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>

1 files changed, 31 insertions, 14 deletions

diff --git a/src/sql/drivers/sqlite2/qsql_sqlite2.cpp b/src/sql/drivers/sqlite2/qsql_sqlite2.cpp
index 98438708b9..a170cb90be 100644
--- a/src/sql/drivers/sqlite2/qsql_sqlite2.cpp
+++ b/src/sql/drivers/sqlite2/qsql_sqlite2.cpp
@@ -77,6 +77,8 @@ static QVariant::Type nameToType(const QString& typeName)
 
 class QSQLite2DriverPrivate : public QSqlDriverPrivate
 {
+    Q_DECLARE_PUBLIC(QSQLite2Driver)
+
 public:
     QSQLite2DriverPrivate();
     sqlite *access;
@@ -93,8 +95,9 @@ class QSQLite2ResultPrivate;
 
 class QSQLite2Result : public QSqlCachedResult
 {
+    Q_DECLARE_PRIVATE(QSQLite2Result)
     friend class QSQLite2Driver;
-    friend class QSQLite2ResultPrivate;
+
 public:
     explicit QSQLite2Result(const QSQLite2Driver* db);
     ~QSQLite2Result();
@@ -108,15 +111,15 @@ protected:
     QSqlRecord record() const Q_DECL_OVERRIDE;
     void detachFromResultSet() Q_DECL_OVERRIDE;
     void virtual_hook(int id, void *data) Q_DECL_OVERRIDE;
-
-private:
-    QSQLite2ResultPrivate* d;
 };
 
-class QSQLite2ResultPrivate
+class QSQLite2ResultPrivate: public QSqlCachedResultPrivate
 {
+    Q_DECLARE_PUBLIC(QSQLite2Result)
+
 public:
-    QSQLite2ResultPrivate(QSQLite2Result *res);
+    Q_DECLARE_SQLDRIVER_PRIVATE(QSQLite2Driver);
+    QSQLite2ResultPrivate(QSQLite2Result *q, const QSQLite2Driver *drv);
     void cleanup();
     bool fetchNext(QSqlCachedResult::ValueCache &values, int idx, bool initialFetch);
     bool isSelect();
@@ -124,7 +127,6 @@ public:
     void init(const char **cnames, int numCols);
     void finalize();
 
-    QSQLite2Result* q;
     sqlite *access;
 
     // and we have too keep our own struct for the data (sqlite works via
@@ -141,13 +143,19 @@ public:
 
 static const uint initial_cache_size = 128;
 
-QSQLite2ResultPrivate::QSQLite2ResultPrivate(QSQLite2Result* res) : q(res), access(0), currentTail(0),
-    currentMachine(0), skippedStatus(false), skipRow(false), utf8(false)
+QSQLite2ResultPrivate::QSQLite2ResultPrivate(QSQLite2Result *q, const QSQLite2Driver *drv)
+    : QSqlCachedResultPrivate(q, drv),
+      currentTail(0),
+      currentMachine(0),
+      skippedStatus(false),
+      skipRow(false),
+      utf8(false)
 {
 }
 
 void QSQLite2ResultPrivate::cleanup()
 {
+    Q_Q(QSQLite2Result);
     finalize();
     rInf.clear();
     currentTail = 0;
@@ -161,6 +169,7 @@ void QSQLite2ResultPrivate::cleanup()
 
 void QSQLite2ResultPrivate::finalize()
 {
+    Q_Q(QSQLite2Result);
     if (!currentMachine)
         return;
 
@@ -178,6 +187,7 @@ void QSQLite2ResultPrivate::finalize()
 // called on first fetch
 void QSQLite2ResultPrivate::init(const char **cnames, int numCols)
 {
+    Q_Q(QSQLite2Result);
     if (!cnames)
         return;
 
@@ -204,6 +214,7 @@ void QSQLite2ResultPrivate::init(const char **cnames, int numCols)
 
 bool QSQLite2ResultPrivate::fetchNext(QSqlCachedResult::ValueCache &values, int idx, bool initialFetch)
 {
+    Q_Q(QSQLite2Result);
     // may be caching.
     const char **fvals;
     const char **cnames;
@@ -270,17 +281,17 @@ bool QSQLite2ResultPrivate::fetchNext(QSqlCachedResult::ValueCache &values, int
 }
 
 QSQLite2Result::QSQLite2Result(const QSQLite2Driver* db)
-: QSqlCachedResult(db)
+    : QSqlCachedResult(*new QSQLite2ResultPrivate(this, db))
 {
-    d = new QSQLite2ResultPrivate(this);
-    d->access = db->d_func()->access;
-    d->utf8 = db->d_func()->utf8;
+    Q_D(QSQLite2Result);
+    d->access = d->drv_d_func()->access;
+    d->utf8 = d->drv_d_func()->utf8;
 }
 
 QSQLite2Result::~QSQLite2Result()
 {
+    Q_D(QSQLite2Result);
     d->cleanup();
-    delete d;
 }
 
 void QSQLite2Result::virtual_hook(int id, void *data)
@@ -293,6 +304,7 @@ void QSQLite2Result::virtual_hook(int id, void *data)
 */
 bool QSQLite2Result::reset (const QString& query)
 {
+    Q_D(QSQLite2Result);
     // this is where we build a query.
     if (!driver())
         return false;
@@ -336,6 +348,7 @@ bool QSQLite2Result::reset (const QString& query)
 
 bool QSQLite2Result::gotoNext(QSqlCachedResult::ValueCache& row, int idx)
 {
+    Q_D(QSQLite2Result);
     return d->fetchNext(row, idx, false);
 }
 
@@ -346,11 +359,13 @@ int QSQLite2Result::size()
 
 int QSQLite2Result::numRowsAffected()
 {
+    Q_D(const QSQLite2Result);
     return sqlite_changes(d->access);
 }
 
 QSqlRecord QSQLite2Result::record() const
 {
+    Q_D(const QSQLite2Result);
     if (!isActive() || !isSelect())
         return QSqlRecord();
     return d->rInf;
@@ -358,11 +373,13 @@ QSqlRecord QSQLite2Result::record() const
 
 void QSQLite2Result::detachFromResultSet()
 {
+    Q_D(QSQLite2Result);
     d->finalize();
 }
 
 QVariant QSQLite2Result::handle() const
 {
+    Q_D(const QSQLite2Result);
     return QVariant::fromValue(d->currentMachine);
 }