input/curl: limit the receive buffer size

NEWS

@@ -2,6 +2,8 @@ ver 0.16.4 (2011/??/??)
 * fix memory leaks
 * don't resume playback when seeking to another song while paused
 * apply follow_inside_symlinks to absolute symlinks
+* input:
+  - curl: limit the receive buffer size
 * decoder:
   - ffmpeg: workaround for semantic API change in recent ffmpeg versions
   - flac: validate the sample rate when scanning the tag

src/input/curl_input_plugin.c

@@ -43,6 +43,13 @@
 #define G_LOG_DOMAIN "input_curl"
 
 /**
+ * Do not buffer more than this number of bytes.  It should be a
+ * reasonable limit that doesn't make low-end machines suffer too
+ * much, but doesn't cause stuttering on high-latency lines.
+ */
+static const size_t CURL_MAX_BUFFERED = 512 * 1024;
+
+/**
  * Buffers created by input_curl_writefunction().
  */
 struct buffer {
@@ -144,6 +151,25 @@ input_curl_finish(void)
 	curl_global_cleanup();
 }
 
+/**
+ * Determine the total sizes of all buffers, including portions that
+ * have already been consumed.
+ */
+G_GNUC_PURE
+static size_t
+curl_total_buffer_size(const struct input_curl *c)
+{
+	size_t total = 0;
+
+	for (GList *i = g_queue_peek_head_link(c->buffers);
+	     i != NULL; i = g_list_next(i)) {
+		struct buffer *buffer = i->data;
+		total += buffer->size;
+	}
+
+	return total;
+}
+
 static void
 buffer_free_callback(gpointer data, G_GNUC_UNUSED gpointer user_data)
 {
@@ -473,6 +499,10 @@ static int
 input_curl_buffer(struct input_stream *is, GError **error_r)
 {
 	struct input_curl *c = (struct input_curl *)is;
+
+	if (curl_total_buffer_size(c) >= CURL_MAX_BUFFERED)
+		return 0;
+
 	CURLMcode mcode;
 	int running_handles;
 	bool ret;