Optimize: Remove temporary allocations in QMeshData::attributeNames.

This is called frequently and was previously triggering many temporary
data allocations. By using a separated QStringList and QVector, we
can keep the behavior of the QHash and can remove the temporaries.

Change-Id: Idd7db916341037e98b78730d4f599990041ec706
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

3 files changed, 22 insertions, 11 deletions

diff --git a/src/render/io/qmeshdata.cpp b/src/render/io/qmeshdata.cpp
index af26770a2..08cd1da09 100644
--- a/src/render/io/qmeshdata.cpp
+++ b/src/render/io/qmeshdata.cpp
@@ -71,13 +71,19 @@ QMeshData::QMeshData(QMeshDataPrivate &dd)
 {
 }
 
-void QMeshData::addAttribute(const QString &name, QAbstractAttributePtr attr)
+void QMeshData::addAttribute(const QString &name, const QAbstractAttributePtr &attr)
 {
     Q_D(QMeshData);
-    d->m_attributes.insert(name, attr);
+    const int i = d->m_attributesNames.indexOf(name);
+    if (i != -1) {
+        d->m_attributes[i] = attr;
+    } else {
+        d->m_attributesNames.append(name);
+        d->m_attributes.append(attr);
+    }
 }
 
-void QMeshData::setIndexAttribute(QAbstractAttributePtr attr)
+void QMeshData::setIndexAttribute(const QAbstractAttributePtr &attr)
 {
     Q_D(QMeshData);
     d->m_indexAttr = attr;
@@ -86,13 +92,17 @@ void QMeshData::setIndexAttribute(QAbstractAttributePtr attr)
 QStringList QMeshData::attributeNames() const
 {
     Q_D(const QMeshData);
-    return d->m_attributes.keys();
+    return d->m_attributesNames;
 }
 
-QAbstractAttributePtr QMeshData::attributeByName(QString name) const
+QAbstractAttributePtr QMeshData::attributeByName(const QString &name) const
 {
     Q_D(const QMeshData);
-    return d->m_attributes.value(name);
+    const int i = d->m_attributesNames.indexOf(name);
+    if (i != -1)
+        return d->m_attributes[i];
+    else
+        return QAbstractAttributePtr();
 }
 
 QAbstractAttributePtr QMeshData::indexAttribute() const
@@ -134,7 +144,7 @@ QList<QAbstractBufferPtr> QMeshData::buffers() const
     if (d->m_indexAttr)
         r.insert(d->m_indexAttr->buffer());
 
-    Q_FOREACH (QAbstractAttributePtr v, d->m_attributes.values())
+    Q_FOREACH (const QAbstractAttributePtr &v, d->m_attributes)
         r.insert(v->buffer());
 
     return r.toList();
diff --git a/src/render/io/qmeshdata.h b/src/render/io/qmeshdata.h
index 613f1190a..20b4008fb 100644
--- a/src/render/io/qmeshdata.h
+++ b/src/render/io/qmeshdata.h
@@ -78,11 +78,11 @@ public:
     explicit QMeshData(PrimitiveTypes primitiveType = Triangles);
     virtual ~QMeshData();
 
-    void addAttribute(const QString& name, QAbstractAttributePtr attr);
-    void setIndexAttribute(QAbstractAttributePtr attr);
+    void addAttribute(const QString &name, const QAbstractAttributePtr &attr);
+    void setIndexAttribute(const QAbstractAttributePtr &attr);
 
     QStringList attributeNames() const;
-    QAbstractAttributePtr attributeByName(QString name) const;
+    QAbstractAttributePtr attributeByName(const QString &name) const;
     QAbstractAttributePtr indexAttribute() const;
 
     static const QString defaultPositionAttributeName() { return QStringLiteral("vertexPosition"); }
diff --git a/src/render/io/qmeshdata_p.h b/src/render/io/qmeshdata_p.h
index 4774d5915..6e74b2370 100644
--- a/src/render/io/qmeshdata_p.h
+++ b/src/render/io/qmeshdata_p.h
@@ -66,7 +66,8 @@ public:
     Q_DECLARE_PUBLIC(QMeshData)
     QMeshData *q_ptr;
 
-    QMap<QString, QAbstractAttributePtr> m_attributes;
+    QStringList m_attributesNames;
+    QVector<QAbstractAttributePtr> m_attributes;
     QAbstractAttributePtr m_indexAttr;
     QAxisAlignedBoundingBox m_bbox;
     int m_verticesPerPatch;