Introduce a SubString String type

Use it in regexp matching. There's probably other places where
we should use this as well.

Change-Id: Ie2774acff0a5ec7b1c26c564fa40e65fecea29d4
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

4 files changed, 50 insertions, 12 deletions

diff --git a/src/qml/jsruntime/qv4regexpobject.cpp b/src/qml/jsruntime/qv4regexpobject.cpp
index f95719b25f..9a5afdf308 100644
--- a/src/qml/jsruntime/qv4regexpobject.cpp
+++ b/src/qml/jsruntime/qv4regexpobject.cpp
@@ -343,7 +343,7 @@ ReturnedValue RegExpPrototype::execFirstMatch(const FunctionObject *b, const Val
     if (r->value()->captureCount()) {
         int start = matchOffsets[0];
         int end = matchOffsets[1];
-        retVal = (start != -1) ? scope.engine->newString(s.mid(start, end - start))->asReturnedValue() : Encode::undefined();
+        retVal = (start != -1) ? scope.engine->memoryManager->alloc<ComplexString>(str->d(), start, end - start)->asReturnedValue() : Encode::undefined();
     }
 
     RegExpCtor::Data *dd = regExpCtor->d();
@@ -394,7 +394,7 @@ ReturnedValue RegExpPrototype::method_exec(const FunctionObject *b, const Value
     for (int i = 0; i < len; ++i) {
         int start = matchOffsets[i * 2];
         int end = matchOffsets[i * 2 + 1];
-        v = (start != -1) ? scope.engine->newString(s.mid(start, end - start))->asReturnedValue() : Encode::undefined();
+        v = (start != -1) ? scope.engine->memoryManager->alloc<ComplexString>(str->d(), start, end - start)->asReturnedValue() : Encode::undefined();
         array->arrayPut(i, v);
     }
     array->setArrayLengthUnchecked(len);
diff --git a/src/qml/jsruntime/qv4string.cpp b/src/qml/jsruntime/qv4string.cpp
index bdfb8af3f6..932ccf13ef 100644
--- a/src/qml/jsruntime/qv4string.cpp
+++ b/src/qml/jsruntime/qv4string.cpp
@@ -59,8 +59,13 @@ void Heap::String::markObjects(Heap::Base *that, MarkStack *markStack)
         return;
 
     ComplexString *cs = static_cast<ComplexString *>(s);
-    cs->left->mark(markStack);
-    cs->right->mark(markStack);
+    if (cs->subtype == StringType_AddedString) {
+        cs->left->mark(markStack);
+        cs->right->mark(markStack);
+    } else {
+        Q_ASSERT(cs->subtype == StringType_SubString);
+        cs->left->mark(markStack);
+    }
 }
 
 DEFINE_MANAGED_VTABLE(String);
@@ -111,6 +116,18 @@ void Heap::ComplexString::init(String *l, String *r)
         simplifyString();
 }
 
+void Heap::ComplexString::init(Heap::String *ref, int from, int len)
+{
+    Q_ASSERT(ref->length() >= from + len);
+    Base::init();
+
+    subtype = String::StringType_SubString;
+
+    left = ref;
+    this->from = from;
+    this->len = len;
+}
+
 void Heap::String::destroy() {
     if (text) {
         internalClass->engine->memoryManager->changeUnmanagedHeapSizeUsage(qptrdiff(-text->size) * (int)sizeof(QChar));
@@ -124,7 +141,7 @@ uint String::toUInt(bool *ok) const
 {
     *ok = true;
 
-    if (subtype() == Heap::String::StringType_Unknown)
+    if (subtype() >= Heap::String::StringType_Unknown)
         d()->createHashValue();
     if (subtype() == Heap::String::StringType_ArrayIndex)
         return d()->stringHash;
@@ -156,7 +173,10 @@ void Heap::String::simplifyString() const
     append(this, ch);
     text = result.data_ptr();
     text->ref.ref();
+    const ComplexString *cs = static_cast<const ComplexString *>(this);
     identifier = 0;
+    cs->left = cs->right = nullptr;
+
     internalClass->engine->memoryManager->changeUnmanagedHeapSizeUsage(qptrdiff(text->size) * (qptrdiff)sizeof(QChar));
     subtype = StringType_Unknown;
 }
@@ -171,10 +191,14 @@ void Heap::String::append(const String *data, QChar *ch)
         const String *item = worklist.back();
         worklist.pop_back();
 
