Add form-upload example

examples/form-upload/Makefile

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+PROG ?= example
+
+all: $(PROG)
+	$(DEBUGGER) ./$(PROG)
+
+$(PROG):
+	$(CC) ../../mongoose.c -I../.. $(CFLAGS) $(EXTRA) -o $(PROG) main.c
+
+clean:
+	rm -rf $(PROG) *.o *.dSYM *.gcov *.gcno *.gcda *.obj *.exe *.ilk *.pdb log.txt

examples/form-upload/main.c

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+// Copyright (c) 2021 Cesanta Software Limited
+// All rights reserved
+
+#include "mongoose.h"
+
+// HTTP request handler function. It implements the following endpoints:
+//   /upload - prints all submitted form elements
+//   all other URI - serves web_root/ directory
+static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+  if (ev == MG_EV_HTTP_MSG) {
+    struct mg_http_message *hm = (struct mg_http_message *) ev_data;
+    LOG(LL_INFO, ("New request to: [%.*s]", (int) hm->uri.len, hm->uri.ptr));
+    if (mg_http_match_uri(hm, "/upload")) {
+      struct mg_http_part part;
+      size_t ofs = 0;
+      while ((ofs = mg_http_next_multipart(hm->body, ofs, &part)) > 0) {
+        LOG(LL_INFO,
+            ("Name: [%.*s] Filename: [%.*s] Body: [%.*s]", (int) part.name.len,
+             part.name.ptr, (int) part.filename.len, part.filename.ptr,
+             (int) part.body.len, part.body.ptr));
+      }
+      mg_http_reply(c, 200, "", "Thank you!");
+    } else {
+      struct mg_http_serve_opts opts = {.root_dir = "web_root"};
+      mg_http_serve_dir(c, ev_data, &opts);
+    }
+  }
+}
+
+int main(void) {
+  struct mg_mgr mgr;
+  struct mg_timer t1;
+
+  mg_mgr_init(&mgr);
+  mg_log_set("3");
+  mg_http_listen(&mgr, "http://localhost:8000", cb, NULL);
+
+  for (;;) mg_mgr_poll(&mgr, 50);
+  mg_mgr_free(&mgr);
+
+  return 0;
+}

examples/form-upload/web_root/index.html

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+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <title>example</title>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <style>
+      #container { margin-right: auto; margin-left: auto; max-width: 480px; }
+      #info { background: #e0f0f0; border-radius: .5em; padding: 2em;  }
+      #wrapper { margin-top: 1em; }
+      form * { margin: 0.2em 0; }
+    </style>
+  </head>
+  <body>
+    <div id="container">
+      <div id="info">
+        Mongoose always buffers a full HTTP message before invoking
+        MG_EV_HTTP_MSG event. Big POST request require of lot
+        of RAM to buffer everything. Therefore, standard form uploads
+        should be used only when Mongoose runs on a system with lots of RAM.
+        Otherwise, please see <code>file-updload</code> example, how
+        a big file could be uploaded to a device with little RAM.
+        <br/><br/>
+        In this example, a standard HTML form upload is used, which uses
+        <code>multipart-form-data</code> encoding with
+        several variables and file upload. On a server side, a
+        <code>mg_http_next_multipart()</code> API is used to iterate over
+        all submitted form elements and print their payload.
+      </div>
+      <div id="wrapper">
+        <form action="/upload" method="post" enctype="multipart/form-data">
+          <input type="text" name="field1" value="type some text here" /> <br/>
+          <input type="file" name="file1" /> </br>
+          <button type="submit">submit form</button>
+        </form>
+      </div>
+    </div>
+  </body>
+</html>