Use UtilityProcessHost to patch files.

chrome/browser/component_updater/component_patcher.h

 // Copyright 2013 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.
 
 // Component updates can be either differential updates or full updates.
 // Full updates come in CRX format; differential updates come in CRX-style
 // archives, but have a different magic number. They contain "commands.json", a
 // list of commands for the patcher to follow. The patcher uses these commands,
 // the other files in the archive, and the files from the existing installation
 // of the component to create the contents of a full update, which is then
@@ skipping 10 matching lines @@
 // and allowed to, and fall back to a full update if it fails.
 //
 // After installation (diff or full), the component updater records "fp", the
 // fingerprint of the installed files, to later identify the existing files to
 // the server so that a proper differential update can be provided next cycle.
 
 
 #ifndef CHROME_BROWSER_COMPONENT_UPDATER_COMPONENT_PATCHER_H_
 #define CHROME_BROWSER_COMPONENT_UPDATER_COMPONENT_PATCHER_H_
 
-#include "base/basictypes.h"
 #include "base/callback_forward.h"
-#include "base/compiler_specific.h"
+#include "base/memory/ref_counted.h"
 #include "chrome/browser/component_updater/component_unpacker.h"
 
 namespace base {
 class FilePath;
 }
 
 namespace component_updater {
 
 class ComponentInstaller;
+class DeltaUpdateOp;
 
-// Applies a delta patch to a single file. Specifically, creates a file at
-// |output_file| using |input_file| patched according to the algorithm
-// specified by |patch_type| using |patch_file|. Sets the value of error to
-// the error code of the failing patch operation, if there is such a failure.
-class ComponentPatcher {
- public:
-  // The type of a patch file.
-  enum PatchType {
-    kPatchTypeUnknown,
-    kPatchTypeCourgette,
-    kPatchTypeBsdiff,
-  };
-
-  virtual ComponentUnpacker::Error Patch(PatchType patch_type,
-                                         const base::FilePath& input_file,
-                                         const base::FilePath& patch_file,
-                                         const base::FilePath& output_file,
-                                         int* error) = 0;
-  virtual ~ComponentPatcher() {}
+// The type of a patch file.
+enum PatchType {
+  kPatchTypeUnknown,
+  kPatchTypeCourgette,
+  kPatchTypeBsdiff,
 };
 
-class ComponentPatcherCrossPlatform : public ComponentPatcher {
+// Encapsulates a task for applying a differential update to a component.
+class ComponentPatcher : public base::RefCountedThreadSafe<ComponentPatcher> {
  public:
-  ComponentPatcherCrossPlatform();
-  virtual ComponentUnpacker::Error Patch(PatchType patch_type,
-                                         const base::FilePath& input_file,
-                                         const base::FilePath& patch_file,
-                                         const base::FilePath& output_file,
-                                         int* error) OVERRIDE;
+  // Takes an unpacked differential CRX (|input_dir|) and a component installer,
+  // and sets up the class to create a new (non-differential) unpacked CRX.
+  // If |in_process| is true, patching will be done completely within the
+  // existing process. Otherwise, some steps of patching may be done
+  // out-of-process.
+  ComponentPatcher(const base::FilePath& input_dir,
+                   const base::FilePath& unpack_dir,
+                   ComponentInstaller* installer,
+                   bool in_process,
+                   scoped_refptr<base::SequencedTaskRunner> task_runner);
+
+  // Starts patching files. This member function returns immediately, after
+  // posting a task to do the patching. When patching has been completed,
+  // |callback| will be called with the error codes if any error codes were
+  // encountered.
+  void Start(
+      const base::Callback<void(ComponentUnpacker::Error, int)>& callback);

[Sorin Jianu, 2014/02/27 20:53:57]

A typedef could help making the code prettier throughout.

[waffles, 2014/02/28 00:52:43]

Done.

+
  private:
-  DISALLOW_COPY_AND_ASSIGN(ComponentPatcherCrossPlatform);
+  friend class base::RefCountedThreadSafe<ComponentPatcher>;
+
+  virtual ~ComponentPatcher();
+
+  void StartPatching();
+
+  void PatchNextFile();
+
+  void DonePatchingFile(ComponentUnpacker::Error error, int extended_error);
+
+  void DonePatching(ComponentUnpacker::Error error, int extended_error);
+
+  const base::FilePath input_dir_;
+  const base::FilePath unpack_dir_;
+  ComponentInstaller* const installer_;
+  const bool in_process_;
+  base::Callback<void(ComponentUnpacker::Error, int)> callback_;
+  scoped_ptr<base::ListValue> commands_;

[Sorin Jianu, 2014/02/27 20:53:57]

do we need values.h?

[waffles, 2014/02/28 00:52:43]

Yes thank you.

+  base::ValueVector::const_iterator next_command_;
+  scoped_refptr<DeltaUpdateOp> current_operation_;
+  scoped_refptr<base::SequencedTaskRunner> task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(ComponentPatcher);
 };
 
-// This function takes an unpacked differential CRX (|input_dir|) and a
-// component installer, and creates a new (non-differential) unpacked CRX, which
-// is then installed normally.
-// The non-differential files are written into the |unpack_dir| directory.
-// When finished, calls the callback, passing error codes if any errors were
-// encountered.
-void DifferentialUpdatePatch(
-    const base::FilePath& input_dir,
-    const base::FilePath& unpack_dir,
-    ComponentPatcher* component_patcher,
-    ComponentInstaller* installer,
-    base::Callback<void(ComponentUnpacker::Error, int)> callback);
-
 }  // namespace component_updater
 
 #endif  // CHROME_BROWSER_COMPONENT_UPDATER_COMPONENT_PATCHER_H_