qsql: apply Qt's PIMPL idiom to Q*ResultPrivate

QResult and QResultPrivate are not derived from QObject and
QObjectPrivate respectively, but can still benefit from Qt's
PIMPL idiom. There are several interrelated aspects to this:

  - Base all driver ResultPrivate classes on QResultPrivate.
    Previously, each level in the Result hierarchy tended to keep
    its own private data class.

  - The ResultPrivate class initializes its own Result (q_ptr)
    and Driver members. This ensures that these pointers are
    correctly set in time for the ResultPrivate constructors
    and Result constructors. This is more efficient and makes
    it a lot easier to follow what's being allocated, initialized,
    and cleaned-up.

  - Use macros Q_DECLARE_PRIVATE, Q_DECLARE_PUBLIC, Q_D, and
    Q_Q for access to and from ResultPrivate objects.

  - ResultPrivate classes refer frequently to their counterpart
    DriverPrivate. Various patterns were used to do this. Now
    Q_DECLARE_SQLDRIVER_PRIVATE arranges this uniformly while
    hiding ugly casting. It creates a public method in the
    ResultPrivate returning the correctly typed pointer to the
    corresponding DriverPrivate object. Since the method is public,
    the Result class and helper classes and functions can also use it.

  - The explicit const is removed from QResultPrivate::sqldriver,
    even though it is treated (mostly) like a const within the
    context of Result and ResultPrivate. This is the same pattern
    seen in Qt's PIMPL idiom. The macro created getter methods
    take care of const.

  - qsql_mysql was using a signal/slot connection to zero its own
    copy of the driver pointer when the driver was destroyed. This is
    no longer necessary.

Change-Id: Ida4933bc92fb3e9a05ea4b53b48085894734e36e
Reviewed-by: Israel Lins Albuquerque <israelins85@yahoo.com.br>
Reviewed-by: Mark Brand <mabrand@mabrand.nl>

2 files changed, 35 insertions, 16 deletions

diff --git a/src/sql/drivers/db2/qsql_db2.cpp b/src/sql/drivers/db2/qsql_db2.cpp
index 48cf41e562..cc16a68916 100644
--- a/src/sql/drivers/db2/qsql_db2.cpp
+++ b/src/sql/drivers/db2/qsql_db2.cpp
@@ -66,6 +66,8 @@ static const SQLSMALLINT qParamType[4] = { SQL_PARAM_INPUT, SQL_PARAM_INPUT, SQL
 
 class QDB2DriverPrivate : public QSqlDriverPrivate
 {
+    Q_DECLARE_PUBLIC(QDB2Driver)
+
 public:
     QDB2DriverPrivate() : QSqlDriverPrivate(), hEnv(0), hDbc(0) { dbmsType = QSqlDriver::DB2; }
     SQLHANDLE hEnv;
@@ -77,8 +79,10 @@ class QDB2ResultPrivate;
 
 class QDB2Result: public QSqlResult
 {
+    Q_DECLARE_PRIVATE(QDB2Result)
+
 public:
-    QDB2Result(const QDB2Driver *dr, const QDB2DriverPrivate *dp);
+    QDB2Result(const QDB2Driver *drv);
     ~QDB2Result();
     bool prepare(const QString &query) Q_DECL_OVERRIDE;
     bool exec() Q_DECL_OVERRIDE;
@@ -98,15 +102,17 @@ protected:
     void virtual_hook(int id, void *data) Q_DECL_OVERRIDE;
     void detachFromResultSet() Q_DECL_OVERRIDE;
     bool nextResult() Q_DECL_OVERRIDE;
-
-private:
-    QDB2ResultPrivate *d;
 };
 
