SVG and expat

Adobe SVG Viewer

The full name of the SVG format is "Scalable Vector Graphics", which generally means "variable vector drawing files". Its main purpose is to improve the quality of the first image on the webpage, files in this format can contain gradient layer, animation, self-processing, special effects, and other functions, so that images on webpages can be "active", not just images, in addition, it has a framework to replace "dynamic GIF" files. After installation, You can first connect to the Adobe SVG test page to see if it is actually usable. As you can see, it means that your browser can view the SVG format. If you want to create an SVG file, go to the SVG webpage of Adobe and check its release note. There are some usage skills and current restrictions, this will be helpful to you.

 

Expat is an XML parsing library written in C language. James Clark created this library and is now the technical leader of the W3 organization that develops XML standards. The current version is 2.0. The development team led by Clark Cooper was responsible for development at sourceforge.net from 2.0.

Expat is a lightweight XML interpreter based on the sax model that is not verified (by default, v1.2 starts to provide verification interfaces and needs to be manually processed.

Currently, XML parsing mainly involves two models: Sax and Dom.

Specifically, SAX (Simple API for XML) is an event-based parsing method. The basic principle is to analyze the XML document and notify the user of the resolution result by triggering an event. In this way, the memory usage is small and the speed is fast, but the user program is complicated accordingly.

The dom (Document Object Model) analyzes the entire XML document at one time and stores the parsing results in a tree structure in the memory. At the same time, it provides users with a series of interfaces to access and edit the tree structure. This method occupies a large amount of memory and is often slower than sax. However, it can provide users with an object-oriented access interface, which is more user-friendly.

For a specific XML document, its correctness is divided into two levels. First, the format must comply with the basic XML format requirements. For example, the first line must have a declaration, and the label nesting layers must be consistent, is a qualified XML file called well-formatted. However, an XML document must meet the corresponding standards in terms of semantics because of its different content. These standards are defined by the corresponding DTD file or schema file, XML files that meet these definition requirements are called valid.

Therefore, the parser can be divided into two types: verification and non-verification. Yes. It verifies the XML file with the corresponding DTD file according to the declaration in the XML file to check whether it meets the requirements of the DTD file. For non-validation purposes, the DTD file is ignored and can be parsed as long as the basic format is correct.

For more information, the XML parsing library is summarized as follows:

Name	Access interface	Verification supported or not	Remarks
Expat	Sax	Manual
Libxml2	Sax/DOM	Yes
Tinyxml	Dom	No
XML 4C	Sax/DOM	Yes	And xerces-C, but with ICU, it seems better to be internationalized
Xerces-C	Sax/DOM	Yes
XML Booster	Local	Not clear	This library does not know much about it. It seems like YACC can generate a specific parser, and the efficiency should be very high (see the name as well ).