Introduce a helper for OPENFILENAME struct to make certain logic testable.

ui/base/win/open_file_name_win.cc

+// Copyright (c) 2014 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/base/win/open_file_name_win.h"
+
+#include "base/files/file_path.h"
+#include "base/strings/string_util.h"
+
+namespace ui {
+namespace win {
+
+OpenFileName::OpenFileName(HWND parent_window, DWORD flags) {
+  ::ZeroMemory(&openfilename_, sizeof(openfilename_));
+  openfilename_.lStructSize = sizeof(openfilename_);
+
+  // According to http://support.microsoft.com/?scid=kb;en-us;222003&x=8&y=12,
+  // The lpstrFile Buffer MUST be NULL Terminated.
+  filename_buffer_[0] = 0;
+  openfilename_.lpstrFile = filename_buffer_;
+  openfilename_.nMaxFile = arraysize(filename_buffer_);
+
+  openfilename_.Flags = flags;
+  openfilename_.hwndOwner = parent_window;
+}
+
+OpenFileName::~OpenFileName() {
+}
+
+void OpenFileName::SetInitialSelection(const base::FilePath& initial_directory,
+                                       const base::FilePath& initial_filename) {
+  // First reset to the default case.
+  // According to http://support.microsoft.com/?scid=kb;en-us;222003&x=8&y=12,
+  // The lpstrFile Buffer MUST be NULL Terminated.
+  filename_buffer_[0] = 0;
+  openfilename_.lpstrFile = filename_buffer_;
+  openfilename_.nMaxFile = arraysize(filename_buffer_);
+  openfilename_.lpstrInitialDir = NULL;
+  initial_directory_buffer_.clear();
+
+  if (initial_directory.empty())
+    return;
+
+  initial_directory_buffer_ = initial_directory.value();
+  openfilename_.lpstrInitialDir = initial_directory_buffer_.c_str();
+
+  if (initial_filename.empty())
+    return;
+
+  // The filename is ignored if no initial directory is supplied.
+  base::wcslcpy(filename_buffer_,
+                initial_filename.value().c_str(),
+                arraysize(filename_buffer_));
+}
+
+base::FilePath OpenFileName::GetSingleResult() {
+  base::FilePath directory;
+  std::vector<base::FilePath> filenames;
+  GetResult(&directory, &filenames);
+  if (filenames.size() != 1)
+    return base::FilePath();
+  return directory.Append(filenames[0]);
+}
+
+void OpenFileName::GetResult(base::FilePath* directory,
+                             std::vector<base::FilePath>* filenames) {
+  DCHECK(filenames->empty());
+  const wchar_t* selection = openfilename_.lpstrFile;
+  while (*selection) {  // Empty string indicates end of list.
+    filenames->push_back(base::FilePath(selection));
+    // Skip over filename and null-terminator.
+    selection += filenames->back().value().length() + 1;
+  }
+  if (filenames->size() == 1) {
+    // When there is one file, it contains the path and filename.
+    *directory = (*filenames)[0].DirName();
+    (*filenames)[0] = (*filenames)[0].BaseName();
+  } else if (filenames->size() > 1) {
+    // Otherwise, the first string is the path, and the remainder are
+    // filenames.
+    *directory = (*filenames)[0];
+    filenames->erase(filenames->begin());
+  }
+}
+
+}  // namespace win
+}  // namespace ui