PTrailer (ICEpdf API)

java.lang.Object
- org.icepdf.core.pobjects.Dictionary
- - org.icepdf.core.pobjects.PTrailer

```
public class PTrailer
extends Dictionary
```
The trailer of a PDF file enables an application reading the file to quickly find the cross-reference table and certain special objects. Applications should read a PDF file from its end. The last line of the file contains only the end-of-file marker, %%EOF.

A document can have more then one trailer reference. It is important to use the addTrailer() method if a subsequent trailer is found, or the addPreviousTrailer() method if a previous trailer is found, depending on if the PDF file is being read linearly, or via random access seeking.

If the Prev key entry is present then the document has more then one cross-reference section. There is a numerical value, which is typically associated with the trailer, that comes after startxref, and before %%EOF. It is byte offset from the beginning of the file to the beginning of the last cross-reference section.

In a regular PDF, it's the address of the current xref table. In a linearized PDF, it's the address of the xref table at the file beginning, or zero. In an updated PDF, it's the address of the current xref table. In all cases, the LastCrossReferenceSection field, at the end of the PDF file, points to the byte offset from the beginning of the file, of the "last" xref section, which means the xref section with the highest precedence. For each xref section, its following trailer section has a Prev field, which points to the byte offset from the beginning of the file, of the xref section with one less degree of precedence.

Since:

1.1

Field Summary

Fields
Modifier and Type	Field and Description
`static Name`	`ENCRYPT_KEY`
`static Name`	`ID_KEY`
`static Name`	`INFO_KEY`
`static Name`	`PREV_KEY`
`static Name`	`ROOT_KEY`
`static Name`	`SIZE_KEY`
`static Name`	`XREFSTM_KEY`

Fields inherited from class org.icepdf.core.pobjects.Dictionary
entries, FORM_TYPE_KEY, inited, isDeleted, isNew, LENGTH_KEY, library, SUBTYPE_KEY, TYPE_KEY

Constructor Summary

Constructors
Constructor and Description
`PTrailer(Library library, java.util.HashMap dictionary, CrossReference xrefTable, CrossReference xrefStream)` Create a new PTrailer object

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`protected void`	`addNextTrailer(PTrailer nextTrailer)` Add the trailer dictionary to the current trailer object's dictionary.
`protected void`	`addPreviousTrailer(PTrailer previousTrailer)`
`protected CrossReference`	`getCrossReferenceStream()` Gets the cross reference stream.
`protected CrossReference`	`getCrossReferenceTable()` Gets the cross reference table.
`java.util.HashMap`	`getDictionary()` Get the trailer object's dictionary.
`java.util.HashMap<java.lang.Object,java.lang.Object>`	`getEncrypt()` The document's encryption dictionary Required : if document is encrypted; PDF 1.1
`java.util.List`	`getID()` A vector of two strings constituting a file identifier Optional : PDF 1.1.
`PInfo`	`getInfo()` The document's information dictionary Optional : must be an indirect reference.
`int`	`getNumberOfObjects()` Gets the total number of entries in the file's cross-reference table, as defined by the combination of the original section and all updated sections.
`long`	`getPosition()`
`long`	`getPrev()` Gets the byte offset from the beginning of the file to the beginning of the previous cross-reference section.
`protected CrossReference`	`getPrimaryCrossReference()` Depending on if the PDF file is version 1.4 or before, or 1.5 or after, it may have a cross reference table, or cross reference stream, or both.
`Catalog`	`getRootCatalog()` Gets the Catalog entry for this PDF document.
`Reference`	`getRootCatalogReference()` Gets the catalog reference for the PDF document contained in the file.
`protected void`	`loadXRefStmIfApplicable()`
`protected void`	`onDemandLoadAndSetupPreviousTrailer()`
`void`	`setPosition(long pos)` After this PTrailer is parsed, we store it's location within the PDF here, for future use.
`java.lang.String`	`toString()` Returns a summary of the PTrailer dictionary values.

Methods inherited from class org.icepdf.core.pobjects.Dictionary
getEntries, getFloat, getInt, getLibrary, getNumber, getObject, getPObjectReference, init, isDeleted, isNew, setDeleted, setNew, setPObjectReference

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

- Field Detail
  - SIZE_KEY
```
public static final Name SIZE_KEY
```
  - PREV_KEY
```
public static final Name PREV_KEY
```
  - ROOT_KEY
```
public static final Name ROOT_KEY
```
  - ENCRYPT_KEY
```
public static final Name ENCRYPT_KEY
```
  - INFO_KEY
```
public static final Name INFO_KEY
```
  - ID_KEY
```
public static final Name ID_KEY
```
  - XREFSTM_KEY
```
public static final Name XREFSTM_KEY
```
- Constructor Detail
  - PTrailer
```
public PTrailer(Library library,
                java.util.HashMap dictionary,
                CrossReference xrefTable,
                CrossReference xrefStream)
```
    Create a new PTrailer object
    
