Merge 92408 - Make sure that AudioArray is 16-byte aligned

Source/WebCore/platform/audio/AudioArray.h

Index: Source/WebCore/platform/audio/AudioArray.h
===================================================================
--- Source/WebCore/platform/audio/AudioArray.h	(revision 93809)
+++ Source/WebCore/platform/audio/AudioArray.h	(working copy)
@@ -30,16 +30,70 @@
 #define AudioArray_h
 
 #include <string.h>
+#include <wtf/FastMalloc.h>
 #include <wtf/Vector.h>
 
 namespace WebCore {
 
 template<typename T>
-class AudioArray : public Vector<T> {
+class AudioArray {
 public:
-    AudioArray() : Vector<T>(0) { }
-    explicit AudioArray(size_t n) : Vector<T>(n, 0) { }
+    AudioArray() : m_allocation(0), m_alignedData(0), m_size(0) { }
+    explicit AudioArray(size_t n) : m_allocation(0), m_alignedData(0), m_size(0)
+    {
+        allocate(n);
+    }
 
+    ~AudioArray()
+    {
+        fastFree(m_allocation);
+    }
+
+    // It's OK to call allocate() multiple times, but data will *not* be copied from an initial allocation
+    // if re-allocated. Allocations are zero-initialized.
+    void allocate(size_t n)
+    {
+        // 16-byte alignment for 128bit SIMD.
+        const size_t alignment = 16;
+
+        if (m_allocation)
+            fastFree(m_allocation);
+        
+        bool isAllocationGood = false;
+        
+        while (!isAllocationGood) {
+            // Initially we try to allocate the exact size, but if it's not aligned
+            // then we'll have to reallocate and from then on allocate extra.
+            static size_t extraAllocationBytes = 0;
+
+            T* allocation = static_cast<T*>(fastMalloc(sizeof(T) * n + extraAllocationBytes));
+            T* alignedData = alignedAddress(allocation, alignment);
+
+            if (alignedData == allocation || extraAllocationBytes == alignment) {
+                m_allocation = allocation;
+                m_alignedData = alignedData;
+                m_size = n;
+                isAllocationGood = true;
+                zero();
+            } else {
+                extraAllocationBytes = alignment; // always allocate extra after the first alignment failure.
+                fastFree(allocation);
+            }
+        }
+    }
+
+    T* data() { return m_alignedData; }
+    const T* data() const { return m_alignedData; }
+    size_t size() const { return m_size; }
+
+    T& at(size_t i)
+    {
+        ASSERT(i < size());
+        return data()[i];
+    }
+
+    T& operator[](size_t i) { return at(i); }
+
     void zero() { memset(this->data(), 0, sizeof(T) * this->size()); }
 
     void zeroRange(unsigned start, unsigned end)
@@ -61,6 +115,17 @@
 
         memcpy(this->data() + start, sourceData, sizeof(T) * (end - start));
     }
+
+private:
+    static T* alignedAddress(T* address, intptr_t alignment)
+    {
+        intptr_t value = reinterpret_cast<intptr_t>(address);
+        return reinterpret_cast<T*>((value + alignment - 1) & ~(alignment - 1));
+    }
+
+    T* m_allocation;
+    T* m_alignedData;
+    size_t m_size;
 };
 
 typedef AudioArray<float> AudioFloatArray;