Create VisualElementsManifest.xml from template -- install VisualElements in the version directory

chrome/installer/util/file_from_template_work_item.h

+// 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.
+
+#ifndef CHROME_INSTALLER_UTIL_FILE_FROM_TEMPLATE_WORK_ITEM_H_
+#define CHROME_INSTALLER_UTIL_FILE_FROM_TEMPLATE_WORK_ITEM_H_
+#pragma once
+
+#include <map>
+
+#include "base/file_path.h"
+#include "base/scoped_temp_dir.h"
+#include "chrome/installer/util/work_item.h"
+
+// A WorkItem subclass that takes a template in which variables are surrounded
+// by |kVariableDefiner| (e.g. "this is a $VARIABLE$ to be replaced") and
+// replaces their value as specified by the provided mappings before writing the
+// resulting file to the specified destination directory.
+// NOTE: All templates should end with the .template extension.
+class FileFromTemplateWorkItem : public WorkItem {
+ public:
+  virtual ~FileFromTemplateWorkItem();
+
+  virtual bool Do();
+
+  virtual void Rollback();
+
+ private:
+  friend class WorkItem;
+
+  // |source_path| specifies file containing the template to be written out
+  // to |dest_path|. To facilitate rollback, the caller needs to supply a
+  // temporary directory, |temp_dir| to save the original files if they exist
+  // under |dest_path|.
+  // |mappings| is a key-value mapping of each variable (key) found in the file
+  // which will be replaced by its value in |dest_path|.
+  // |dest_path| will be overwritten if it already exists.
+  FileFromTemplateWorkItem(const FilePath& source_path,
+                           const FilePath& dest_path,
+                           const FilePath& temp_dir,
+                           const std::map<string16, string16>& mappings);
+
+  // Source path to read the template from.
+  FilePath source_path_;
+
+  // Destination path to write the template to.
+  FilePath dest_path_;
+
+  // Temporary directory to backup |dest_path_| (if it already exists).
+  FilePath temp_dir_;
+
+  // The key-value pairs used to replace template variables by their values.
+  std::map<string16, string16> mappings_;
+
+  // Temporary directory into which the original |dest_path_| has been moved.
+  ScopedTempDir backup_path_;
+
+  // Whether the original files have been moved to backup path under
+  // temporary directory. If true, moving back is needed during rollback.
+  bool moved_to_backup_;
+};
+
+#endif  // CHROME_INSTALLER_UTIL_FILE_FROM_TEMPLATE_WORK_ITEM_H_