Adds a generator for writing messages to disk

mojo/public/bindings/tests/message_generator.cc

Index: mojo/public/bindings/tests/message_generator.cc
diff --git a/mojo/public/bindings/tests/message_generator.cc b/mojo/public/bindings/tests/message_generator.cc
new file mode 100644
index 0000000000000000000000000000000000000000..171a62cbfedf20bcee8ddfd027d8d0521b01da95
--- /dev/null
+++ b/mojo/public/bindings/tests/message_generator.cc
@@ -0,0 +1,63 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.

[viettrungluu, 2014/04/01 22:02:50]

Three things:
- The contents of mojo/public/bindings/tests have moved.
- This isn't actually a test of the bindings itself, so it probably doesn't
belong there.
- Probably, as the base/ includes suggest, it doesn't need to live under
mojo/public at all. I'd suggest mojo/tools/.

[viettrungluu, 2014/04/01 22:11:43]

On second thought, maybe it should be under public/ somewhere. I'd have to think
about where.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/file_util.h"
+#include "base/files/file_path.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+#include "mojo/public/bindings/lib/message_builder.h"
+#include "mojo/public/bindings/lib/message_internal.h"
+#include "mojo/public/cpp/bindings/message.h"
+
+// This file is used to generate various files corresponding to mojo
+// messages. The various binding implementations can parse these to verify they
+// correctly decode messages.
+//
+// The output consists of each byte of the message encoded in a hex string with
+// a newline after it.
+namespace mojo {
+namespace {
+
+std::string BinaryToHex(const base::StringPiece& piece) {
+  std::string result;
+  result.reserve(piece.size() * 5);
+  for (size_t i = 0; i < piece.size(); ++i) {
+    result.append("0X");

[viettrungluu, 2014/04/01 22:11:43]

Also, I suggest just using StringAppendF.

(As a side commentary, it'd probably be helpful to have it prepend some
explanatory header, e.g., "# This file is generated by ....")

+    result.append(base::HexEncode(piece.data() + i, 1));
+    result.push_back('\n');
+  }
+  return result;
+}
+
+// Generates a message of type MessageData. The message uses the name 21,
+// with 4 bytes of payload: 0x9, 0x8, 0x7, 0x6.
+void GenerateMessageDataMessage(const base::FilePath& path) {

[viettrungluu, 2014/04/01 22:11:43]

I think this should be factored into several pieces:
- a WriteMessageToFile() (that takes a Message and a file[*]); probably this
function should go into a library
- something that actually generates the Message and filename (possibly you could
do this directly in main())
The reason is that I think that we should have many more "golden" messages, not
just the single one you have below.

[*] Probably you should avoid the base/ dependency and just use stdio.h. Maybe
it should take a FILE*.

+  internal::MessageBuilder builder(static_cast<uint32_t>(21),
+                                   static_cast<size_t>(4));
+  char* data = static_cast<char*>(builder.buffer()->Allocate(4));
+  DCHECK(data);
+  data[0] = 9;
+  data[1] = 8;
+  data[2] = 7;
+  data[3] = 6;
+
+  Message message;
+  builder.Finish(&message);
+  std::string string_message;
+  const std::string hex_message(BinaryToHex(
+      base::StringPiece(reinterpret_cast<const char*>(message.data()),
+                        message.data_num_bytes())));
+  CHECK_EQ(static_cast<int>(hex_message.size()),
+           base::WriteFile(path, hex_message.data(), hex_message.size()));
+}
+
+}  // namespace
+}  // namespace mojo
+
+int main(int argc, char** argv) {
+  mojo::GenerateMessageDataMessage(
+      base::FilePath(FILE_PATH_LITERAL("message_data.txt")));
+  return 0;
+}