-        if (item->subtype >= StringType_Complex) {
+        if (item->subtype == StringType_AddedString) {
             const ComplexString *cs = static_cast<const ComplexString *>(item);
             worklist.push_back(cs->right);
             worklist.push_back(cs->left);
+        } else if (item->subtype == StringType_SubString) {
+            const ComplexString *cs = static_cast<const ComplexString *>(item);
+            memcpy(ch, cs->left->toQString().constData() + cs->from, cs->len*sizeof(QChar));
+            ch += cs->len;
         } else {
             memcpy(ch, item->text->data(), item->text->size * sizeof(QChar));
             ch += item->text->size;
diff --git a/src/qml/jsruntime/qv4string_p.h b/src/qml/jsruntime/qv4string_p.h
index d1b38f4336..41039bca88 100644
--- a/src/qml/jsruntime/qv4string_p.h
+++ b/src/qml/jsruntime/qv4string_p.h
@@ -71,6 +71,7 @@ struct Q_QML_PRIVATE_EXPORT String : Base {
         StringType_ArrayIndex,
         StringType_Unknown,
         StringType_AddedString,
+        StringType_SubString,
         StringType_Complex = StringType_AddedString
     };
 
@@ -124,10 +125,13 @@ Q_STATIC_ASSERT(std::is_trivial< String >::value);
 #ifndef V4_BOOTSTRAP
 struct ComplexString : String {
     void init(String *l, String *n);
-    mutable uint nestingLevel;
+    void init(String *ref, int from, int len);
     mutable String *left;
     mutable String *right;
-    mutable int largestSubLength;
+    union {
+        mutable int largestSubLength;
+        int from;
+    };
     int len;
 };
 Q_STATIC_ASSERT(std::is_trivial< ComplexString >::value);
@@ -172,7 +176,7 @@ struct Q_QML_PRIVATE_EXPORT String : public Managed {
         return d()->hashValue();
     }
     uint asArrayIndex() const {
-        if (subtype() == Heap::String::StringType_Unknown)
+        if (subtype() >= Heap::String::StringType_Unknown)
             d()->createHashValue();
         Q_ASSERT(d()->subtype < Heap::String::StringType_Complex);
         if (subtype() == Heap::String::StringType_ArrayIndex)
diff --git a/src/qml/jsruntime/qv4stringobject.cpp b/src/qml/jsruntime/qv4stringobject.cpp
index b4c50170cf..4cc4a5c0cb 100644
--- a/src/qml/jsruntime/qv4stringobject.cpp
+++ b/src/qml/jsruntime/qv4stringobject.cpp
@@ -200,6 +200,15 @@ void StringPrototype::init(ExecutionEngine *engine, Object *ctor)
     defineDefaultProperty(QStringLiteral("trim"), method_trim);
 }
 
+static Heap::String *thisAsString(ExecutionEngine *v4, const Value *thisObject)
+{
+    if (String *s = thisObject->stringValue())
+        return s->d();
+    if (const StringObject *thisString = thisObject->as<StringObject>())
+        return thisString->d()->string;
+    return thisObject->toString(v4);
+}
+
 static QString getThisString(ExecutionEngine *v4, const Value *thisObject)
 {
     if (String *s = thisObject->stringValue())
@@ -649,11 +658,12 @@ ReturnedValue StringPrototype::method_search(const FunctionObject *b, const Valu
 ReturnedValue StringPrototype::method_slice(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc)
 {
     ExecutionEngine *v4 = b->engine();
-    const QString text = getThisString(v4, thisObject);
+    Heap::String *s = thisAsString(v4, thisObject);
     if (v4->hasException)
         return QV4::Encode::undefined();
+    Q_ASSERT(s);
 
-    const double length = text.length();
+    const double length = s->length();
 
     double start = argc ? argv[0].toInteger() : 0;
     double end = (argc < 2 || argv[1].isUndefined())
@@ -673,7 +683,7 @@ ReturnedValue StringPrototype::method_slice(const FunctionObject *b, const Value
     const int intEnd = int(end);
 
     int count = qMax(0, intEnd - intStart);
-    return Encode(v4->newString(text.mid(intStart, count)));
+    return Encode(v4->memoryManager->alloc<ComplexString>(s, intStart, count));
 }
 
 ReturnedValue StringPrototype::method_split(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc)