brought back 7.5 file-upload as file-upload-multiple-posts; updated to latest API

renamed form-upload to file-upload-html-form
renamed file-upload to file-upload-single-post

examples/file-upload-single-post/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/file-upload-single-post/README.md

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+See detailed tutorial at https://mongoose.ws/tutorials/file-uploads/

examples/file-upload-single-post/main.c

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+// Copyright (c) 2020 Cesanta Software Limited
+// All rights reserved
+//
+// Streaming upload example. Demonstrates how to use chunked encoding
+// to send large payload in smaller chunks. To test, use curl utility:
+//
+// curl http://localhost:8000/upload?name=a.txt --data-binary @large_file.txt
+
+#include "mongoose.h"
+
+// HTTP request handler function. It implements the following endpoints:
+//   /upload - Saves the next file chunk
+//   all other URI - serves web_root/ directory
+static void cb(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+  struct mg_http_message *hm = (struct mg_http_message *) ev_data;
+  if (ev == MG_EV_HTTP_CHUNK && mg_http_match_uri(hm, "/upload")) {
+    MG_INFO(("Got chunk len %lu", (unsigned long) hm->chunk.len));
+    MG_INFO(("Query string: [%.*s]", (int) hm->query.len, hm->query.ptr));
+    // MG_INFO(("Chunk data:\n%.*s", (int) hm->chunk.len, hm->chunk.ptr));
+    mg_http_delete_chunk(c, hm);
+    if (hm->chunk.len == 0) {
+      MG_INFO(("Last chunk received, sending response"));
+      mg_http_reply(c, 200, "", "ok (chunked)\n");
+    }
+  } else if (ev == MG_EV_HTTP_MSG && mg_http_match_uri(hm, "/upload")) {
+    MG_INFO(("Got all %lu bytes!", (unsigned long) hm->body.len));
+    MG_INFO(("Query string: [%.*s]", (int) hm->query.len, hm->query.ptr));
+    // MG_INFO(("Body:\n%.*s", (int) hm->body.len, hm->body.ptr));
+    mg_http_reply(c, 200, "", "ok (%lu)\n", (unsigned long) hm->body.len);
+  } else if (ev == MG_EV_HTTP_MSG) {
+    struct mg_http_serve_opts opts = {.root_dir = "web_root"};
+    mg_http_serve_dir(c, hm, &opts);
+  }
+}
+
+int main(void) {
+  struct mg_mgr mgr;
+
+  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/file-upload-single-post/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; }
+    </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.
+        <br><br>
+        In order to upload large files to a memory-constrained system, use
+        <code>MG_EV_HTTP_CHUNK</code> on a server side. It fires when
+        a partial HTTP message has been received (or a chunk-encoded chunk).
+        Use <code>mg_http_delete_chunk()</code> to release chunk memory.
+        When 0-sized chunk is received, that's the end of the message.
+        Use <code>MG_MAX_RECV_SIZE</code> build constant to limit
+        maximum chunk size on a server side.
+        <br><br>
+        In this example, JavaScript code uses "fetch()" browser API.
+        Uploaded file is not saved, but rather printed by server side.
+      </div>
+      <div id="wrapper">
+        <input type="file" id="el1" style="display: none"/>
+        <button id="el2">choose file...</button>
+        <div id="el3" style="margin-top: 1em;"></div>
+      </div>
+    </div>
+  </body>
+  <script>
+
+    // When user clicks on a button, trigger file selection dialog
+    document.getElementById('el2').onclick = function(ev) {
+      document.getElementById('el1').click();
+    };
+
+    // If user selected a file, read it into memory and trigger sendFileData()
+    document.getElementById('el1').onchange = function(ev) {
+      if (!ev.target.files[0]) return;
+      var f = ev.target.files[0], r = new FileReader();
+      r.readAsArrayBuffer(f);
+      r.onload = function() {
+        ev.target.value = '';
+        document.getElementById('el3').innerText = 'Uploading...';
+        fetch('/upload?name=' + encodeURIComponent(f.name), {
+          method: 'POST',
+          body: r.result,
+        }).then(function(res) {
+          document.getElementById('el3').innerText = 'Uploaded ' + r.result.byteLength + ' bytes';
+        });
+      };
+    };
+
+  </script>
+</html>