storage/mozStorageAsyncStatementExecution.h
author Jim Blandy <jimb@mozilla.com>
Tue, 12 Feb 2019 08:16:16 +0000
changeset 458932 414b2c238839c321dee78a9d927c968f1e52ae79
parent 448947 6f3709b3878117466168c40affa7bca0b60cf75b
child 472056 e1993a1f09ac53cd1a04fdf6a87f8cad8e44f73e
permissions -rw-r--r--
Bug 1145201: Replace EnqueuePromiseJobCallback and GetIncumbentGlobalCallback with new JobQueue abstract base class. r=arai,smaug While the behavior of ECMAScript Promises and their associated job queue is covered by the ECMAScript standard, the HTML specification amends that with additional behavior the web platform requires. To support this, SpiderMonkey provides hooks the embedding can set to replace SpiderMonkey's queue with its own implementation. At present, these hooks are C-style function-pointer-and-void-pointer pairs, which are awkward to handle and mistake-prone, as passing a function the wrong void* is not a type error. Later patches in this series must add new hooks, making a bad situation worse. A C++ abstract base class is a well-typed alternative. This introduces a new `JS::JobQueue` abstract class, and adapts SpiderMonkey's internal job queue and Gecko's customization to use it. `GetIncumbentGlobalCallback` and `EnqueuePromiseJobCallback` become virtual methods. Within SpiderMonkey, the patch gathers the various fields of JSContext that implement the internal queue into their own type, js::InternalJobQueue. Various jsfriendapi functions become veneers for calls to methods specific to the derived class. The InternalJobQueue type itself remains private to SpiderMonkey, as it uses types like TraceableFifo, derived from Fifo, that are not part of SpiderMonkey's public API. Within Gecko, CycleCollectedJSContext acquires JS::JobQueue as a private base class, and a few static methods are cleaned up nicely. There are a few other hooks defined in js/public/Promise.h that might make sense to turn into virtual methods on JobQueue. For example, DispatchToEventLoopCallback, used for resolving promises of results from off-main-thread tasks, is probably necessarily connected to the JobQueue implementation in use, so it might not be sensible to set one without the other. But it was left unchanged to reduce this patch's size. Differential Revision: https://phabricator.services.mozilla.com/D17544

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozStorageAsyncStatementExecution_h
#define mozStorageAsyncStatementExecution_h

#include "nscore.h"
#include "nsTArray.h"
#include "nsAutoPtr.h"
#include "mozilla/Mutex.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/Attributes.h"
#include "nsIRunnable.h"

#include "SQLiteMutex.h"
#include "mozIStoragePendingStatement.h"
#include "mozIStorageStatementCallback.h"
#include "mozStorageHelper.h"

struct sqlite3_stmt;

namespace mozilla {
namespace storage {

class Connection;
class ResultSet;
class StatementData;

class AsyncExecuteStatements final : public nsIRunnable,
                                     public mozIStoragePendingStatement {
 public:
  NS_DECL_THREADSAFE_ISUPPORTS
  NS_DECL_NSIRUNNABLE
  NS_DECL_MOZISTORAGEPENDINGSTATEMENT

  /**
   * Describes the state of execution.
   */
  enum ExecutionState {
    PENDING = -1,
    COMPLETED = mozIStorageStatementCallback::REASON_FINISHED,
    CANCELED = mozIStorageStatementCallback::REASON_CANCELED,
    ERROR = mozIStorageStatementCallback::REASON_ERROR
  };

  typedef nsTArray<StatementData> StatementDataArray;

  /**
   * Executes a statement in the background, and passes results back to the
   * caller.
   *
   * @param aStatements
   *        The statements to execute and possibly bind in the background.
   *        Ownership is transfered from the caller.
   * @param aConnection
   *        The connection that created the statements to execute.
   * @param aNativeConnection
   *        The native Sqlite connection that created the statements to execute.
   * @param aCallback
   *        The callback that is notified of results, completion, and errors.
   * @param _stmt
   *        The handle to control the execution of the statements.
   */
  static nsresult execute(StatementDataArray &aStatements,
                          Connection *aConnection, sqlite3 *aNativeConnection,
                          mozIStorageStatementCallback *aCallback,
                          mozIStoragePendingStatement **_stmt);

  /**
   * Indicates when events on the calling thread should run or not.  Certain
   * events posted back to the calling thread should call this see if they
   * should run or not.
   *
   * @pre mMutex is not held
   *
   * @returns true if the event should notify still, false otherwise.
   */
  bool shouldNotify();

