Lib:Architecture/Object Layer
From GNUpdf
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Overview
This page contain a description of the object layer in the GNU PDF Library.
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Object Layer Architecture
This layer implements the concepts of PDF objects and PDF documents as a structured hierarchy of objects. An API is provided to manipulate that structure and the objects that compose it. Since the object hierarchy can be quite complex a garbage collection mechanism is provided to the client of the layer.
The functionality provided by this layer is implemented in several modules.
- Document Module
- This module implements the abstraction of object level documents. An object-level document is a hierarchy of objects that conforms a PDF document. Facilities to get the objects from a document and to create new objects into a document are also provided. A cache of objects and a garbage collection algorithm is also implemented in this module.
- Object Module
- This module implements the several PDF objects and provides functions to manipulate the attributes of the objects associated with an object-level document.
- Reader Module
- This module implements the functionality to get PDF objects from a base-level stream. A lexer and a parser are used to transform PDF source code into the objects managed by a document-level document.
- Writer Module
- This module implements the functionality to create a textual version of PDF objects. The textual representation of objects are then written into a given base level stream.
