QmlBasicScript should work on the actual JS AST tree

1 files changed, 853 insertions, 0 deletions

diff --git a/src/declarative/qml/qmlbasicscript.cpp b/src/declarative/qml/qmlbasicscript.cpp
new file mode 100644
index 0000000..3d74b37
--- /dev/null
+++ b/src/declarative/qml/qmlbasicscript.cpp
@@ -0,0 +1,853 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Qt Software Information (qt-info@nokia.com)
+**
+** This file is part of the $MODULE$ of the Qt Toolkit.
+**
+** $TROLLTECH_DUAL_LICENSE$
+**
+****************************************************************************/
+
+#include "qmlbasicscript_p.h"
+#include <QColor>
+#include <QDebug>
+#include <private/qmlengine_p.h>
+#include <private/qmlcontext_p.h>
+#include <QStack>
+#include <qfxperf.h>
+#include <private/qmlrefcount_p.h>
+#include <private/javascriptast_p.h>
+#include <private/javascriptengine_p.h>
+
+QT_BEGIN_NAMESPACE
+
+struct ScriptInstruction {
+    enum {
+        Load,       // fetch
+        Fetch,       // fetch
+
+        Add,         // NA
+        Subtract,    // NA
+        Multiply,    // NA
+        Equals,      // NA
+        And,         // NA
+
+        Int,         // integer
+        Bool,        // boolean
+    } type;
+
+    union {
+        struct {
+            int idx;
+        } fetch;
+        struct {
+            int value;
+        } integer;
+        struct {
+            bool value;
+        } boolean;
+    };
+};
+
+DEFINE_BOOL_CONFIG_OPTION(scriptWarnings, QML_SCRIPT_WARNINGS);
+
+class QmlBasicScriptPrivate
+{
+public:
+    enum Flags { OwnData = 0x00000001 };
+    
+    int size;
+    int stateSize;
+    int instructionCount;
+    int exprLen;
+
+    ScriptInstruction *instructions() const { return (ScriptInstruction *)((char *)this + sizeof(QmlBasicScriptPrivate)); }
+
+    const char *expr() const
+    {
+        return (const char *)(instructions() + instructionCount);
+    }
+
+    const char *data() const 
+    {
+        return (const char *)(instructions() + instructionCount) + exprLen + 1;
+    }
+
+    static unsigned int alignRound(int s)
+    {
+        if (s % 4) 
+            s += 4 - (s % 4);
+        return s;
+    }
+};
+
+QDebug operator<<(QDebug lhs, const QmlBasicScriptNodeCache &rhs)
+{
+    switch(rhs.type) {
+    case QmlBasicScriptNodeCache::Invalid:
+        lhs << "Invalid";
+        break;
+    case QmlBasicScriptNodeCache::Core:
+        lhs << "Core" << rhs.object << rhs.core;
+        break;
+    case QmlBasicScriptNodeCache::Attached: 
+        lhs << "Attached" << rhs.object << rhs.attached;
+        break;
+    case QmlBasicScriptNodeCache::Signal: 
+        lhs << "Signal" << rhs.object << rhs.core;
+        break;
+    case QmlBasicScriptNodeCache::SignalProperty: 
+        lhs << "SignalProperty" << rhs.object << rhs.core;
+        break;
+    case QmlBasicScriptNodeCache::Variant: 
+        lhs << "Variant" << rhs.context;
+        break;
+    }
+
+    return lhs;
+}
+
+void QmlBasicScriptNodeCache::clear()
+{
+    object = 0;
+    metaObject = 0;
+    type = Invalid;
+}
+
+static QVariant toObjectOrVariant(const QVariant &v)
+{
+    switch(v.type()) {
+        case QVariant::String:
+        case QVariant::UInt:
+        case QVariant::Int:
+        case 135:
+        case QVariant::Double:
+        case QVariant::Color:
+        case QVariant::Bool:
+        default:
+            return v;
+        case QVariant::UserType:
+            {
+                QObject *o = QmlMetaType::toQObject(v);
+                if (o)
+                    return qVariantFromValue(o);
+                else
+                    return v;
+            }
+            break;
+    }
+}
+
+static QVariant fetch_value(QObject *o, int idx, int type)
+{
+    switch(type) {
+        case QVariant::String:
+            {
+                QString val;
+                void *args[] = { &val, 0 };
+                QMetaObject::metacall(o, QMetaObject::ReadProperty, idx, args);
+                return QVariant(val);
+            }
+            break;
+        case QVariant::UInt:
+            {
+                uint val;
+                void *args[] = { &val, 0 };
+                QMetaObject::metacall(o, QMetaObject::ReadProperty, idx, args);
+                return QVariant(val);
+            }
