Package de.intarsys.pdf.cos

This package implements the low level document and its datatypes according to the pdf specification.

See:
Description

Interface Summary

ICOSContainer	A low level interface for polymorphic access to an object containing a COSObject.
ICOSDocumentFactory	An object that is able to create a COSDocument with the help of a locator object that designates the physical source.
ICOSDocumentListener	A listener for changes in a COSDocument.
ICOSExceptionHandler	An object that can handle exceptions encountered when dealing with COSObject instances.
ICOSMonitor
ICOSObjectListener	A listener for changes in a COSObject.
ICOSObjectVisitor	An interface for visiting a COS object structure.
ICOSProxyVisitor	An interface for visiting a proxy to a COSObject

Class Summary

COSArray	A COSArray represents an indexed collection of COSDocumentElement instances.
COSBasedObject	The abstract superclass for all objects/data structures that are build on the basic COSObject types.
COSBasedObject.MetaClass	The meta class implementation
COSBoolean	Abstract class for the representation of boolean values
COSCatalog	The document catalog object of the PDF document.
COSCatalog.MetaClass	The meta class implementation
COSCompositeObject	A superclass implementation for all containers of other COSObject instances.
COSDictionary	Represents a collection of associations (Map).
COSDictionary.Entry
COSDocument	This is a COS level representation of a pdf document.
COSDocumentElement	This is a cos level representation of the elements that may be contained in a cos container.
COSDocumentFactory	The VM singleton for accessing a ICOSDocumentFactory.
COSFalse	Represents the boolean value "false".
COSFixed	Represents floating point numbers in pdf.
COSIndirectObject	An object representing an indirect object within a COSDocument.
COSInfoDict	The document information dictionary..
COSInfoDict.MetaClass	The meta class implementation
COSInteger	This class represents integer numbers in pdf
COSName	A name object.
COSNull	The null object
COSNumber	Abstract superclass for numeric objects in a pdf document
COSObject	Abstract superclass for all COS level object types
COSObjectKey	An object that is used as a lookup key for COS objects.
COSObjectProxy	A "proxy object" used to intercept the visitor callback from the serializer.
COSObjectWalkerDeep	Adapter implementation for visiting a COS object structure, including indirect references.
COSObjectWalkerShallow	Adapter implementation for visiting a COS object structure without navigating the indirect references.
COSPrimitiveObject	Primitive COS datatypes.
COSStream	An object representing stream data in a PDF document.
COSString	The string representation for a pdf document
COSTools	Some tools to ease life with COS.
COSTrailer	The document trailer.
COSTrailer.MetaClass	The meta class implementation
COSTrue	Represents the boolean value "true"
MetaClass
StandardDocumentFactory	A simple factory that creates a new document from the locator.

Exception Summary

COSRuntimeException	An exception indicating an unexpected COS related error at runtime.
COSSwapException	An exception while swapping a COSObject.
COSVisitorException	An exceptional condition while performing an ICOSObjectVisitor.

Package de.intarsys.pdf.cos Description

This package implements the low level document and its datatypes according to the pdf specification.

Every PDF document is finally composed using COS primitive and composite objects. These objects are aggregated to a COSDocument. The available primitives are

• Boolean: true or false
• Name: A special unique string like object, most often used as a key for dictionaries.
• Fixed: A fixed point real number.
• Integer: An integer number
• String: A string object

COS objects are composed using

• Array: A dynamic indexed collection implementation.
• Dictionary: A associative (Map) data structure.

Kind of hybrid structure is a

• Stream: A sequence of bytes, combined with a dictionary with additional information about the stream itself.

This implementation uses a special object representing "null", COSNull. A lookup in a composite will never return an ordinary Java null, always COSNull, so you are never forced to check (obj == null || obj.isFoo()). Another useful convention is the "marshalling" using the "as" flavor of methods. This methods will return either Java "null" or an instance of the requested type. These conventions help around the sometimes lazy implemented data structures of the PDF documents available out there.

In a COS structure, other standalone objects and substructures can be referenced. This is represented using COSIndirectObject. An indirect object is not returned by the standard accessors or iterators from composite COS objects, you will always receive the dereferenced COS object. To access the reference itself, you have to use the "basic" flavor of methods.

Based on these purely technical objects without PDF domain specific behavior the meaningful data types like "Rectangle", "Page" and so on are defined. This is reflected in the framework provided by COSBasedObject, the super class for all PDF domain objects. Only a few are defined directly in the COS level itself, the most of them are found in the "pd" package.

While this seems not to be too complicated, this implementation is a quite complex and powerful one, supporting things like

• update propagation
• lazy reading
• swapping
• state management (for example for simple undo)
• preserve COS invariants that in most implementations lead to failures in the resulting documents that are hard to debug, like constraints on containement, identity etc.