C bindings: Implement _DeepCopy() & some unittests.

mojo/public/c/bindings/tests/testing_util.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_TESTS_TESTING_UTIL_H_
+#define MOJO_PUBLIC_C_BINDINGS_TESTS_TESTING_UTIL_H_
+
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "mojo/public/c/bindings/buffer.h"
+#include "mojo/public/c/system/handle.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+// This will copy the supplied |in_struct| and compare it against the new
+// copy, expecting them to be the same. It compares the encoded version to be
+// sure that they are the same, since a unencoded version will have pointers
+// pointing to separate objects in the two copies, whereas encoded versions will
+// only have relative offsets for pointers. The new copy will remain encoded,
+// and the original will be decoded.
+// This function won't work for structs with handles, and will crash.
+template <typename T>
+void CopyAndCompare(
+    MojomBuffer* buf,
+    T* in_struct,
+    size_t in_struct_size,
+    T* (*copy_fn)(struct MojomBuffer* in_buffer, T* in_struct),
+    void (*encode_fn)(T* inout_struct,
+                      uint32_t size,
+                      struct MojomHandleBuffer* inout_handle_buffer),
+    void (*decode_fn)(T* inout_struct,
+                      uint32_t size,
+                      MojoHandle* handles,
+                      uint32_t num_handles)) {
+  T* out_struct = copy_fn(buf, in_struct);
+  ASSERT_TRUE(out_struct);
+  EXPECT_EQ(in_struct_size, buf->num_bytes_used);
+
+  encode_fn(in_struct, in_struct_size, NULL);
+  encode_fn(out_struct, buf->num_bytes_used, NULL);
+  EXPECT_EQ(0, memcmp(in_struct, out_struct, buf->num_bytes_used));
+
+  decode_fn(in_struct, in_struct_size, NULL, 0);
+}
+
+#endif  // MOJO_PUBLIC_C_BINDINGS_TESTS_TESTING_UTIL_H_