GPU/GL: Add StorageBuf implementation

Almost 1:1 identical to UniformBuf implementation.

source/blender/gpu/opengl/gl_storage_buffer.hh

@@ -0,0 +1,62 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2020 Blender Foundation.
+ * All rights reserved.
+ */
+
+/** \file
+ * \ingroup gpu
+ */
+
+#pragma once
+
+#include "MEM_guardedalloc.h"
+
+#include "gpu_storage_buffer_private.hh"
+
+#include "glew-mx.h"
+
+namespace blender {
+namespace gpu {
+
+/**
+ * Implementation of Storage Buffers using OpenGL.
+ */
+class GLStorageBuf : public StorageBuf {
+ private:
+  /** Slot to which this UBO is currently bound. -1 if not bound. */
+  int slot_ = -1;
+  /** OpenGL Object handle. */
+  GLuint ssbo_id_ = 0;
+  /** Usage type. */
+  GPUUsageType usage_;
+
+ public:
+  GLStorageBuf(size_t size, GPUUsageType usage, const char *name);
+  ~GLStorageBuf();
+
+  void update(const void *data) override;
+  void bind(int slot) override;
+  void unbind() override;
+
+ private:
+  void init();
+
+  MEM_CXX_CLASS_ALLOC_FUNCS("GLStorageBuf");
+};
+
+}  // namespace gpu
+}  // namespace blender