+/**
+ * Convert a GL texture binding enum such as GL_TEXTURE_BINDING_2D
+ * into the corresponding Mesa texture target index.
+ * \return TEXTURE_x_INDEX or -1 if binding is invalid
+ */
+static int
+tex_binding_to_index(const struct gl_context *ctx, GLenum binding)
+{
+ switch (binding) {
+ case GL_TEXTURE_BINDING_1D:
+ return _mesa_is_desktop_gl(ctx) ? TEXTURE_1D_INDEX : -1;
+ case GL_TEXTURE_BINDING_2D:
+ return TEXTURE_2D_INDEX;
+ case GL_TEXTURE_BINDING_3D:
+ return ctx->API != API_OPENGLES ? TEXTURE_3D_INDEX : -1;
+ case GL_TEXTURE_BINDING_CUBE_MAP:
+ return ctx->Extensions.ARB_texture_cube_map
+ ? TEXTURE_CUBE_INDEX : -1;
+ case GL_TEXTURE_BINDING_RECTANGLE:
+ return _mesa_is_desktop_gl(ctx) && ctx->Extensions.NV_texture_rectangle
+ ? TEXTURE_RECT_INDEX : -1;
+ case GL_TEXTURE_BINDING_1D_ARRAY:
+ return _mesa_is_desktop_gl(ctx) && ctx->Extensions.EXT_texture_array
+ ? TEXTURE_1D_ARRAY_INDEX : -1;
+ case GL_TEXTURE_BINDING_2D_ARRAY:
+ return (_mesa_is_desktop_gl(ctx) && ctx->Extensions.EXT_texture_array)
+ || _mesa_is_gles3(ctx)
+ ? TEXTURE_2D_ARRAY_INDEX : -1;
+ case GL_TEXTURE_BINDING_BUFFER:
+ return ctx->API == API_OPENGL_CORE &&
+ ctx->Extensions.ARB_texture_buffer_object ?
+ TEXTURE_BUFFER_INDEX : -1;
+ case GL_TEXTURE_BINDING_CUBE_MAP_ARRAY:
+ return _mesa_is_desktop_gl(ctx) && ctx->Extensions.ARB_texture_cube_map_array
+ ? TEXTURE_CUBE_ARRAY_INDEX : -1;
+ case GL_TEXTURE_BINDING_2D_MULTISAMPLE:
+ return _mesa_is_desktop_gl(ctx) && ctx->Extensions.ARB_texture_multisample
+ ? TEXTURE_2D_MULTISAMPLE_INDEX : -1;
+ case GL_TEXTURE_BINDING_2D_MULTISAMPLE_ARRAY:
+ return _mesa_is_desktop_gl(ctx) && ctx->Extensions.ARB_texture_multisample
+ ? TEXTURE_2D_MULTISAMPLE_ARRAY_INDEX : -1;
+ default:
+ return -1;
+ }
+}
+