org.apache.tika.parser.pdf.updates

Class StartXRefScanner

java.lang.Object

org.apache.tika.parser.pdf.updates.StartXRefScanner

public class StartXRefScanner
extends Object

This is a first draft of a scanner to extract incremental updates out of PDFs. It effectively scans the bytestream looking for startxref\\s*(\\d+)\\s*(%%EOF\n?)? It does not validate that the startxrefs point to actual xrefs.

If the number component ends at the literal end of the file (e.g. the file is truncated or malformed), the startxref will not be reported.

There may be false positives, especially in adversarial settings. For example, there may be a startxref string in a comment or inside a stream or object.

The good parts come directly from PDFBox.

Constructor Summary

Constructors

Constructor and Description
StartXRefScanner(org.apache.pdfbox.io.RandomAccessRead source)

Method Summary

Modifier and Type	Method and Description
protected boolean	isEOL(int c) This will tell if the next byte to be read is an end of line byte.
protected boolean	isWhitespace(int c)
protected long	readLong()
protected StringBuilder	readStringNumber() This method is used to read a token by the readLong() method.
List<StartXRefOffset>	scan()
protected void	skipSpaces() This will skip all spaces and comments that are present.
protected void	skipWhiteSpaces()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

StartXRefScanner

public StartXRefScanner(org.apache.pdfbox.io.RandomAccessRead source)

Method Detail

scan

public List<StartXRefOffset> scan()
                           throws IOException

Throws:

IOException

skipWhiteSpaces

protected void skipWhiteSpaces()
                        throws IOException

Throws:

IOException

isWhitespace

protected boolean isWhitespace(int c)

readLong

protected long readLong()
                 throws IOException

Throws:

IOException

skipSpaces

protected void skipSpaces()
                   throws IOException

This will skip all spaces and comments that are present.

Throws:

IOException - If there is an error reading from the stream.

readStringNumber

protected final StringBuilder readStringNumber()
                                        throws IOException

This method is used to read a token by the readLong() method. Valid delimiters are any non digit values.

Returns:

the token to parse as integer or long by the calling method.

Throws:

IOException - throws by the source methods.

isEOL

protected boolean isEOL(int c)

This will tell if the next byte to be read is an end of line byte.

Parameters:

c - The character to check against end of line

Returns:

true if the next byte is 0x0A or 0x0D.