+            break;
+        case QVariant::Int:
+            {
+                int val;
+                void *args[] = { &val, 0 };
+                QMetaObject::metacall(o, QMetaObject::ReadProperty, idx, args);
+                return QVariant(val);
+            }
+            break;
+        case 135:
+            {
+                float val;
+                void *args[] = { &val, 0 };
+                QMetaObject::metacall(o, QMetaObject::ReadProperty, idx, args);
+                return QVariant(val);
+            }
+            break;
+        case QVariant::Double:
+            {
+                double val;
+                void *args[] = { &val, 0 };
+                QMetaObject::metacall(o, QMetaObject::ReadProperty, idx, args);
+                return QVariant(val);
+            }
+            break;
+        case QVariant::Color:
+            {
+                QColor val;
+                void *args[] = { &val, 0 };
+                QMetaObject::metacall(o, QMetaObject::ReadProperty, idx, args);
+                return QVariant(val);
+            }
+            break;
+        case QVariant::Bool:
+            {
+                bool val;
+                void *args[] = { &val, 0 };
+                QMetaObject::metacall(o, QMetaObject::ReadProperty, idx, args);
+                return QVariant(val);
+            }
+            break;
+        default:  
+            {
+                if (QmlMetaType::isObject(type)) {
+                    // NOTE: This assumes a cast to QObject does not alter the 
+                    // object pointer
+                    QObject *val = 0;
+                    void *args[] = { &val, 0 };
+                    QMetaObject::metacall(o, QMetaObject::ReadProperty, idx, args);
+                    return QVariant::fromValue(val);
+                } else {
+                    QVariant var = o->metaObject()->property(idx).read(o);
+                    if (QmlMetaType::isObject(var.userType())) {
+                        QObject *obj = 0;
+                        obj = *(QObject **)var.data();
+                        var = QVariant::fromValue(obj);
+                    }
+                    return var;
+                }
+            }
+            break;
+    };
+}
+
+QVariant QmlBasicScriptNodeCache::value(const char *) const
+{
+    //QFxPerfTimer<QFxPerf::BasicScriptValue> pt;
+    switch(type) {
+    case Invalid:
+        break;
+    case Core:
+        return fetch_value(object, core, coreType);
+        break;
+    case Attached:
+        return qVariantFromValue(static_cast<QObject *>(attached));
+        break;
+    case Signal:
+        // XXX
+        Q_ASSERT(!"Not implemented");
+        break;
+    case SignalProperty:
+        break;
+    case Variant:
+        return context->propertyValues[contextIndex];
+    };
+    return QVariant();
+}
+
+struct QmlBasicScriptCompiler
+{
+    QmlBasicScriptCompiler()
+    : script(0), stateSize(0) {}
+    QmlBasicScript *script;
+    int stateSize;
+
+    bool compile(JavaScript::AST::Node *);
+
+    bool compileExpression(JavaScript::AST::Node *);
+
+    bool tryConstant(JavaScript::AST::Node *);
+    bool parseConstant(JavaScript::AST::Node *);
+    bool tryName(JavaScript::AST::Node *);
+    bool parseName(JavaScript::AST::Node *);
+    bool tryBinaryExpression(JavaScript::AST::Node *);
+    bool compileBinaryExpression(JavaScript::AST::Node *);
+
+    QByteArray data;
+    QList<ScriptInstruction> bytecode;
+};
+
+/*!
+    \internal
+    \class QmlBasicScript
+    \brief The QmlBasicScript class provides a fast implementation of a limited subset of JavaScript bindings.
+
+    QmlBasicScript instances are used to accelerate binding.  Instead of using
+    the slower, fully fledged JavaScript engine, many simple bindings can be
+    evaluated using the QmlBasicScript engine.
+
+    To see if the QmlBasicScript engine can handle a binding, call compile()
+    and check the return value, or isValid() afterwards.  
+
+    To evaluate the binding, the QmlBasicScript instance needs some memory in
+    which to cache state.  This may be allocated by calling newScriptState()
+    and destroyed by calling deleteScriptState().  The state data is then passed
+    to the run() method when evaluating the binding.
