b != 0 && b < 0x09 || b > 0x0a && b < 0x20 && b != 0x0d)
                {
                    // control character or > 0x7f -> we have binary data
                    noBinData = false;
                    break;
                }
                // find the start of a PDF operator
                if (startOpIdx == -1 && !(b == 0 || b == 9 || b == 0x20 || b == 0x0a || b == 0x0d))
                {
                    startOpIdx = bIdx;
                }
                else if (startOpIdx != -1 && endOpIdx == -1 &&
                         (b == 0 || b == 9 || b == 0x20 || b == 0x0a || b == 0x0d))
                {
                    endOpIdx = bIdx;
                }
            }

            // PDFBOX-3742: just assuming that 1-3 non blanks is a PDF operator isn't enough
            if (endOpIdx != -1 && startOpIdx != -1)
            {
                // usually, the operator here is Q, sometimes EMC (PDFBOX-2376).
                String s = new String(binCharTestArr, startOpIdx, endOpIdx - startOpIdx);
                if (!"Q".equals(s) && !"EMC".equals(s))
                {
                    noBinData = false;
                }
            }

            if (readBytes == maxBinCharTestLength) // only if not close to eof
            {
                // a PDF operator is 1-3 bytes long
                if (startOpIdx != -1 && endOpIdx == -1)
                {
                    endOpIdx = maxBinCharTestLength;
                }
                if (endOpIdx != -1 && startOpIdx != -1 && endOpIdx - startOpIdx > 3)
                {
                    noBinData = false;
                }
            }
            pdfSource.unread(binCharTestArr, 0, readBytes);
        }
        if (!noBinData)
        {
            LOG.warn("ignoring 'EI' assumed to be in the middle of inline image");
        }
        return noBinData;
    }

    /**
     * This will read an operator from the stream.
     *
     * @return The operator that was read from the stream.
     *
     * @throws IOException If there is an error reading from the stream.
     */
    protected String readOperator() throws IOException
    {
        skipSpaces();

        //average string size is around 2 and the normal string buffer size is
        //about 16 so lets save some space.
        StringBuffer buffer = new StringBuffer(4);
        int nextChar = pdfSource.peek();
        while(
            nextChar != -1 && // EOF
            !isWhitespace(nextChar) &&
            !isClosing(nextChar) &&
            nextChar != '[' &&
            nextChar != '<' &&
            nextChar != '(' &&
            nextChar != '/' &&
            (nextChar < '0' ||
             nextChar > '9' ) )
        {
            char currentChar = (char)pdfSource.read();
            nextChar = pdfSource.peek();
            buffer.append( currentChar );
            // Type3 Glyph description has operators with a number in the name
            if (currentChar == 'd' && (nextChar == '0' || nextChar == '1') ) 
            {
                buffer.append( (char)pdfSource.read() );
                nextChar = pdfSource.peek();
            }
        }
        return buffer.toString();
    }
    
    
    private boolean isSpaceOrReturn( int c )
    {
        return c == 10 || c == 13 || c == 32;
    }

    /**
     * Checks if the next char is a space or a return.
     * 
     * @return true if the next char is a space or a return
     * @throws IOException if something went wrong
     */
    private boolean hasNextSpaceOrReturn() throws IOException
    {
        return isSpaceOrReturn( pdfSource.peek() );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void clearResources()
    {
        super.clearResources();
        if (streamObjects != null)
        {
            streamObjects.clear();
            streamObjects = null;
        }
    }
}
 















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