+/**
+ * Get the matching mesa_format for a shader image format GL enum.
+ */
+mesa_format
+_mesa_get_shader_image_format(GLenum format);
+
+/**
+ * Get the GL image format class for a shader image format GL enum
+ */
+GLenum
+_mesa_get_image_format_class(GLenum format);
+
+/**
+ * Return whether an image format should be supported based on the current API
+ * version of the context.
+ */
+bool
+_mesa_is_shader_image_format_supported(const struct gl_context *ctx,
+ GLenum format);
+
+/**
+ * Get a single image unit struct with the default state.
+ */
+struct gl_image_unit
+_mesa_default_image_unit(struct gl_context *ctx);
+
+/**
+ * Initialize a context's shader image units to the default state.
+ */
+void
+_mesa_init_image_units(struct gl_context *ctx);
+
+/**
+ * Return GL_TRUE if the state of the image unit passed as argument is valid
+ * and access from the shader is allowed. Otherwise loads from this unit
+ * should return zero and stores should have no effect.
+ *
+ * The result depends on context state other than the passed image unit, part
+ * of the _NEW_TEXTURE set.
+ */
+GLboolean
+_mesa_is_image_unit_valid(struct gl_context *ctx, struct gl_image_unit *u);
+