Transform ImagePreReader into PreReadFile.

chrome/app/image_pre_reader_win.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.
-
-// This file defines utility functions to pre-read a PE Image in order to
-// avoid hard page faults when the image is subsequently loaded into memory
-// for execution.
-
-#ifndef CHROME_APP_IMAGE_PRE_READER_WIN_H_
-#define CHROME_APP_IMAGE_PRE_READER_WIN_H_
-
-#include "base/basictypes.h"
-
-// This class defines static helper functions to pre-read a PE Image in order
-// to avoid hard page faults when the image is subsequently loaded into memory
-// for execution.
-class ImagePreReader {
- public:
-  // Reads the file passed in as a PE Image and touches pages to avoid
-  // subsequent hard page faults during LoadLibrary. The size to be pre-read
-  // is passed in. If it is 0 then the whole file is paged in. The step size
-  // which indicates the number of bytes to skip after every page touched is
-  // also passed in.
-  //
-  // This function checks the Windows version to determine which pre-reading
-  // mechanism to use.
-  static bool PreReadImage(const wchar_t* file_path,
-                           size_t size_to_read,
-                           size_t step_size);
-
-  // Loads the file passed in as PE Image and touches a percentage of the
-  // pages in each of the image's sections to avoid subsequent hard page
-  // faults during LoadLibrary.
-  //
-  // This function checks the Windows version to determine which pre-reading
-  // mechanism to use.
-  //
-  // The percentage of the file to be read is an integral value between 0 and
-  // 100, inclusive. If it is 0 then this is a NOP, if it is 100 (or greater)
-  // then the whole file is paged in sequentially via PreReadImage. Otherwise,
-  // for each section, in order, the given percentage of the blocks in that
-  // section are paged in, starting at the beginning of each section. For
-  // example: if percentage is 30 and there is a .text section and a .data
-  // section, then the first 30% of .text will be paged and the first 30% of
-  // .data will be paged in.
-  //
-  // The max_chunk_size indicates the number of bytes to read off the disk in
-  // each step (for Vista and greater, where this is the way the pages are
-  // warmed).
-  //
-  // This function is intended to be used in the context of a PE image with
-  // an optimized layout, such that the blocks in each section are arranged
-  // with the data and code most needed for startup moved to the front.
-  // See also: http://code.google.com/p/chromium/issues/detail?id=98508
-  static bool PartialPreReadImage(const wchar_t* file_path,
-                                  size_t percentage,
-                                  size_t max_chunk_size);
-
-  // Helper function used by PartialPreReadImage on Windows versions (Vista+)
-  // where reading through the file on disk serves to warm up the page cache.
-  // Exported for unit-testing purposes.
-  static bool PartialPreReadImageOnDisk(const wchar_t* file_path,
-                                        size_t percentage,
-                                        size_t max_chunk_size);
-
-  // Helper function used by PartialPreReadImage on Windows versions (XP) where
-  // cheaply loading the image then stepping through its address space serves
-  // to warm up the page cache. Exported for unit-testing purposes.
-  static bool PartialPreReadImageInMemory(const wchar_t* file_path,
-                                          size_t percentage);
-};  // namespace internal
-
-#endif  // CHROME_APP_IMAGE_PRE_READER_WIN_H_