Stub for ARC print Bridge

components/arc/print/arc_print_bridge.cc

Index: components/arc/print/arc_print_bridge.cc
diff --git a/components/arc/print/arc_print_bridge.cc b/components/arc/print/arc_print_bridge.cc
new file mode 100644
index 0000000000000000000000000000000000000000..dc2ac8dd2527b0746205cd8db0012ac3f406b24b
--- /dev/null
+++ b/components/arc/print/arc_print_bridge.cc
@@ -0,0 +1,88 @@
+// 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.
+
+#include "components/arc/print/arc_print_bridge.h"
+
+#include <utility>
+
+#include "ash/common/shell_delegate.h"
+#include "ash/common/wm_shell.h"
+#include "ash/new_window_delegate.h"
+#include "ash/shell.h"
+#include "base/files/file.h"
+#include "base/files/scoped_file.h"
+#include "base/logging.h"
+#include "base/strings/utf_string_conversions.h"
+#include "base/threading/thread_checker.h"
+#include "components/arc/arc_bridge_service.h"
+#include "mojo/edk/embedder/embedder.h"
+#include "url/gurl.h"
+
+namespace arc {
+
+ArcPrintBridge::ArcPrintBridge(ArcBridgeService* bridge_service)
+    : ArcService(bridge_service), binding_(this) {
+  arc_bridge_service()->AddObserver(this);
+}
+
+ArcPrintBridge::~ArcPrintBridge() {
+  arc_bridge_service()->RemoveObserver(this);
+}
+
+void ArcPrintBridge::OnPrintInstanceReady() {
+  mojom::PrintInstance* print_instance = arc_bridge_service()->print_instance();
+  if (!print_instance) {
+    LOG(ERROR) << "OnPrintInstanceReady called, but no print instance found";
+    return;
+  }
+
+  print_instance->Init(binding_.CreateInterfacePtrAndBind());
+}
+
+void ArcPrintBridge::Print(mojo::ScopedHandle file) {

[Luis Héctor Chávez, 2016/07/11 18:27:53]

This function runs in the UI thread, which shouldn't be doing I/O.
Unfortunately, the I/O thread is unavailable from components/arc, so you might
have to move your code to chrome/browser/chromeos/arc, where you can access the
various BrowserThreads.

[Sergey Poromov, 2016/07/13 16:58:42]

Done.

+  LOG(ERROR) << "Print called!!! " << file.get().value();

[Luis Héctor Chávez, 2016/07/11 18:27:53]

Try to keep debugging statements to a minimum. If you absolutely need to keep
them, use VLOG(2)

[Sergey Poromov, 2016/07/13 16:58:42]

Done.

+
+  if (!file.is_valid()) {
+    LOG(ERROR) << "handle is invalid";
+    return;
+  }
+
+  mojo::edk::ScopedPlatformHandle scoped_platform_handle;
+  MojoResult mojo_result = mojo::edk::PassWrappedPlatformHandle(
+      file.release().value(), &scoped_platform_handle);
+  if (mojo_result != MOJO_RESULT_OK) {
+    LOG(ERROR) << "PassWrappedPlatformHandle failed: " << mojo_result;
+    return;
+  }
+
+  base::ScopedFD fd(scoped_platform_handle.release().handle);
+
+  base::FileDescriptor fn(fd.release(), true);

[Luis Héctor Chávez, 2016/07/11 18:27:53]

This seems unnecessary. You can use |fd.get()| instead of |fn.fd|. Plus
base::FileDescriptor does not call close() when it goes out of scope.

[Sergey Poromov, 2016/07/13 16:58:42]

Done.

+  LOG(ERROR) << "File opened";
+  base::File fl(fn.fd);

[Luis Héctor Chávez, 2016/07/11 18:27:53]

This also feels unnecessary. Plus it will double-close the fd.

[Sergey Poromov, 2016/07/13 16:58:42]

Done.

+  LOG(ERROR) << "File length" << fl.GetLength();

[Luis Héctor Chávez, 2016/07/11 18:27:53]

Huh, I was not expecting this would work with pipes.

[Sergey Poromov, 2016/07/13 16:58:42]

Done.

+
+  base::FilePath filePath(FILE_PATH_LITERAL("/tmp/test.pdf"));

[Luis Héctor Chávez, 2016/07/11 18:27:53]

Can you use base::CreateTemporaryFile instead? Also, is it possible to have some
RAII wrapper to ensure that the file gets deleted when this method returns?

[Sergey Poromov, 2016/07/13 16:58:42]

Done.

+  base::File out(filePath,
+      base::File::FLAG_CREATE_ALWAYS | base::File::FLAG_WRITE);
+
+  char buf[8192];
+  int bytes;

[Luis Héctor Chávez, 2016/07/11 18:27:53]

size_t

[Sergey Poromov, 2016/07/13 16:58:42]

Done.

+  while ((bytes = read(fn.fd, buf, 8192)) > 0) {

[Luis Héctor Chávez, 2016/07/11 18:27:53]

Try to model this after base::ReadFromFD. This does not handle EINTR correctly.

[Sergey Poromov, 2016/07/13 16:58:42]

ReadFromFD doesn't return amount of read bytes. We need it to correctly write
into a file below. Wrapped in HANDLE_EINTR.

+    LOG(ERROR) << "READ " << bytes;
+    out.WriteAtCurrentPos(buf, bytes);
+  }
+
+  LOG(ERROR) << "Result code: " << errno;

[Luis Héctor Chávez, 2016/07/11 18:27:53]

VPLOG(2)? That'll convert errno into its string representation.

[Sergey Poromov, 2016/07/13 16:58:42]

Done.

+
+  out.Flush();
+  out.Close();

[Luis Héctor Chávez, 2016/07/11 18:27:53]

You can just do

{
  base::File out(...);
  // Write to out
}

base::File::~File() calls Close() and it should flush it before.

[Sergey Poromov, 2016/07/13 16:58:42]

Done.

+  fd.release();

[Luis Héctor Chávez, 2016/07/11 18:27:53]

This is unnecessary.

[Sergey Poromov, 2016/07/13 16:58:42]

Done.

+
+  GURL gurl("file:///tmp/test.pdf");
+  ash::WmShell::Get()->delegate()->OpenUrl(gurl);
+
+}
+
+}  // namespace arc