C bindings: Implement _Validate(), and some pre-requisites

mojom/generators/c/templates/struct.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 GenerateStructDeclarations = `
 {{- /* . (dot) refers to the Go type |cgen.StructTemplate| */ -}}
 {{define "GenerateStructDeclarations" -}}
 {{- $struct := . -}}
@@ skipping 33 matching lines @@
   const struct {{$struct.Name}}* in_data);
 
 void {{$struct.Name}}_EncodePointersAndHandles(
   struct {{$struct.Name}}* inout_struct, uint32_t in_struct_size,
   struct MojomHandleBuffer* inout_handle_buffer);
 
 void {{$struct.Name}}_DecodePointersAndHandles(
   struct {{$struct.Name}}* inout_struct, uint32_t in_struct_size,
   MojoHandle inout_handles[], uint32_t in_num_handles);
 
+MojomValidationResult {{$struct.Name}}_Validate(
+  const struct {{$struct.Name}}* in_struct, uint32_t in_struct_size,
+  uint32_t in_num_handles);
+
 {{end}}
 `
 
 // TODO(vardhan): Move other struct constant definitions in here.
 const GenerateStructDefinitions = `
 {{- /* . (dot) refers to the Go type |cgen.StructTemplate| */ -}}
 {{define "GenerateStructDefinitions" -}}
 {{- $struct := . -}}
 
 {{range $const := $struct.Constants -}}
@@ skipping 18 matching lines @@
 
 void {{$struct.Name}}_DecodePointersAndHandles(
   struct {{$struct.Name}}* inout_struct, uint32_t in_struct_size,
   MojoHandle inout_handles[], uint32_t in_num_handles) {
   MojomStruct_DecodePointersAndHandles(
     &{{$struct.Name}}__TypeDesc,
     (struct MojomStructHeader*)inout_struct, in_struct_size,
     inout_handles, in_num_handles);
 }
 
+MojomValidationResult {{$struct.Name}}_Validate(
+  const struct {{$struct.Name}}* in_struct, uint32_t in_struct_size,
+  uint32_t in_num_handles) {
+  struct MojomValidationContext context = {
+    .next_handle_index = 0,
+    .next_pointer = (char*)in_struct + in_struct->header_.num_bytes,
+  };
+  return MojomStruct_Validate(
+    &{{$struct.Name}}__TypeDesc,
+    (struct MojomStructHeader*)in_struct, in_struct_size, in_num_handles,
+    &context);
+}
+
 {{end}}
 `