Differential updates for components.

chrome/browser/component_updater/component_patcher.h

Index: chrome/browser/component_updater/component_patcher.h
diff --git a/chrome/browser/component_updater/component_patcher.h b/chrome/browser/component_updater/component_patcher.h
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+// Copyright (c) 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
+// installed normally.
+// Component updates are specified by the 'codebasediff' attribute of an
+// updatecheck response:
+//   <updatecheck codebase="http://example.com/extension_1.2.3.4.crx"
+//                hash="12345" size="9854" status="ok" version="1.2.3.4"
+//                prodversionmin="2.0.143.0"
+//                codebasediff="http://example.com/diff_1.2.3.4.crx"
+//                hashdiff="123" sizediff="101"
+//                fp="1.123" />
+// The component updater will attempt a differential update if it is available
+// 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/compiler_specific.h"
+#include "chrome/browser/component_updater/component_unpacker.h"
+
+namespace base {
+class FilePath;
+}
+
+class ComponentInstaller;
+
+// 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() {}
+};
+
+class ComponentPatcherCrossPlatform : public 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;
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ComponentPatcherCrossPlatform);
+};
+
+// 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.
+// Sets |error| to the error code of the first failing patch operation.
+ComponentUnpacker::Error DifferentialUpdatePatch(
+    const base::FilePath& input_dir,
+    const base::FilePath& unpack_dir,
+    ComponentPatcher* component_patcher,
+    ComponentInstaller* installer,
+    int* error);
+
+#endif  // CHROME_BROWSER_COMPONENT_UPDATER_COMPONENT_PATCHER_H_