C++处理XML文件

简单说一下使用 TinyXML来解析处理XML（eXtensible Markup Language 可扩展标记语言）文件。
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TinyXML简简介

TinyXML是Lee Thomason发布的一个开源库，非常便于使用C++对DOM式的文档进行读、写。他的主页上有对TinyXML的简单介绍。源码可以在Sourceforge上进行下载。

TinyXML库的所有六个文件，即：
- tinystr.h
- tinyxml.h
- tinystr.cpp
- tinyxml.cpp
- tinyxmlerror.cpp
- tinyxmlparser.cpp
只需要将这六个文件添加到工程中，就可以使用TinyXML.

TinyXML不能做的 what it doesn’t do.

TinyXML doesn’t parse or use DTDs (Document Type Definitions) or XSLs (eXtensible Stylesheet Language.)

使用TinyXML的相关工程

• TinyXPath

  TinyXPath is a small footprint XPath syntax decoder, written in C++.

• TinyXML++

  TinyXML++ is a completely new interface to TinyXML that uses MANY of the C++ strengths. Templates, exceptions, and much better error handling.

特性

使用STL

直接在库文件 tinyxml.h 首先加上 “#define TIXML_USE_STL” 即可使用标准库

UTF-8

通常TinyXML会尝试检测并使用源文件中的编码格式，也可以使用 TIXML_DEFAULT_ENCODING宏来强制声明使用的源文件编码格式

打印

TinyXML can print output in several different ways that all have strengths and limitations.

• Print(FILE*)
  streamed directl to the FILE object, there’s no memory overhead in the TinyXML code.
  used by Print() and SaveFile()
• operator <<
  integrates with standard C++ iostreams; output in “network printing” mode without line breaks, good for network transmission and moving XML between C++ objects, but hard for a human to read.
• TiXMLPrinter
  output to a std::string or memory buffer

Streams

#undef TIXML_USE_STL

// tolerant of ill formed XML
C style output:

• based on *FILE
• Print() and SaveFile()

C style input:

• based on *FILE
• Parse() and LoadFile()

#define TIXML_USE_STL
// not tolerant of ill formed XML

C++ style output:
indtended for network transmission rather than readability(maybe slower)
- based on std::ostream
- operator <<

C++ style input: useful for network transmission

• based on std::istream
• operator >>

White space

TiXmlBase::SetCondenseWhileSpace(bool)

在解析XML文件之前应调用 TiXmlBase::SetCondenseWhiteSpace(bool)来设置默认是否压缩空白符，设置好后，一般不用再改动。

Handles 优化的句柄检验

TiXmlElement *root = document.FirstChildElement("Document");if(root){    TiXmlElement *element = root->FirstChildElement("Element");    if(element)    {        TiXmlElement *child = element->FirstChildElement("Child");        if(child)        {            TiXmlElement *child2 = child->NextSiblingElement("Child");            if(child2)            {                // Finally do someting useful....            }        }    }}

使用TiXmlHandle类，将以上代码优化为：

TiXmlHandle docHandle(&document);TiXmlElement *child2 = docHandle.FirstChild("Document").FirstChild\                        ("Element").Child("Child",1).ToElement();if(child2){    // do something useful...}

Row and Column tracking (useful !!!)

TiXmlBase::Row()
TiXmlBase::Column()
TiXmlDocument::SetTabSize()

How TinyXML works

最直观的使用案例

如下的demo.xml文件：

<?xml version="1.0" standalone=no><!-- our to do list data --><ToDo>    <Item priority="1">Go to the <bold>Toy store!</bold></Item>    <Item>        Do bills    </Item></ToDo>

使用C++代码：

TiXmlDocument doc("demo.xml");doc.LoadFile();

源文件中的声明 <?xml version="1.0" standalone=no> 自动被处理成TiXmlDeclaration类。It will be the first child ofthe document node.

<!-- our to do list data> will become a TiXmlComment object.

“ToDo” tag defines a TiXmlElement object, it has not any attributes but 2 other elements.

<Item priority="1"> creates another TiXmlElement which is a child of the “ToDo” element.

Go to the is a TiXmlText, a child of “Item” TiXmlElement.

<bold> another TiXmlElement, and is a child of the “Item” element.

更多关于TinyXML的教程可以参见库文件目录/docs/下的tutorial0.html文件.