浅谈使用Rapidxml 库遇到的问题和分析过程(分享)

我们发现第8行有一个&判断 查看print_no_indenting的定义：

// Printing flags
const int print_no_indenting = 0x1;  //!< Printer flag instructing the printer to suppress indenting of XML. See print() function.

据此我们就可以分析了，按照开发风格统一的思想，parse也应该有相同的标志定义

省略分析parse流程..

我也顺便去查看了官方文档，确实和我预想的一样，贴一下头文件中对这些标志的描述，详细信息可参考官方文档

// Parsing flags

  //! Parse flag instructing the parser to not create data nodes. 
  //! Text of first data node will still be placed in value of parent element,unless rapidxml::parse_no_element_values flag is also specified.
  //! Can be combined with other flags by use of | operator.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_no_data_nodes = 0x1;      

  //! Parse flag instructing the parser to not use text of first data node as a value of parent element.
  //! Can be combined with other flags by use of | operator.
  //! Note that child data nodes of element node take precendence over its value when printing. 
  //! That is,if element has one or more child data nodes <em>and</em> a value,the value will be ignored.
  //! Use rapidxml::parse_no_data_nodes flag to prevent creation of data nodes if you want to manipulate data using values of elements.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_no_element_values = 0x2;
  
  //! Parse flag instructing the parser to not place zero terminators after strings in the source text.
  //! By default zero terminators are placed,modifying source text.
  //! Can be combined with other flags by use of | operator.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_no_string_terminators = 0x4;
  
  //! Parse flag instructing the parser to not translate entities in the source text.
  //! By default entities are translated,modifying source text.
  //! Can be combined with other flags by use of | operator.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_no_entity_translation = 0x8;
  
  //! Parse flag instructing the parser to disable UTF-8 handling and assume plain 8 bit characters.
  //! By default,UTF-8 handling is enabled.
  //! Can be combined with other flags by use of | operator.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_no_utf8 = 0x10;
  
  //! Parse flag instructing the parser to create XML declaration node.
  //! By default,declaration node is not created.
  //! Can be combined with other flags by use of | operator.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_declaration_node = 0x20;
  
  //! Parse flag instructing the parser to create comments nodes.
  //! By default,comment nodes are not created.
  //! Can be combined with other flags by use of | operator.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_comment_nodes = 0x40;
  
  //! Parse flag instructing the parser to create DOCTYPE node.
  //! By default,doctype node is not created.
  //! Although W3C specification allows at most one DOCTYPE node,RapidXml will silently accept documents with more than one.
  //! Can be combined with other flags by use of | operator.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_doctype_node = 0x80;
  
  //! Parse flag instructing the parser to create PI nodes.
  //! By default,PI nodes are not created.
  //! Can be combined with other flags by use of | operator.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_pi_nodes = 0x100;
  
  //! Parse flag instructing the parser to validate closing tag names. 
  //! If not set,name inside closing tag is irrelevant to the parser.
  //! By default,closing tags are not validated.
  //! Can be combined with other flags by use of | operator.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_validate_closing_tags = 0x200;
  
  //! Parse flag instructing the parser to trim all leading and trailing whitespace of data nodes.
  //! By default,whitespace is not trimmed. 
  //! This flag does not cause the parser to modify source text.
  //! Can be combined with other flags by use of | operator.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_trim_whitespace = 0x400;

  //! Parse flag instructing the parser to condense all whitespace runs of data nodes to a single space character.
  //! Trimming of leading and trailing whitespace of data is controlled by rapidxml::parse_trim_whitespace flag.
  //! By default,whitespace is not normalized. 
  //! If this flag is specified,source text will be modified.
  //! Can be combined with other flags by use of | operator.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_normalize_whitespace = 0x800;

  // Compound flags
  
  //! Parse flags which represent default behaviour of the parser. 
  //! This is always equal to 0,so that all other flags can be simply ored together.
  //! Normally there is no need to inconveniently disable flags by anding with their negated (~) values.
  //! This also means that meaning of each flag is a <i>negation</i> of the default setting. 
  //! For example,if flag name is rapidxml::parse_no_utf8,it means that utf-8 is <i>enabled</i> by default,//! and using the flag will disable it.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_default = 0;
  
  //! A combination of parse flags that forbids any modifications of the source text. 
  //! This also results in faster parsing. However,note that the following will occur:
  //! <ul>
  //! <li>names and values of nodes will not be zero terminated,you have to use xml_base::name_size() and xml_base::value_size() functions to determine where name and value ends</li>
  //! <li>entities will not be translated</li>
  //! <li>whitespace will not be normalized</li>
  //! </ul>
  //! See xml_document::parse() function.
  const int parse_non_destructive = parse_no_string_terminators | parse_no_entity_translation;
  
  //! A combination of parse flags resulting in fastest possible parsing,without sacrificing important data.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_fastest = parse_non_destructive | parse_no_data_nodes;
  
  //! A combination of parse flags resulting in largest amount of data being extracted. 
  //! This usually results in slowest parsing.
  //! <br><br>
  //! See xml_document::parse() function.
  const int parse_full = parse_declaration_node | parse_comment_nodes | parse_doctype_node | parse_pi_nodes | parse_validate_closing_tags;

根据以上提供的信息我们改下之前的源代码：

将

 doc.parse<0>(requestFile.data());//解析xml
 auto nodeRoot = doc.first_node("");//获取第一个节点，也就是Root节点
 

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