swaybar: rewrite i3bar protocol handling

This now correctly handles an incoming json infinite array by shifting
most of the heavy listing to the json-c parser, as well as sending
multiple statuses at once. It also removes the struct
i3bar_protocol_state and moves its members into the status_line struct,
allowing the same buffer to be used for both protocols.

include/swaybar/status_line.h

@@ -1,5 +1,6 @@
 #ifndef _SWAYBAR_STATUS_LINE_H
 #define _SWAYBAR_STATUS_LINE_H
+#include <json-c/json.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdbool.h>
@@ -12,23 +13,6 @@ enum status_protocol {
 	PROTOCOL_I3BAR,
 };
 
-enum json_node_type {
-	JSON_NODE_UNKNOWN,
-	JSON_NODE_ARRAY,
-	JSON_NODE_STRING,
-};
-
-struct i3bar_protocol_state {
-	bool click_events;
-	char *buffer;
-	size_t buffer_size;
-	size_t buffer_index;
-	const char *current_node;
-	bool escape;
-	size_t depth;
-	enum json_node_type nodes[16];
-};
-
 struct i3bar_block {
 	struct wl_list link;
 	int ref_count;
@@ -58,9 +42,13 @@ struct status_line {
 	const char *text;
 	struct wl_list blocks; // i3bar_block::link
 
+	bool click_events;
 	char *buffer;
 	size_t buffer_size;
-	struct i3bar_protocol_state i3bar_state;
+	size_t buffer_index;
+	bool started;
+	bool expecting_comma;
+	json_tokener *tokener;
 };
 
 struct status_line *status_line_init(char *cmd);

swaybar/i3bar.c

@@ -1,6 +1,7 @@
 #define _POSIX_C_SOURCE 200809L
 #include <json-c/json.h>
 #include <linux/input-event-codes.h>
+#include <ctype.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -24,24 +25,19 @@ void i3bar_block_unref(struct i3bar_block *block) {
 	}
 }
 
-static bool i3bar_parse_json(struct status_line *status, const char *text) {
+static void i3bar_parse_json(struct status_line *status,
+		struct json_object *json_array) {
 	struct i3bar_block *block, *tmp;
 	wl_list_for_each_safe(block, tmp, &status->blocks, link) {
 		wl_list_remove(&block->link);
 		i3bar_block_unref(block);
 	}
-	json_object *results = json_tokener_parse(text);
-	if (!results) {
-		status_error(status, "[failed to parse i3bar json]");
-		return false;
-	}
-	wlr_log(WLR_DEBUG, "Got i3bar json: '%s'", text);
-	for (size_t i = 0; i < json_object_array_length(results); ++i) {
+	for (size_t i = 0; i < json_object_array_length(json_array); ++i) {
 		json_object *full_text, *short_text, *color, *min_width, *align, *urgent;
 		json_object *name, *instance, *separator, *separator_block_width;
 		json_object *background, *border, *border_top, *border_bottom;
 		json_object *border_left, *border_right, *markup;
-		json_object *json = json_object_array_get_idx(results, i);
+		json_object *json = json_object_array_get_idx(json_array, i);
 		if (!json) {
 			continue;
 		}
@@ -110,96 +106,133 @@ static bool i3bar_parse_json(struct status_line *status, const char *text) {
 			json_object_get_int(border_right) : 1;
 		wl_list_insert(&status->blocks, &block->link);
 	}
-	json_object_put(results);
-	return true;
 }
 
 bool i3bar_handle_readable(struct status_line *status) {
-	struct i3bar_protocol_state *state = &status->i3bar_state;
+	while (!status->started) { // look for opening bracket
+		for (size_t c = 0; c < status->buffer_index; ++c) {
+			if (status->buffer[c] == '[') {
+				status->started = true;
+				status->buffer_index -= ++c;
+				memmove(status->buffer, &status->buffer[c], status->buffer_index);
+				break;
+			} else if (!isspace(status->buffer[c])) {
+				status_error(status, "[invalid json]");
+				return true;
+			}
+		}
+		if (status->started) {
+			break;
+		}
 
-	char *cur = &state->buffer[state->buffer_index];
-	ssize_t n = read(status->read_fd, cur,
-			state->buffer_size - state->buffer_index);
-	if (n == -1) {
-		status_error(status, "[failed to read from status command]");
+		errno = 0;
+		ssize_t read_bytes = read(status->read_fd, status->buffer, status->buffer_size);
+		if (read_bytes > -1) {
+			status->buffer_index = read_bytes;
+		} else if (errno == EAGAIN) {
 			return false;
+		} else {
+			status_error(status, "[error reading from status command]");
+			return true;
+		}
 	}
 