-class QDB2ResultPrivate
+class QDB2ResultPrivate: public QSqlResultPrivate
 {
+    Q_DECLARE_PUBLIC(QDB2Result)
+
 public:
-    QDB2ResultPrivate(const QDB2DriverPrivate* d): dp(d), hStmt(0)
+    Q_DECLARE_SQLDRIVER_PRIVATE(QDB2Driver)
+    QDB2ResultPrivate(QDB2Result *q, const QDB2Driver *drv)
+        : QSqlResultPrivate(q, drv),
+          hStmt(0)
     {}
     ~QDB2ResultPrivate()
     {
@@ -125,7 +131,6 @@ public:
         valueCache.clear();
     }
 
-    const QDB2DriverPrivate* dp;
     SQLHANDLE hStmt;
     QSqlRecord recInf;
     QVector<QVariant*> valueCache;
@@ -171,8 +176,8 @@ static QString qDB2Warn(const QDB2DriverPrivate* d)
 
 static QString qDB2Warn(const QDB2ResultPrivate* d)
 {
-    return (qWarnDB2Handle(SQL_HANDLE_ENV, d->dp->hEnv) + QLatin1Char(' ')
-             + qWarnDB2Handle(SQL_HANDLE_DBC, d->dp->hDbc)
+    return (qWarnDB2Handle(SQL_HANDLE_ENV, d->drv_d_func()->hEnv) + QLatin1Char(' ')
+             + qWarnDB2Handle(SQL_HANDLE_DBC, d->drv_d_func()->hDbc)
              + qWarnDB2Handle(SQL_HANDLE_STMT, d->hStmt));
 }
 
@@ -497,7 +502,7 @@ static bool qMakeStatement(QDB2ResultPrivate* d, bool forwardOnly, bool setForwa
     SQLRETURN r;
     if (!d->hStmt) {
         r = SQLAllocHandle(SQL_HANDLE_STMT,
-                            d->dp->hDbc,
+                            d->drv_d_func()->hDbc,
                             &d->hStmt);
         if (r != SQL_SUCCESS) {
             qSqlWarning(QLatin1String("QDB2Result::reset: Unable to allocate statement handle"), d);
@@ -536,30 +541,31 @@ static bool qMakeStatement(QDB2ResultPrivate* d, bool forwardOnly, bool setForwa
 
 QVariant QDB2Result::handle() const
 {
+    Q_D(const QDB2Result);
     return QVariant(qRegisterMetaType<SQLHANDLE>("SQLHANDLE"), &d->hStmt);
 }
 
 /************************************/
 
-QDB2Result::QDB2Result(const QDB2Driver* dr, const QDB2DriverPrivate* dp)
-    : QSqlResult(dr)
+QDB2Result::QDB2Result(const QDB2Driver *drv)
+    : QSqlResult(*new QDB2ResultPrivate(this, drv))
 {
-    d = new QDB2ResultPrivate(dp);
 }
 
 QDB2Result::~QDB2Result()
 {
+    Q_D(const QDB2Result);
     if (d->hStmt) {
         SQLRETURN r = SQLFreeHandle(SQL_HANDLE_STMT, d->hStmt);
         if (r != SQL_SUCCESS)
             qSqlWarning(QLatin1String("QDB2Driver: Unable to free statement handle ")
                         + QString::number(r), d);
     }
-    delete d;
 }
 
 bool QDB2Result::reset (const QString& query)
 {
+    Q_D(QDB2Result);
     setActive(false);
     setAt(QSql::BeforeFirstRow);
     SQLRETURN r;
@@ -596,6 +602,7 @@ bool QDB2Result::reset (const QString& query)
 
 bool QDB2Result::prepare(const QString& query)
 {
+    Q_D(QDB2Result);
     setActive(false);
     setAt(QSql::BeforeFirstRow);
     SQLRETURN r;
@@ -620,6 +627,7 @@ bool QDB2Result::prepare(const QString& query)
 
 bool QDB2Result::exec()
 {
+    Q_D(QDB2Result);
     QList<QByteArray> tmpStorage; // holds temporary ptrs
     QVarLengthArray<SQLINTEGER, 32> indicators(boundValues().count());
 
