1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/storage/public/mozStorageHelper.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,181 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +#ifndef MOZSTORAGEHELPER_H
1.10 +#define MOZSTORAGEHELPER_H
1.11 +
1.12 +#include "nsAutoPtr.h"
1.13 +
1.14 +#include "mozIStorageAsyncConnection.h"
1.15 +#include "mozIStorageConnection.h"
1.16 +#include "mozIStorageStatement.h"
1.17 +#include "nsError.h"
1.18 +
1.19 +/**
1.20 + * This class wraps a transaction inside a given C++ scope, guaranteeing that
1.21 + * the transaction will be completed even if you have an exception or
1.22 + * return early.
1.23 + *
1.24 + * aCommitOnComplete controls whether the transaction is committed or rolled
1.25 + * back when it goes out of scope. A common use is to create an instance with
1.26 + * commitOnComplete = FALSE (rollback), then call Commit on this object manually
1.27 + * when your function completes successfully.
1.28 + *
1.29 + * Note that nested transactions are not supported by sqlite, so if a transaction
1.30 + * is already in progress, this object does nothing. Note that in this case,
1.31 + * you may not get the transaction type you ask for, and you won't be able
1.32 + * to rollback.
1.33 + *
1.34 + * Note: This class is templatized to be also usable with internal data
1.35 + * structures. External users of this class should generally use
1.36 + * |mozStorageTransaction| instead.
1.37 + */
1.38 +template<typename T, typename U>
1.39 +class mozStorageTransactionBase
1.40 +{
1.41 +public:
1.42 + mozStorageTransactionBase(T* aConnection,
1.43 + bool aCommitOnComplete,
1.44 + int32_t aType = mozIStorageConnection::TRANSACTION_DEFERRED)
1.45 + : mConnection(aConnection),
1.46 + mHasTransaction(false),
1.47 + mCommitOnComplete(aCommitOnComplete),
1.48 + mCompleted(false)
1.49 + {
1.50 + // We won't try to get a transaction if one is already in progress.
1.51 + if (mConnection)
1.52 + mHasTransaction = NS_SUCCEEDED(mConnection->BeginTransactionAs(aType));
1.53 + }
1.54 + ~mozStorageTransactionBase()
1.55 + {
1.56 + if (mConnection && mHasTransaction && ! mCompleted) {
1.57 + if (mCommitOnComplete)
1.58 + mConnection->CommitTransaction();
1.59 + else
1.60 + mConnection->RollbackTransaction();
1.61 + }
1.62 + }
1.63 +
1.64 + /**
1.65 + * Commits the transaction if one is in progress. If one is not in progress,
1.66 + * this is a NOP since the actual owner of the transaction outside of our
1.67 + * scope is in charge of finally comitting or rolling back the transaction.
1.68 + */
1.69 + nsresult Commit()
1.70 + {
1.71 + if (!mConnection || mCompleted)
1.72 + return NS_OK; // no connection, or already done
1.73 + mCompleted = true;
1.74 + if (! mHasTransaction)
1.75 + return NS_OK; // transaction not ours, ignore
1.76 + nsresult rv = mConnection->CommitTransaction();
1.77 + if (NS_SUCCEEDED(rv))
1.78 + mHasTransaction = false;
1.79 +
1.80 + return rv;
1.81 + }
1.82 +
1.83 + /**
1.84 + * Rolls back the transaction in progress. You should only call this function
1.85 + * if this object has a real transaction (HasTransaction() = true) because
1.86 + * otherwise, there is no transaction to roll back.
1.87 + */
1.88 + nsresult Rollback()
1.89 + {
1.90 + if (!mConnection || mCompleted)
1.91 + return NS_OK; // no connection, or already done
1.92 + mCompleted = true;
1.93 + if (! mHasTransaction)
1.94 + return NS_ERROR_FAILURE;
1.95 +
1.96 + // It is possible that a rollback will return busy, so we busy wait...
1.97 + nsresult rv = NS_OK;
1.98 + do {
1.99 + rv = mConnection->RollbackTransaction();
1.100 + if (rv == NS_ERROR_STORAGE_BUSY)
1.101 + (void)PR_Sleep(PR_INTERVAL_NO_WAIT);
1.102 + } while (rv == NS_ERROR_STORAGE_BUSY);
1.103 +
1.104 + if (NS_SUCCEEDED(rv))
1.105 + mHasTransaction = false;
1.106 +
1.107 + return rv;
1.108 + }
1.109 +
1.110 + /**
1.111 + * Returns whether this object wraps a real transaction. False means that
1.112 + * this object doesn't do anything because there was already a transaction in
1.113 + * progress when it was created.
1.114 + */
1.115 + bool HasTransaction()
1.116 + {
1.117 + return mHasTransaction;
1.118 + }
1.119 +
1.120 + /**
1.121 + * This sets the default action (commit or rollback) when this object goes
1.122 + * out of scope.
1.123 + */
1.124 + void SetDefaultAction(bool aCommitOnComplete)
1.125 + {
1.126 + mCommitOnComplete = aCommitOnComplete;
1.127 + }
1.128 +
1.129 +protected:
1.130 + U mConnection;
1.131 + bool mHasTransaction;
1.132 + bool mCommitOnComplete;
1.133 + bool mCompleted;
1.134 +};
1.135 +
1.136 +/**
1.137 + * An instance of the mozStorageTransaction<> family dedicated
1.138 + * to |mozIStorageConnection|.
1.139 + */
1.140 +typedef mozStorageTransactionBase<mozIStorageConnection,
1.141 + nsCOMPtr<mozIStorageConnection> >
1.142 +mozStorageTransaction;
1.143 +
1.144 +
1.145 +
1.146 +/**
1.147 + * This class wraps a statement so that it is guaraneed to be reset when
1.148 + * this object goes out of scope.
1.149 + *
1.150 + * Note that this always just resets the statement. If the statement doesn't
1.151 + * need resetting, the reset operation is inexpensive.
1.152 + */
1.153 +class MOZ_STACK_CLASS mozStorageStatementScoper
1.154 +{
1.155 +public:
1.156 + mozStorageStatementScoper(mozIStorageStatement* aStatement)
1.157 + : mStatement(aStatement)
1.158 + {
1.159 + }
1.160 + ~mozStorageStatementScoper()
1.161 + {
1.162 + if (mStatement)
1.163 + mStatement->Reset();
1.164 + }
1.165 +
1.166 + /**
1.167 + * Call this to make the statement not reset. You might do this if you know
1.168 + * that the statement has been reset.
1.169 + */
1.170 + void Abandon()
1.171 + {
1.172 + mStatement = nullptr;
1.173 + }
1.174 +
1.175 +protected:
1.176 + nsCOMPtr<mozIStorageStatement> mStatement;
1.177 +};
1.178 +
1.179 +// Use this to make queries uniquely identifiable in telemetry
1.180 +// statistics, especially PRAGMAs. We don't include __LINE__ so that
1.181 +// queries are stable in the face of source code changes.
1.182 +#define MOZ_STORAGE_UNIQUIFY_QUERY_STR "/* " __FILE__ " */ "
1.183 +
1.184 +#endif /* MOZSTORAGEHELPER_H */