+
+    To further accelerate binding, QmlBasicScript can return a precompiled 
+    version of itself that can be saved for future use.  Call compileData() to
+    get an opaque pointer to the compiled state, and compileDataSize() for the
+    size of this data in bytes.  This data can be saved and passed to future
+    instances of the QmlBasicScript constructor.  The initial copy of compile
+    data is owned by the QmlBindScript instance on which compile() was called.
+*/
+
+/*!
+    Create a new QmlBasicScript instance.
+*/
+QmlBasicScript::QmlBasicScript()
+: flags(0), d(0), rc(0)
+{
+}
+
+/*!
+    Create a new QmlBasicScript instance from saved \a data.
+
+    \a data \b must be data previously acquired from calling compileData() on a
+    previously created QmlBasicScript instance.  Any other data will almost
+    certainly cause the QmlBasicScript engine to crash.
+
+    \a data must continue to be valid throughout the QmlBasicScript instance 
+    life.  It does not assume ownership of the memory.
+
+    If \a owner is set, it is referenced on creation and dereferenced on 
+    destruction of this instance.
+*/
+QmlBasicScript::QmlBasicScript(const char *data, QmlRefCount *owner)
+: flags(0), d((QmlBasicScriptPrivate *)data), rc(owner)
+{
+    if (rc) rc->addref();
+}
+
+/*!
+    Return the text of the script expression.
+ */
+QByteArray QmlBasicScript::expression() const
+{
+    if (!d)
+        return QByteArray();
+    else
+        return QByteArray(d->expr());
+}
+
+/*!
+    Destroy the script instance.
+*/
+QmlBasicScript::~QmlBasicScript()
+{
+    if (flags & QmlBasicScriptPrivate::OwnData)
+        free(d);
+    if (rc) rc->release();
+    d = 0;
+    rc = 0;
+}
+
+/*!
+    Clear this script.  The object will then be in its initial state, as though
+    it were freshly constructed with default constructor.
+*/
+void QmlBasicScript::clear()
+{
+    if (flags & QmlBasicScriptPrivate::OwnData)
+        free(d);
+    if (rc) rc->release();
+    d = 0;
+    rc = 0;
+    flags = 0;
+}
+
+/*!
+    Return the script state memory for this script instance.  This memory should
+    only be destroyed by calling deleteScriptState().
+ */
+void *QmlBasicScript::newScriptState()
+{
+    if (!d) {
+        return 0;
+    } else  {
+        void *rv = ::malloc(d->stateSize * sizeof(QmlBasicScriptNodeCache));
+        ::memset(rv, 0, d->stateSize * sizeof(QmlBasicScriptNodeCache));
+        return rv;
+    }
+}
+
+/*!
+    Delete the \a data previously allocated by newScriptState().
+ */
+void QmlBasicScript::deleteScriptState(void *data)
+{
+    if (!data) return;
+    Q_ASSERT(d);
+    clearCache(data);
+    free(data);
+}
+
+/*!
+    Dump the script instructions to stderr for debugging.
+ */
+void QmlBasicScript::dump()
+{
+    if (!d)
+        return;
+
+    qWarning() << d->instructionCount << "instructions:";
+    const char *data = d->data();
+    for (int ii = 0; ii < d->instructionCount; ++ii) {
+        const ScriptInstruction &instr = d->instructions()[ii];
+
+        switch(instr.type) {
+        case ScriptInstruction::Load:
+            qWarning().nospace() << "LOAD\t\t" << instr.fetch.idx << "\t\t" 
+                                 << QByteArray(data + instr.fetch.idx);
+            break;
+        case ScriptInstruction::Fetch:
+            qWarning().nospace() << "FETCH\t\t" << instr.fetch.idx << "\t\t" 
+                                 << QByteArray(data + instr.fetch.idx);
+            break;
+        case ScriptInstruction::Add:
+            qWarning().nospace() << "ADD";
+            break;
+        case ScriptInstruction::Subtract:
+            qWarning().nospace() << "SUBTRACT";
+            break;
+        case ScriptInstruction::Multiply:
+            qWarning().nospace() << "MULTIPLY";
+            break;
+        case ScriptInstruction::Equals:
+            qWarning().nospace() << "EQUALS";
+            break;
+        case ScriptInstruction::Int:
+            qWarning().nospace() << "INT\t\t" << instr.integer.value;
+            break;
+        case ScriptInstruction::Bool:
+            qWarning().nospace() << "BOOL\t\t" << instr.boolean.value;
+            break;
+        default:
+            qWarning().nospace() << "UNKNOWN";
+            break;
+        }
+    }
+}
+
+/*!
