Add Chromium-only Blender WebEngine parity work

blender-5.2.0/extern/opensubdiv-source/opensubdiv/vtr/stackBuffer.h

@@ -0,0 +1,210 @@
+//
+//   Copyright 2015 DreamWorks Animation LLC.
+//
+//   Licensed under the terms set forth in the LICENSE.txt file available at
+//   https://opensubdiv.org/license.
+//
+#ifndef OPENSUBDIV3_VTR_STACK_BUFFER_H
+#define OPENSUBDIV3_VTR_STACK_BUFFER_H
+
+#include "../version.h"
+
+namespace OpenSubdiv {
+namespace OPENSUBDIV_VERSION {
+
+namespace Vtr {
+namespace internal {
+
+//
+//  The StackBuffer class is intended solely to take the place of VLAs (Variable
+//  Length Arrays) which most compilers support, but are not strictly standard C++.
+//  Portability concerns forces us to make use of either alloca() or some other
+//  mechanism to create small arrays on the stack that are typically based on the
+//  valence of a vertex -- small in general, but occasionally large.
+//
+//  Note also that since the intent of this is to replace VLAs -- not general
+//  std::vectors -- support for std::vector functionality is intentionally limited
+//  and STL-like naming is avoided.  Like a VLA there is no incremental growth.
+//  Support for resizing is available to reuse an instance at the beginning of a
+//  loop with a new size, but resizing in this case reinitializes all elements.
+//
+
+template <typename TYPE, unsigned int SIZE, bool POD_TYPE = false>
+class StackBuffer
+{
+public:
+    typedef unsigned int size_type;
+
+public:
+    //  Constructors and destructor -- declared inline below:
+    StackBuffer();
+    StackBuffer(size_type size);
+    ~StackBuffer();
+
+public:
+    //  Note the reliance on implicit casting so that it can be used similar to
+    //  a VLA.  This removes the need for operator[] as the resulting TYPE* will
+    //  natively support [].  (The presence of both TYPE* and operator[] also
+    //  causes an ambiguous overloading error with 32-bit MSVC builds.)
+
+    operator TYPE const * () const { return _data; }
+    operator TYPE *       ()       { return _data; }
+
+    size_type GetSize() const { return _size; }
+
+    void SetSize(size_type size);
+    void Reserve(size_type capacity);
+
+private:
+    //  Non-copyable:
+    StackBuffer(const StackBuffer<TYPE,SIZE,POD_TYPE> &) { }
+    StackBuffer& operator=(const StackBuffer<TYPE,SIZE,POD_TYPE> &) { return *this; }
+
+    void allocate(size_type capacity);
+    void deallocate();
+    void construct();
+    void destruct();
+
+private:
+    TYPE *     _data;
+    size_type  _size;
+    size_type  _capacity;
+
+    //  Is alignment an issue here?  The staticData arena will at least be double-word
+    //  aligned within this struct, which meets current and most anticipated needs.
+    char   _staticData[SIZE * sizeof(TYPE)];
+    char * _dynamicData;
+};
+
+
+//
+//  Core allocation/deallocation methods:
+//
+template <typename TYPE, unsigned int SIZE, bool POD_TYPE>
+inline void
+StackBuffer<TYPE,SIZE,POD_TYPE>::allocate(size_type capacity) {
+
+    //  Again, is alignment an issue here?  C++ spec says new will return pointer
+    //  "suitably aligned" for conversion to pointers of other types, which implies
+    //  at least an alignment of 16.
+    _dynamicData = static_cast<char*>(::operator new(capacity * sizeof(TYPE)));
+
+    _data = reinterpret_cast<TYPE*>(_dynamicData);
+    _capacity = capacity;
+}
+
+template <typename TYPE, unsigned int SIZE, bool POD_TYPE>
+inline void
+StackBuffer<TYPE,SIZE,POD_TYPE>::deallocate() {
+
+    ::operator delete(_dynamicData);
+
+    _data = reinterpret_cast<TYPE*>(_staticData);
+    _capacity = SIZE;
+}
+
+//
+//  Explicit element-wise construction and destruction within allocated memory.
+//  Compilers do not always optimize out the iteration here even when there is
+//  no construction or destruction, so the POD_TYPE arguement can be used to
+//  force this when/if it becomes an issue (and it has been in some cases).
+//
+template <typename TYPE, unsigned int SIZE, bool POD_TYPE>
+inline void
+StackBuffer<TYPE,SIZE,POD_TYPE>::construct() {
+
+    for (size_type i = 0; i < _size; ++i) {
+        (void) new (&_data[i]) TYPE;
+    }
+}
+template <typename TYPE, unsigned int SIZE, bool POD_TYPE>
+inline void
+StackBuffer<TYPE,SIZE,POD_TYPE>::destruct() {
+
+    for (size_type i = 0; i < _size; ++i) {
+        _data[i].~TYPE();
+    }
+}
+
+//
+//  Inline constructors and destructor:
+//
+template <typename TYPE, unsigned int SIZE, bool POD_TYPE>
+inline
+StackBuffer<TYPE,SIZE,POD_TYPE>::StackBuffer() :
+    _data(reinterpret_cast<TYPE*>(_staticData)),
+    _size(0),
+    _capacity(SIZE),
+    _dynamicData(0) {
+
+}
+
+template <typename TYPE, unsigned int SIZE, bool POD_TYPE>
+inline
+StackBuffer<TYPE,SIZE,POD_TYPE>::StackBuffer(size_type size) :
+    _data(reinterpret_cast<TYPE*>(_staticData)),
+    _size(size),
+    _capacity(SIZE),
+    _dynamicData(0) {
+
+    if (size > SIZE) {
+        allocate(size);
+    }
+    if (!POD_TYPE) {
+        construct();
+    }
+}
+
+template <typename TYPE, unsigned int SIZE, bool POD_TYPE>
+inline
+StackBuffer<TYPE,SIZE,POD_TYPE>::~StackBuffer() {
+
+    if (!POD_TYPE) {
+        destruct();
+    }
+    deallocate();
+}
+
+//
+//  Inline sizing methods:
+//
+template <typename TYPE, unsigned int SIZE, bool POD_TYPE>
+inline void
+StackBuffer<TYPE,SIZE,POD_TYPE>::Reserve(size_type capacity) {
+
+    if (capacity > _capacity) {
+        if (!POD_TYPE) {
+            destruct();
+        }
+        deallocate();
+        allocate(capacity);
+    }
+}
+
+template <typename TYPE, unsigned int SIZE, bool POD_TYPE>
+inline void
+StackBuffer<TYPE,SIZE,POD_TYPE>::SetSize(size_type size)
+{
+    if (!POD_TYPE) {
+        destruct();
+    }
+    if (size == 0) {
+        deallocate();
+    } else if (size > _capacity) {
+        deallocate();
+        allocate(size);
+    }
+    _size = size;
+    if (!POD_TYPE) {
+        construct();
+    }
+}
+
+} // end namespace internal
+} // end namespace Vtr
+
+} // end namespace OPENSUBDIV_VERSION
+using namespace OPENSUBDIV_VERSION;
+} // end namespace OpenSubdiv
+
+#endif /* OPENSUBDIV3_VTR_STACK_BUFFER_H */