book

Perl and XML

by Erik T. Ray, Jason McIntosh

April 2002

Intermediate to advanced

218 pages

6h 12m

English

O'Reilly Media, Inc.

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AssumptionsHow This Book Is OrganizedResourcesThe perl-xml Mailing ListCPANFont ConventionsHow to Contact UsAcknowledgments
1.1. Why Use Perl with XML?1.2. XML Is Simple with XML::Simple1.3. XML Processors1.4. A Myriad of Modules1.5. Keep in Mind...1.6. XML Gotchas
2.1. A Brief History of XML2.2. Markup, Elements, and Structure2.3. Namespaces2.4. Spacing2.5. Entities2.6. Unicode, Character Sets, and Encodings2.7. The XML Declaration2.8. Processing Instructions and Other Markup2.9. Free-Form XML and Well-Formed Documents2.10. Declaring Elements and Attributes2.11. Schemas2.11.1. Other Schema Strategies2.12. Transformations
3.1. XML Parsers3.1.1. Example (of What Not to Do): A Well-Formedness Checker3.2. XML::Parser3.2.1. Example: Well-Formedness Checker Revisited3.2.2. Parsing Styles3.3. Stream-Based Versus Tree-Based Processing3.4. Putting Parsers to Work3.5. XML::LibXML3.6. XML::XPath3.7. Document Validation3.7.1. DTDs3.7.2. Schemas3.8. XML::Writer3.8.1. Other Methods of Output3.9. Character Sets and Encodings3.9.1. Unicode, Perl, and XML3.9.2. Unicode Encodings3.9.2.1. UTF-83.9.2.2. UTF-163.9.2.3. UTF-323.9.3. Other Encodings3.9.3.1. Core Perl support3.9.4. Encoding Conversion3.9.4.1. iconv and Text::Iconv3.9.4.2. Unicode::String3.9.4.3. Byte order marks
4.1. Working with Streams4.2. Events and Handlers4.3. The Parser as Commodity4.4. Stream Applications4.5. XML::PYX4.6. XML::Parser
5.1. SAX Event Handlers5.2. DTD Handlers5.3. External Entity Resolution5.4. Drivers for Non-XML Sources5.5. A Handler Base Class5.6. XML::Handler::YAWriter as a Base Handler Class5.7. XML::SAX: The Second Generation5.7.1. XML::SAX::ParserFactory5.7.2. SAX2 Handler Interface5.7.2.1. Content event handlers5.7.2.2. Entity resolver5.7.2.3. Lexical event handlers5.7.2.4. Error event handlers and catching exceptions5.7.3. SAX2 Parser Interface5.7.4. Example: A Driver5.7.5. Installing Your Own Parser
6.1. XML Trees6.2. XML::Simple6.3. XML::Parser’s Tree Mode6.4. XML::SimpleObject6.5. XML::TreeBuilder6.6. XML::Grove
7.1. DOM and Perl7.2. DOM Class Interface Reference7.2.1. Document7.2.1.1. Properties7.2.1.2. Methods7.2.2. DocumentFragment7.2.3. DocumentType7.2.3.1. Properties7.2.4. Node7.2.4.1. Properties7.2.4.2. Methods7.2.5. NodeList7.2.5.1. Properties7.2.5.2. Methods7.2.6. NamedNodeMap7.2.6.1. Properties7.2.6.2. Methods7.2.7. CharacterData7.2.7.1. Properties7.2.7.2. Methods7.2.8. Element7.2.8.1. Properties7.2.8.2. Methods7.2.9. Attr7.2.9.1. Properties7.2.10. Text7.2.10.1. Methods7.2.11. CDATASection7.2.12. ProcessingInstruction7.2.12.1. Properties7.2.13. Comment7.2.14. EntityReference7.2.15. Entity7.2.15.1. Properties7.2.16. Notation7.2.16.1. Properties7.3. XML::DOM7.4. XML::LibXML

8.1. Tree Climbers8.2. XPath8.3. XSLT8.4. Optimized Tree Processing
9.1. XML Modules9.2. XML::RSS9.2.1. Introduction to RSS9.2.2. Using XML::RSS9.2.2.1. Parsing9.2.2.2. Inheriting from XML::Parser9.2.3. The Object Model9.2.4. Input: User or File9.2.5. Off-the-Cuff Output9.3. XML Programming Tools9.3.1. XML::Generator::DBI9.3.2. Further Ruminations on DBI and SAX9.4. SOAP::Lite9.4.1. First Example: A Temperature Converter9.4.2. Second Example: An ISBN Lookup Engine
10.1. Perl and XML Namespaces10.2. Subclassing10.2.1. Subclassing Example: XML::ComicsML10.3. Converting XML to HTML with XSLT10.3.1. Example: Apache::DocBook10.4. A Comics Index

Content preview from Perl and XML

Chapter 4. Event Streams

Now that you’re all warmed up with parsers and have enough knowledge to make you slightly dangerous, we’ll analyze one of the two important styles of XML processing: event streams. We’ll look at some examples that show the basic theory of stream processing and graduate with a full treatment of the standard Simple API for XML (SAX).

Working with Streams

In the world of computer science, a stream is a sequence of data chunks to be processed. A file, for example, is a sequence of characters (one or more bytes each, depending on the encoding). A program using this data can open a filehandle to the file, creating a character stream, and it can choose to read in data in chunks of whatever size it chooses. Streams can be dynamically generated too, whether from another program, received over a network, or typed in by a user. A stream is an abstraction, making the source of the data irrelevant for the purpose of processing.

To summarize, here are a stream’s important qualities:

It consists of a sequence of data fragments.
The order of fragments transmitted is significant.
The source of data (e.g., file or program output) is not important.

XML streams are just clumpy character streams. Each data clump, called a token in parser parlance, is a conglomeration of one or more characters. Each token corresponds to a type of markup, such as an element start or end tag, a string of character data, or a processing instruction. It’s very easy for parsers to dice up XML in ...