1 /****************************************************************************

     2 **

     3 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).

     4 ** All rights reserved.

     5 ** Contact: Nokia Corporation (qt-info@nokia.com)

     6 **

     7 ** This file is part of the QtScript module of the Qt Toolkit.

     8 **

     9 ** $QT_BEGIN_LICENSE:LGPL-ONLY$

    10 ** GNU Lesser General Public License Usage

    11 ** This file may be used under the terms of the GNU Lesser

    12 ** General Public License version 2.1 as published by the Free Software

    13 ** Foundation and appearing in the file LICENSE.LGPL included in the

    14 ** packaging of this file.  Please review the following information to

    15 ** ensure the GNU Lesser General Public License version 2.1 requirements

    16 ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.

    17 **

    18 ** If you have questions regarding the use of this file, please contact

    19 ** Nokia at qt-info@nokia.com.

    20 ** $QT_END_LICENSE$

    21 **

    22 ****************************************************************************/

    23 

    24 #include "config.h"

    25 #include "qscriptstaticscopeobject_p.h"

    26 

    27 namespace JSC

    28 {

    29     ASSERT_CLASS_FITS_IN_CELL(QT_PREPEND_NAMESPACE(QScriptStaticScopeObject));

    30 }

    31 

    32 QT_BEGIN_NAMESPACE

    33 

    34 /*!

    35   \class QScriptStaticScopeObject

    36   \internal

    37 

    38     Represents a static scope object.

    39 

    40     This class allows the VM to determine at JS script compile time whether

    41     the object has a given property or not. If the object has the property,

    42     a fast, index-based read/write operation will be used. If the object

    43     doesn't have the property, the compiler knows it can safely skip this

    44     object when dynamically resolving the property. Either way, this can

    45     greatly improve performance.

    46 

    47   \sa QScriptContext::pushScope()

    48 */

    49 

    50 const JSC::ClassInfo QScriptStaticScopeObject::info = { "QScriptStaticScopeObject", 0, 0, 0 };

    51 

    52 /*!

    53     Creates a static scope object with a fixed set of undeletable properties.

    54 

    55     It's not possible to add new properties to the object after construction.

    56 */

    57 QScriptStaticScopeObject::QScriptStaticScopeObject(WTF::NonNullPassRefPtr<JSC::Structure> structure,

    58                                                    int propertyCount, const PropertyInfo* props)

    59     : JSC::JSVariableObject(structure, new Data(/*canGrow=*/false))

    60 {

    61     int index = growRegisterArray(propertyCount);

    62     for (int i = 0; i < propertyCount; ++i, --index) {

    63         const PropertyInfo& prop = props[i];

    64         JSC::SymbolTableEntry entry(index, prop.attributes);

    65         symbolTable().add(prop.identifier.ustring().rep(), entry);

    66         registerAt(index) = prop.value;

    67     }

    68 }

    69 

    70 /*!

    71     Creates an empty static scope object.

    72 

    73     Properties can be added to the object after construction, either by

    74     calling QScriptValue::setProperty(), or by pushing the object on the

    75     scope chain; variable declarations ("var" statements) and function

    76     declarations in JavaScript will create properties on the scope object.

    77 

    78     Note that once the scope object has been used in a closure and the

    79     resulting function has been compiled, it's no longer safe to add

    80     properties to the scope object (because the VM will bypass this

    81     object the next time the function is executed).

    82 */

    83 QScriptStaticScopeObject::QScriptStaticScopeObject(WTF::NonNullPassRefPtr<JSC::Structure> structure)

    84     : JSC::JSVariableObject(structure, new Data(/*canGrow=*/true))

    85 {

    86 }

    87 

    88 QScriptStaticScopeObject::~QScriptStaticScopeObject()

    89 {

    90     delete d;

    91 }

    92 

    93 bool QScriptStaticScopeObject::getOwnPropertySlot(JSC::ExecState*, const JSC::Identifier& propertyName, JSC::PropertySlot& slot)

    94 {

    95     return symbolTableGet(propertyName, slot);

    96 }

    97 

    98 bool QScriptStaticScopeObject::getOwnPropertyDescriptor(JSC::ExecState*, const JSC::Identifier& propertyName, JSC::PropertyDescriptor& descriptor)

    99 {

   100     return symbolTableGet(propertyName, descriptor);

   101 }

   102 

   103 void QScriptStaticScopeObject::putWithAttributes(JSC::ExecState* exec, const JSC::Identifier &propertyName, JSC::JSValue value, unsigned attributes)

   104 {

   105     if (symbolTablePutWithAttributes(propertyName, value, attributes))

   106         return;

   107     Q_ASSERT(d_ptr()->canGrow);

   108     addSymbolTableProperty(propertyName, value, attributes);

   109 }

   110 

   111 void QScriptStaticScopeObject::put(JSC::ExecState* exec, const JSC::Identifier& propertyName, JSC::JSValue value, JSC::PutPropertySlot&)

   112 {

   113     if (symbolTablePut(propertyName, value))

   114         return;

   115     Q_ASSERT(d_ptr()->canGrow);

   116     addSymbolTableProperty(propertyName, value, /*attributes=*/0);

   117 }

   118 

   119 bool QScriptStaticScopeObject::deleteProperty(JSC::ExecState*, const JSC::Identifier&)

   120 {

   121     return false;

   122 }

   123 

   124 void QScriptStaticScopeObject::markChildren(JSC::MarkStack& markStack)

   125 {

   126     JSC::Register* registerArray = d_ptr()->registerArray.get();

   127     if (!registerArray)

   128         return;

   129     markStack.appendValues(reinterpret_cast<JSC::JSValue*>(registerArray), d_ptr()->registerArraySize);

   130 }

   131 

   132 void QScriptStaticScopeObject::addSymbolTableProperty(const JSC::Identifier& name, JSC::JSValue value, unsigned attributes)

   133 {

   134     int index = growRegisterArray(1);

   135     JSC::SymbolTableEntry newEntry(index, attributes | JSC::DontDelete);

   136     symbolTable().add(name.ustring().rep(), newEntry);

   137     registerAt(index) = value;

   138 }

   139 

   140 /*!

   141   Grows the register array by \a count elements, and returns the offset of

   142   the newly added elements (note that the register file grows downwards,

   143   starting at index -1).

   144 */

   145 int QScriptStaticScopeObject::growRegisterArray(int count)

   146 {

   147     size_t oldSize = d_ptr()->registerArraySize;

   148     size_t newSize = oldSize + count;

   149     JSC::Register* registerArray = new JSC::Register[newSize];

   150     if (d_ptr()->registerArray)

   151         memcpy(registerArray + count, d_ptr()->registerArray.get(), oldSize * sizeof(JSC::Register));

   152     setRegisters(registerArray + newSize, registerArray);

   153     d_ptr()->registerArraySize = newSize;

   154     return -oldSize - 1;

   155 }

   156 

   157 QT_END_NAMESPACE