+    Return true if this is a valid script binding, otherwise returns false.
+ */
+bool QmlBasicScript::isValid() const
+{
+    return d != 0;
+}
+
+/*!
+    Compile \a v and return true if the compilation is successful, otherwise
+    returns false.
+ */
+bool QmlBasicScript::compile(const QmlParser::Variant &v)
+{
+    if (!v.asAST()) return false;
+
+    QByteArray expr = v.asScript().toLatin1();
+    const char *src = expr.constData();
+
+    QmlBasicScriptCompiler bsc;
+    bsc.script = this;
+
+    if (d) {
+        if (flags & QmlBasicScriptPrivate::OwnData)
+            free(d);
+        d = 0;
+        flags = 0;
+    }
+
+    if (bsc.compile(v.asAST())) {
+        int len = ::strlen(src);
+        flags = QmlBasicScriptPrivate::OwnData;
+        int size = sizeof(QmlBasicScriptPrivate) + 
+                   bsc.bytecode.count() * sizeof(ScriptInstruction) + 
+                   QmlBasicScriptPrivate::alignRound(bsc.data.count() + len + 1);
+        d = (QmlBasicScriptPrivate *) malloc(size);
+        d->size = size;
+        d->stateSize = bsc.stateSize;
+        d->instructionCount = bsc.bytecode.count();
+        d->exprLen = len;
+        ::memcpy((char *)d->expr(), src, len + 1);
+        for (int ii = 0; ii < d->instructionCount; ++ii) 
+            d->instructions()[ii] = bsc.bytecode.at(ii);
+        ::memcpy((char *)d->data(), bsc.data.constData(), bsc.data.count());
+    } 
+
+    return d != 0;
+}
+
+bool QmlBasicScriptCompiler::compile(JavaScript::AST::Node *node)
+{
+    return compileExpression(node);
+}
+
+using namespace JavaScript;
+bool QmlBasicScriptCompiler::tryConstant(JavaScript::AST::Node *node)
+{
+    if (node->kind == AST::Node::Kind_TrueLiteral || 
+        node->kind == AST::Node::Kind_FalseLiteral)
+        return true;
+
+    if (node->kind == AST::Node::Kind_NumericLiteral) {
+        AST::NumericLiteral *lit = static_cast<AST::NumericLiteral *>(node);
+
+        return lit->suffix == AST::NumericLiteral::noSuffix &&
+               double(int(lit->value)) == lit->value;
+    }
+
+    return false;
+}
+
+bool QmlBasicScriptCompiler::parseConstant(JavaScript::AST::Node *node)
+{
+    ScriptInstruction instr;
+
+    if (node->kind == AST::Node::Kind_NumericLiteral) {
+        AST::NumericLiteral *lit = static_cast<AST::NumericLiteral *>(node);
+        instr.type = ScriptInstruction::Int;
+        instr.integer.value = int(lit->value);
+    } else {
+        instr.type = ScriptInstruction::Bool;
+        instr.boolean.value = node->kind == AST::Node::Kind_TrueLiteral;
+    }
+
+    bytecode.append(instr);
+
+    return true;
+}
+
+bool QmlBasicScriptCompiler::tryName(JavaScript::AST::Node *node)
+{
+    return node->kind == AST::Node::Kind_IdentifierExpression ||
+           node->kind == AST::Node::Kind_FieldMemberExpression;
+}
+
+bool QmlBasicScriptCompiler::parseName(AST::Node *node)
+{
+    bool load = false;
+
+    QString name;
+    if (node->kind == AST::Node::Kind_IdentifierExpression) {
+        name = static_cast<AST::IdentifierExpression *>(node)->name->asString();
+        load = true;
+    } else if (node->kind == AST::Node::Kind_FieldMemberExpression) {
+        AST::FieldMemberExpression *expr = static_cast<AST::FieldMemberExpression *>(node);
+
+        if (!parseName(expr->base))
+            return false;
+
+        name = expr->name->asString();
+    } else {
+        return false;
+    }
+
+    int nref = data.count();
+    data.append(name.toUtf8());
+    data.append('\0');
+    ScriptInstruction instr;
+    if (load)
+        instr.type = ScriptInstruction::Load;
+    else
