Allow to stop receiving message from on_msg_recv_callback

[wonder-mice]

I need a way to tell wslay to stop calling on_msg_recv_callback (because my message queue is already full and I only can drop message if they will continue to come) and to return. When I decide that I'm ready to receive more messages, I will call wslay_event_recv() once again.

Don't see any existing way to achieve that. Suggesting this patch to address this issue.

[tatsuhiro-t]

Changing callback signature will break API compatibility.
I think using wslay_event_set_error() can tell the library to return immediately.
The existing use of wslay_event_set_error() is described in http://wslay.sourceforge.net/man/wslay_event_context_server_init.html.
For example, we use that function to set error code in recv_callback.

[wonder-mice]

What do you think about that?

diff --git a/lib/wslay_event.c b/lib/wslay_event.c
index 5d11516..2454d5f 100644
--- a/lib/wslay_event.c
+++ b/lib/wslay_event.c
@@ -716,7 +716,8 @@ int wslay_event_recv(wslay_event_context_ptr ctx)
               arg.msg_length = msg_length;
               arg.status_code = status_code;
               ctx->error = 0;
-              stop = ctx->callbacks.on_msg_recv_callback(ctx, &arg, ctx->user_data);
+              ctx->callbacks.on_msg_recv_callback(ctx, &arg, ctx->user_data);
+              stop = ctx->error;
             }
             free(msg);
           }

[tatsuhiro-t]

Yeah, something like that.
I prefer adding new enum value to wslay_error, and check the desired value explicitly here.