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

mojo/public/c/bindings/struct.h

 // 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.
 
 #ifndef MOJO_PUBLIC_C_BINDINGS_STRUCT_H_
 #define MOJO_PUBLIC_C_BINDINGS_STRUCT_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "mojo/public/c/bindings/buffer.h"
 #include "mojo/public/c/bindings/lib/type_descriptor.h"
+#include "mojo/public/c/bindings/lib/util.h"
 #include "mojo/public/c/system/macros.h"
 
 MOJO_BEGIN_EXTERN_C
 
 struct MojomStructHeader {
   // |num_bytes| includes the size of this struct header along with the
   // accompanying struct data. |num_bytes| must be rounded up to 8 bytes.
   uint32_t num_bytes;
   uint32_t version;
 };
@@ skipping 26 matching lines @@
     uint32_t in_struct_size,
     struct MojomHandleBuffer* inout_handles_buffer);
 
 // Decodes the mojom struct described by the |inout_struct| buffer; note that
 // any references from the struct are also in |inout_struct|, and they are
 // recursively decoded. Decodes all offsets to pointers, and decodes all handles
 // by moving them out of |inout_handles| array using the encoded index into the
 // array.
 // |in_type_desc|: Describes the pointer and handle fields of the mojom struct.
 // |inout_struct|: Contains the struct, and any other references outside of the
-//              struct.
-// |in_struct_size|: Contains the struct, and any other references outside of
-//                   the struct.
+//                 struct.
+// |in_struct_size|: Size of the buffer backed by |inout_struct| in bytes.
 // |inout_handles|: Mojo handles are in this array, and are referenced by index
 //                  in |inout_buf|.
 // |in_num_handles|: Size in # of number elements available in |inout_handles|.
 void MojomStruct_DecodePointersAndHandles(
     const struct MojomTypeDescriptorStruct* in_type_desc,
     struct MojomStructHeader* inout_struct,
     uint32_t in_struct_size,
     MojoHandle* inout_handles,
     uint32_t in_num_handles);
 
+// Validates the mojom struct described by the |in_struct| buffer. Any
+// references from the struct are also recursively validated, and are expected
+// to be in the same buffer backing |in_struct|.
+// |in_type_desc|: Describes the pointer and handle fields of the mojom struct.
+// |inout_struct|: Buffer containing the struct, and any other references
+//                 outside of the struct.
+// |in_struct_size|: Size of the buffer backed by |inout_struct| in bytes.
+// |in_num_handles|: Number of valid handles expected to be referenced from
+//                   |in_struct|.
+// |inout_context|: An initialized context that contains the expected location
+//                  of the next pointer and next offset. This is used to
+//                  validate that no two pointers or handles are shared.
+MojomValidationResult MojomStruct_Validate(
+    const struct MojomTypeDescriptorStruct* in_type_desc,
+    const struct MojomStructHeader* in_struct,
+    uint32_t in_struct_size,
+    uint32_t in_num_handles,
+    struct MojomValidationContext* inout_context);
+
 MOJO_END_EXTERN_C
 
 #endif  // MOJO_PUBLIC_C_BINDINGS_STRUCT_H_