Rust: Add validation support to code generator

mojom/generators/rust/templates/interface.tmpl.go

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package templates
 
 const GenerateEndpoint = `
 {{- /* . (dot) refers to a string which is the endpoint's name */ -}}
 {{- define "GenerateEndpoint" -}}
 {{- $endpoint := . -}}
@@ skipping 82 matching lines @@
 
 {{- $req_option := printf "%s%s" $interface.Name "RequestOption" }}
 {{- $rsp_option := printf "%s%s" $interface.Name "ResponseOption" }}
 
 pub enum {{$req_option}} {
 {{range $message := $interface.Messages}}    {{$message.Name}}({{$message.RequestStruct.Name}}),
 {{end}}
 }
 
 impl MojomMessageOption for {{$req_option}} {
-    fn decode_payload(ordinal: u32, buffer: &[u8], handles: Vec<UntypedHandle>) -> Self {
-         match ordinal {
-{{range $message := $interface.Messages}}             {{$message.Name}}::ORDINAL => {{$req_option}}::{{$message.Name}}({{$message.RequestStruct.Name}}::deserialize(buffer, handles)),
-{{end}}             _ => panic!("Unknown message found: {}", ordinal),
-         }
+    fn decode_payload(header: MessageHeader, buffer: &[u8], handles: Vec<UntypedHandle>) -> Result<Self, ValidationError> {
+         match header.name {
+{{range $message := $interface.Messages}}             {{$message.Name}}::ORDINAL => {
+                if header.flags != {{- if eq $message.ResponseStruct.Name "" -}}
+                           message::MESSAGE_HEADER_NO_FLAG
+                           {{- else -}}
+                           message::MESSAGE_HEADER_EXPECT_RESPONSE
+                           {{- end -}} {
+                    return Err(ValidationError::MessageHeaderInvalidFlags);
+                }
+                match {{$message.RequestStruct.Name}}::deserialize(buffer, handles) {
+                    Ok(value) => Ok({{$req_option}}::{{$message.Name}}(value)),
+                    Err(err) => return Err(err),
+                }
+            },
+{{end}}             _ => Err(ValidationError::MessageHeaderUnknownMethod),
+        }
     }
 }
 
 pub enum {{$rsp_option}} {
 {{range $message := $interface.Messages}}
 {{- if ne $message.ResponseStruct.Name ""}}    {{$message.Name}}({{$message.ResponseStruct.Name}}),
 {{end -}}
 {{end}}
 }
 
 impl MojomMessageOption for {{$rsp_option}} {
-    fn decode_payload(ordinal: u32, buffer: &[u8], handles: Vec<UntypedHandle>) -> Self {
-         match ordinal {
+    fn decode_payload(header: MessageHeader, buffer: &[u8], handles: Vec<UntypedHandle>) -> Result<Self, ValidationError> {
+        if header.flags != message::MESSAGE_HEADER_IS_RESPONSE {
+            return Err(ValidationError::MessageHeaderInvalidFlags);
+        }
+        match header.name {
 {{range $message := $interface.Messages}}
-{{- if ne $message.ResponseStruct.Name ""}}             {{$message.Name}}::ORDINAL => {{$rsp_option}}::{{$message.Name}}({{$message.ResponseStruct.Name}}::deserialize(buffer, handles)),
+{{- if ne $message.ResponseStruct.Name ""}}             {{$message.Name}}::ORDINAL => {
+                match {{$message.ResponseStruct.Name}}::deserialize(buffer, handles) {
+                    Ok(value) => Ok({{$rsp_option}}::{{$message.Name}}(value)),
+                    Err(err) => return Err(err),
+                }
+            },
 {{end -}}
-{{end}}             _ => panic!("Unknown message found, or message has no response: {}", ordinal),
-         }
+{{end}}             _ => Err(ValidationError::MessageHeaderUnknownMethod),
+        }
     }
 }
 
 {{range $message := $interface.Messages -}}
 /// Message: {{$message.Name}}
 pub mod {{$message.Name}} {
     pub const ORDINAL: u32 = {{$message.MessageOrdinal}};
     pub const MIN_VERSION: u32 = {{$message.MinVersion}};
 }
 {{template "GenerateStruct" $message.RequestStruct}}
@@ skipping 19 matching lines @@
                            {{$message.Name}}::ORDINAL,
                            message::MESSAGE_HEADER_IS_RESPONSE)
     }
 }
 impl {{$interface.Name}}Response for {{$message.RequestStruct.Name}} {}
 
 {{- end}}
 {{- end -}}
 {{- end -}}
 `