+/*
+ * set filter for an event
+ * Return negative error value on error.
+ * Return size of returned session payload data if OK.
+ */
+
+int lttng_set_event_filter(struct lttng_handle *handle,
+ const char *event_name, const char *channel_name,
+ const char *filter_expression)
+{
+ struct lttcomm_session_msg lsm;
+ struct filter_parser_ctx *ctx;
+ FILE *fmem;
+ int ret = 0;
+
+ /* Safety check. */
+ if (handle == NULL) {
+ return -1;
+ }
+
+ if (!filter_expression) {
+ return 0;
+ }
+
+ /*
+ * casting const to non-const, as the underlying function will
+ * use it in read-only mode.
+ */
+ fmem = lttng_fmemopen((void *) filter_expression,
+ strlen(filter_expression), "r");
+ if (!fmem) {
+ fprintf(stderr, "Error opening memory as stream\n");
+ return -ENOMEM;
+ }
+ ctx = filter_parser_ctx_alloc(fmem);
+ if (!ctx) {
+ fprintf(stderr, "Error allocating parser\n");
+ ret = -ENOMEM;
+ goto alloc_error;
+ }
+ ret = filter_parser_ctx_append_ast(ctx);
+ if (ret) {
+ fprintf(stderr, "Parse error\n");
+ ret = -EINVAL;
+ goto parse_error;
+ }
+ ret = filter_visitor_set_parent(ctx);
+ if (ret) {
+ fprintf(stderr, "Set parent error\n");
+ ret = -EINVAL;
+ goto parse_error;
+ }
+ if (print_xml) {
+ ret = filter_visitor_print_xml(ctx, stdout, 0);
+ if (ret) {
+ fflush(stdout);
+ fprintf(stderr, "XML print error\n");
+ ret = -EINVAL;
+ goto parse_error;
+ }
+ }
+
+ dbg_printf("Generating IR... ");
+ fflush(stdout);
+ ret = filter_visitor_ir_generate(ctx);
+ if (ret) {
+ fprintf(stderr, "Generate IR error\n");
+ ret = -EINVAL;
+ goto parse_error;
+ }
+ dbg_printf("done\n");
+
+ dbg_printf("Validating IR... ");
+ fflush(stdout);
+ ret = filter_visitor_ir_check_binary_op_nesting(ctx);
+ if (ret) {
+ ret = -EINVAL;
+ goto parse_error;
+ }
+ dbg_printf("done\n");
+
+ dbg_printf("Generating bytecode... ");
+ fflush(stdout);
+ ret = filter_visitor_bytecode_generate(ctx);
+ if (ret) {
+ fprintf(stderr, "Generate bytecode error\n");
+ ret = -EINVAL;
+ goto parse_error;
+ }
+ dbg_printf("done\n");
+ dbg_printf("Size of bytecode generated: %u bytes.\n",
+ bytecode_get_len(&ctx->bytecode->b));
+
+ memset(&lsm, 0, sizeof(lsm));
+
+ lsm.cmd_type = LTTNG_SET_FILTER;
+
+ /* Copy channel name */
+ copy_string(lsm.u.filter.channel_name, channel_name,
+ sizeof(lsm.u.filter.channel_name));
+ /* Copy event name */
+ copy_string(lsm.u.filter.event_name, event_name,
+ sizeof(lsm.u.filter.event_name));
+ lsm.u.filter.bytecode_len = sizeof(ctx->bytecode->b)
+ + bytecode_get_len(&ctx->bytecode->b);
+
+ copy_lttng_domain(&lsm.domain, &handle->domain);
+
+ copy_string(lsm.session.name, handle->session_name,
+ sizeof(lsm.session.name));
+
+ ret = ask_sessiond_varlen(&lsm, &ctx->bytecode->b,
+ lsm.u.filter.bytecode_len, NULL);
+
+ filter_bytecode_free(ctx);
+ filter_ir_free(ctx);
+ filter_parser_ctx_free(ctx);
+ if (fclose(fmem) != 0) {
+ perror("fclose");
+ }
+ return ret;
+
+parse_error:
+ filter_bytecode_free(ctx);
+ filter_ir_free(ctx);
+ filter_parser_ctx_free(ctx);
+alloc_error:
+ if (fclose(fmem) != 0) {
+ perror("fclose");
+ }
+ return ret;
+}
+