Multipart message view (#862)

* multipart::message_view
* Make multipart::message_view non-returnable
* Store message headers by reference

CMakeLists.txt

@@ -19,7 +19,7 @@ if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
 endif()
 
 # Set required C++ standard
-set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
 
 # Default to build type "Release" unless tests are being built

docs/guides/multipart.md

@@ -17,15 +17,15 @@ The structure of a multipart request is typically consistent of:<br>
 - `--<boundary>--`<br><br>
 
 ## Multipart messages in Crow
-Crow supports multipart requests and responses though `crow::multipart::message`.<br>
+Crow supports multipart requests and responses though `crow::multipart::message` and `crow::multipart::message_view`, where `crow::multipart::message` owns the contents of the message and `crow::multipart::message_view` stores views into its parts.<br>
 A message can be created either by defining the headers, boundary, and individual parts and using them to create the message. or simply by reading a `crow::request`.<br><br>
 
 Once a multipart message has been made, the individual parts can be accessed throughout `msg.parts`, `parts` is an `std::vector`.<br><br>
 
 <span class="tag">[:octicons-feed-tag-16: v1.0](https://github.com/CrowCpp/Crow/releases/v1.0)</span>
 
 
-Part headers are organized in a similar way to request and response headers, and can be retrieved via `crow::multipart::get_header_object("header-key")`. This function returns a `crow::multipart::header` object.<br><br>
+Part headers are organized in a similar way to request and response headers, and can be retrieved via `crow::multipart::get_header_object("header-key")`. This function returns a `crow::multipart::header` object for owning message and `crow::multipart::header_view` for non-owning message.<br><br>
 
 The message's individual body parts can be accessed by name using `msg.get_part_by_name("part-name")`.<br><br>
 

examples/example.cpp

@@ -210,7 +210,7 @@ int main()
     // Take a multipart/form-data request and print out its body
     CROW_ROUTE(app, "/multipart")
     ([](const crow::request& req) {
-        crow::multipart::message msg(req);
+        crow::multipart::message_view msg(req);
         CROW_LOG_INFO << "body of the first part " << msg.parts[0].body;
         return "it works!";
     });

examples/example_file_upload.cpp

@@ -6,7 +6,7 @@ int main()
 
     CROW_ROUTE(app, "/uploadfile")
       .methods(crow::HTTPMethod::Post)([](const crow::request& req) {
-          crow::multipart::message file_message(req);
+          crow::multipart::message_view file_message(req);
           for (const auto& part : file_message.part_map)
           {
               const auto& part_name = part.first;
@@ -27,7 +27,7 @@ int main()
                       CROW_LOG_ERROR << "Part with name \"InputFile\" should have a file";
                       return crow::response(400);
                   }
-                  const std::string outfile_name = params_it->second;
+                  const std::string outfile_name{params_it->second};
 
                   for (const auto& part_header : part_value.headers)
                   {

include/crow.h

@@ -16,6 +16,7 @@
 #include "crow/parser.h"
 #include "crow/http_response.h"
 #include "crow/multipart.h"
+#include "crow/multipart_view.h"
 #include "crow/routing.h"
 #include "crow/middleware.h"
 #include "crow/middleware_context.h"

include/crow/ci_map.h

@@ -1,15 +1,17 @@
 #pragma once
 
+#include <string_view>
 #include <locale>
 #include <unordered_map>
+
 #include "crow/utility.h"
 
 namespace crow
 {
     /// Hashing function for ci_map (unordered_multimap).
     struct ci_hash
     {
-        size_t operator()(const std::string& key) const
+        size_t operator()(const std::string_view key) const
         {
             std::size_t seed = 0;
             std::locale locale;
@@ -31,7 +33,7 @@ namespace crow
     /// Equals function for ci_map (unordered_multimap).
     struct ci_key_eq
     {
-        bool operator()(const std::string& l, const std::string& r) const
+        bool operator()(const std::string_view l, const std::string_view r) const
         {
             return utility::string_equals(l, r);
         }