api: introduce RootContext::on_create_child_context() callback to allow RootContext propagate configuration into HttpContext/StreamContext

Author: yskopets

src/dispatcher.rs

@@ -95,6 +95,45 @@ impl Dispatcher {
         }
     }
 
+    /// Lets the root context to create its child context.
+    fn create_child_context(&self, context_id: u32, root_context_id: u32) -> bool {
+        if !self.roots.borrow().contains_key(&root_context_id) {
+            panic!("invalid root_context_id")
+        }
+        if let Some(child_context) = self
+            .roots
+            .borrow_mut()
+            .get_mut(&root_context_id)
+            .and_then(|root| root.on_create_child_context(context_id))
+        {
+            match child_context {
+                ChildContext::HttpContext(http_context) => {
+                    if self
+                        .http_streams
+                        .borrow_mut()
+                        .insert(context_id, http_context)
+                        .is_some()
+                    {
+                        panic!("duplicate context_id")
+                    }
+                }
+                ChildContext::StreamContext(stream_context) => {
+                    if self
+                        .streams
+                        .borrow_mut()
+                        .insert(context_id, stream_context)
+                        .is_some()
+                    {
+                        panic!("duplicate context_id")
+                    }
+                }
+            }
+            true
+        } else {
+            false
+        }
+    }
+
     fn create_stream_context(&self, context_id: u32, root_context_id: u32) {
         if !self.roots.borrow().contains_key(&root_context_id) {
             panic!("invalid root_context_id")
@@ -145,6 +184,8 @@ impl Dispatcher {
     fn on_create_context(&self, context_id: u32, root_context_id: u32) {
         if root_context_id == 0 {
             self.create_root_context(context_id)
+        } else if self.create_child_context(context_id, root_context_id) {
+            // root context created a child context by himself
         } else if self.new_http_stream.get().is_some() {
             self.create_http_context(context_id, root_context_id);
         } else if self.new_stream.get().is_some() {

src/traits.rs

@@ -99,6 +99,12 @@ pub trait Context {
     }
 }
 
+/// Represents a child context of the root context.
+pub enum ChildContext {
+    StreamContext(Box<dyn StreamContext>),
+    HttpContext(Box<dyn HttpContext>),
+}
+
 pub trait RootContext: Context {
     fn on_vm_start(&mut self, _vm_configuration_size: usize) -> bool {
         true
@@ -121,6 +127,12 @@ pub trait RootContext: Context {
     fn on_queue_ready(&mut self, _queue_id: u32) {}
 
     fn on_log(&mut self) {}
+
+    fn on_create_child_context(&mut self, _context_id: u32) -> Option<ChildContext> {
+        // for the sake of compatibility with `set_http_context` and `set_stream_context` API,
+        // root context is not required to create its child context.
+        None
+    }
 }
 
 pub trait StreamContext: Context {