add env var to control size of multicast streamer buffer (#561)

* add env var for multicast streamer

Signed-off-by: Andrey Parfenov <a1994ndrey@gmail.com>

src/board_controller/inc/multicast_streamer.h

@@ -11,11 +11,7 @@ class MultiCastStreamer : public Streamer
 {
 
 public:
-    static int get_packages_in_chunk ()
-    {
-        // todo add env variable to set size
-        return 3;
-    }
+    static int get_packages_in_chunk ();
 
     MultiCastStreamer (const char *ip, int port, int data_len);
     ~MultiCastStreamer ();

src/board_controller/multicast_streamer.cpp

@@ -1,3 +1,4 @@
+#include <cstdlib>
 #include <string.h>
 #include <string>
 
@@ -7,6 +8,27 @@
 #include "multicast_streamer.h"
 
 
+int MultiCastStreamer::get_packages_in_chunk ()
+{
+    int size = 3;
+    if (const char *env_p = std::getenv ("BRAINFLOW_MULTICAST_SIZE"))
+    {
+        std::string str_env = env_p;
+        try
+        {
+            int parsed_size = std::stoi (str_env);
+            if ((parsed_size > 0) && (parsed_size < 15))
+            {
+                size = parsed_size;
+            }
+        }
+        catch (...)
+        {
+        }
+    }
+    return size;
+}
+
 MultiCastStreamer::MultiCastStreamer (const char *ip, int port, int data_len)
     : Streamer (data_len, "streaming_board", ip, std::to_string (port))
 {