gecko/storage/src/mozStorageAsyncStatementExecution.h

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 * Contributor(s):
 *   Shawn Wilsher <me@shawnwilsher.com> (Original Author)
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#ifndef _mozStorageAsyncStatementExecution_h_
#define _mozStorageAsyncStatementExecution_h_

#include "nscore.h"
#include "nsTArray.h"
#include "nsAutoPtr.h"
#include "nsThreadUtils.h"

#include "mozIStoragePendingStatement.h"
#include "mozIStorageStatementCallback.h"

struct sqlite3_stmt;
class mozStorageTransaction;
class mozStorageResultSet;

namespace mozilla {
namespace storage {

class Connection;

class AsyncExecuteStatements : public nsIRunnable
                             , public mozIStoragePendingStatement
{
public:
  NS_DECL_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<sqlite3_stmt *> sqlite3_stmt_array;

  /**
   * Executes a statement in the background, and passes results back to the
   * caller.
   *
   * @param aStatements
   *        The SQLite statements to execute in the background.  Ownership is
   *        transfered from the caller.
   * @param aConnection
   *        The 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(sqlite3_stmt_array &aStatements,
                          Connection *aConnection,
                          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.
   *
   * @returns true if the event should notify still, false otherwise.
   */
  bool shouldNotify();

private:
  AsyncExecuteStatements(sqlite3_stmt_array &aStatements,
                         mozIStorageConnection *aConnection,
                         mozIStorageStatementCallback *aCallback);

  /**
   * Initializes the object so it can be run on the background thread.
   */
  nsresult initialize();

  ~AsyncExecuteStatements();

  /**
   * Executes a given statement until completion, an error occurs, or we are
   * canceled.  If aLastStatement is true, we should set mState accordingly.
   *
   * @pre mLock 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);

  /**
   * 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 mLock is 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 mLock is not held
   */
  nsresult notifyComplete();

  /**
   * Notifies callback about an error.
   *
   * @pre mLock is not held
   *
   * @param aErrorCode
   *        The error code defined in mozIStorageError for the error.
   * @param aMessage
   *        The error string, if any.
   */
  nsresult notifyError(PRInt32 aErrorCode, const char *aMessage);

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

  sqlite3_stmt_array mStatements;
  mozIStorageConnection *mConnection;
  mozStorageTransaction *mTransactionManager;
  mozIStorageStatementCallback *mCallback;
  nsCOMPtr<nsIThread> mCallingThread;
  nsRefPtr<mozStorageResultSet> mResultSet;

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

  /**
   * The start time since our last set of results.
   */
  PRIntervalTime 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 tat protects our state from changing between threads.
   * This includes the following variables:
   *   - mState
   *   - 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).
   */
  PRLock *mLock;
};

} // namespace storage
} // namespace mozilla

#endif // _mozStorageAsyncStatementExecution_h_