- A prototype which allows to expose CanvasPixelArray functionality...

src/objects.h

Index: src/objects.h
===================================================================
--- src/objects.h	(revision 2544)
+++ src/objects.h	(working copy)
@@ -52,6 +52,7 @@
 //         - JSValue
 //       - Array
 //         - ByteArray
+//         - PixelArray
 //         - FixedArray
 //           - DescriptorArray
 //           - HashTable
@@ -95,7 +96,6 @@
 //  HeapObject: [32 bit direct pointer] (4 byte aligned) | 01
 //  Failure:    [30 bit signed int] 11
 
-
 // Ecma-262 3rd 8.6.1
 enum PropertyAttributes {
   NONE              = v8::None,
@@ -270,6 +270,7 @@
   V(ODDBALL_TYPE)                               \
   V(PROXY_TYPE)                                 \
   V(BYTE_ARRAY_TYPE)                            \
+  V(PIXEL_ARRAY_TYPE)                           \
   V(FILLER_TYPE)                                \
                                                 \
   V(ACCESSOR_INFO_TYPE)                         \
@@ -659,6 +660,7 @@
   JS_GLOBAL_PROPERTY_CELL_TYPE,
   PROXY_TYPE,
   BYTE_ARRAY_TYPE,
+  PIXEL_ARRAY_TYPE,
   FILLER_TYPE,
   SMI_TYPE,
 
@@ -760,6 +762,7 @@
 
   inline bool IsNumber();
   inline bool IsByteArray();
+  inline bool IsPixelArray();
   inline bool IsFailure();
   inline bool IsRetryAfterGC();
   inline bool IsOutOfMemoryFailure();
@@ -1302,6 +1305,11 @@
 class JSObject: public HeapObject {
  public:
   enum DeleteMode { NORMAL_DELETION, FORCE_DELETION };
+  enum ElementsKind {
+    FAST_ELEMENTS,
+    DICTIONARY_ELEMENTS,
+    PIXEL_ELEMENTS
+  };
 
   // [properties]: Backing storage for properties.
   // properties is a FixedArray in the fast case, and a Dictionary in the
@@ -1313,10 +1321,13 @@
 
   // [elements]: The elements (properties with names that are integers).
   // elements is a FixedArray in the fast case, and a Dictionary in the slow
-  // case.
-  DECL_ACCESSORS(elements, FixedArray)  // Get and set fast elements.
+  // case or a PixelArray in a special case.
+  DECL_ACCESSORS(elements, Array)  // Get and set fast elements.
   inline void initialize_elements();
+  inline ElementsKind GetElementsKind();
   inline bool HasFastElements();
+  inline bool HasDictionaryElements();
+  inline bool HasPixelElements();
   inline NumberDictionary* element_dictionary();  // Gets slow elements.
 
   // Collects elements starting at index 0.
@@ -2440,6 +2451,43 @@
 };
 
 
+// PixelArray represents a fixed size byte array with special sematics used for
+// implementing the CanvasPixelArray object. Please see the specification at:
+// http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#canvaspixelarray
+// In particular write access clamps the values to 0 or 255 if the value
+// used is outside this range.
+class PixelArray: public Array {
+ public:
+  // [external_pointer]: The pointer to the external memory area backing this
+  // pixel array.
+  DECL_ACCESSORS(external_pointer, uint8_t)  // Pointer to the data store.
+  
+  // Setter and getter.
+  inline uint8_t get(int index);
+  inline void set(int index, uint8_t value);
+
+  // This accessor applies the correct conversion from Smi, HeapNumber and
+  // undefined and clamps the converted value between 0 and 255.
+  Object* SetValue(uint32_t index, Object* value);
+
+  // Casting.
+  static inline PixelArray* cast(Object* obj);
+
+#ifdef DEBUG
+  void PixelArrayPrint();
+  void PixelArrayVerify();
+#endif  // DEBUG
+
+  // PixelArray headers are not quadword aligned.
+  static const int kExternalPointerOffset = Array::kAlignedSize;
+  static const int kHeaderSize = kExternalPointerOffset + kPointerSize;
+  static const int kAlignedSize = OBJECT_SIZE_ALIGN(kHeaderSize);
+  
+private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(PixelArray);
+};
+
+
 // Code describes objects with on-the-fly generated machine code.
 class Code: public HeapObject {
  public: