summaryrefslogtreecommitdiff
path: root/json.c
diff options
context:
space:
mode:
Diffstat (limited to 'json.c')
-rw-r--r--json.c444
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
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-26 04:40:36 +0000