第二人生的源码分析(六十九)使用LLXmlTree类来分析XML配置文件

前面已经介绍使用expat库来分析XML数据，那么在第二人生里是怎么样分析XML配置文件的呢？现在就来分析这方面的问题，先来看看第二人生分析配置文件调用关系，如下：
1. LLAppViewerWin32::init()
2. LLAppViewer::init()
3. LLControlGroup::loadFromFile()
4. LLXmlTree::parseFile()
5. LLXmlTreeParser::parseFile()
6. LLXmlParser::parseFile()

从这个调用关系，可以看到分析配置文件是调用类LLControlGroup、类LLXmlTree、类LLXmlTreeParser和类LLXmlParser共同完成这项任务的。类LLControlGroup是控件的状态保存，类LLXmlTree是把XML数据按树表示，类LLXmlTreeParser是保存树形节点的分析类，类LLXmlParser与上面介绍使用expat类一样的，都是封装expat库函数。因此，现在先来看类LLXmlParser类的声明，如下：
#001 class LLXmlParser
#002 {
#003 public:

构造函数和析构函数。
#004 LLXmlParser();
#005 virtual ~LLXmlParser();
#006

这个函数分析给出文件名称的XML文件。
#007 // Parses entire file
#008 BOOL parseFile(const std::string &path);
#009

分析给出缓冲区的XML数据。
#010 // Parses some input. Returns 0 if a fatal error is detected.
#011 // The last call must have isFinal true;
#012 // len may be zero for this call (or any other).
#013 S32 parse( const char* buf, int len, int isFinal );
#014

获取出错的字符串。
#015 const char* getErrorString();
#016

获取当前行号。
#017 S32 getCurrentLineNumber();
#018

获取当前行的列号。
#019 S32 getCurrentColumnNumber();
#020

获取XML元素节点的深度。
#021 S32 getDepth() { return mDepth; }
#022
#023 protected:

处理元素开始和结束的函数。
#024 // atts is array of name/value pairs, terminated by 0;
#025 // names and values are 0 terminated.
#026 virtual void startElement(const char *name, const char **atts) {}
#027
#028 virtual void endElement(const char *name) {}
#029
#030 // s is not 0 terminated.
#031 virtual void characterData(const char *s, int len) {}
#032
#033 // target and data are 0 terminated
#034 virtual void processingInstruction(const char *target, const char *data) {}
#035
#036 // data is 0 terminated
#037 virtual void comment(const char *data) {}
#038
#039 virtual void startCdataSection() {}
#040
#041 virtual void endCdataSection() {}
#042
#043 // This is called for any characters in the XML document for
#044 // which there is no applicable handler. This includes both
#045 // characters that are part of markup which is of a kind that is
#046 // not reported (comments, markup declarations), or characters
#047 // that are part of a construct which could be reported but
#048 // for which no handler has been supplied. The characters are passed
#049 // exactly as they were in the XML document except that
#050 // they will be encoded in UTF-8. Line boundaries are not normalized.
#051 // Note that a byte order mark character is not passed to the default handler.
#052 // There are no guarantees about how characters are divided between calls
#053 // to the default handler: for example, a comment might be split between
#054 // multiple calls.
#055 virtual void defaultData(const char *s, int len) {}
#056
#057 // This is called for a declaration of an unparsed (NDATA)
#058 // entity. The base argument is whatever was set by XML_SetBase.
#059 // The entityName, systemId and notationName arguments will never be null.
#060 // The other arguments may be.
#061 virtual void unparsedEntityDecl(
#062 const char *entityName,
#063 const char *base,
#064 const char *systemId,
#065 const char *publicId,
#066 const char *notationName) {}
#067
#068 public:
#069 ///////////////////////////////////////////////////////////////////////////////
#070 // Pseudo-private methods. These are only used by internal callbacks.
#071

下面这些函数是静态函数，在里面都是调用本类的虚函数来处理的。
#072 static void startElementHandler(void *userData, const XML_Char *name, const XML_Char **atts);
#073 static void endElementHandler(void *userData, const XML_Char *name);
#074 static void characterDataHandler(void *userData, const XML_Char *s, int len);
#075 static void processingInstructionHandler(void *userData, const XML_Char *target, const XML_Char *data);
#076 static void commentHandler(void *userData, const XML_Char *data);
#077 static void startCdataSectionHandler(void *userData);
#078 static void endCdataSectionHandler(void *userData);
#079 static void defaultDataHandler( void *userData, const XML_Char *s, int len);
#080 static void unparsedEntityDeclHandler(
#081 void *userData,
#082 const XML_Char *entityName,
#083 const XML_Char *base,
#084 const XML_Char *systemId,
#085 const XML_Char *publicId,
#086 const XML_Char *notationName);
#087
#088
#089 protected:
#090 XML_Parser mParser;
#091 int mDepth;
#092 char mAuxErrorString[1024]; /*Flawfinder: ignore*/
#093 };
#094

通过上面的类在构造函数里创建expat库，并且在函数LLXmlParser::parseFile读取XML文件的数据，提供给expat分析，这样就会生成XML树表的数据。下一次再来分析类LLXmlTreeParser。