    Parameters:
    
    dictionary - dictionary associated with the trailer
- Method Detail
  - getNumberOfObjects
```
public int getNumberOfObjects()
```
    Gets the total number of entries in the file's cross-reference table, as defined by the combination of the original section and all updated sections. Equivalently, this value is 1 greater than the highest object number used in the file.
    - Note: Any object in a cross-reference section whose number is greater than this value is ignored and considered missing.
    Required : must not be an indirect reference
    Returns:
    
    total number of entries in the file's cross-reference table
  - getPrev
```
public long getPrev()
```
    Gets the byte offset from the beginning of the file to the beginning of the previous cross-reference section.
    (Present only if the file has more than one cross-reference section; must not be an indirect reference)
    
    Returns:
    
    byte offset from beginning of the file to the beginning of the previous cross-reference section
  - getPrimaryCrossReference
```
protected CrossReference getPrimaryCrossReference()
```
    Depending on if the PDF file is version 1.4 or before, or 1.5 or after, it may have a cross reference table, or cross reference stream, or both. If there are both, then the cross reference table has precedence.
    
    Returns:
    
    the cross reference object with the highest precedence, for this trailer
  - getCrossReferenceTable
```
protected CrossReference getCrossReferenceTable()
```
    Gets the cross reference table.
    
    Returns:
    
    cross reference table object; null, if one does not exist.
  - getCrossReferenceStream
```
protected CrossReference getCrossReferenceStream()
```
    Gets the cross reference stream.
    
    Returns:
    
    cross reference stream object; null, if one does not exist.
  - getRootCatalogReference
```
public Reference getRootCatalogReference()
```
    Gets the catalog reference for the PDF document contained in the file.
    Required : must not be an indirect reference
    
    Returns:
    
    reference number of catalog reference.
  - getRootCatalog
```
public Catalog getRootCatalog()
```
    Gets the Catalog entry for this PDF document.
    
    Returns:
    
    Catalog entry.
  - getEncrypt
```
public java.util.HashMap<java.lang.Object,java.lang.Object> getEncrypt()
```
    The document's encryption dictionary
    Required : if document is encrypted; PDF 1.1
    
    Returns:
    
    encryption dictionary
  - getInfo
```
public PInfo getInfo()
```
    The document's information dictionary
    Optional : must be an indirect reference.
    
    Returns:
    
    information dictionary
  - getID
```
public java.util.List getID()
```
    A vector of two strings constituting a file identifier
    Optional : PDF 1.1.
    
    Returns:
    
    vector containing constituting file identifier
  - getPosition
```
public long getPosition()
```
    Returns:
    
    The position in te file where this trailer is located
  - setPosition
```
public void setPosition(long pos)
```
    After this PTrailer is parsed, we store it's location within the PDF here, for future use.
  - addNextTrailer
```
protected void addNextTrailer(PTrailer nextTrailer)
```
    Add the trailer dictionary to the current trailer object's dictionary.
    
    Parameters:
    
    nextTrailer - document trailer object
  - addPreviousTrailer
```
protected void addPreviousTrailer(PTrailer previousTrailer)
```
  - onDemandLoadAndSetupPreviousTrailer
```
protected void onDemandLoadAndSetupPreviousTrailer()
```
  - loadXRefStmIfApplicable
```
protected void loadXRefStmIfApplicable()
```
  - getDictionary
```
public java.util.HashMap getDictionary()
```
    Get the trailer object's dictionary.
    
    Returns:
    
    dictionary
  - toString
```
public java.lang.String toString()
```
    Returns a summary of the PTrailer dictionary values.
    
    Overrides:
    
    toString in class Dictionary
    
    Returns:
    
    dictionary values.

Class PTrailer

Field Summary

Fields inherited from class org.icepdf.core.pobjects.Dictionary

Constructor Summary

Method Summary

Methods inherited from class org.icepdf.core.pobjects.Dictionary

Methods inherited from class java.lang.Object

Field Detail

SIZE_KEY

PREV_KEY

ROOT_KEY

ENCRYPT_KEY

INFO_KEY

ID_KEY

XREFSTM_KEY

Constructor Detail

PTrailer

Method Detail

getNumberOfObjects

getPrev

getPrimaryCrossReference

getCrossReferenceTable

getCrossReferenceStream

getRootCatalogReference

getRootCatalog

getEncrypt

getInfo

getID

getPosition

setPosition

addNextTrailer

addPreviousTrailer

onDemandLoadAndSetupPreviousTrailer

loadXRefStmIfApplicable

getDictionary

toString