Restore QList backward compatibility

Add detach3 and append2, leaving the old functions as they were.
This ensures that new code will use the optimized version of QList,
and old code will just continue calling the old functions.

Reviewed-by: Thiago

2 files changed, 56 insertions, 3 deletions

diff --git a/src/corelib/tools/qlist.cpp b/src/corelib/tools/qlist.cpp
index d954160..868bed1 100644
--- a/src/corelib/tools/qlist.cpp
+++ b/src/corelib/tools/qlist.cpp
@@ -98,12 +98,45 @@ QListData::Data *QListData::detach()
  *
  *  \internal
  */
+#if QT_VERSION >= 0x050000
+#  error "Remove QListData::detach2(), it is only required for binary compatibility for 4.3.x to 4.5.x"
+#endif
 QListData::Data *QListData::detach2()
 {
     Data *x = d;
     Data* t = static_cast<Data *>(qMalloc(DataHeaderSize + x->alloc * sizeof(void *)));
     Q_CHECK_PTR(t);
 
+    ::memcpy(x, d, DataHeaderSize + d->alloc * sizeof(void *));
+
+    t->ref = 1;
+    t->sharable = true;
+    t->alloc = x->alloc;
+    if (!t->alloc) {
+        t->begin = 0;
+        t->end = 0;
+    } else {
+        t->begin = x->begin;
+        t->end   = x->end;
+    }
+    d = t;
+
+    return x;
+}
+
+/*!
+ *  Detaches the QListData by reallocating new memory.
+ *  Returns the old (shared) data, it is up to the caller to deref() and free()
+ *  For the new data node_copy needs to be called.
+ *
+ *  \internal
+ */
+QListData::Data *QListData::detach3()
+{
+    Data *x = d;
+    Data* t = static_cast<Data *>(qMalloc(DataHeaderSize + x->alloc * sizeof(void *)));
+    Q_CHECK_PTR(t);
+
     t->ref = 1;
     t->sharable = true;
     t->alloc = x->alloc;
@@ -150,6 +183,9 @@ void **QListData::append()
 }
 
 // ensures that enough space is available to append the list
+#if QT_VERSION >= 0x050000
+#  error "Remove QListData::append(), it is only required for binary compatibility up to 4.5.x"
+#endif
 void **QListData::append(const QListData& l)
 {
     Q_ASSERT(d->ref == 1);
@@ -158,6 +194,21 @@ void **QListData::append(const QListData& l)
     if (n) {
         if (e + n > d->alloc)
             realloc(grow(e + l.d->end - l.d->begin));
+        ::memcpy(d->array + d->end, l.d->array + l.d->begin, n*sizeof(void*));
+        d->end += n;
+    }
+    return d->array + e;
+}
+
+// ensures that enough space is available to append the list
+void **QListData::append2(const QListData& l)
+{
+    Q_ASSERT(d->ref == 1);
+    int e = d->end;
+    int n = l.d->end - l.d->begin;
+    if (n) {
+        if (e + n > d->alloc)
+            realloc(grow(e + l.d->end - l.d->begin));
         d->end += n;
     }
     return d->array + e;
diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index ab6f7bd..331f448 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -72,13 +72,15 @@ struct Q_CORE_EXPORT QListData {
     enum { DataHeaderSize = sizeof(Data) - sizeof(void *) };
 
     Data *detach(); // remove in 5.0
-    Data *detach2();
+    Data *detach2(); // remove in 5.0
+    Data *detach3();
     void realloc(int alloc);
     static Data shared_null;
     Data *d;
     void **erase(void **xi);
     void **append();
     void **append(const QListData &l);
+    void **append2(const QListData &l); // remove in 5.0
     void **prepend();
     void **insert(int i);
     void remove(int i);
@@ -593,7 +595,7 @@ template <typename T>
 Q_OUTOFLINE_TEMPLATE void QList<T>::detach_helper()
 {
     Node *n = reinterpret_cast<Node *>(p.begin());
-    QListData::Data *x = p.detach2();
+    QListData::Data *x = p.detach3();
     QT_TRY {
         node_copy(reinterpret_cast<Node *>(p.begin()), reinterpret_cast<Node *>(p.end()), n);
     } QT_CATCH(...) {
@@ -693,7 +695,7 @@ template <typename T>
 Q_OUTOFLINE_TEMPLATE QList<T> &QList<T>::operator+=(const QList<T> &l)
 {
     detach();
-    Node *n = reinterpret_cast<Node *>(p.append(l.p));
+    Node *n = reinterpret_cast<Node *>(p.append2(l.p));
     QT_TRY{
         node_copy(n, reinterpret_cast<Node *>(p.end()), reinterpret_cast<Node *>(l.p.begin()));
     } QT_CATCH(...) {