Add HTTP support and update checking

code/cpp-httplib-0.19.0/example/upload.cc

@@ -0,0 +1,61 @@
+//
+//  upload.cc
+//
+//  Copyright (c) 2019 Yuji Hirose. All rights reserved.
+//  MIT License
+//
+
+#include <fstream>
+#include <httplib.h>
+#include <iostream>
+using namespace httplib;
+using namespace std;
+
+const char *html = R"(
+<form id="formElem">
+  <input type="file" name="image_file" accept="image/*">
+  <input type="file" name="text_file" accept="text/*">
+  <input type="submit">
+</form>
+<script>
+  formElem.onsubmit = async (e) => {
+    e.preventDefault();
+    let res = await fetch('/post', {
+      method: 'POST',
+      body: new FormData(formElem)
+    });
+    console.log(await res.text());
+  };
+</script>
+)";
+
+int main(void) {
+  Server svr;
+
+  svr.Get("/", [](const Request & /*req*/, Response &res) {
+    res.set_content(html, "text/html");
+  });
+
+  svr.Post("/post", [](const Request &req, Response &res) {
+    auto image_file = req.get_file_value("image_file");
+    auto text_file = req.get_file_value("text_file");
+
+    cout << "image file length: " << image_file.content.length() << endl
+         << "image file name: " << image_file.filename << endl
+         << "text file length: " << text_file.content.length() << endl
+         << "text file name: " << text_file.filename << endl;
+
+    {
+      ofstream ofs(image_file.filename, ios::binary);
+      ofs << image_file.content;
+    }
+    {
+      ofstream ofs(text_file.filename);
+      ofs << text_file.content;
+    }
+
+    res.set_content("done", "text/plain");
+  });
+
+  svr.listen("localhost", 1234);
+}