+        instr.type = ScriptInstruction::Fetch;
+    instr.fetch.idx = nref;
+    bytecode.append(instr);
+    ++stateSize;
+
+    return true;
+}
+
+bool QmlBasicScriptCompiler::compileExpression(JavaScript::AST::Node *node)
+{
+    if (tryBinaryExpression(node))
+        return compileBinaryExpression(node);
+    else if (tryConstant(node))
+        return parseConstant(node);
+    else if (tryName(node))
+        return parseName(node);
+    else
+        return false;
+}
+
+bool QmlBasicScriptCompiler::tryBinaryExpression(AST::Node *node)
+{
+    if (node->kind == AST::Node::Kind_BinaryExpression) {
+        AST::BinaryExpression *expr = 
+            static_cast<AST::BinaryExpression *>(node);
+
+        if (expr->op == QSOperator::Add ||
+            expr->op == QSOperator::Sub ||
+            expr->op == QSOperator::Equal ||
+            expr->op == QSOperator::And ||
+            expr->op == QSOperator::Mul)
+            return true;
+    }
+    return false;
+}
+
+bool QmlBasicScriptCompiler::compileBinaryExpression(AST::Node *node)
+{
+    if (node->kind == AST::Node::Kind_BinaryExpression) {
+        AST::BinaryExpression *expr = 
+            static_cast<AST::BinaryExpression *>(node);
+
+        if (!compileExpression(expr->left)) return false;
+        if (!compileExpression(expr->right)) return false;
+
+        ScriptInstruction instr;
+        switch (expr->op) {
+        case QSOperator::Add:
+            instr.type = ScriptInstruction::Add;
+            break;
+        case QSOperator::Sub:
+            instr.type = ScriptInstruction::Subtract;
+            break;
+        case QSOperator::Equal:
+            instr.type = ScriptInstruction::Equals;
+            break;
+        case QSOperator::And:
+            instr.type = ScriptInstruction::And;
+            break;
+        case QSOperator::Mul:
+            instr.type = ScriptInstruction::Multiply;
+            break;
+        default:
+            return false;
+        }
+
+        bytecode.append(instr);
+        return true;
+    } 
+    return false;
+}
+
+/*!
+    \internal
+*/
+void QmlBasicScript::clearCache(void *voidCache)
+{
+    QmlBasicScriptNodeCache *dataCache =
+        reinterpret_cast<QmlBasicScriptNodeCache *>(voidCache);
+
+    for (int ii = 0; ii < d->stateSize; ++ii) {
+        if (!dataCache[ii].isCore() && !dataCache[ii].isVariant() && 
+            dataCache[ii].object) {
+            QMetaObject::removeGuard(&dataCache[ii].object);
+            dataCache[ii].object = 0;
+        }
+        dataCache[ii].clear();
+    }
+}
+
+void QmlBasicScript::guard(QmlBasicScriptNodeCache &n)
+{
+    if (n.object) {
+        if (n.isVariant()) {
+        } else if (n.isCore()) {
+            n.metaObject = 
+                n.object->metaObject();
+        } else {
+            QMetaObject::addGuard(&n.object);
+        }
+    }
+}
+
+bool QmlBasicScript::valid(QmlBasicScriptNodeCache &n, QObject *obj)
+{
+    return n.object == obj && 
+                       (!n.isCore() || obj->metaObject() == n.metaObject); 
+}
+
+
+/*!
+    \enum QmlBasicScript::CacheState
+    \value NoChange The query has not change.  Any previous monitoring is still
+    valid.
+    \value Incremental The query has been incrementally changed.  Any previous 
+    monitoring is still valid, but needs to have the fresh properties added to
+    it.
+    \value Reset The entire query has been reset from the beginning.  Any previous
+    monitoring is now invalid.
+*/
+
+/*!
+    Run the script in \a context and return the result.  \a voidCache should 
+    contain state memory previously acquired from newScript. 