-	if (n == (ssize_t)(state->buffer_size - state->buffer_index)) {
-		state->buffer_size = state->buffer_size * 2;
-		char *new_buffer = realloc(state->buffer, state->buffer_size);
-		if (!new_buffer) {
-			free(state->buffer);
-			status_error(status, "[failed to allocate buffer]");
+	struct json_object *last_object = NULL;
+	struct json_object *test_object;
+	size_t buffer_pos = 0;
+	while (true) {
+		// since the incoming stream is an infinite array
+		// parsing is split into two parts
+		// first, attempt to parse the current object, reading more if the
+		// parser indicates that the current object is incomplete, and failing
+		// if the parser fails
+		// second, look for separating comma, ignoring whitespace, failing if
+		// any other characters are encountered
+		if (status->expecting_comma) {
+			for (; buffer_pos < status->buffer_index; ++buffer_pos) {
+				if (status->buffer[buffer_pos] == ',') {
+					status->expecting_comma = false;
+					++buffer_pos;
+					break;
+				} else if (!isspace(status->buffer[buffer_pos])) {
+					status_error(status, "[invalid i3bar json]");
 					return true;
 				}
-		state->current_node += new_buffer - state->buffer;
-		cur += new_buffer - state->buffer;
-		state->buffer = new_buffer;
 			}
-
-	cur[n] = '\0';
-	bool redraw = false;
-	while (*cur) {
-		if (state->nodes[state->depth] == JSON_NODE_STRING) {
-			if (!state->escape && *cur == '"') {
-				--state->depth;
+			if (buffer_pos < status->buffer_index) {
+				continue; // look for new object without reading more input
 			}
-			state->escape = !state->escape && *cur == '\\';
+			buffer_pos = status->buffer_index = 0;
 		} else {
-			switch (*cur) {
-			case '[':
-				++state->depth;
-				if (state->depth >
-						sizeof(state->nodes) / sizeof(state->nodes[0])) {
-					status_error(status, "[i3bar json too deep]");
-					return false;
+			test_object = json_tokener_parse_ex(status->tokener,
+					&status->buffer[buffer_pos], status->buffer_index - buffer_pos);
+			if (json_tokener_get_error(status->tokener) == json_tokener_success) {
+				if (json_object_get_type(test_object) == json_type_array) {
+					if (last_object) {
+						json_object_put(last_object);
+					}
+					last_object = test_object;
+				} else {
+					json_object_put(test_object);
 				}
-				state->nodes[state->depth] = JSON_NODE_ARRAY;
-				if (state->depth == 1) {
-					state->current_node = cur;
+
+				buffer_pos += status->tokener->char_offset;
+				status->expecting_comma = true;
+
+				if (buffer_pos < status->buffer_index) {
+					continue; // look for comma without reading more input
+				}
+				buffer_pos = status->buffer_index = 0;
+			} else if (json_tokener_get_error(status->tokener) == json_tokener_continue) {
+				if (status->buffer_index < status->buffer_size) {
+					// move the object to the start of the buffer
+					status->buffer_index -= buffer_pos;
+					memmove(status->buffer, &status->buffer[buffer_pos],
+							status->buffer_index);
+				} else {
+					// expand buffer
+					status->buffer_size *= 2;
+					char *new_buffer = realloc(status->buffer, status->buffer_size);
+					if (new_buffer) {
+						status->buffer = new_buffer;
+					} else {
+						free(status->buffer);
+						status_error(status, "[failed to allocate buffer]");
+						return true;
 					}
-				break;
-			case ']':
-				if (state->nodes[state->depth] != JSON_NODE_ARRAY) {
+				}
+			} else {
 				status_error(status, "[failed to parse i3bar json]");
-					return false;
+				return true;
 			}
-				--state->depth;
-				if (state->depth == 0) {
-					// cur[1] is valid since cur[0] != '\0'
-					char p = cur[1];
-					cur[1] = '\0';
-					redraw = i3bar_parse_json(
-							status, state->current_node) || redraw;
-					cur[1] = p;
-					memmove(state->buffer, cur,
-							state->buffer_size - (cur - state->buffer));
-					cur = state->buffer;
-					state->current_node = cur + 1;
 		}
+
+		errno = 0;
+		ssize_t read_bytes = read(status->read_fd, &status->buffer[status->buffer_index],
+				status->buffer_size - status->buffer_index);
+		if (read_bytes > -1) {
+			status->buffer_index += read_bytes;
+		} else if (errno == EAGAIN) {
 			break;
-			case '"':
-				++state->depth;
-				if (state->depth >
-						sizeof(state->nodes) / sizeof(state->nodes[0])) {
-					status_error(status, "[i3bar json too deep]");
-					return false;
-				}
-				state->nodes[state->depth] = JSON_NODE_STRING;
-				break;
+		} else {
+			status_error(status, "[error reading from status command]");
+			return true;
 		}
 	}
-		++cur;
+
+	if (last_object) {
+		i3bar_parse_json(status, last_object);
+		json_object_put(last_object);
+		return true;
+	} else {
+		return false;
 	}
-	state->buffer_index = cur - state->buffer;
-	return redraw;
 }
 
