Refine subprocess_call API

src/core/client_config/subchannel.c

@@ -32,3 +32,51 @@
  */
 
 #include "src/core/client_config/subchannel.h"
+
+#include <grpc/support/alloc.h>
+
+struct grpc_subchannel {
+  gpr_refcount refs;
+};
+
+struct grpc_subchannel_call {
+  grpc_subchannel *subchannel;
+  gpr_refcount refs;
+};
+
+#define SUBCHANNEL_CALL_TO_CALL_STACK(call) (((grpc_call_stack *)(call)) + 1)
+
+/*
+ * grpc_subchannel implementation
+ */
+
+void grpc_subchannel_ref(grpc_subchannel *channel) { gpr_ref(&channel->refs); }
+
+void grpc_subchannel_unref(grpc_subchannel *channel) {
+  if (gpr_unref(&channel->refs)) {
+    gpr_free(channel);
+  }
+}
+
+/*
+ * grpc_subchannel_call implementation
+ */
+
+void grpc_subchannel_call_ref(grpc_subchannel_call *call) {
+  gpr_ref(&call->refs);
+}
+
+void grpc_subchannel_call_unref(grpc_subchannel_call *call) {
+  if (gpr_unref(&call->refs)) {
+    grpc_call_stack_destroy(SUBCHANNEL_CALL_TO_CALL_STACK(call));
+    grpc_subchannel_unref(call->subchannel);
+    gpr_free(call);
+  }
+}
+
+void grpc_subchannel_call_process_op(grpc_subchannel_call *call,
+                                     grpc_transport_stream_op *op) {
+  grpc_call_stack *call_stack = SUBCHANNEL_CALL_TO_CALL_STACK(call);
+  grpc_call_element *top_elem = grpc_call_stack_element(call_stack, 0);
+  top_elem->filter->start_transport_stream_op(top_elem, op);
+}

src/core/client_config/subchannel.h

@@ -60,10 +60,12 @@ void grpc_subchannel_notify_on_state_change(grpc_subchannel *channel,
                                             grpc_connectivity_state *state,
                                             grpc_iomgr_closure *notify);
 
-/** construct a call */
-grpc_subchannel_call *grpc_subchannel_create_call(
-    grpc_subchannel *subchannel, grpc_call_element *parent,
-    grpc_transport_stream_op *initial_op);
+/** construct a call (asynchronously) */
+void grpc_subchannel_create_call(grpc_subchannel *subchannel,
+                                 grpc_call_element *parent,
+                                 grpc_transport_stream_op *initial_op,
+                                 grpc_subchannel_call **target,
+                                 grpc_iomgr_closure *notify);
 
 /** continue processing a transport op */
 void grpc_subchannel_call_process_op(grpc_subchannel_call *subchannel_call,