Axiom.RenderSystems.OpenGLES.GLESHardwareVertexBuffer.LockImpl C# (CSharp) Method

		protected override IntPtr LockImpl( int offset, int length, BufferLocking locking )
		{
			All access = 0;
			if ( isLocked )
			{
				throw new AxiomException( "Invalid attempt to lock an vertex buffer that has already been locked" );
			}

			IntPtr retPtr = IntPtr.Zero;
			if ( length < MapBufferThreshold )
			{
				retPtr = ( (GLESHardwareBufferManager)HardwareBufferManager.Instance ).AllocateScratch( length );
				if ( retPtr != IntPtr.Zero )
				{
					_lockedToScratch = true;
					_scratchOffset = offset;
					_scratchSize = length;
					_scratchPtr = retPtr;
					_scratchUploadOnUnlock = ( locking != BufferLocking.ReadOnly );

					if ( locking != BufferLocking.Discard )
					{
						ReadData( offset, length, retPtr );
					}
				}
			}
			else
			{
				throw new AxiomException( "Invalid Buffer lockSize" );
			}

			if ( retPtr == IntPtr.Zero )
			{
				OpenGL.BindBuffer( All.ArrayBuffer, _bufferId );
				// Use glMapBuffer
				if ( locking == BufferLocking.Discard )
				{
					OpenGL.BufferData( All.ArrayBuffer, new IntPtr( sizeInBytes ), IntPtr.Zero, GLESHardwareBufferManager.GetGLUsage( usage ) );
				}
				if ( ( usage & BufferUsage.WriteOnly ) != 0 )
					access = All.WriteOnlyOes;

				IntPtr pBuffer = OpenGLOES.MapBuffer( All.ArrayBuffer, access );
				if ( pBuffer == IntPtr.Zero )
				{
					throw new AxiomException( "Vertex Buffer: Out of memory" );
				}

				unsafe
				{
					// return offset
					retPtr = (IntPtr)( (byte*)pBuffer + offset );
				}

				_lockedToScratch = false;
			}
			isLocked = true;

			return retPtr;
		}