Question

这段代码应该解析请求，提取URI路径，然后提取每个单独的头及其值，然后将所有提取的变量传递给std::vector <const char*> cva，最终将传递给std::vector<std::vector<const char*>> nv (config.nv.push_back(std::move(cva));) < / p>

我在这里遇到的问题很少：

似乎解析正确发生但是我存储/传递提取变量内容的方式由于误解了变量的存储/检索方式以及它们在C ++中的范围而无法正常工作（很可能是因为我几乎没有开始学习C ++）或一些我不知道的更大的问题。
我插入了一些print语句，表明我的解析已经正确完成。
但是for循环（在结尾处）具有与预期不同的输出。在这里我经历了另一个问题cva.push_back(nullptr)，如果我保留这个语句，for循环打印第一个元素然后退出，但是当我删除该语句时，它工作正常。为什么？

我很感激任何帮助，尤其是我希望了解更多关于C ++的知识，但似乎我在一个太高级的问题上遇到了磕磕绊绊

// I already have a reqlines vector<std::string> variable holding my requests
// each request is formed as follows 
// http://<hostname>:<portnumber>/path<TAB>header1:value1<TAB>header2:value2<TAB>header3:tab3<TAB>header4:tab4<etc.....>
// Pretty much a TAB separated string with request at beginning followed by extra headers

   std::vector<std::string> paths;
   std::vector<std::string> extraheaders;
   std::vector<std::vector<std::string>> tokenized;
   int count = 0;   // keeps track of each request number so I can access its corresponding extra headers from extraheaders vector

   if (condition is met){

        // creating which will be used to store my requests paths as well as extra headers
        // This has to be a const char * vector since it will be used by an external library which requires such type
        std::vector<const char *> cva;

        for (auto &req : reqlines){
                unsigned int pos = req.find_first_of("\t", 0);
                if (pos == -1){
                        paths.push_back(req);
                        extraheaders.push_back(" ");
                } else {
                        paths.push_back(req.substr(0, pos));
                        extraheaders.push_back(req.substr(pos+1, std::string::npos));
                }
        }

        for (auto &path : paths){
                cva.push_back(":path");
                cva.push_back(path.c_str()); // adding the URI path into cva variable  

                // explode function which returns a std::vector<std::string> when passing an std::string to it
                tokenized.push_back(explode(extraheaders[count], '      '));  // extracting the vector<std::string> of all extra headers

        //      if (tokenized[count][0].compare(" ") == 0){
        //              printf("   %d   element is empty is skipped  \n");
        //      }else { 

                for (auto &tok : tokenized[count]){   // looping through extra headers of request number "count", parsing header name/value and adding it to cva
                    printf(" %d   tok  %s\n", __LINE__, tok.c_str());
                    printf(" %d   tok address    %d\n", __LINE__, &tok);
                    unsigned int pos = tok.find_first_of(":", 0);
                    if (pos == -1 )
                        printf("  %d  there are no headers \n", __LINE__);
                    else {
                        printf("header name:   %s\n", (tok.substr(0, pos)).c_str());
                        printf("header value:   %s\n", (tok.substr(pos+1, std::string::npos)).c_str());
                        cva.push_back((tok.substr(0, pos)).c_str());
                        cva.push_back((tok.substr(pos+1, std::string::npos)).c_str());
                    }
                }
                cva.push_back(":version");  // adding version header
                cva.push_back("HTTP/1.1");  // adding version header number
                cva.push_back(nullptr);  // adding nullptr (which is how nv is expecting cva to be terminated)
                count++;

                // passing the cva content to nv 
                config.nv.push_back(std::move(cva));
        }

        // Below are the printing statement to check the values of the different variables I created and populated 
        // above, my problem is that the population process puts some values into my variables however printing
        // the content of the those variables shows different values from what I am expecting

                std::cout << "          " << std::endl << std::endl;
                std::cout << "Printing cva" << std::endl;
                for (auto &elem : cva){
                        std::cout << &elem << "   " <<elem << std::endl;
                }
                std::cout << "          " << std::endl << std::endl;
                std::cout << "Printing paths" << std::endl;
                for (auto &path : paths){
                        std::cout << &path << "    " << path << std::endl;
                }
                std::cout << "          " << std::endl << std::endl;
                std::cout << "Printing headers" << std::endl;
                for (auto &hed : extraheaders) {
                        std::cout << &hed << "    "<<hed << std::endl;
                }
}

<小时/> 假设我有一个看起来像这样的文件：

https://<endpoint>:<port>/path1
https://<endpoint>:<port>/path2<TAB>PCC:1234<TAB>Cookie:dsgfshg
https://<endpoint>:<port>/path3<TAB>PCC:5678
https://<endpoint>:<port>/path4
https://<endpoint>:<port>/path5

预期输出应为：

Printing cva
:path  
path1  
:path  
path2  
:PCC  
1234  
:Cookie  
dsgfshg  
:path  
path3  
:PCC  
5678  
:path  
path4  
:path  
path5

但实际输出是：

Printing cva
:path  
path1  
:path  
path2
:PCC  
5678  //Different - Wrong value
      //Different - Cookie + value is missing
:path  
path3  
:PCC  
5678  
:path  
path4  
:path  
path5

注意：打印headers和path缺失，因为它们是相同的

C ++向量，内存中的变量表示，const char *

0 个答案: