Introduce flags to indicate the QArrayData type

These flags allow us to determine what type of data QArrayData is
carrying. There are currently only two supported types:
 - raw data type: constructed via fromRawData or static data
 - allocated data type: regular data done via heap allocation

The QArrayData object is usually allocated on the heap, unless its own
reference count is -1 (indicating static const QArrayData). Such
object should have a type of RawDataType, since we can't call free().

Add GrowsBackward for completeness as well as the StaticDataFlags
default for static data.

Change-Id: Icc915a468a2acf2eae91a94e82451f852d382c92
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

5 files changed, 16 insertions, 22 deletions

diff --git a/src/corelib/text/qbytearray.cpp b/src/corelib/text/qbytearray.cpp
index d70977b841..fa328a6d26 100644
--- a/src/corelib/text/qbytearray.cpp
+++ b/src/corelib/text/qbytearray.cpp
@@ -63,7 +63,7 @@
 #include <string.h>
 #include <stdlib.h>
 
-#define IS_RAW_DATA(d) ((d)->offset != sizeof(QByteArrayData))
+#define IS_RAW_DATA(d) (!(d)->isMutable())
 
 QT_BEGIN_NAMESPACE
 
@@ -4469,16 +4469,13 @@ QByteArray QByteArray::fromRawData(const char *data, int size)
 */
 QByteArray &QByteArray::setRawData(const char *data, uint size)
 {
-    if (d->ref.isShared() || d->allocatedCapacity()) {
+    if (!data || !size) {
+        clear();
+    } else if (d->ref.isShared() || (d->flags & Data::RawDataType) == 0) {
         *this = fromRawData(data, size);
     } else {
-        if (data) {
-            d->size = size;
-            d->offset = data - reinterpret_cast<char *>(d);
-        } else {
-            d->offset = sizeof(QByteArrayData);
-            d->size = 0;
-        }
+        d->size = size;
+        d->offset = data - reinterpret_cast<char *>(d);
     }
     return *this;
 }
diff --git a/src/corelib/text/qbytearray.h b/src/corelib/text/qbytearray.h
index c161e92743..611cacc646 100644
--- a/src/corelib/text/qbytearray.h
+++ b/src/corelib/text/qbytearray.h
@@ -495,7 +495,7 @@ inline const char *QByteArray::data() const
 inline const char *QByteArray::constData() const
 { return d->data(); }
 inline void QByteArray::detach()
-{ if (d->ref.isShared() || (d->offset != sizeof(QByteArrayData))) reallocData(uint(d->size) + 1u, d->detachFlags()); }
+{ if (d->ref.isShared() || !d->isMutable()) reallocData(uint(d->size) + 1u, d->detachFlags()); }
 inline bool QByteArray::isDetached() const
 { return !d->ref.isShared(); }
 inline QByteArray::QByteArray(const QByteArray &a) noexcept : d(a.d)
diff --git a/src/corelib/text/qstring.cpp b/src/corelib/text/qstring.cpp
index e00f2998b0..d0f141e079 100644
--- a/src/corelib/text/qstring.cpp
+++ b/src/corelib/text/qstring.cpp
@@ -100,7 +100,7 @@
 #define ULLONG_MAX quint64_C(18446744073709551615)
 #endif
 
-#define IS_RAW_DATA(d) ((d)->offset != sizeof(QStringData))
+#define IS_RAW_DATA(d) (!(d)->isMutable())
 
 QT_BEGIN_NAMESPACE
 
@@ -2272,7 +2272,7 @@ void QString::resize(int size)
 
     if (d->ref.isShared() || uint(size) + 1u > d->allocatedCapacity())
         reallocData(uint(size) + 1u, true);
-    if (d->alloc) {
+    if (d->flags & Data::AllocatedDataType) {
         d->size = size;
         d->data()[size] = '\0';
     }
@@ -9149,16 +9149,13 @@ QString QString::fromRawData(const QChar *unicode, int size)
 */
 QString &QString::setRawData(const QChar *unicode, int size)
 {
-    if (d->ref.isShared() || d->allocatedCapacity()) {
+    if (!unicode || !size) {
+        clear();
+    } else if (d->ref.isShared() || !IS_RAW_DATA(d)) {
         *this = fromRawData(unicode, size);
     } else {
-        if (unicode) {
-            d->size = size;
-            d->offset = reinterpret_cast<const char *>(unicode) - reinterpret_cast<char *>(d);
-        } else {
-            d->offset = sizeof(QStringData);
-            d->size = 0;
-        }
+        d->size = size;
+        d->offset = reinterpret_cast<const char *>(unicode) - reinterpret_cast<char *>(d);
     }
     return *this;
 }
diff --git a/src/corelib/text/qstring.h b/src/corelib/text/qstring.h
index 4d853bfc72..03d83eeab9 100644
--- a/src/corelib/text/qstring.h
+++ b/src/corelib/text/qstring.h
@@ -1041,7 +1041,7 @@ inline QChar *QString::data()
 inline const QChar *QString::constData() const
 { return reinterpret_cast<const QChar*>(d->data()); }
 inline void QString::detach()
-{ if (d->ref.isShared() || (d->offset != sizeof(QStringData))) reallocData(uint(d->size) + 1u); }
+{ if (d->ref.isShared() || !d->isMutable()) reallocData(uint(d->size) + 1u); }
 inline bool QString::isDetached() const
 { return !d->ref.isShared(); }
 inline void QString::clear()
diff --git a/src/corelib/text/qstringliteral.h b/src/corelib/text/qstringliteral.h
index b407bf6bc0..796909dcab 100644
--- a/src/corelib/text/qstringliteral.h
+++ b/src/corelib/text/qstringliteral.h
@@ -75,7 +75,7 @@ Q_STATIC_ASSERT_X(sizeof(qunicodechar) == 2,
     /**/
 
 #define Q_STATIC_STRING_DATA_HEADER_INITIALIZER_WITH_OFFSET(size, offset) \
-    { Q_REFCOUNT_INITIALIZE_STATIC, QArrayData::DefaultAllocationFlags, size, 0, offset } \
+    { Q_REFCOUNT_INITIALIZE_STATIC, QArrayData::StaticDataFlags, size, 0, offset } \
     /**/
 
 #define Q_STATIC_STRING_DATA_HEADER_INITIALIZER(size) \