Crow/examples/example_file_upload.cpp

#include "crow.h"

int main()
{
    crow::SimpleApp app;

    CROW_ROUTE(app, "/uploadfile")
      .methods(crow::HTTPMethod::Post)([](const crow::request& req) {
          crow::multipart::message file_message(req);
          for (const auto& part : file_message.part_map)
          {
              const auto& part_name = part.first;
              const auto& part_value = part.second;
              CROW_LOG_DEBUG << "Part: " << part_name;
              if ("InputFile" == part_name)
              {
                  // Extract the file name
                  auto headers_it = part_value.headers.find("Content-Disposition");
                  if (headers_it == part_value.headers.end())
                  {
                      CROW_LOG_ERROR << "No Content-Disposition found";
                      return crow::response(400);
                  }
                  auto params_it = headers_it->second.params.find("filename");
                  if (params_it == headers_it->second.params.end())
                  {
                      CROW_LOG_ERROR << "Part with name \"InputFile\" should have a file";
                      return crow::response(400);
                  }
                  const std::string outfile_name = params_it->second;

                  for (const auto& part_header : part_value.headers)
                  {
                      const auto& part_header_name = part_header.first;
                      const auto& part_header_val = part_header.second;
                      CROW_LOG_DEBUG << "Header: " << part_header_name << '=' << part_header_val.value;
                      for (const auto& param : part_header_val.params)
                      {
                          const auto& param_key = param.first;
                          const auto& param_val = param.second;
                          CROW_LOG_DEBUG << " Param: " << param_key << ',' << param_val;
                      }
                  }

                  // Create a new file with the extracted file name and write file contents to it
                  std::ofstream out_file(outfile_name);
                  if (!out_file)
                  {
                      CROW_LOG_ERROR << " Write to file failed\n";
                      continue;
                  }
                  out_file << part_value.body;
                  out_file.close();
                  CROW_LOG_INFO << " Contents written to " << outfile_name << '\n';
              }
              else
              {
                  CROW_LOG_DEBUG << " Value: " << part_value.body << '\n';
              }
          }
          return crow::response(200);
      });

    // enables all log
    app.loglevel(crow::LogLevel::Debug);

    app.port(18080)
      .multithreaded()
      .run();

    return 0;
}