Boost表达式sregex分配和捕获组问题

Boost Xpressive sregex assignment and capture group issue

本文关键字：问题 表达式 sregex 分配 Boost      更新时间：2023-10-16

我注意到boost表达式sregex赋值中的奇怪行为。请参阅下面的代码。第一个不起作用的代码片段具有sregex对象初始赋值，然后在主表达式中使用。第二个运行良好的代码片段没有任何先前的sregex赋值(除了最后一个主代码)。请让我知道，如果我使用boost表达式api不正确。

不工作的代码 

  mark_tag Value1(1), Value2(2), Value3(3), Value4(4), Value5(5), Value6(6), Value7(7);
  boost::xpressive::sregex name,multicast,rtsp;
  name = ( (Value1 =  (+boost::xpressive::set[_w|_d|'-'|'_'|as_xpr(' ')]) )  >> ',' );
  name1 =
       ( (Value2 = icase(as_xpr("mark1:") ) )
    >> (Value3 =  (+boost::xpressive::set[_d|'.']) )
    >> ':'
    >> (Value4 =  (+boost::xpressive::set[_d]) ) >> optional(as_xpr(",")) );
  name2 =
       ( (Value5 = icase(as_xpr("mark2:") ) )
    >> (Value6 =  (+boost::xpressive::set[_d|'.']) )
    >> ':'
    >> (Value7 =  (+boost::xpressive::set[_d]) ) >> optional(as_xpr(",")) ) ;
   boost::xpressive::sregex pt = bos
    >> (
    name
    >> repeat<0,2>(
    name1
    |
    name2)
    )
    >> eos;

    boost::trim(string_to_parse);
    smatch what;
    if ( !regex_search(string_to_parse, what, pt)) {
        std::stringstream ss;
        ss << "Unable to parse: " << string_to_parse;
        throw parse::MyException(ss.str());
    }
    std::string Value1_str = what[Value1]; // print them later
    std::string Value2_str = what[Value2]; // print them later
    std::string Value3_str = what[Value3]; // print them later
    std::string Value4_str = what[Value4]; // print them later
    std::string Value5_str = what[Value5]; // print them later
    std::string Value6_str = what[Value6]; // print them later
    std::string Value7_str = what[Value7]; // print them later

string_to_parse = NameX,mark1:192.168.1.100:5555,mark2:192.168.1.101:5556; (failed parsing)表示what[<>]不包含任何值。

有效的代码

   mark_tag Value1(1), Value2(2), Value3(3), Value4(4), Value5(5), Value6(6), Value7(7);
   sregex pt = bos
    >> (
    ( (Value1 =  (+boost::xpressive::set[_w|_d|'-'|'_'|as_xpr(' ')]) ) >> ',' )
    >> repeat<0,2>(
    ( (Value2 = icase(as_xpr("mark1:") ) ) >> (Value3 =  (+boost::xpressive::set[_d|'.']) ) >> ':' >> (Value4 =  (+boost::xpressive::set[_d]) ) >> optional(as_xpr(",")) )
    |
    ( (Value5 = icase(as_xpr("mark2:") ) ) >> (Value6 =  (+boost::xpressive::set[_d|'.']) ) >> ':' >> (Value7 =  (+boost::xpressive::set[_d]) ) >> optional(as_xpr(",")) ) )
    )
    >> eos;
    boost::trim(string_to_parse);
    smatch what;
    if ( !regex_search(string_to_parse, what, pt)) {
        std::stringstream ss;
        ss << "Unable to parse: " << string_to_parse;
        throw parse::MyException(ss.str());
    }
    std::string Value1_str = what[Value1]; // print them later
    std::string Value2_str = what[Value2]; // print them later
    std::string Value3_str = what[Value3]; // print them later
    std::string Value4_str = what[Value4]; // print them later
    std::string Value5_str = what[Value5]; // print them later
    std::string Value6_str = what[Value6]; // print them later
    std::string Value7_str = what[Value7]; // print them later

string_to_parse = NameX,mark1:192.168.1.100:5555,mark2:192.168.1.101:5556;(通过解析)

当您用嵌套的正则表达式匹配模式时，您将得到嵌套的匹配结果。

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