Finalize a CL originally by departed intern ycxiao@ that detaches the loading of cookies from the...

chrome/browser/net/sqlite_persistent_cookie_store.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 "chrome/browser/net/sqlite_persistent_cookie_store.h"
 
 #include <list>
 
 #include "base/basictypes.h"
+#include "base/bind.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram.h"
 #include "base/string_util.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_restrictions.h"
 #include "chrome/browser/diagnostics/sqlite_diagnostics.h"
 #include "content/browser/browser_thread.h"
 #include "googleurl/src/gurl.h"
 #include "sql/meta_table.h"
 #include "sql/statement.h"
 #include "sql/transaction.h"
 
 using base::Time;
 
 // This class is designed to be shared between any calling threads and the
 // database thread.  It batches operations and commits them on a timer.

[Randy Smith (Not in Mondays), 2011/09/07 19:04:07]

nit: Could you add a comment here about thread access?  This class is accessed
on multiple threads, and a couple of member functions are protected by locks,
and at least one (db_) is protected by serialization (though less so than it
used to be) and I'd feel easier if there was a comment somewhere that summarized
all of that.

[erikwright (departed), 2011/09/08 02:48:58]

I hope my new comment seems an improvement to you. db_ should no longer be
accessed off the DB thread (except a DCHECK in Load() on db_ == NULL).

There is an implementation comment on lock_ regarding the members it protects.

 class SQLitePersistentCookieStore::Backend
     : public base::RefCountedThreadSafe<SQLitePersistentCookieStore::Backend> {
  public:
   explicit Backend(const FilePath& path)
       : path_(path),
         db_(NULL),
         num_pending_(0),
         clear_local_state_on_exit_(false) {
   }
 
   // Creates or load the SQLite database.
-  bool Load(std::vector<net::CookieMonster::CanonicalCookie*>* cookies);
+  bool Load(const LoadedCallback& loaded_callback);
 
   // Batch a cookie addition.
   void AddCookie(const net::CookieMonster::CanonicalCookie& cc);
 
   // Batch a cookie access time update.
   void UpdateCookieAccessTime(const net::CookieMonster::CanonicalCookie& cc);
 
   // Batch a cookie deletion.
   void DeleteCookie(const net::CookieMonster::CanonicalCookie& cc);
 
@@ skipping 32 matching lines @@
 
     OperationType op() const { return op_; }
     const net::CookieMonster::CanonicalCookie& cc() const { return cc_; }
 
    private:
     OperationType op_;
     net::CookieMonster::CanonicalCookie cc_;
   };
 
  private:
+  // Creates or load the SQLite database on DB thread.
+  void LoadAndNotifyOnDBThread(const LoadedCallback& loaded_callback);
+  // Notify the CookieMonster when loading complete.
+  void NotifyOnIOThread(
+      const LoadedCallback& loaded_callback,
+      bool load_success,
+      const std::vector<net::CookieMonster::CanonicalCookie*>& cookies);
+  // Initialize the data base.
+  bool InitializeDatabase();
+  // Load cookies to the data base, and read cookies.
+  bool LoadInternal(std::vector<net::CookieMonster::CanonicalCookie*>* cookies);
+
   // Batch a cookie operation (add or delete)
   void BatchOperation(PendingOperation::OperationType op,
                       const net::CookieMonster::CanonicalCookie& cc);
   // Commit our pending operations to the database.
   void Commit();
   // Close() executed on the background thread.
   void InternalBackgroundClose();
 
   FilePath path_;
   scoped_ptr<sql::Connection> db_;
@@ skipping 43 matching lines @@
   // Try to create the index every time. Older versions did not have this index,
   // so we want those people to get it. Ignore errors, since it may exist.
   db->Execute("CREATE INDEX IF NOT EXISTS cookie_times ON cookies"
               " (creation_utc)");
   return true;
 }
 
 }  // namespace
 
 bool SQLitePersistentCookieStore::Backend::Load(
-    std::vector<net::CookieMonster::CanonicalCookie*>* cookies) {
+    const LoadedCallback& loaded_callback) {
   // This function should be called only once per instance.
   DCHECK(!db_.get());
+  BrowserThread::PostTask(
+      BrowserThread::DB, FROM_HERE,
+      base::Bind(&Backend::LoadAndNotifyOnDBThread, base::Unretained(this),
+                 loaded_callback));
+  return true;
+}
 
