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 #include "mozIStorageStatement.h"
  44
  45
  46 /**
  47  * This class wraps a transaction inside a given C++ scope, guaranteeing that
  48  * the transaction will be completed even if you have an exception or
  49  * return early.
  50  *
  51  * aCommitOnComplete controls whether the transaction is committed or rolled
  52  * back when it goes out of scope. A common use is to create an instance with
  53  * commitOnComplete = FALSE (rollback), then call Commit on this object manually
  54  * when your function completes successfully.
  55  *
  56  * Note that nested transactions are not supported by sqlite, so if a transaction
  57  * is already in progress, this object does nothing. Note that in this case,
  58  * you may not get the transaction type you ask for, and you won't be able
  59  * to rollback.
  60  */
  61 class mozStorageTransaction
  62 {
  63 public:
  64   mozStorageTransaction(mozIStorageConnection* aConnection,
  65                         PRBool aCommitOnComplete,
  66                         PRInt32 aType = mozIStorageConnection::TRANSACTION_DEFERRED)
  67     : mConnection(aConnection),
  68       mHasTransaction(PR_FALSE),
  69       mCommitOnComplete(aCommitOnComplete),
  70       mCompleted(PR_FALSE)
  71   {
  72     // We won't try to get a transaction if one is already in progress.
  73     if (mConnection)
  74       mHasTransaction = NS_SUCCEEDED(mConnection->BeginTransactionAs(aType));
  75   }
  76   ~mozStorageTransaction()
  77   {
  78     if (mConnection && mHasTransaction && ! mCompleted) {
  79       if (mCommitOnComplete)
  80         mConnection->CommitTransaction();
  81       else
  82         mConnection->RollbackTransaction();
  83     }
  84   }
  85
  86   /**
  87    * Commits the transaction if one is in progress. If one is not in progress,
  88    * this is a NOP since the actual owner of the transaction outside of our
  89    * scope is in charge of finally comitting or rolling back the transaction.
  90    */
  91   nsresult Commit()
  92   {
  93     if (!mConnection || mCompleted)
  94       return NS_OK; // no connection, or already done
  95     mCompleted = PR_TRUE;
  96     if (! mHasTransaction)
  97       return NS_OK; // transaction not ours, ignore
  98     return mConnection->CommitTransaction();
  99   }
 100
 101   /**
 102    * Rolls back the transaction in progress. You should only call this function
 103    * if this object has a real transaction (HasTransaction() = true) because
 104    * otherwise, there is no transaction to roll back.
 105    */
 106   nsresult Rollback()
 107   {
 108     if (!mConnection || mCompleted)
 109       return NS_OK; // no connection, or already done
 110     mCompleted = PR_TRUE;
 111     if (! mHasTransaction)
 112       return NS_ERROR_FAILURE;
 113     return mConnection->RollbackTransaction();
 114   }
 115
 116   /**
 117    * Returns whether this object wraps a real transaction. False means that
 118    * this object doesn't do anything because there was already a transaction in
 119    * progress when it was created.
 120    */
 121   PRBool HasTransaction()
 122   {
 123     return mHasTransaction;
 124   }
 125
 126   /**
 127    * This sets the default action (commit or rollback) when this object goes
 128    * out of scope.
 129    */
 130   void SetDefaultAction(PRBool aCommitOnComplete)
 131   {
 132     mCommitOnComplete = aCommitOnComplete;
 133   }
 134
 135 protected:
 136   nsCOMPtr<mozIStorageConnection> mConnection;
 137   PRBool mHasTransaction;
 138   PRBool mCommitOnComplete;
 139   PRBool mCompleted;
 140 };
 141
 142
 143 /**
 144  * This class wraps a statement so that it is guaraneed to be reset when
 145  * this object goes out of scope.
 146  *
 147  * Note that this always just resets the statement. If the statement doesn't
 148  * need resetting, the reset operation is inexpensive.
 149  */
 150 class NS_STACK_CLASS mozStorageStatementScoper
 151 {
 152 public:
 153   mozStorageStatementScoper(mozIStorageStatement* aStatement)
 154       : mStatement(aStatement)
 155   {
 156   }
 157   ~mozStorageStatementScoper()
 158   {
 159     if (mStatement)
 160       mStatement->Reset();
 161   }
 162
 163   /**
 164    * Call this to make the statement not reset. You might do this if you know
 165    * that the statement has been reset.
 166    */
 167   void Abandon()
 168   {
 169     mStatement = nsnull;
 170   }
 171
 172 protected:
 173   nsCOMPtr<mozIStorageStatement> mStatement;
 174 };
 175
 176 #endif /* _MOZSTORAGEHELPER_H_ */