OpenGL: encapsulate VBOs into a class

internal only for now but this will be handy

irr/src/OpenGL/VBO.cpp

@@ -0,0 +1,51 @@
+// Copyright (C) 2024 sfan5
+// This file is part of the "Irrlicht Engine".
+// For conditions of distribution and use, see copyright notice in irrlicht.h
+
+#include "VBO.h"
+
+#include <cassert>
+#include <mt_opengl.h>
+
+namespace irr
+{
+namespace video
+{
+
+void OpenGLVBO::upload(const void *data, size_t size, size_t offset,
+		GLenum usage, bool mustShrink)
+{
+	bool newBuffer = false;
+	if (!m_name) {
+		GL.GenBuffers(1, &m_name);
+		if (!m_name)
+			return;
+		newBuffer = true;
+	} else if (size > m_size || mustShrink) {
+		// note: mustShrink && offset > 0 is forbidden
+		newBuffer = size != m_size;
+	}
+
+	GL.BindBuffer(GL_ARRAY_BUFFER, m_name);
+
+	if (newBuffer) {
+		assert(offset == 0);
+		GL.BufferData(GL_ARRAY_BUFFER, size, data, usage);
+		m_size = size;
+	} else {
+		GL.BufferSubData(GL_ARRAY_BUFFER, offset, size, data);
+	}
+
+	GL.BindBuffer(GL_ARRAY_BUFFER, 0);
+}
+
+void OpenGLVBO::destroy()
+{
+	if (m_name)
+		GL.DeleteBuffers(1, &m_name);
+	m_name = 0;
+	m_size = 0;
+}
+
+}
+}