sync: Introduce CryptographerProvider interface

Creates a CryptographerProvider interface that can be used to expose the
syncable::Directory's Cryptographer without exposing the directory
itself.  Since the directory's cryptographer is protected by a lock,
this requires the creation of several helper classes to manage the
acquistion of the lock.

This CL includes the interface, an implementationthat exposes the
directory's cryptographer (DirectoryCryptographerProvider) and
a SimpleCryptographerProvider that wraps a non-owned Cryptographer for
testing purposes.

These interfaces will be used to implement and test encryption of
non-blocking sync types.

BUG=351005

Review URL: https://codereview.chromium.org/413833002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@285777 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 195 insertions, 0 deletions

diff --git a/sync/engine/cryptographer_provider.cc b/sync/engine/cryptographer_provider.cc
new file mode 100644
index 0000000..2c16bc4
--- /dev/null
+++ b/sync/engine/cryptographer_provider.cc
@@ -0,0 +1,42 @@
+// Copyright 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 "sync/engine/cryptographer_provider.h"
+
+namespace syncer {
+
+CryptographerProvider::CryptographerProvider() {
+}
+
+CryptographerProvider::~CryptographerProvider() {
+}
+
+ScopedCryptographerRef::ScopedCryptographerRef() {
+}
+
+ScopedCryptographerRef::~ScopedCryptographerRef() {
+}
+
+bool ScopedCryptographerRef::Initialize(ScopedCryptographerInternal* impl) {
+  scoped_cryptographer_internal_.reset(impl);
+  return IsValid();
+}
+
+bool ScopedCryptographerRef::IsValid() const {
+  return !!Get();
+}
+
+Cryptographer* ScopedCryptographerRef::Get() const {
+  if (!scoped_cryptographer_internal_)
+    return NULL;
+  return scoped_cryptographer_internal_->Get();
+}
+
+ScopedCryptographerInternal::ScopedCryptographerInternal() {
+}
+
+ScopedCryptographerInternal::~ScopedCryptographerInternal() {
+}
+
+}  // namespace syncer
diff --git a/sync/engine/cryptographer_provider.h b/sync/engine/cryptographer_provider.h
new file mode 100644
index 0000000..f38bd185
--- /dev/null
+++ b/sync/engine/cryptographer_provider.h
@@ -0,0 +1,64 @@
+// Copyright 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.
+
+#ifndef SYNC_ENGINE_CRYPTOGRAPHER_PROVIDER_H_
+#define SYNC_ENGINE_CRYPTOGRAPHER_PROVIDER_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "sync/base/sync_export.h"
+
+namespace syncer {
+
+class Cryptographer;
+class ScopedCryptographerRef;
+class ScopedCryptographerInternal;
+
+// An interface for providing clients with a ScopedCryptographerRef.
+//
+// Used to expose the syncable::Directory's cryptographer to clients that
+// would otherwise not have access to the Directory.
+class SYNC_EXPORT_PRIVATE CryptographerProvider {
+ public:
+  CryptographerProvider();
+  virtual ~CryptographerProvider();
+
+  virtual bool InitScopedCryptographerRef(ScopedCryptographerRef* scoped) = 0;
+};
+
+// A concrete class representing a reference to a cryptographer.
+//
+// Access to the cryptographer is lost when this class goes out of scope.
+class SYNC_EXPORT_PRIVATE ScopedCryptographerRef {
+ public:
+  ScopedCryptographerRef();
+  ~ScopedCryptographerRef();
+
+  bool Initialize(ScopedCryptographerInternal* impl);
+  bool IsValid() const;
+  Cryptographer* Get() const;
+
+ private:
+  scoped_ptr<ScopedCryptographerInternal> scoped_cryptographer_internal_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedCryptographerRef);
+};
+
+// An interface class used in the implementation of the ScopedCryptographerRef.
