[Feat] (MG_State/Buffer): separate UploadData() into Resize()+UploadData()

MobileGL/MG_State/GLState/BufferState/BufferObject.h

@@ -66,7 +66,8 @@ namespace MobileGL {
 			public:
 				using TargetEnum = BufferTarget;
 
-				void UploadData(DataPtr data);
+				void Resize(SizeT size);
+				void UploadData(DataPtr data, SizeT atOffset);
 				void SetUsage(BufferUsage usage);
 				SizeT GetSize() const;
 				BufferUsage GetUsage() const;
@@ -82,7 +83,8 @@ namespace MobileGL {
 				Data m_data;
 				Bool m_isMapped;
 				BufferMappingAccessBit m_mappingAccess;
-				UniquePtr<Range1D> m_dirtyRange;
+				// UniquePtr<Range1D> m_dirtyRange;
+				Range1D m_dirtyRange;
 			};
 		}
 	}

MobileGL/MG_State/GLState/BufferState/BufferState.cpp

@@ -4,11 +4,21 @@ namespace MobileGL {
 	namespace MG_State {
 		namespace GLState {
 			// BufferObject
-			void BufferObject::UploadData(DataPtr data) {
-				m_size = data.size;
-				memcpy(m_data.data(), data.data, data.size);
-				m_dirtyRange = MakeUnique<Range1D>(0, m_size);
-                m_dirtyRange->UnionUpdate(0, m_size);
+			void BufferObject::Resize(SizeT size) {
+				m_size = size;
+				// Always reserve to power-of-2 size to amortize reallocation cost
+				m_data.reserve(std::bit_ceil(size));
+				m_data.resize(size);
+				// no dirty range == discard all data
+				m_dirtyRange.Update(0, 0);
+			}
+
+			void BufferObject::UploadData(DataPtr data, SizeT atOffset) {
+				assert(atOffset + data.size <= m_size);
+				// m_size = data.size;
+				memcpy(m_data.data() + atOffset, data.data, data.size);
+				// m_dirtyRange = MakeUnique<Range1D>(0, m_size);
+                m_dirtyRange.UnionUpdate(atOffset, atOffset + data.size - 1);
 			}
 
 			void* BufferObject::AcquireMemory(Bool markMapped, Bool read, Bool write) {
@@ -39,7 +49,7 @@ namespace MobileGL {
 			}
 
 			Range1D BufferObject::GetDirtyRange() const {
-				return *m_dirtyRange;
+				return m_dirtyRange;
 			}
 
 			Bool BufferObject::IsMapped() const {