Implement snapshotting for non-Drive non-local file systems.

chrome/browser/chromeos/file_manager/snapshot_manager.cc

Index: chrome/browser/chromeos/file_manager/snapshot_manager.cc
diff --git a/chrome/browser/chromeos/file_manager/snapshot_manager.cc b/chrome/browser/chromeos/file_manager/snapshot_manager.cc
new file mode 100644
index 0000000000000000000000000000000000000000..452eaec1c82d12241cb674a7888bf4fbe350f11a
--- /dev/null
+++ b/chrome/browser/chromeos/file_manager/snapshot_manager.cc
@@ -0,0 +1,155 @@
+// 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 "chrome/browser/chromeos/file_manager/snapshot_manager.h"
+
+#include "base/bind.h"
+#include "base/file_util.h"
+#include "base/files/file_path.h"
+#include "base/sequenced_task_runner.h"
+#include "base/sys_info.h"
+#include "base/task_runner_util.h"
+#include "chrome/browser/chromeos/file_manager/app_id.h"
+#include "chrome/browser/chromeos/file_manager/fileapi_util.h"
+#include "chrome/browser/profiles/profile.h"
+#include "content/public/browser/browser_thread.h"
+#include "google_apis/drive/task_util.h"
+#include "third_party/cros_system_api/constants/cryptohome.h"
+#include "webkit/common/blob/shareable_file_reference.h"
+
+namespace file_manager {
+namespace {
+
+// Name of the directory for storing the snapshot files under the storage
+// partition path.
+const base::FilePath::CharType kFileManagerSnapshotDirectoryName[] =
+    FILE_PATH_LITERAL("FileDialogSnapshot");
+
+// Cleans up the specified directory.
+void DeleteDirectory(const base::FilePath& directory) {

[hashimoto, 2014/06/19 02:26:01]

nit: What is the point of having this function instead of directory calling
Bind() with base::DeleteFile?

[kinaba, 2014/06/19 04:41:56]

Good catch. Removed.
(Actually I hadn't been able to figure out base::IgnoreResult is usable in this
case.)

+  base::DeleteFile(directory, true /* recursive */);
+}
+
+// Returns true if there is sufficient disk space in |directory| for file
+// |size|. Besides, it heuristically cleans up old files under |directory|.
+bool MakeSpaceIfNecessary(const base::FilePath& directory, int64 size) {
+  int64 free_space = base::SysInfo::AmountOfFreeDiskSpace(directory);
+  free_space -= cryptohome::kMinFreeSpaceInBytes;
+
+  // TODO(kinaba): clean old snapshot files.
+  return (size <= free_space);
+}
+
+// Part of CreateManagedSnapshot. Used for retaining |file_ref| until the
+// blocking pool job finished. After returning from this function, |file_ref| is
+// freed on the IO thread.
+void CopyDone(
+    const SnapshotManager::LocalPathCallback& callback,
+    const scoped_refptr<webkit_blob::ShareableFileReference>& file_ref,
+    const base::FilePath& local_path) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+  callback.Run(local_path);
+}
+
+// Part of CreateManagedSnapshot.
+// Copy |path| into |directory| with space management.
+base::FilePath CopyOnBlockingPool(const base::FilePath& directory,
+                                  const base::FilePath& path) {
+  base::File::Info info;
+  base::FilePath copied;
+  if (!base::GetFileInfo(path, &info) ||
+      !base::CreateDirectory(directory) ||
+      !MakeSpaceIfNecessary(directory, info.size) ||
+      !base::CreateTemporaryFileInDir(directory, &copied) ||
+      !base::CopyFile(path, copied)) {
+    return base::FilePath();
+  }
+  return copied;
+}
+
+// Part of CreateManagedSnapshot. Copies the created file to a temporary
+// path. The snapshot file itself may be removed once |file_ref| is deleted.
+void OnCreateSnapshotFile(
+    scoped_refptr<base::SequencedTaskRunner> task_runner,
+    const base::FilePath& base_path,
+    const SnapshotManager::LocalPathCallback& callback,
+    base::File::Error result,
+    const base::File::Info& file_info,
+    const base::FilePath& platform_path,
+    const scoped_refptr<webkit_blob::ShareableFileReference>& file_ref) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+
+  if (result != base::File::FILE_OK) {
+    callback.Run(base::FilePath());
+    return;
+  }
+
+  base::PostTaskAndReplyWithResult(
+      task_runner,
+      FROM_HERE,
+      base::Bind(&CopyOnBlockingPool, base_path, platform_path),
+      base::Bind(&CopyDone, callback, file_ref));
+}
+
+// Part of CreateManagedSnapshot. Runs CreateSnapshotFile method of fileapi.
+void CreateSnapshotFileOnIOThread(
+    scoped_refptr<fileapi::FileSystemContext> context,
+    scoped_refptr<base::SequencedTaskRunner> task_runner,
+    const base::FilePath& base_path,
+    const fileapi::FileSystemURL& url,
+    const SnapshotManager::LocalPathCallback& callback) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+
+  context->operation_runner()->CreateSnapshotFile(
+      url, base::Bind(&OnCreateSnapshotFile, task_runner, base_path, callback));
+}
+
+}  // namespace
+
+SnapshotManager::SnapshotManager(Profile* profile)
+    : profile_(profile) {
+  base::SequencedWorkerPool* pool =
+      content::BrowserThread::GetBlockingPool();
+  task_runner_ = pool->GetSequencedTaskRunner(pool->GetSequenceToken());
+}
+
+SnapshotManager::~SnapshotManager() {
+  if (task_runner_ && !base_path_.empty()) {

[hashimoto, 2014/06/19 02:26:01]

nit: In which case task_runner_ becomes NULL?

[kinaba, 2014/06/19 04:41:56]

Never.

+    // Clean up all snapshots in the current run.
+    task_runner_->PostTask(
+        FROM_HERE, base::Bind(&DeleteDirectory, base_path_));

[hashimoto, 2014/06/19 02:26:01]

I don't remember in which order objects are destructed during a shutdown.
Did you confirm that task_runner_ is still alive when SnapshotManager is
destroyed?
How about having DCHECK(posted)?

[kinaba, 2014/06/19 04:41:56]

It is still alive at this point (profile destruction). Added DCHECK.

+  }
+}
+
+void SnapshotManager::CreateManagedSnapshot(
+    const base::FilePath& absolute_file_path,
+    const LocalPathCallback& callback) {
+  fileapi::FileSystemContext* context =
+      util::GetFileSystemContextForExtensionId(profile_, kFileManagerAppId);
+  DCHECK(context);
+
+  GURL url;
+  if (!util::ConvertAbsoluteFilePathToFileSystemUrl(
+          profile_, absolute_file_path, kFileManagerAppId, &url)) {
+    callback.Run(base::FilePath());
+    return;
+  }
+
+  if (base_path_.empty()) {

[hashimoto, 2014/06/19 02:26:01]

nit: Why can't this be initialized in the ctor?

[kinaba, 2014/06/19 04:41:56]

StorageParition/FileSystemContext related part is not yet initialized at that
point.

+    base_path_ = context->partition_path().Append(
+        kFileManagerSnapshotDirectoryName);
+  }
+
+  content::BrowserThread::PostTask(
+      content::BrowserThread::IO,
+      FROM_HERE,
+      base::Bind(&CreateSnapshotFileOnIOThread,
+                 make_scoped_refptr(context),
+                 task_runner_,
+                 base_path_,
+                 context->CrackURL(url),
+                 google_apis::CreateRelayCallback(callback)));
+}
+
+}  // namespace file_manager