-  // Ensure the parent directory for storing cookies is created before reading
-  // from it.  We make an exception to allow IO on the UI thread here because
-  // we are going to disk anyway in db_->Open.  (This code will be moved to the
-  // DB thread as part of http://crbug.com/52909.)
-  {
-    base::ThreadRestrictions::ScopedAllowIO allow_io;
-    const FilePath dir = path_.DirName();
-    if (!file_util::PathExists(dir) && !file_util::CreateDirectory(dir))
-      return false;
+void SQLitePersistentCookieStore::Backend::LoadAndNotifyOnDBThread(
+    const LoadedCallback& loaded_callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::DB));
+  std::vector<net::CookieMonster::CanonicalCookie*> cookies;
+
+  bool load_success = LoadInternal(&cookies);
+
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE, base::Bind(
+      &SQLitePersistentCookieStore::Backend::NotifyOnIOThread,
+      base::Unretained(this), loaded_callback, load_success, cookies));
+}
+
+void SQLitePersistentCookieStore::Backend::NotifyOnIOThread(
+    const LoadedCallback& loaded_callback,
+    bool load_success,
+    const std::vector<net::CookieMonster::CanonicalCookie*>& cookies) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  loaded_callback.Run(cookies);
+}
+
+bool SQLitePersistentCookieStore::Backend::InitializeDatabase() {
+  const FilePath dir = path_.DirName();
+  if (!file_util::PathExists(dir) && !file_util::CreateDirectory(dir)) {
+    return false;
   }
 
   db_.reset(new sql::Connection);
   if (!db_->Open(path_)) {
     NOTREACHED() << "Unable to open cookie DB.";
     db_.reset();
     return false;
   }
 
   db_->set_error_delegate(GetErrorHandlerForCookieDb());
 
   if (!EnsureDatabaseVersion() || !InitTable(db_.get())) {
     NOTREACHED() << "Unable to open cookie DB.";
     db_.reset();
     return false;
   }
 
   db_->Preload();
+  return true;
+}
+
+bool SQLitePersistentCookieStore::Backend::LoadInternal(
+    std::vector<net::CookieMonster::CanonicalCookie*>* cookies) {
+  if (!InitializeDatabase()) {
+    return false;
+  }
 
   // Slurp all the cookies into the out-vector.
   sql::Statement smt(db_->GetUniqueStatement(
       "SELECT creation_utc, host_key, name, value, path, expires_utc, secure, "
       "httponly, last_access_utc FROM cookies"));
   if (!smt) {
     NOTREACHED() << "select statement prep failed";
     db_.reset();
     return false;
   }
@@ skipping 267 matching lines @@
     file_util::Delete(path_, false);
 }
 
 void SQLitePersistentCookieStore::Backend::SetClearLocalStateOnExit(
     bool clear_local_state) {
   base::AutoLock locked(lock_);
   clear_local_state_on_exit_ = clear_local_state;
 }
 SQLitePersistentCookieStore::SQLitePersistentCookieStore(const FilePath& path)
     : backend_(new Backend(path)) {
+  DCHECK(!BrowserThread::CurrentlyOn(BrowserThread::DB));
 }
 
 SQLitePersistentCookieStore::~SQLitePersistentCookieStore() {
   if (backend_.get()) {
     backend_->Close();
     // Release our reference, it will probably still have a reference if the
     // background thread has not run Close() yet.
     backend_ = NULL;
   }
 }
 
-bool SQLitePersistentCookieStore::Load(
-    std::vector<net::CookieMonster::CanonicalCookie*>* cookies) {
-  return backend_->Load(cookies);
+bool SQLitePersistentCookieStore::Load(const LoadedCallback& loaded_callback) {
+  return backend_->Load(loaded_callback);
 }
 
 void SQLitePersistentCookieStore::AddCookie(
     const net::CookieMonster::CanonicalCookie& cc) {
   if (backend_.get())
     backend_->AddCookie(cc);
 }
 
 void SQLitePersistentCookieStore::UpdateCookieAccessTime(
     const net::CookieMonster::CanonicalCookie& cc) {
@@ skipping 12 matching lines @@
   if (backend_.get())
     backend_->SetClearLocalStateOnExit(clear_local_state);
 }
 
 void SQLitePersistentCookieStore::Flush(Task* completion_task) {
   if (backend_.get())
     backend_->Flush(completion_task);
   else if (completion_task)
     MessageLoop::current()->PostTask(FROM_HERE, completion_task);
 }