full json parser

1 files changed, 444 insertions, 0 deletions

diff --git a/json.c b/json.c
new file mode 100644
index 0000000..1b74e10
--- /dev/null
+++ b/json.c
@@ -0,0 +1,444 @@
+// JSON parser for LSP
+// provides FAST(ish) parsing but SLOW lookup
+// this is especially fast for small objects
+
+typedef struct {
+	u32 pos;
+	u32 len;
+} JSONString;
+
+typedef struct JSONValue JSONValue;
+
+typedef struct {
+	u32 len;
+	// this is an index into the values array
+	//   values[items..items+len] store the names
+	//   values[items+len..items+2*len] store the values
+	u32 items;
+} JSONObject;
+
+typedef struct {
+	u32 len;
+	// this is an index into the values array
+	//    values[elements..elements+len] are the elements
+	u32 elements;
+} JSONArray;
+
+enum {
+	JSON_NULL,
+	JSON_FALSE,
+	JSON_TRUE,
+	JSON_NUMBER,
+	JSON_STRING,
+	JSON_OBJECT,
+	JSON_ARRAY
+};
+
+struct JSONValue {
+	u8 type;
+	union {
+		double number;
+		JSONString string;
+		JSONArray array;
+		JSONObject object;
+	} val;
+};
+
+
+typedef struct {
+	char error[64];
+	const char *text;
+	// root = values[0]
+	JSONValue *values;
+} JSON;
+
+#define SKIP_WHITESPACE while (json_is_space(text[index])) ++index;
+
+
+static bool json_parse_value(JSON *json, u32 *p_index, JSONValue *val);
+
+// defining this instead of using isspace seems to be faster
+// probably because isspace depends on the locale.
+static inline bool json_is_space(char c) {
+	return c == ' ' || c == '\n' || c == '\r' || c == '\t';
+}
+
+static void json_debug_print_value(const JSON *json, u32 idx) {
+	JSONValue *value = &json->values[idx];
+	switch (value->type) {
+	case JSON_NULL: printf("null"); break;
+	case JSON_FALSE: printf("false"); break;
+	case JSON_TRUE: printf("true"); break;
+	case JSON_NUMBER: printf("%f", value->val.number); break;
+	case JSON_STRING: {
+		JSONString *string = &value->val.string;
+		printf("\"%.*s\"",
+			(int)string->len,
+			json->text + string->pos);
+		} break;
+	case JSON_ARRAY: {
+		JSONArray *array = &value->val.array;
+		printf("[");
+		for (u32 i = 0; i < array->len; ++i) {
+			json_debug_print_value(json, array->elements + i);
+			printf(", ");
+		}
+		printf("]");
+	} break;
+	case JSON_OBJECT: {
+		JSONObject *obj = &value->val.object;
+		printf("{");
+		for (u32 i = 0; i < obj->len; ++i) {
+			json_debug_print_value(json, obj->items + i);
+			printf(": ");
+			json_debug_print_value(json, obj->items + obj->len + i);
+			printf(", ");
+		}
+		printf("}");
+		} break;
+	}
+}
+
+// count number of comma-separated values until
+// closing ] or }
+static u32 json_count(JSON *json, u32 index) {
+	int bracket_depth = 0;
+	int brace_depth = 0;
+	u32 count = 1;
+	const char *text = json->text;
+	SKIP_WHITESPACE;
+	// special case: empty object/array
+	if (text[index] == '}' || text[index] == ']')
+		return 0;
+	
+// 	int mark[5000] = {0};
+	for (; ; ++index) {
+		switch (text[index]) {
+		case '\0':
+			return 0; // bad no closing bracket
+		case '[':
+			++bracket_depth;
+			break;
+		case ']':
+			--bracket_depth;
+			if (bracket_depth < 0)
+				return count;
+			break;
+		case '{':
+			++brace_depth;
+// 			mark[index] = 1;
+			break;
+		case '}':
+			--brace_depth;
+// 			mark[index] = 1;
+			if (brace_depth < 0){
+			// useful visualization for debugging
+// 			for (int i = 0; text[i]; ++i ){
+// 				switch (mark[i]){
+// 				case 1: printf("\x1b[91m"); break;
+// 				case 2: printf("\x1b[92m"); break;
+// 				}
+// 				printf("%c",text[i]);
+// 				if (mark[i]) printf("\x1b[0m");
+// 			}
+// 			printf("\n");
+			
