Add support for handling responses to gen_server calls

redwirelabs · Sep 1, 2024 · 7d2b8c9 · 7d2b8c9
1 parent 5fd91c6
commit 7d2b8c9
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Showing 4 changed files with 96 additions and 8 deletions.
diff --git a/lib/bacnet.ex b/lib/bacnet.ex
@@ -12,7 +12,12 @@ defmodule Bacnet do
     GenServer.start_link(__MODULE__, nil, name: __MODULE__)
   end
 
-  @impl GenServer
+  @spec add_device(device :: term) :: :ok | {:error, term}
+  def add_device(device) do
+    GenServer.call({:global, :bacnetd}, {:add_device, device})
+  end
+
+  end  @impl GenServer
   def init(_) do
     {:ok, nil}
   end

diff --git a/src/ei_client.c b/src/ei_client.c
@@ -77,6 +77,19 @@ bool ei_client_send(char *process_name, ei_x_buff *msg)
   return ret == 0 ? true : false;
 }
 
+bool ei_client_send_to(erlang_pid *pid, ei_x_buff *msg)
+{
+  if (!client.ready) {
+    return false;
+  }
+
+  pthread_mutex_lock(&client.lock);
+  int ret = ei_send(client.fd, pid, msg->buff, msg->index);
+  pthread_mutex_unlock(&client.lock);
+
+  return ret == 0 ? true : false;
+}
+
 bool ei_client_call(char *module, char *func, ei_x_buff *args, ei_x_buff *out)
 {
   pthread_mutex_lock(&client.lock);

diff --git a/src/ei_client.h b/src/ei_client.h
@@ -5,6 +5,7 @@
 
 bool ei_client_config(const char *nodename, const char *cookie);
 bool ei_client_send(char *process_name, ei_x_buff *msg);
+bool ei_client_send_to(erlang_pid *pid, ei_x_buff *msg);
 bool ei_client_call(char *module, char *func, ei_x_buff *msg, ei_x_buff *out);
 bool ei_client_recv(erlang_msg *meta, ei_x_buff *msg);
 

diff --git a/src/main.c b/src/main.c
@@ -5,8 +5,12 @@
 #include "ei_client.h"
 #include "ei_log.h"
 
+#define STRINGIFY(x) #x
+#define TOSTR(x) STRINGIFY(x)
+#define ERL_TUPLE TOSTR(ERL_SMALL_TUPLE_EXT) TOSTR(ERL_SMALL_TUPLE_EXT)
+
 static arg_t args;
-static void unimplemented(const char *msg_type);
+static void handle_call(char *buf, int *index, ei_x_buff *reply);
 
 int main(int argc, char **argv)
 {
@@ -31,22 +35,59 @@ int main(int argc, char **argv)
 
     int index = 0;
     int version = 0;
-    int arity = 0;
+    ei_term t = { 0 };
     char msg_type[MAXATOMLEN] = { 0 };
 
     char *buf = msg.buff;
     bool bad_msg = (false
           || ei_decode_version(buf, &index, &version)
-          || ei_decode_tuple_header(buf, &index, &arity)
-          || (arity < 2)
+          || ei_decode_tuple_header(buf, &index, &t.size)
+          || (t.size < 2)
           || ei_decode_atom(buf, &index, msg_type));
 
     if (bad_msg) {
       goto cleanup;
     }
 
     if (strcmp(msg_type, "$gen_call") == 0) {
-      unimplemented("$gen_call");
+      erlang_pid from_pid;
+      erlang_ref from_ref;
+
+      // request {:"$gen_call", {PID, [:alias | REF]}, TUPLE}}
+      bool bad_msg = (false
+            || ei_decode_tuple_header(buf, &index, &t.size)
+            || (t.size != 2)
+            || ei_decode_pid(buf, &index, &from_pid)
+            || ei_decode_list_header(buf, &index, &t.size)
+            || (t.size != 1)
+            || ei_decode_atom(buf, &index, t.value.atom_name)
+            || strcmp(t.value.atom_name, "alias")
+            || ei_decode_ref(buf, &index, &from_ref)
+            || ei_get_type(buf, &index, (int *)&t.ei_type, &t.size)
+            || memchr(ERL_TUPLE, t.ei_type, sizeof(ERL_TUPLE)) == NULL);
+
+      if (bad_msg) {
+        LOG_ERR("Failed decoding message");
+        goto cleanup;
+      }
+
+      // reply {[:alias | REF], REPLY}
+      ei_x_buff reply;
+      ei_x_new_with_version(&reply);
+      ei_x_encode_tuple_header(&reply, 2);
+      ei_x_encode_list_header(&reply, 1);
+      ei_x_encode_atom(&reply, "alias");
+      ei_x_encode_ref(&reply, &from_ref);
+
+      handle_call(buf, &index, &reply);
+
+      if (!ei_client_send_to(&from_pid, &reply)) {
+        LOG_ERR("Unable to send reply");
+      }
+
+      ei_x_free(&reply);
+    } else {
+      LOG_WRN("bacnetd: unknown message type %s", msg_type);
     }
 
   cleanup:
@@ -56,7 +97,35 @@ int main(int argc, char **argv)
   return 0;
 }
 
-static void unimplemented(const char *msg_type)
+static void add_device(char *buf, int *index, ei_x_buff *reply)
+{
+  ei_x_encode_tuple_header(reply, 2);
+  ei_x_encode_atom(reply, "error");
+  ei_x_encode_atom(reply, "unimplemented");
+}
+
+static void handle_call(char *buf, int *index, ei_x_buff *reply)
 {
-  LOG_WRN("bacnetd: %s unimplemented", msg_type);
+  int size = 0;
+  char call_type[MAXATOMLEN] = { 0 };
+
+  bool bad_msg = (false
+        || ei_decode_tuple_header(buf, index, &size)
+        || ei_decode_atom(buf, index, call_type));
+
+  if (bad_msg) {
+    ei_x_encode_tuple_header(reply, 2);
+    ei_x_encode_atom(reply, "error");
+    ei_x_encode_atom(reply, "bad_request");
+    return;
+  }
+
+  if (strcmp(call_type, "add_device") == 0) {
+    add_device(buf, index, reply);
+  }
+  else {
+    ei_x_encode_tuple_header(reply, 2);
+    ei_x_encode_atom(reply, "error");
+    ei_x_encode_atom(reply, "unimplemented");
+  }
 }