Print Preview: Fix failure to save with long page title

ui/shell_dialogs/select_file_dialog.cc

 // Copyright (c) 2012 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 "ui/shell_dialogs/select_file_dialog.h"
 
 #include <stddef.h>
+#include <algorithm>
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "ui/shell_dialogs/select_file_dialog_factory.h"
 #include "ui/shell_dialogs/select_file_policy.h"
 #include "ui/shell_dialogs/selected_file_info.h"
@@ skipping 49 matching lines @@
     ui::SelectFilePolicy* policy) {
   if (dialog_factory_) {
     SelectFileDialog* dialog = dialog_factory_->Create(listener, policy);
     if (dialog)
       return dialog;
   }
 
   return CreateSelectFileDialog(listener, policy);
 }
 
+namespace {

[Lei Zhang, 2017/04/13 19:33:53]

There's already one up on line 20.

[rbpotter, 2017/04/13 20:53:56]

Done.

+
+base::FilePath GetShortenedFilePath(const base::FilePath& path) {

[Lei Zhang, 2017/04/13 19:33:53]

Can you add a comment to explain why we need this?

[rbpotter, 2017/04/13 20:53:56]

Done.

+  base::FilePath filename = path.BaseName();
+  base::FilePath short_path = path;
+  const size_t kMaxNameLength = 255;
+  if (filename.value().length() > kMaxNameLength) {

[Lei Zhang, 2017/04/13 19:33:53]

Flip to <=, and then return early.

[rbpotter, 2017/04/13 20:53:56]

Done.

+    base::FilePath::StringType extension = filename.FinalExtension();
+    filename = filename.RemoveFinalExtension();
+    // 1 for . plus 12 for longest known extension.
+    size_t max_extension_length = 13;
+    if (filename.value().length() < kMaxNameLength) {

[Lei Zhang, 2017/04/13 19:33:53]

I think you can omit this check. If the |filename| length is say, 300, then
we'll end up with std::max(13, 255 - 300), which is still 13.

[rbpotter, 2017/04/13 20:53:56]

Both kMaxNameLength and filename.value().length() are size_ts as is
max_extension_length, so I did this to avoid casting in the std::max
call. What would be preferable between casting vs checking the values?

[Lei Zhang, 2017/04/13 21:13:44]

Try writing 13U instead?

+      max_extension_length = std::max(
+          max_extension_length, kMaxNameLength - filename.value().length());
+    }
+    if (extension.length() >= max_extension_length) {
+      // Take the last max_extension_length - 1 characters (save 1 character
+      // for the '.').
+      base::FilePath::StringType new_extension;
+      new_extension[0] = base::FilePath::kExtensionSeparator;

[Lei Zhang, 2017/04/13 19:33:53]

Isn't this an out of bounds access since |new_extension| starts out with length
0? Just do:

base::FilePath::StringType new_extension = base::FilePath::kExtensionSeparator;

[rbpotter, 2017/04/13 20:53:56]

That doesn't work since the extension separator is a CharType, but
I changed this to use push_back instead, which should prevent the
out of bounds access.

+      extension = new_extension.append(
+          extension.substr(extension.length() - max_extension_length + 1,
+                           max_extension_length - 1));
+    }
+    short_path = path.DirName().Append(
+        filename.value().substr(0, kMaxNameLength - extension.length()));
+    short_path = short_path.AddExtension(extension);
+  }
+  return short_path;
+}
+
+}  // namespace
+
 void SelectFileDialog::SelectFile(
     Type type,
     const base::string16& title,
     const base::FilePath& default_path,
     const FileTypeInfo* file_types,
     int file_type_index,
     const base::FilePath::StringType& default_extension,
     gfx::NativeWindow owning_window,
     void* params) {
   DCHECK(listener_);
 
   if (select_file_policy_.get() &&
       !select_file_policy_->CanOpenSelectFileDialog()) {
     select_file_policy_->SelectFileDenied();
 
     // Inform the listener that no file was selected.
     // Post a task rather than calling FileSelectionCanceled directly to ensure
     // that the listener is called asynchronously.
     base::ThreadTaskRunnerHandle::Get()->PostTask(
         FROM_HERE,
         base::Bind(&SelectFileDialog::CancelFileSelection, this, params));
     return;
   }
 
+  base::FilePath path = GetShortenedFilePath(default_path);
+
   // Call the platform specific implementation of the file selection dialog.
-  SelectFileImpl(type, title, default_path, file_types, file_type_index,
+  SelectFileImpl(type, title, path, file_types, file_type_index,
                  default_extension, owning_window, params);
 }
 
 bool SelectFileDialog::HasMultipleFileTypeChoices() {
   return HasMultipleFileTypeChoicesImpl();
 }
 
 SelectFileDialog::SelectFileDialog(Listener* listener,
                                    ui::SelectFilePolicy* policy)
     : listener_(listener),
       select_file_policy_(policy) {
   DCHECK(listener_);
 }
 
 SelectFileDialog::~SelectFileDialog() {}
 
 void SelectFileDialog::CancelFileSelection(void* params) {
   if (listener_)
     listener_->FileSelectionCanceled(params);
 }
 
 }  // namespace ui