+				return count;
+			}
+			break;
+		case ',':
+			if (bracket_depth == 0 && brace_depth == 0)
+				++count;
+			break;
+		case '"': {
+			++index; // skip opening "
+			int escaped = 0;
+			for (; ; ++index) {
+// 				mark[index] = 2;
+				switch (text[index]) {
+				case '\0': return 0; // bad no closing quote
+				case '\\': escaped = !escaped; break;
+				case '"':
+					if (!escaped)
+						goto done;
+					escaped = false;
+					break;
+				default:
+					escaped = false;
+					break;
+				}
+			}
+			done:;
+			} break;
+		}
+	}
+}
+
+static bool json_parse_object(JSON *json, u32 *p_index, JSONObject *object) {
+	u32 index = *p_index;
+	const char *text = json->text;
+	++index; // go past {
+	u32 count = json_count(json, index);
+	object->len = count;
+	object->items = arr_len(json->values);
+	arr_set_len(json->values, arr_len(json->values) + 2 * count);
+	
+	for (u32 i = 0; i < count; ++i) {
+		if (i > 0) {
+			if (text[index] != ',') {
+				strbuf_printf(json->error, "stuff after value in object");
+				return false;
+			}
+			++index;
+		}
+		SKIP_WHITESPACE;
+		JSONValue name = {0}, value = {0};
+		if (!json_parse_value(json, &index, &name))
+			return false;
+		SKIP_WHITESPACE;
+		if (text[index] != ':') {
+			strbuf_printf(json->error, "stuff after name in object");
+			return false;
+		}
+		++index; // skip :
+		SKIP_WHITESPACE;
+		if (!json_parse_value(json, &index, &value))
+			return false;
+		SKIP_WHITESPACE;
+		json->values[object->items + i] = name;
+		json->values[object->items + count + i] = value;
+	}
+	
+	if (text[index] != '}') {
+		strbuf_printf(json->error, "mismatched brackets or quotes.");
+		return false;
+	}
+	++index; // skip }
+	*p_index = index;
+	return true;
+}
+
+static bool json_parse_array(JSON *json, u32 *p_index, JSONArray *array) {
+	u32 index = *p_index;
+	const char *text = json->text;
+	++index; // go past [
+	u32 count = json_count(json, index);
+	array->len = count;
+	array->elements = arr_len(json->values);
+	
+	arr_set_len(json->values, arr_len(json->values) + count);
+	
+	SKIP_WHITESPACE;
+	
+	for (u32 i = 0; i < count; ++i) {
+		if (i > 0) {
+			if (text[index] != ',') {
+				strbuf_printf(json->error, "stuff after element in array");
+				return false;
+			}
+			++index;
+		}
+		SKIP_WHITESPACE;
+		JSONValue element = {0};
+		if (!json_parse_value(json, &index, &element))
+			return false;
+		SKIP_WHITESPACE;
+		json->values[array->elements + i] = element;
+	}
+	
+	if (text[index] != ']') {
+		strbuf_printf(json->error, "mismatched brackets or quotes.");
+		return false;
+	}
+	++index; // skip ]
+	*p_index = index;
+	return true;
+}
+
+static bool json_parse_string(JSON *json, u32 *p_index, JSONString *string) {
+	u32 index = *p_index;
+	++index; // skip opening "
+	string->pos = index;
+	const char *text = json->text;
+	bool escaped = false;
+	for (; ; ++index) {
+		switch (text[index]) {
+		case '"':
+			if (!escaped)
+				goto done;
+			escaped = false;
+			break;
+		case '\\':
+			escaped = !escaped;
+			break;
+		case '\0':
+			strbuf_printf(json->error, "string literal goes to end of JSON");
+			return false;
+		default:
+			escaped = false;
+			break;
+		}
+	}
+	done:
+	string->len = index - string->pos;
+	++index; // skip closing "
+	*p_index = index;
+	return true;
+}
+
+static bool json_parse_number(JSON *json, u32 *p_index, double *number) {
+	char *endp = NULL;
+	const char *text = json->text;
+	u32 index = *p_index;
+	*number = strtod(text + index, &endp);
+	if (endp == text + index) {
+		strbuf_printf(json->error, "bad number");
