CrossRefStream (JHOVE - JSTOR/Harvard Object Validation Environment 1.16.0 API)

java.lang.Object
- edu.harvard.hul.ois.jhove.module.pdf.CrossRefStream

```
public class CrossRefStream
extends Object
```
This class implements the Cross-Reference Stream, an alternative to the Cross-Reference Table starting in PDF 1.4. A cross-reference stream is identified by a startxref keyword, as opposed to the xref keyword which identifies the old-style cross-reference table. JHOVE supports only FlateDecode as a filter for cross-reference streams. This is consistent with the implementation limitation described in Appendix H of the PDF manual for Acrobat 6 and earlier.

Author:

Gary McGath

Constructor Summary

Constructors
Constructor and Description

CrossRefStream(PdfStream xstrm)
Constructor.

Constructors
Constructor and Description
`CrossRefStream(PdfStream xstrm)` Constructor.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`int`	`getContentStreamIndex()` Returns the content stream index of the last object read.
`int`	`getContentStreamObjNum()` Returns the object number of the content stream in which this object is stored.
`int`	`getCrossRefTableSize()` Returns the total number of objects in the document's cross-reference table at the time this stream was written.
`int`	`getFreeCount()` Returns the number of free objects detected.
`int`	`getObjNum()` Returns number of the last object read by `readNextObject ()`.
`int`	`getOffset()` Returns the offset of the last object read.
`long`	`getPrevXref()` Returns the offset of the previous cross-reference stream, or -1 if none is specified.
`void`	`initRead(RandomAccessFile raf)` Prepares for reading the Stream.
`boolean`	`isObjCompressed()` Returns `true` if the last object read by `readNextObject ()` is a compressed object.
`boolean`	`isValid()` Returns `true` if the PdfStream object meets the requirements of a cross-reference stream.
`boolean`	`readNextObject()` Reads the next object in the stream.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - CrossRefStream
```
public CrossRefStream(PdfStream xstrm)
```
    Constructor.
    
    Parameters:
    
    xstrm - PdfStream object which contains a presumed cross-reference stream.
- Method Detail
  - isValid
```
public boolean isValid()
```
    Returns true if the PdfStream object meets the requirements of a cross-reference stream. Also extracts information from the dictionary for subsequent processing.
  - initRead
```
public void initRead(RandomAccessFile raf)
              throws IOException,
                     PdfException
```
    Prepares for reading the Stream. If the filter list includes one which we don't support, throws a PdfException.
    
    Throws:
    
    IOException
    
    PdfException
  - readNextObject
```
public boolean readNextObject()
                       throws IOException
```
    Reads the next object in the stream. After calling readObject, it is possible to call accessors to get information about the object. For the moment, we punt on the question of how to deal with Object Streams. Free objects are skipped over while being counted. After readNextObject() returns false, the caller may call getFreeCount() to determine the number of free objects.
    Returns: true if there is an object, false if no more objects are available. Throws: IOException
  getObjNum public int getObjNum() Returns number of the last object read by readNextObject (). Do not call if readNextObject () returns false. isObjCompressed public boolean isObjCompressed() Returns true if the last object read by readNextObject () is a compressed object. Do not call if readNextObject () returns false. getFreeCount public int getFreeCount() Returns the number of free objects detected. This may be called after readNextObject returns false, signifying that all the objects have been read and all the free objects counted. getCrossRefTableSize public int getCrossRefTableSize() Returns the total number of objects in the document's cross-reference table at the time this stream was written. getOffset public int getOffset() Returns the offset of the last object read. This is meaningful only if the last object read was type 1 (uncompressed). getContentStreamObjNum public int getContentStreamObjNum() Returns the object number of the content stream in which this object is stored. This is meaningful only if the last object read was type 2 (compressed in content stream). getPrevXref public long getPrevXref() Returns the offset of the previous cross-reference stream, or -1 if none is specified. getContentStreamIndex public int getContentStreamIndex() Returns the content stream index of the last object read. This is meaningful only if the last object read was type 2 (compressed in content stream).

Class CrossRefStream

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

CrossRefStream

Method Detail

isValid

initRead

readNextObject

getObjNum

isObjCompressed

getFreeCount

getCrossRefTableSize

getOffset

getContentStreamObjNum

getPrevXref

getContentStreamIndex