 enum hotspot_event_handling i3bar_block_send_click(struct status_line *status,
 		struct i3bar_block *block, int x, int y, enum x11_button button) {
 	wlr_log(WLR_DEBUG, "block %s clicked", block->name ? block->name : "(nil)");
-	if (!block->name || !status->i3bar_state.click_events) {
+	if (!block->name || !status->click_events) {
 		return HOTSPOT_PROCESS;
 	}
 

swaybar/render.c

@@ -177,7 +177,7 @@ static uint32_t render_status_block(cairo_t *cairo,
 		*x -= margin;
 	}
 
-	if (output->bar->status->i3bar_state.click_events) {
+	if (output->bar->status->click_events) {
 		struct swaybar_hotspot *hotspot = calloc(1, sizeof(struct swaybar_hotspot));
 		hotspot->x = *x;
 		hotspot->y = 0;

swaybar/status_line.c

@@ -32,11 +32,6 @@ void status_error(struct status_line *status, const char *text) {
 bool status_handle_readable(struct status_line *status) {
 	ssize_t read_bytes = 1;
 	switch (status->protocol) {
-	case PROTOCOL_I3BAR:
-		if (i3bar_handle_readable(status) > 0) {
-			return true;
-		}
-		break;
 	case PROTOCOL_UNDEF:
 		errno = 0;
 		read_bytes = getline(&status->buffer,
@@ -61,7 +56,7 @@ bool status_handle_readable(struct status_line *status) {
 			if (json_object_object_get_ex(header, "click_events", &click_events)
 					&& json_object_get_boolean(click_events)) {
 				wlr_log(WLR_DEBUG, "Enabling click events.");
-				status->i3bar_state.click_events = true;
+				status->click_events = true;
 				if (write(status->write_fd, "[\n", 2) != 2) {
 					status_error(status, "[failed to write to status command]");
 					json_object_put(header);
@@ -70,13 +65,11 @@ bool status_handle_readable(struct status_line *status) {
 			}
 			json_object_put(header);
 
-			status->protocol = PROTOCOL_I3BAR;
-			free(status->buffer);
 			wl_list_init(&status->blocks);
-			status->i3bar_state.buffer_size = 4096;
-			status->i3bar_state.buffer =
-				malloc(status->i3bar_state.buffer_size);
-			return false;
+			status->tokener = json_tokener_new();
+			status->buffer_index = getdelim(&status->buffer,
+					&status->buffer_size, EOF, status->read);
+			return i3bar_handle_readable(status);
 		}
 
 		wlr_log(WLR_DEBUG, "Using text protocol.");
@@ -99,10 +92,11 @@ bool status_handle_readable(struct status_line *status) {
 				return true;
 			}
 		}
+	case PROTOCOL_I3BAR:
+		return i3bar_handle_readable(status);
 	default:
 		return false;
 	}
-	return false;
 }
 
 struct status_line *status_line_init(char *cmd) {
@@ -147,19 +141,14 @@ struct status_line *status_line_init(char *cmd) {
 void status_line_free(struct status_line *status) {
 	status_line_close_fds(status);
 	kill(status->pid, SIGTERM);
-	switch (status->protocol) {
-	case PROTOCOL_I3BAR: {
+	if (status->protocol == PROTOCOL_I3BAR) {
 		struct i3bar_block *block, *tmp;
 		wl_list_for_each_safe(block, tmp, &status->blocks, link) {
 			wl_list_remove(&block->link);
 			i3bar_block_unref(block);
 		}
-		free(status->i3bar_state.buffer);
-		break;
 	}
-	default:
+	json_tokener_free(status->tokener);
 	free(status->buffer);
-		break;
-	}
 	free(status);
 }