storage/public/mozStorageHelper.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* ***** BEGIN LICENSE BLOCK *****
   3  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   4  *
   5  * The contents of this file are subject to the Mozilla Public License Version
   6  * 1.1 (the "License"); you may not use this file except in compliance with
   7  * the License. You may obtain a copy of the License at
   8  * http://www.mozilla.org/MPL/
   9  *
  10  * Software distributed under the License is distributed on an "AS IS" basis,
  11  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  12  * for the specific language governing rights and limitations under the
  13  * License.
  14  *
  15  * The Original Code is Storage code
  16  *
  17  * The Initial Developer of the Original Code is
  18  * Google Inc.
  19  * Portions created by the Initial Developer are Copyright (C) 2005
  20  * the Initial Developer. All Rights Reserved.
  21  *
  22  * Contributor(s):
  23  *   Brett Wilson <brettw@gmail.com>
  24  *
  25  * Alternatively, the contents of this file may be used under the terms of
  26  * either the GNU General Public License Version 2 or later (the "GPL"), or
  27  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  28  * in which case the provisions of the GPL or the LGPL are applicable instead
  29  * of those above. If you wish to allow use of your version of this file only
  30  * under the terms of either the GPL or the LGPL, and not to allow others to
  31  * use your version of this file under the terms of the MPL, indicate your
  32  * decision by deleting the provisions above and replace them with the notice
  33  * and other provisions required by the GPL or the LGPL. If you do not delete
  34  * the provisions above, a recipient may use your version of this file under
  35  * the terms of any one of the MPL, the GPL or the LGPL.
  36  *
  37  * ***** END LICENSE BLOCK ***** */
  38
  39 #ifndef _MOZSTORAGEHELPER_H_
  40 #define _MOZSTORAGEHELPER_H_
  41
  42 #include "mozIStorageConnection.h"
  43
  44
  45 /**
  46  * This class wraps a transaction inside a given C++ scope, guaranteeing that
  47  * the transaction will be completed even if you have an exception or
  48  * return early.
  49  *
  50  * aCommitOnComplete controls whether the transaction is committed or rolled
  51  * back when it goes out of scope. A common use is to create an instance with
  52  * commitOnComplete = FALSE (rollback), then call Commit on this object manually
  53  * when your function completes successfully.
  54  *
  55  * Note that nested transactions are not supported by sqlite, so if a transaction
  56  * is already in progress, this object does nothing. Note that in this case,
  57  * you may not get the transaction type you ask for, and you won't be able
  58  * to rollback.
  59  */
  60 class mozStorageTransaction
  61 {
  62 public:
  63   mozStorageTransaction(mozIStorageConnection* aConnection,
  64                         PRBool aCommitOnComplete,
  65                         PRInt32 aType = mozIStorageConnection::TRANSACTION_DEFERRED)
  66     : mConnection(aConnection),
  67       mHasTransaction(PR_FALSE),
  68       mCommitOnComplete(aCommitOnComplete),
  69       mCompleted(PR_FALSE)
  70   {
  71     if (mConnection) {
  72       PRBool transactionInProgress = PR_FALSE;
  73       mConnection->GetTransactionInProgress(&transactionInProgress);
  74       mHasTransaction = ! transactionInProgress;
  75       if (mHasTransaction)
  76         mConnection->BeginTransactionAs(aType);
  77     }
  78   }
  79   ~mozStorageTransaction()
  80   {
  81     if (mConnection && mHasTransaction && ! mCompleted) {
  82       if (mCommitOnComplete)
  83         mConnection->CommitTransaction();
  84       else
  85         mConnection->RollbackTransaction();
  86     }
  87   }
  88
  89   /**
  90    * Commits the transaction if one is in progress. If one is not in progress,
  91    * this is a NOP since the actual owner of the transaction outside of our
  92    * scope is in charge of finally comitting or rolling back the transaction.
  93    */
  94   nsresult Commit()
  95   {
  96     if (!mConnection || mCompleted)
  97       return NS_OK; // no connection, or already done
  98     mCompleted = PR_TRUE;
  99     if (! mHasTransaction)
 100       return NS_OK; // transaction not ours, ignore
 101     return mConnection->CommitTransaction();
 102   }
 103
 104   /**
 105    * Rolls back the transaction in progress. You should only call this function
 106    * if this object has a real transaction (HasTransaction() = true) because
 107    * otherwise, there is no transaction to roll back.
 108    */
 109   nsresult Rollback()
 110   {
 111     if (!mConnection || mCompleted)
 112       return NS_OK; // no connection, or already done
 113     mCompleted = PR_TRUE;
 114     if (! mHasTransaction)
 115       return NS_ERROR_FAILURE;
 116     return mConnection->RollbackTransaction();
 117   }
 118
 119   /**
 120    * Returns whether this object wraps a real transaction. False means that
 121    * this object doesn't do anything because there was already a transaction in
 122    * progress when it was created.
 123    */
 124   PRBool HasTransaction()
 125   {
 126     return mHasTransaction;
 127   }
 128
 129   /**
 130    * This sets the default action (commit or rollback) when this object goes
 131    * out of scope.
 132    */
 133   void SetDefaultAction(PRBool aCommitOnComplete)
 134   {
 135     mCommitOnComplete = aCommitOnComplete;
 136   }
 137
 138 protected:
 139   nsCOMPtr<mozIStorageConnection> mConnection;
 140   PRBool mHasTransaction;
 141   PRBool mCommitOnComplete;
 142   PRBool mCompleted;
 143 };
 144
 145
 146 /**
 147  * This class wraps a statement so that it is guaraneed to be reset when
 148  * this object goes out of scope.
 149  *
 150  * Note that this always just resets the statement. If the statement doesn't
 151  * need resetting, the reset operation is inexpensive.
 152  */
 153 class NS_STACK_CLASS mozStorageStatementScoper
 154 {
 155 public:
 156   mozStorageStatementScoper(mozIStorageStatement* aStatement)
 157       : mStatement(aStatement)
 158   {
 159   }
 160   ~mozStorageStatementScoper()
 161   {
 162     if (mStatement)
 163       mStatement->Reset();
 164   }
 165
 166   /**
 167    * Call this to make the statement not reset. You might do this if you know
 168    * that the statement has been reset.
 169    */
 170   void Abandon()
 171   {
 172     mStatement = nsnull;
 173   }
 174
 175 protected:
 176   nsCOMPtr<mozIStorageStatement> mStatement;
 177 };
 178
 179 #endif /* _MOZSTORAGEHELPER_H_ */