Add mg_http_stream_body() helper for generic streaming uploads

tutorials/http/file-upload-single-post/main.c

@@ -1,10 +1,11 @@
 // Copyright (c) 2020-2024 Cesanta Software Limited
 // All rights reserved
 //
-// Streaming upload example. Demonstrates how to use MG_EV_READ events
+// Streaming upload example. Demonstrates how to use mg_http_stream_body()
 // to save a large file without buffering it fully in memory.
+// The file is saved as /tmp/a.txt.
 //
-// curl http://localhost:8000/upload?name=a.txt --data-binary @large_file.txt
+// curl http://localhost:8000/fs/a.txt --data-binary @large_file.txt
 
 #include "mongoose.h"
 
@@ -28,48 +29,24 @@ static const char *s_tls_key =
     "4hf5Gx17YJkq5/z3k6ogPDPpoAYWIw1/sw==\n"
     "-----END EC PRIVATE KEY-----\n";
 
-struct upload_state {
-  size_t expected;  // POST data length, bytes
-  size_t received;  // Already received bytes
-  void *fp;         // Opened uploaded file
-};
-
-static void handle_uploads(struct mg_connection *c, int ev, void *ev_data) {
-  struct upload_state *us = (struct upload_state *) c->data;
+static void upload(struct mg_http_message *hm, struct mg_str *data, void **p) {
   struct mg_fs *fs = &mg_fs_posix;
-
-  // Catch /upload requests early, without buffering whole body
-  // When we receive MG_EV_HTTP_HDRS event, that means we've received all
-  // HTTP headers but not necessarily full HTTP body
-  if (ev == MG_EV_HTTP_HDRS) {
-    struct mg_http_message *hm = (struct mg_http_message *) ev_data;
-    if (mg_match(hm->uri, mg_str("/upload/*"), NULL)) {
-      char path[MG_PATH_MAX];
-      mg_snprintf(path, sizeof(path), "%s/%.*s", UPLOAD_DIR, hm->uri.len - 8,
-                  hm->uri.buf + 8);
-      us->expected = hm->body.len;  // Store number of bytes we expect
-      mg_iobuf_del(&c->recv, 0, hm->head.len);  // Delete HTTP headers
-      c->pfn = NULL;  // Silence HTTP protocol handler, we'll use MG_EV_READ
-      if (mg_path_is_sane(mg_str(path))) {
-        fs->rm(path);                        // Delete file if it exists
-        us->fp = fs->op(path, MG_FS_WRITE);  // Open file for writing
-      }
-    }
-  }
-
-  // Catch uploaded file data for both MG_EV_READ and MG_EV_HTTP_HDRS
-  if (us->expected > 0 && c->recv.len > 0) {
-    us->received += c->recv.len;
-    if (us->fp) fs->wr(us->fp, c->recv.buf, c->recv.len);  // Write to file
-    c->recv.len = 0;  // Delete received data
-    if (us->received >= us->expected) {
-      // Uploaded everything. Send response back
-      MG_INFO(("Uploaded %lu bytes", us->received));
-      mg_http_reply(c, 200, NULL, "%lu ok\n", us->received);
-      if (us->fp) fs->cl(us->fp);  // Close file
-      memset(us, 0, sizeof(*us));  // Cleanup upload state
-      c->is_draining = 1;          // Close connection when response gets sent
+  if (hm != NULL) {
+    char path[MG_PATH_MAX];
+    MG_INFO(("UPLOAD BEGIN, URI %.*s ", hm->uri.len, hm->uri.buf));
+    mg_snprintf(path, sizeof(path), "%s/%.*s", UPLOAD_DIR, hm->uri.len - 4,
+                hm->uri.buf + 4);
+    *p = NULL;
+    if (mg_path_is_sane(mg_str(path))) {
+      fs->rm(path);                     // Delete file if it exists
+      *p = fs->op(path, MG_FS_WRITE);  // Open file for writing
     }
+  } else if (data != NULL) {
+    MG_INFO(("UPLOAD DATA, %zu bytes", data->len));
+    if (*p) fs->wr(*p, data->buf, data->len);  // Write to file
+  } else {
+    MG_INFO(("UPLOAD END %p", p));
+    if (*p) fs->cl(*p), *p = NULL;
   }
 }
 
@@ -78,16 +55,13 @@ static void fn(struct mg_connection *c, int ev, void *ev_data) {
     struct mg_tls_opts opts = {.cert = mg_str(s_tls_cert),
                                .key = mg_str(s_tls_key)};
     mg_tls_init(c, &opts);
-  }
-
-  handle_uploads(c, ev, ev_data);
-
-  // Non-upload requests, we serve normally
-  // NOTE: handle_uploads() may delete request and reset c->pfn
-  if (ev == MG_EV_HTTP_MSG && c->pfn != NULL) {
+  } else if (ev == MG_EV_HTTP_MSG && c->pfn != NULL) {
     struct mg_http_serve_opts opts = {.root_dir = "web_root"};
     mg_http_serve_dir(c, ev_data, &opts);
   }
+
+  // Handle upload requests to /fs/*
+  mg_http_stream_body(c, ev, ev_data, mg_str("/fs/*"), upload);
 }
 
 int main(void) {

tutorials/http/file-upload-single-post/web_root/index.html

@@ -50,7 +50,7 @@
       r.onload = function() {
         ev.target.value = '';
         document.getElementById('el3').innerText = 'Uploading...';
-        fetch(`/upload/${encodeURIComponent(f.name)}`, {
+        fetch(`/fs/${encodeURIComponent(f.name)}`, {
           method: 'POST',
           body: r.result,
         }).then(function(res) {