+ */
+QVariant QmlBasicScript::run(QmlContext *context, void *voidCache, CacheState *cached)
+{
+    if (!isValid())
+        return QVariant();
+
+    QmlBasicScriptNodeCache *dataCache =
+        reinterpret_cast<QmlBasicScriptNodeCache *>(voidCache);
+    int dataCacheItem; 
+    QStack<QVariant> stack;
+
+    bool resetting = false;
+    bool hasReset = false;
+
+    const char *data = d->data();
+
+    if (dataCache[0].type == QmlBasicScriptNodeCache::Invalid) {
+        resetting = true;
+        hasReset = true;
+    }
+
+    CacheState state = NoChange;
+
+    dataCacheItem = 0;
+    for (int idx = 0; idx < d->instructionCount; ++idx) {
+        const ScriptInstruction &instr = d->instructions()[idx];
+
+        switch(instr.type) {
+            case ScriptInstruction::Load: // either an object or a property
+            case ScriptInstruction::Fetch: // can only be a property
+            {
+                const char *id = data + instr.fetch.idx;
+                QmlBasicScriptNodeCache &n = dataCache[dataCacheItem];
+
+                if (instr.type == ScriptInstruction::Load) {
+
+                    if (n.type == QmlBasicScriptNodeCache::Invalid) {
+                        context->engine()->d_func()->loadCache(n, QLatin1String(id), static_cast<QmlContextPrivate*>(context->d_ptr));
+                        state = Incremental;
+                    }
+
+                    if(!n.isValid())
+                        qWarning("ReferenceError: %s is not defined", id);
+
+                } else { // instr.type == ScriptInstruction::Fetch
+
+                    QVariant o = stack.pop();
+                    QObject *obj = qvariant_cast<QObject *>(o);
+                    if (!obj) {
+                        if (n.type == QmlBasicScriptNodeCache::Invalid) {
+                            if (scriptWarnings())
+                                qWarning() << "QmlBasicScript: Unable to convert" << o;
+                            *cached = state;
+                            return QVariant();
+                        } else {
+                            clearCache(dataCache);
+                            *cached = Reset;
+                            CacheState dummy;
+                            return run(context, voidCache, &dummy);
+                        }
+                    } else if (n.type == QmlBasicScriptNodeCache::Invalid) {
+                        context->engine()->d_func()->fetchCache(n, QLatin1String(id), obj);
+                        guard(n);
+                        state = Incremental;
+                    } else if (!valid(n, obj)) {
+                        clearCache(dataCache);
+                        *cached = Reset;
+                        CacheState dummy;
+                        return run(context, voidCache, &dummy);
+                    }
+
+                }
+
+                QVariant var = n.value(id);
+                stack.push(var);
+                ++dataCacheItem;
+            }
+                break;
+            case ScriptInstruction::Int:
+                stack.push(QVariant(instr.integer.value));
+                break;
+            case ScriptInstruction::Bool:
+                stack.push(QVariant(instr.boolean.value));
+                break;
+            case ScriptInstruction::Add:
+                {
+                    QVariant rhs = stack.pop();
+                    QVariant lhs = stack.pop();
+
+                    stack.push(rhs.toDouble() + lhs.toDouble());
+                }
+                break;
+            case ScriptInstruction::Subtract:
+                {
+                    QVariant rhs = stack.pop();
+                    QVariant lhs = stack.pop();
+
+                    stack.push(lhs.toDouble() - rhs.toDouble());
+                }
+                break;
+            case ScriptInstruction::Multiply:
+                {
+                    QVariant rhs = stack.pop();
+                    QVariant lhs = stack.pop();
+
+                    stack.push(rhs.toDouble() * lhs.toDouble());
+                }
+                break;
+            case ScriptInstruction::Equals:
+                {
+                    QVariant rhs = stack.pop();
+                    QVariant lhs = stack.pop();
+
+                    stack.push(rhs == lhs);
+                }
+                break;
+            case ScriptInstruction::And:
+                {
+                    QVariant rhs = stack.pop();
+                    QVariant lhs = stack.pop();
+
+                    stack.push(rhs.toBool() && lhs.toBool());
+                }
+                break;
+            default:
+                break;
+        }
+    }
+
+    *cached = state;
+
+    if (stack.isEmpty())
+        return QVariant();
+    else
+        return stack.top();
+}
+
+/*!
+    Return a pointer to the script's compile data, or null if there is no data.
+ */
+const char *QmlBasicScript::compileData() const
+{
+    return (const char *)d;
+}
+
+/*!
+    Return the size of the script's compile data, or zero if there is no data.
+    The size will always be a multiple of 4.
+ */
+unsigned int QmlBasicScript::compileDataSize() const
+{
+    if (d)
+        return d->size;
+    else
+        return 0;
+}
+
+bool QmlBasicScript::isSingleLoad() const
+{
+    if (!d)
+        return false;
+
+    return d->instructionCount == 1 &&
+           d->instructions()[0].type == ScriptInstruction::Load;
+}
+
+QByteArray QmlBasicScript::singleLoadTarget() const
+{
+    if (!isSingleLoad())
+        return QByteArray();
+
+    // We know there is one instruction and it is a load
+    return QByteArray(d->data() + d->instructions()[0].fetch.idx);
+}
+
+
+QT_END_NAMESPACE