Add 1st cut of FileSystemUsageTracker that tracks the usage changes in FileSystem API.

webkit/fileapi/file_system_usage_tracker.cc

+// Copyright (c) 2011 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 "webkit/fileapi/file_system_usage_tracker.h"
+
+#include "base/file_path.h"
+#include "base/file_util.h"
+#include "base/logging.h"
+#include "base/message_loop_proxy.h"
+#include "base/scoped_ptr.h"
+#include "base/task.h"
+#include "googleurl/src/gurl.h"
+#include "webkit/fileapi/file_system_path_manager.h"
+
+namespace fileapi {
+
+class FileSystemUsageTracker::GetUsageTask
+    : public base::RefCountedThreadSafe<GetUsageTask> {
+ public:
+  GetUsageTask(
+      FileSystemUsageTracker* tracker,
+      scoped_refptr<base::MessageLoopProxy> file_message_loop,
+      std::string fs_name,
+      const FilePath& origin_base_path)
+      : tracker_(tracker),
+        file_message_loop_(file_message_loop),
+        origin_message_loop_(
+            base::MessageLoopProxy::CreateForCurrentThread()),
+        fs_name_(fs_name),
+        fs_usage_(0),
+        origin_base_path_(origin_base_path) {
+  }
+
+  virtual ~GetUsageTask() {}
+
+  void Start() {
+    if (tracker_)

[michaeln, 2011/02/09 00:25:36]

can tracker_ ever be null?

[kinuko, 2011/02/09 05:22:36]

Just a paranoid check... changed this to DCHECK.

+      tracker_->RegisterUsageTask(this);
+    file_message_loop_->PostTask(
+        FROM_HERE, NewRunnableMethod(this, &GetUsageTask::RunOnFileThread));
+  }
+
+  void RunOnFileThread() {

[michaeln, 2011/02/09 00:25:36]

can this method be private?

[kinuko, 2011/02/09 05:22:36]

I'm planning to add a base class and make make this method protected, but yes
for now.  Done.

[kinuko, 2011/02/09 05:25:59]

Oops, please ignore my previous comment.  Just made this private.

+    DCHECK(file_message_loop_->BelongsToCurrentThread());
+
+    // TODO(dmikurube): add the code that retrieves the origin usage here.

[michaeln, 2011/02/09 00:25:36]

This could tie up the file thread for quite some time. Is it ok to monopolize it
for the duration?

[kinuko, 2011/02/09 05:22:36]

In our current plan, the monopolization should only happen for the 1st time this
code runs (i.e. 1st run after the installation) and after crashes.  I'm also
thinking to call this in a less visible way (eagerly or lazily depending on how
the API is called), but for now it's just a single simple task and no one calls
this yet.

(The half-baked design doc:
https://docs.google.com/a/google.com/document/d/1EIFQDvGFo4pswyd5-v-o2tDNlhvG...)

+
+    origin_message_loop_->PostTask(
+        FROM_HERE, NewRunnableMethod(this, &GetUsageTask::Completed));
+  }
+
+  void Cancel() {
+    DCHECK(origin_message_loop_->BelongsToCurrentThread());
+    tracker_ = NULL;
+  }
+
+ private:
+  void Completed() {
+    DCHECK(origin_message_loop_->BelongsToCurrentThread());
+    if (tracker_) {
+      tracker_->UnregisterUsageTask(this);
+      tracker_->DidGetOriginUsage(fs_name_, fs_usage_);
+    }
+  }
+
+  FileSystemUsageTracker* tracker_;
+  scoped_refptr<base::MessageLoopProxy> file_message_loop_;
+  scoped_refptr<base::MessageLoopProxy> origin_message_loop_;

[michaeln, 2011/02/09 00:25:36]

the term 'origin' in this data member could be confusing since its a different
meaning than the other use of 'origin' in this class... consider a different
name?

[ericu, 2011/02/09 02:05:22]

I think just changing it to "original_message_loop_" would be enough.  Or
caller_message_loop_ or something like that would work too.

