Clean up state handling for ICU and iconv based codecs

Get rid of the hack for the FreeFunction and instead add a proper
function pointer to clear the data to the ConverterState struct.

Change-Id: I104aae1a4381c69f1a254713ec76e1aeaa862cdc
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/corelib/codecs/qiconvcodec.cpp

@@ -121,7 +121,7 @@ void QIconvCodec::IconvState::saveChars(const char *c, int count)
 
 static void qIconvCodecStateFree(QTextCodec::ConverterState *state)
 {
-    delete reinterpret_cast<QIconvCodec::IconvState *>(state->d);
+    delete reinterpret_cast<QIconvCodec::IconvState *>(state->d[0]);
 }
 
 Q_GLOBAL_STATIC(QThreadStorage<QIconvCodec::IconvState *>, toUnicodeState)
@@ -139,15 +139,14 @@ QString QIconvCodec::convertToUnicode(const char* chars, int len, ConverterState
 
     if (convState) {
         // stateful conversion
-        pstate = reinterpret_cast<IconvState **>(&convState->d);
-        if (convState->d) {
+        pstate = reinterpret_cast<IconvState **>(&convState->d[0]);
+        if (convState->d[0]) {
             // restore state
             remainingCount = convState->remainingChars;
             remainingBuffer = (*pstate)->buffer;
         } else {
             // first time
-            convState->flags |= FreeFunction;
-            QTextCodecUnalignedPointer::encode(convState->state_data, qIconvCodecStateFree);
+            convState->clearFn = qIconvCodecStateFree;
         }
     } else {
         QThreadStorage<QIconvCodec::IconvState *> *ts = toUnicodeState();

src/corelib/codecs/qicucodec.cpp

@@ -60,7 +60,7 @@ typedef QList<QByteArray>::ConstIterator ByteArrayListConstIt;
 
 static void qIcuCodecStateFree(QTextCodec::ConverterState *state)
 {
-    ucnv_close(static_cast<UConverter *>(state->d));
+    ucnv_close(static_cast<UConverter *>(state->d[0]));
 }
 
 bool qTextCodecNameMatch(const char *n, const char *h)
@@ -569,18 +569,17 @@ UConverter *QIcuCodec::getConverter(QTextCodec::ConverterState *state) const
 {
     UConverter *conv = nullptr;
     if (state) {
-        if (!state->d) {
+        if (!state->d[0]) {
             // first time
-            state->flags |= QTextCodec::FreeFunction;
-            QTextCodecUnalignedPointer::encode(state->state_data, qIcuCodecStateFree);
+            state->clearFn = qIcuCodecStateFree;
             UErrorCode error = U_ZERO_ERROR;
-            state->d = ucnv_open(m_name, &error);
-            ucnv_setSubstChars(static_cast<UConverter *>(state->d),
+            state->d[0] = ucnv_open(m_name, &error);
+            ucnv_setSubstChars(static_cast<UConverter *>(state->d[0]),
                                state->flags & QTextCodec::ConvertInvalidToNull ? "\0" : "?", 1, &error);
             if (U_FAILURE(error))
                 qDebug("getConverter(state) ucnv_open failed %s %s", m_name, u_errorName(error));
         }
-        conv = static_cast<UConverter *>(state->d);
+        conv = static_cast<UConverter *>(state->d[0]);
     }
     if (!conv) {
         // stateless conversion

src/corelib/codecs/qtextcodec.cpp

@@ -343,10 +343,19 @@ static void setup() {}
 */
 QTextCodec::ConverterState::~ConverterState()
 {
-    if (flags & FreeFunction)
-        (QTextCodecUnalignedPointer::decode(state_data))(this);
-    else if (d)
-        free(d);
+    clear();
+}
+
+void QTextCodec::ConverterState::clear()
+{
+    if (clearFn)
+        clearFn(this);
+    remainingChars = 0;
+    invalidChars = 0;
+    state_data[0] = 0;
+    state_data[1] = 0;
+    state_data[2] = 0;
+    state_data[3] = 0;
 }
 
 /*!

src/corelib/codecs/qtextcodec.h

@@ -92,20 +92,25 @@ public:
     enum ConversionFlag {
         DefaultConversion,
         ConvertInvalidToNull = 0x80000000,
-        IgnoreHeader = 0x1,
-        FreeFunction = 0x2
+        IgnoreHeader = 0x1
     };
     Q_DECLARE_FLAGS(ConversionFlags, ConversionFlag)
 
     struct Q_CORE_EXPORT ConverterState {
         ConverterState(ConversionFlags f = DefaultConversion)
-            : flags(f), remainingChars(0), invalidChars(0), d(nullptr) { state_data[0] = state_data[1] = state_data[2] = 0; }
+            : flags(f), state_data{0, 0, 0, 0} {}
         ~ConverterState();
         ConversionFlags flags;
-        int remainingChars;
-        int invalidChars;
-        uint state_data[3];
-        void *d;
+        int remainingChars = 0;
+        int invalidChars = 0;
+
+        union {
+            uint state_data[4];
+            void *d[2];
+        };
+        void clear();
+        using ClearDataFn = void (*)(ConverterState *);
+        ClearDataFn clearFn = nullptr;
     private:
         Q_DISABLE_COPY(ConverterState)
     };

src/corelib/codecs/qtextcodec_p.h

@@ -66,21 +66,6 @@ QT_BEGIN_NAMESPACE
 
 typedef void (*QTextCodecStateFreeFunction)(QTextCodec::ConverterState*);
 
-struct QTextCodecUnalignedPointer
-{
-    static inline QTextCodecStateFreeFunction decode(const uint *src)
-    {
-        quintptr data;
-        memcpy(&data, src, sizeof(data));
-        return reinterpret_cast<QTextCodecStateFreeFunction>(data);
-    }
-    static inline void encode(uint *dst, QTextCodecStateFreeFunction fn)
-    {
-        quintptr data = reinterpret_cast<quintptr>(fn);
-        memcpy(dst, &data, sizeof(data));
-    }
-};
-
 bool qTextCodecNameMatch(const char *a, const char *b);
 
 #else // without textcodec:

src/corelib/serialization/qtextstream.cpp

@@ -364,12 +364,14 @@ static void copyConverterStateHelper(QTextCodec::ConverterState *dest,
 {
     // ### QTextCodec::ConverterState's copy constructors and assignments are
     // private. This function copies the structure manually.
-    Q_ASSERT(!src->d);
+    Q_ASSERT(!src->clearFn);
     dest->flags = src->flags;
+    dest->remainingChars = src->remainingChars;
     dest->invalidChars = src->invalidChars;
     dest->state_data[0] = src->state_data[0];
     dest->state_data[1] = src->state_data[1];
     dest->state_data[2] = src->state_data[2];
+    dest->state_data[3] = src->state_data[3];
 }
 #endif
 
@@ -787,7 +789,7 @@ inline void QTextStreamPrivate::consume(int size)
 inline void QTextStreamPrivate::saveConverterState(qint64 newPos)
 {
 #if QT_CONFIG(textcodec)
-    if (readConverterState.d) {
+    if (readConverterState.clearFn) {
         // converter cannot be copied, so don't save anything
         // don't update readBufferStartDevicePos either
         return;