@@ -871,6 +879,7 @@ bool QDB2Result::exec()
 
 bool QDB2Result::fetch(int i)
 {
+    Q_D(QDB2Result);
     if (isForwardOnly() && i < at())
         return false;
     if (i == at())
@@ -905,6 +914,7 @@ bool QDB2Result::fetch(int i)
 
 bool QDB2Result::fetchNext()
 {
+    Q_D(QDB2Result);
     SQLRETURN r;
     d->clearValueCache();
     r = SQLFetchScroll(d->hStmt,
@@ -922,6 +932,7 @@ bool QDB2Result::fetchNext()
 
 bool QDB2Result::fetchFirst()
 {
+    Q_D(QDB2Result);
     if (isForwardOnly() && at() != QSql::BeforeFirstRow)
         return false;
     if (isForwardOnly())
@@ -943,6 +954,7 @@ bool QDB2Result::fetchFirst()
 
 bool QDB2Result::fetchLast()
 {
+    Q_D(QDB2Result);
     d->clearValueCache();
 
     int i = at();
@@ -974,6 +986,7 @@ bool QDB2Result::fetchLast()
 
 QVariant QDB2Result::data(int field)
 {
+    Q_D(QDB2Result);
     if (field >= d->recInf.count()) {
         qWarning("QDB2Result::data: column %d out of range", field);
         return QVariant();
@@ -1080,6 +1093,7 @@ QVariant QDB2Result::data(int field)
 
 bool QDB2Result::isNull(int i)
 {
+    Q_D(const QDB2Result);
     if (i >= d->valueCache.size())
         return true;
 
@@ -1090,6 +1104,7 @@ bool QDB2Result::isNull(int i)
 
 int QDB2Result::numRowsAffected()
 {
+    Q_D(const QDB2Result);
     SQLINTEGER affectedRowCount = 0;
     SQLRETURN r = SQLRowCount(d->hStmt, &affectedRowCount);
     if (r == SQL_SUCCESS || r == SQL_SUCCESS_WITH_INFO)
@@ -1106,6 +1121,7 @@ int QDB2Result::size()
 
 QSqlRecord QDB2Result::record() const
 {
+    Q_D(const QDB2Result);
     if (isActive())
         return d->recInf;
     return QSqlRecord();
@@ -1113,6 +1129,7 @@ QSqlRecord QDB2Result::record() const
 
 bool QDB2Result::nextResult()
 {
+    Q_D(QDB2Result);
     setActive(false);
     setAt(QSql::BeforeFirstRow);
     d->recInf.clear();
@@ -1148,6 +1165,7 @@ void QDB2Result::virtual_hook(int id, void *data)
 
 void QDB2Result::detachFromResultSet()
 {
+    Q_D(QDB2Result);
     if (d->hStmt)
         SQLCloseCursor(d->hStmt);
 }
@@ -1309,8 +1327,7 @@ void QDB2Driver::close()
 
 QSqlResult *QDB2Driver::createResult() const
 {
-    Q_D(const QDB2Driver);
-    return new QDB2Result(this, d);
+    return new QDB2Result(this);
 }
 
 QSqlRecord QDB2Driver::record(const QString& tableName) const
diff --git a/src/sql/drivers/db2/qsql_db2_p.h b/src/sql/drivers/db2/qsql_db2_p.h
index 5f062965f0..0b07456122 100644
--- a/src/sql/drivers/db2/qsql_db2_p.h
+++ b/src/sql/drivers/db2/qsql_db2_p.h
@@ -63,6 +63,8 @@ class Q_EXPORT_SQLDRIVER_DB2 QDB2Driver : public QSqlDriver
 {
     Q_DECLARE_PRIVATE(QDB2Driver)
     Q_OBJECT
+    friend class QDB2ResultPrivate;
+
 public:
     explicit QDB2Driver(QObject* parent = 0);
     QDB2Driver(Qt::HANDLE env, Qt::HANDLE con, QObject* parent = 0);