[kinuko, 2011/02/09 05:22:36]

Indeed.  Done.

+  std::string fs_name_;
+  int64 fs_usage_;
+  FilePath origin_base_path_;
+};
+
+FileSystemUsageTracker::FileSystemUsageTracker(
+    scoped_refptr<base::MessageLoopProxy> file_message_loop,
+    const FilePath& profile_path,
+    bool is_incognito)
+    : file_message_loop_(file_message_loop),
+      base_path_(profile_path.Append(
+          FileSystemPathManager::kFileSystemDirectory)),
+      is_incognito_(is_incognito) {
+  DCHECK(file_message_loop);
+}
+
+FileSystemUsageTracker::~FileSystemUsageTracker() {
+  std::for_each(running_usage_tasks_.begin(),
+                running_usage_tasks_.end(),
+                std::mem_fun(&GetUsageTask::Cancel));
+}
+
+void FileSystemUsageTracker::GetOriginUsage(
+    const GURL& origin_url,
+    fileapi::FileSystemType type,
+    GetUsageCallback* callback_ptr) {
+  DCHECK(callback_ptr);
+  scoped_ptr<GetUsageCallback> callback(callback_ptr);

[michaeln, 2011/02/09 00:25:36]

I'm fuzzy on what is common practice on chrome with regard to who is responsible
for deleting 'callback' instances. I see in FileUtilProxy, they're deleting by
the Proxy class after it has invoked them which matches the semantics you have
here.

[kinuko, 2011/02/09 05:22:36]

In this implementation I chose to make the tracker class takes the ownership of
callbacks.  It doesn't pass the callbacks to the tasks either.  Let me hear if
you have concerns on this design, thanks!

+
+  if (is_incognito_) {
+    // We don't support FileSystem in incognito mode yet.
+    callback->Run(0);
+    return;
+  }
+
+  std::string fs_name = FileSystemPathManager::GetFileSystemName(
+      origin_url, type);
+  if (pending_usage_callbacks_.find(fs_name) !=
+      pending_usage_callbacks_.end()) {
+    // Another get usage task is running.  Add the callback to
+    // the pending queue and return.
+    pending_usage_callbacks_[fs_name].push_back(callback.release());
+    return;
+  }
+
+  // Get the filesystem base path (i.e. "FileSystem/<origin>/<type>",
+  // without unique part).
+  FilePath origin_base_path =
+      FileSystemPathManager::GetFileSystemBaseDirectoryForOriginAndType(
+          base_path_, origin_url, type);
+  if (origin_base_path.empty()) {
+    // The directory does not exist.
+    callback->Run(0);
+    return;
+  }
+
+  pending_usage_callbacks_[fs_name].push_back(callback.release());
+  scoped_refptr<GetUsageTask> task(
+      new GetUsageTask(this, file_message_loop_, fs_name, origin_base_path));
+  task->Start();
+}
+
+void FileSystemUsageTracker::RegisterUsageTask(GetUsageTask* task) {
+  running_usage_tasks_.push_back(task);
+}
+
+void FileSystemUsageTracker::UnregisterUsageTask(GetUsageTask* task) {
+  DCHECK(running_usage_tasks_.front() == task);
+  running_usage_tasks_.pop_front();
+}
+
+void FileSystemUsageTracker::DidGetOriginUsage(
+    const std::string& fs_name, int64 usage) {
+  PendingUsageCallbackMap::iterator cb_list_iter =
+      pending_usage_callbacks_.find(fs_name);
+  DCHECK(cb_list_iter != pending_usage_callbacks_.end());
+  PendingCallbackList cb_list = cb_list_iter->second;
+  for (PendingCallbackList::iterator cb_iter = cb_list.begin();
+        cb_iter != cb_list.end();
+        ++cb_iter) {
+    scoped_ptr<GetUsageCallback> callback(*cb_iter);
+    callback->Run(usage);
+  }
+  pending_usage_callbacks_.erase(cb_list_iter);
+}
+
+}  // namespace fileapi