  /**
   * Used by notifyComplete(), notifyError() and notifyResults() to notify on
   * the calling thread.
   */
  nsresult notifyCompleteOnCallingThread();
  nsresult notifyErrorOnCallingThread(mozIStorageError *aError);
  nsresult notifyResultsOnCallingThread(ResultSet *aResultSet);

 private:
  AsyncExecuteStatements(StatementDataArray &aStatements,
                         Connection *aConnection, sqlite3 *aNativeConnection,
                         mozIStorageStatementCallback *aCallback);
  ~AsyncExecuteStatements();

  /**
   * Binds and then executes a given statement until completion, an error
   * occurs, or we are canceled.  If aLastStatement is true, we should set
   * mState accordingly.
   *
   * @pre mMutex is not held
   *
   * @param aData
   *        The StatementData to bind, execute, and then process.
   * @param aLastStatement
   *        Indicates if this is the last statement or not.  If it is, we have
   *        to set the proper state.
   * @returns true if we should continue to process statements, false otherwise.
   */
  bool bindExecuteAndProcessStatement(StatementData &aData,
                                      bool aLastStatement);

  /**
   * Executes a given statement until completion, an error occurs, or we are
   * canceled.  If aLastStatement is true, we should set mState accordingly.
   *
   * @pre mMutex is not held
   *
   * @param aStatement
   *        The statement to execute and then process.
   * @param aLastStatement
   *        Indicates if this is the last statement or not.  If it is, we have
   *        to set the proper state.
   * @returns true if we should continue to process statements, false otherwise.
   */
  bool executeAndProcessStatement(sqlite3_stmt *aStatement,
                                  bool aLastStatement);

  /**
   * Executes a statement to completion, properly handling any error conditions.
   *
   * @pre mMutex is not held
   *
   * @param aStatement
   *        The statement to execute to completion.
   * @returns true if results were obtained, false otherwise.
   */
  bool executeStatement(sqlite3_stmt *aStatement);

  /**
   * Builds a result set up with a row from a given statement.  If we meet the
   * right criteria, go ahead and notify about this results too.
   *
   * @pre mMutex is not held
   *
   * @param aStatement
   *        The statement to get the row data from.
   */
  nsresult buildAndNotifyResults(sqlite3_stmt *aStatement);

  /**
   * Notifies callback about completion, and does any necessary cleanup.
   *
   * @pre mMutex is not held
   */
  nsresult notifyComplete();

  /**
   * Notifies callback about an error.
   *
   * @pre mMutex is not held
   * @pre mDBMutex is not held
   *
   * @param aErrorCode
   *        The error code defined in mozIStorageError for the error.
   * @param aMessage
   *        The error string, if any.
   * @param aError
   *        The error object to notify the caller with.
   */
  nsresult notifyError(int32_t aErrorCode, const char *aMessage);
  nsresult notifyError(mozIStorageError *aError);

  /**
   * Notifies the callback about a result set.
   *
   * @pre mMutex is not held
   */
  nsresult notifyResults();

  /**
   * Tests whether the current statements should be wrapped in an explicit
   * transaction.
   *
   * @return true if an explicit transaction is needed, false otherwise.
   */
  bool statementsNeedTransaction();

  StatementDataArray mStatements;
  RefPtr<Connection> mConnection;
  sqlite3 *mNativeConnection;
  bool mHasTransaction;
  // Note, this may not be a threadsafe object - never addref/release off
  // the calling thread.  We take a reference when this is created, and
  // release it in the CompletionNotifier::Run() call back to this thread.
  nsCOMPtr<mozIStorageStatementCallback> mCallback;
  nsCOMPtr<nsIThread> mCallingThread;
  RefPtr<ResultSet> mResultSet;

  /**
   * The maximum amount of time we want to wait between results.  Defined by
   * MAX_MILLISECONDS_BETWEEN_RESULTS and set at construction.
   */
  const TimeDuration mMaxWait;

  /**
   * The start time since our last set of results.
   */
  TimeStamp mIntervalStart;

  /**
   * Indicates our state of execution.
   */
  ExecutionState mState;

  /**
   * Indicates if we should try to cancel at a cancelation point.
   */
  bool mCancelRequested;

  /**
   * This is the mutex that protects our state from changing between threads.
   * This includes the following variables:
   *   - mCancelRequested is only set on the calling thread while the lock is
   *     held.  It is always read from within the lock on the background thread,
   *     but not on the calling thread (see shouldNotify for why).
   */
  Mutex &mMutex;

  /**
   * The wrapped SQLite recursive connection mutex.  We use it whenever we call
   * sqlite3_step and care about having reliable error messages.  By taking it
   * prior to the call and holding it until the point where we no longer care
   * about the error message, the user gets reliable error messages.
   */
  SQLiteMutex &mDBMutex;

  /**
   * The instant at which the request was started.
   *
   * Used by telemetry.
   */
  TimeStamp mRequestStartDate;
};

}  // namespace storage
}  // namespace mozilla

#endif  // mozStorageAsyncStatementExecution_h