+//
+// We use this class to allow different implementations of
+// CryptographerProvider to implement InitScopedCryptographer in different
+// ways.  The ScopedCryptographerRef itself must be stack-allocated, so it
+// can't vary depending on which kind of CryptographerProvider is used to
+// intialize it.
+class SYNC_EXPORT_PRIVATE ScopedCryptographerInternal {
+ public:
+  ScopedCryptographerInternal();
+  virtual ~ScopedCryptographerInternal();
+
+  virtual Cryptographer* Get() const = 0;
+};
+
+}  // namespace syncer
+
+#endif  // SYNC_ENGINE_CRYPTOGRAPHER_PROVIDER_H_
diff --git a/sync/engine/directory_cryptographer_provider.cc b/sync/engine/directory_cryptographer_provider.cc
new file mode 100644
index 0000000..a9cd2a2
--- /dev/null
+++ b/sync/engine/directory_cryptographer_provider.cc
@@ -0,0 +1,38 @@
+// Copyright 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 "sync/engine/directory_cryptographer_provider.h"
+
+#include "sync/syncable/directory.h"
+#include "sync/syncable/syncable_read_transaction.h"
+
+namespace syncer {
+
+DirectoryCryptographerProvider::DirectoryCryptographerProvider(
+    syncable::Directory* dir)
+    : dir_(dir) {
+}
+
+DirectoryCryptographerProvider::~DirectoryCryptographerProvider() {
+}
+
+bool DirectoryCryptographerProvider::InitScopedCryptographerRef(
+    ScopedCryptographerRef* scoped) {
+  scoped->Initialize(new ScopedDirectoryCryptographerInternal(dir_));
+  return scoped->IsValid();
+}
+
+ScopedDirectoryCryptographerInternal::ScopedDirectoryCryptographerInternal(
+    syncable::Directory* dir)
+    : dir_(dir), trans_(FROM_HERE, dir) {
+}
+
+ScopedDirectoryCryptographerInternal::~ScopedDirectoryCryptographerInternal() {
+}
+
+Cryptographer* ScopedDirectoryCryptographerInternal::Get() const {
+  return dir_->GetCryptographer(&trans_);
+}
+
+}  // namespace syncer
diff --git a/sync/engine/directory_cryptographer_provider.h b/sync/engine/directory_cryptographer_provider.h
new file mode 100644
index 0000000..36b1c0f
--- /dev/null
+++ b/sync/engine/directory_cryptographer_provider.h
@@ -0,0 +1,51 @@
+// Copyright 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.
+
+#ifndef SYNC_ENGINE_DIRECTORY_CRYPTOGRAPHER_PROVIDER_H_
+#define SYNC_ENGINE_DIRECTORY_CRYPTOGRAPHER_PROVIDER_H_
+
+#include "sync/engine/cryptographer_provider.h"
+
+#include "sync/syncable/syncable_read_transaction.h"
+
+namespace syncer {
+
+namespace syncable {
+class Directory;
+}
+
+// Provides access to the Directory's cryptographer through the
+// CryptographerProvider interface.
+class DirectoryCryptographerProvider : public CryptographerProvider {
+ public:
+  DirectoryCryptographerProvider(syncable::Directory* dir);
+  virtual ~DirectoryCryptographerProvider();
+
+  virtual bool InitScopedCryptographerRef(
+      ScopedCryptographerRef* scoped) OVERRIDE;
+
+ private:
+  syncable::Directory* dir_;
+};
+
+// An implementation detail of the DirectoryCryptographerProvider.  Contains
+// the ReadTransaction used to safely access the Cryptographer.
+class ScopedDirectoryCryptographerInternal
+    : public ScopedCryptographerInternal {
+ public:
+  ScopedDirectoryCryptographerInternal(syncable::Directory* dir);
+  virtual ~ScopedDirectoryCryptographerInternal();
+
+  virtual Cryptographer* Get() const OVERRIDE;
+
+ private:
+  syncable::Directory* dir_;
+  syncable::ReadTransaction trans_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedDirectoryCryptographerInternal);
+};
+
+}  // namespace syncer
+
+#endif  // SYNC_ENGINE_DIRECTORY_CRYPTOGRAPHER_PROVIDER_H_