+
+ /* Delete all feedback objects */
+ _mesa_HashDeleteAll(ctx->TransformFeedback.Objects, delete_cb, ctx);
+ _mesa_DeleteHashTable(ctx->TransformFeedback.Objects);
+
+ /* Delete the default feedback object */
+ assert(ctx->Driver.DeleteTransformFeedback);
+ ctx->Driver.DeleteTransformFeedback(ctx,
+ ctx->TransformFeedback.DefaultObject);
+
+ ctx->TransformFeedback.CurrentObject = NULL;
+}
+
+
+/** Initialize the fields of a gl_transform_feedback_object. */
+void
+_mesa_init_transform_feedback_object(struct gl_transform_feedback_object *obj,
+ GLuint name)
+{
+ if (!obj)
+ return;
+
+ obj->Name = name;
+ obj->RefCount = 1;
+ obj->EverBound = GL_FALSE;
+}
+
+
+/** Default fallback for ctx->Driver.NewTransformFeedback() */
+static struct gl_transform_feedback_object *
+new_transform_feedback(struct gl_context *ctx, GLuint name)
+{
+ struct gl_transform_feedback_object *obj;
+ obj = CALLOC_STRUCT(gl_transform_feedback_object);
+ _mesa_init_transform_feedback_object(obj, name);
+ return obj;
+}
+
+/** Default fallback for ctx->Driver.DeleteTransformFeedback() */
+static void
+delete_transform_feedback(struct gl_context *ctx,
+ struct gl_transform_feedback_object *obj)
+{
+ GLuint i;
+
+ for (i = 0; i < Elements(obj->Buffers); i++) {
+ _mesa_reference_buffer_object(ctx, &obj->Buffers[i], NULL);
+ }
+
+ free(obj->Label);
+ free(obj);
+}
+
+
+/** Default fallback for ctx->Driver.BeginTransformFeedback() */
+static void
+begin_transform_feedback(struct gl_context *ctx, GLenum mode,
+ struct gl_transform_feedback_object *obj)
+{
+ /* nop */
+}
+
+/** Default fallback for ctx->Driver.EndTransformFeedback() */
+static void
+end_transform_feedback(struct gl_context *ctx,
+ struct gl_transform_feedback_object *obj)
+{
+ /* nop */
+}
+
+/** Default fallback for ctx->Driver.PauseTransformFeedback() */
+static void
+pause_transform_feedback(struct gl_context *ctx,
+ struct gl_transform_feedback_object *obj)
+{
+ /* nop */
+}
+
+/** Default fallback for ctx->Driver.ResumeTransformFeedback() */
+static void
+resume_transform_feedback(struct gl_context *ctx,
+ struct gl_transform_feedback_object *obj)
+{
+ /* nop */
+}
+
+
+/**
+ * Plug in default device driver functions for transform feedback.
+ * Most drivers will override some/all of these.
+ */
+void
+_mesa_init_transform_feedback_functions(struct dd_function_table *driver)
+{
+ driver->NewTransformFeedback = new_transform_feedback;
+ driver->DeleteTransformFeedback = delete_transform_feedback;
+ driver->BeginTransformFeedback = begin_transform_feedback;
+ driver->EndTransformFeedback = end_transform_feedback;
+ driver->PauseTransformFeedback = pause_transform_feedback;
+ driver->ResumeTransformFeedback = resume_transform_feedback;
+}
+
+
+/**
+ * Fill in the correct Size value for each buffer in \c obj.
+ *
+ * From the GL 4.3 spec, section 6.1.1 ("Binding Buffer Objects to Indexed
+ * Targets"):
+ *
+ * BindBufferBase binds the entire buffer, even when the size of the buffer
+ * is changed after the binding is established. It is equivalent to calling
+ * BindBufferRange with offset zero, while size is determined by the size of
+ * the bound buffer at the time the binding is used.
+ *
+ * Regardless of the size specified with BindBufferRange, or indirectly with
+ * BindBufferBase, the GL will never read or write beyond the end of a bound
+ * buffer. In some cases this constraint may result in visibly different
+ * behavior when a buffer overflow would otherwise result, such as described
+ * for transform feedback operations in section 13.2.2.
+ */
+static void
+compute_transform_feedback_buffer_sizes(
+ struct gl_transform_feedback_object *obj)
+{
+ unsigned i = 0;
+ for (i = 0; i < MAX_FEEDBACK_BUFFERS; ++i) {
+ GLintptr offset = obj->Offset[i];
+ GLsizeiptr buffer_size
+ = obj->Buffers[i] == NULL ? 0 : obj->Buffers[i]->Size;
+ GLsizeiptr available_space
+ = buffer_size <= offset ? 0 : buffer_size - offset;
+ GLsizeiptr computed_size;
+ if (obj->RequestedSize[i] == 0) {
+ /* No size was specified at the time the buffer was bound, so allow
+ * writing to all available space in the buffer.
+ */
+ computed_size = available_space;
+ } else {
+ /* A size was specified at the time the buffer was bound, however
+ * it's possible that the buffer has shrunk since then. So only
+ * allow writing to the minimum of the specified size and the space
+ * available.
+ */
+ computed_size = MIN2(available_space, obj->RequestedSize[i]);
+ }
+
+ /* Legal sizes must be multiples of four, so round down if necessary. */
+ obj->Size[i] = computed_size & ~0x3;
+ }
+}
+
+
+/**
+ * Compute the maximum number of vertices that can be written to the currently
+ * enabled transform feedback buffers without overflowing any of them.
+ */
+unsigned
+_mesa_compute_max_transform_feedback_vertices(
+ const struct gl_transform_feedback_object *obj,
+ const struct gl_transform_feedback_info *info)
+{
+ unsigned max_index = 0xffffffff;
+ unsigned i;
+
+ for (i = 0; i < info->NumBuffers; ++i) {
+ unsigned stride = info->BufferStride[i];
+ unsigned max_for_this_buffer;
+
+ /* Skip any inactive buffers, which have a stride of 0. */
+ if (stride == 0)
+ continue;
+
+ max_for_this_buffer = obj->Size[i] / (4 * stride);
+ max_index = MIN2(max_index, max_for_this_buffer);
+ }
+
+ return max_index;
+}
+
+
+/**
+ ** Begin API functions
+ **/
+
+
+/**
+ * Figure out which stage of the pipeline is the source of transform feedback
+ * data given the current context state, and return its gl_shader_program.
+ *
+ * If no active program can generate transform feedback data (i.e. no vertex
+ * shader is active), returns NULL.
+ */
+static struct gl_shader_program *
+get_xfb_source(struct gl_context *ctx)
+{
+ int i;
+ for (i = MESA_SHADER_GEOMETRY; i >= MESA_SHADER_VERTEX; i--) {
+ if (ctx->_Shader->CurrentProgram[i] != NULL)
+ return ctx->_Shader->CurrentProgram[i];
+ }
+ return NULL;