Blink JavaScript shared memory prototype.

Source/wtf/ArrayBufferContents.cpp

Index: Source/wtf/ArrayBufferContents.cpp
diff --git a/Source/wtf/ArrayBufferContents.cpp b/Source/wtf/ArrayBufferContents.cpp
index 71f4bf99e84c63f460579f5417e955bda5fcd73f..7c6177923d6d57be77588decbafa9b37d33ce50f 100644
--- a/Source/wtf/ArrayBufferContents.cpp
+++ b/Source/wtf/ArrayBufferContents.cpp
@@ -34,75 +34,101 @@
 
 namespace WTF {
 
-ArrayBufferContents::ArrayBufferContents()
+
+DataHolder::DataHolder()
     : m_data(0)
     , m_sizeInBytes(0)
+    , m_shared(false) { }
+
+DataHolder::~DataHolder()
+{
+    // if (m_data) {
+    //     printf("Destroy data: %p size: %d shared: %d refs: %d\n", m_data, m_sizeInBytes, m_shared, refCount());
+    // }
+    partitionFreeGeneric(WTF::Partitions::getBufferPartition(), m_data);
+    m_data = 0;
+    m_sizeInBytes = 0;
+    m_shared = false;
+}
+
+void DataHolder::adopt(void* data, unsigned sizeInBytes, bool shared)
+{
+    ASSERT(!m_data);
+    m_data = data;
+    m_sizeInBytes = sizeInBytes;
+    m_shared = shared;
+    // printf("Adopt data: %p size: %d shared: %d refs: %d\n", m_data, m_sizeInBytes, m_shared, refCount());
+}
+
+ArrayBufferContents::ArrayBufferContents()
+    : m_holder(adoptRef(new DataHolder()))
     , m_deallocationObserver(0) { }
 
 ArrayBufferContents::ArrayBufferContents(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy policy)
-    : m_data(0)
-    , m_sizeInBytes(0)
+    : m_holder(adoptRef(new DataHolder()))
     , m_deallocationObserver(0)
 {
+    unsigned totalSize = numElements * elementByteSize;
     // Do not allow 32-bit overflow of the total size.
     if (numElements) {
-        unsigned totalSize = numElements * elementByteSize;
         if (totalSize / numElements != elementByteSize) {
-            m_data = 0;
             return;
         }
     }
-    allocateMemory(numElements * elementByteSize, policy, m_data);
-    m_sizeInBytes = numElements * elementByteSize;
+    void* data = 0;
+    allocateMemory(totalSize, policy, data);
+    m_holder->adopt(data, totalSize, false);
 }
 
 ArrayBufferContents::ArrayBufferContents(
-    void* data, unsigned sizeInBytes, ArrayBufferDeallocationObserver* observer)
-    : m_data(data)
-    , m_sizeInBytes(sizeInBytes)
+    void* data, unsigned sizeInBytes, bool shared, ArrayBufferDeallocationObserver* observer)
+    : m_holder(adoptRef(new DataHolder()))
     , m_deallocationObserver(observer)
 {
-    if (!m_data) {
-        ASSERT(!m_sizeInBytes);
-        m_sizeInBytes = 0;
+    if (!data) {
+        ASSERT(!sizeInBytes);
+        sizeInBytes = 0;
         // Allow null data if size is 0 bytes, make sure m_data is valid pointer.
         // (partitionAllocGeneric guarantees valid pointer for size 0)
-        allocateMemory(0, ZeroInitialize, m_data);
+        allocateMemory(0, ZeroInitialize, data);
     }
+    m_holder->adopt(data, sizeInBytes, shared);
 }
 
 ArrayBufferContents::~ArrayBufferContents()
 {
-    freeMemory(m_data, m_sizeInBytes);
+    // freeMemory(m_data, m_sizeInBytes);
     clear();
 }
 
 void ArrayBufferContents::clear()
 {
-    if (m_data && m_deallocationObserver)
-        m_deallocationObserver->arrayBufferDeallocated(m_sizeInBytes);
-    m_data = 0;
-    m_sizeInBytes = 0;
+    if (m_holder->m_data && m_deallocationObserver)
+        m_deallocationObserver->arrayBufferDeallocated(m_holder->m_sizeInBytes);
+    m_holder = adoptRef(new DataHolder());
     m_deallocationObserver = 0;
 }
 
 void ArrayBufferContents::transfer(ArrayBufferContents& other)
 {
-    ASSERT(!other.m_data);
-    other.m_data = m_data;
-    other.m_sizeInBytes = m_sizeInBytes;
-    clear();
+    ASSERT(!other.m_holder->m_data);
+    // TODO mark the memory as allocated in new context?
+    other.m_holder = m_holder;
+    if (!m_holder->m_shared) {
+        clear();
+    }
 }
 
 void ArrayBufferContents::copyTo(ArrayBufferContents& other)
 {
-    ASSERT(!other.m_sizeInBytes);
-    other.freeMemory(other.m_data, other.m_sizeInBytes);
-    allocateMemory(m_sizeInBytes, DontInitialize, other.m_data);
-    if (!other.m_data)
+    ASSERT(!other.m_holder->m_sizeInBytes);
+    other.m_holder = adoptRef(new DataHolder());
+    void* data = 0;
+    allocateMemory(m_holder->m_sizeInBytes, DontInitialize, data);
+    if (!data)
         return;
-    memcpy(other.m_data, m_data, m_sizeInBytes);
-    other.m_sizeInBytes = m_sizeInBytes;
+    memcpy(data, m_holder->m_data, m_holder->m_sizeInBytes);
+    other.m_holder->adopt(data, m_holder->m_sizeInBytes, false);
 }
 
 void ArrayBufferContents::allocateMemory(size_t size, InitializationPolicy policy, void*& data)