+		return false;
+	}
+	index = (u32)(endp - text);
+	*p_index = index;
+	return true;
+}
+
+static bool json_parse_value(JSON *json, u32 *p_index, JSONValue *val) {
+	const char *text = json->text;
+	u32 index = *p_index;
+	SKIP_WHITESPACE;
+	switch (text[index]) {
+	case '{':
+		val->type = JSON_OBJECT;
+		if (!json_parse_object(json, &index, &val->val.object))
+			return false;
+		break;
+	case '[':
+		val->type = JSON_ARRAY;
+		if (!json_parse_array(json, &index, &val->val.array))
+			return false;
+		break;
+	case '"':
+		val->type = JSON_STRING;
+		if (!json_parse_string(json, &index, &val->val.string))
+			return false;
+		break;
+	case ANY_DIGIT:
+		val->type = JSON_NUMBER;
+		if (!json_parse_number(json, &index, &val->val.number))
+			return false;
+		break;
+	case 'f':
+		val->type = JSON_FALSE;
+		if (!str_has_prefix(&text[index], "false"))
+			return false;
+		index += 5;
+		break;
+	case 't':
+		val->type = JSON_TRUE;
+		if (!str_has_prefix(&text[index], "true"))
+			return false;
+		index += 4;
+		break;
+	case 'n':
+		val->type = JSON_NULL;
+		if (!str_has_prefix(&text[index], "null"))
+			return false;
+		index += 4;
+		break;
+	default:
+		strbuf_printf(json->error, "bad value");
+		return false;
+	}
+	*p_index = index;
+	return true;
+}
+
+// NOTE: text must live as long as json!!!
+static bool json_parse(JSON *json, const char *text) {
+	memset(json, 0, sizeof *json);
+	json->text = text;
+	// @TODO: is this a good capacity?
+	arr_reserve(json->values, strlen(text) / 8);
+	arr_addp(json->values); // add root
+	JSONValue val = {0};
+	u32 index = 0;
+	if (!json_parse_value(json, &index, &val))
+		return false;
+	
+	SKIP_WHITESPACE;
+	if (text[index]) {
+		strbuf_printf(json->error, "extra text after end of root object");
+		return false;
+	}
+	json->values[0] = val;
+	return true;
+}
+
+static void json_free(JSON *json) {
+	arr_free(json->values);
+	memset(json, 0, sizeof *json);
+}
+
+#if __unix__
+static void json_test_time_large(const char *filename) {
+	struct timespec start={0},end={0};
+	FILE *fp = fopen(filename,"rb");
+	if (!fp) {
+		perror(filename);
+		return;
+	}
+	
+	fseek(fp,0,SEEK_END);
+	size_t sz = (size_t)ftell(fp);
+	char *buf = calloc(1,sz+1);
+	rewind(fp);
+	fread(buf, 1, sz, fp);
+	fclose(fp);
+	for (int trial = 0; trial < 5; ++trial) {
+		clock_gettime(CLOCK_MONOTONIC, &start);
+		JSON json={0};
+		bool success = json_parse(&json, buf);
+		if (!success) {
+			printf("FAIL: %s\n",json.error);
+			return;
+		}
+		
+		json_free(&json);
+		clock_gettime(CLOCK_MONOTONIC, &end);
+		
+		
+		
+		printf("time: %.1fms\n",
+			((double)end.tv_sec*1e3+(double)end.tv_nsec*1e-6)
+			-((double)start.tv_sec*1e3+(double)start.tv_nsec*1e-6));
+	}
+		
+}
+static void json_test_time_small(void) {
+	struct timespec start={0},end={0};
+	int trials = 50000000;
+	clock_gettime(CLOCK_MONOTONIC, &start);
+	for (int trial = 0; trial < trials; ++trial) {
+		JSON json={0};
+		bool success = json_parse(&json, "{\"hello\":\"there\"}");
+		if (!success) {
+			printf("FAIL: %s\n",json.error);
+			return;
+		}
+		
+		json_free(&json);
+	}
+	clock_gettime(CLOCK_MONOTONIC, &end);
+	printf("time per trial: %.1fns\n",
+		(((double)end.tv_sec*1e9+(double)end.tv_nsec)
+		-((double)start.tv_sec*1e9+(double)start.tv_nsec))
+		/ trials);
+		
+}
+#endif
+
+static void json_debug_print(const JSON *json) {
+	printf("%u values (capacity %u, text length %zu)\n",
+		arr_len(json->values), arr_cap(json->values), strlen(json->text));
+	json_debug_print_value(json, 0);
+}
+
+#undef SKIP_WHITESPACE