tippecanoe/jsonpull.c

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <stdarg.h>
#include "jsonpull.h"

#define SIZE_FOR(i) (((i) + 31) & ~31)

static json_object *add_object(json_type type, json_object *parent, char **error) {
	json_object *o = malloc(sizeof(struct json_object));
	o->type = type;
	o->parent = parent;
	o->array = NULL;
	o->keys = NULL;
	o->values = NULL;
	o->length = 0;

	if (parent != NULL) {
		if (parent->type == JSON_ARRAY) {
			if (SIZE_FOR(parent->length + 1) != SIZE_FOR(parent->length)) {
				parent->array = realloc(parent->array, SIZE_FOR(parent->length + 1) * sizeof(json_object *));
			}

			parent->array[parent->length++] = o;
		} else if (parent->type == JSON_HASH) {
			if (parent->length > 0 && parent->values[parent->length - 1] == NULL) {
				// Hash has key but no value, so this is the value

				parent->values[parent->length - 1] = o;
			} else {
				// No current hash, so this is a key

				if (type != JSON_STRING) {
					*error = "Hash key is not a string";
					free(o);
					return NULL;
				}

				if (SIZE_FOR(parent->length + 1) != SIZE_FOR(parent->length)) {
					parent->keys = realloc(parent->keys, SIZE_FOR(parent->length + 1) * sizeof(json_object *));
					parent->values = realloc(parent->values, SIZE_FOR(parent->length + 1) * sizeof(json_object *));
				}

				parent->keys[parent->length] = o;
				parent->values[parent->length] = NULL;
				parent->length++;
			}
		} else {
			*error = "Parent is not a container";
			free(o);
			return NULL;
		}
	}

	return o;
}

json_object *json_hash_get(json_object *o, char *s) {
	if (o == NULL || o->type != JSON_HASH) {
		return NULL;
	}

	int i;
	for (i = 0; i < o->length; i++) {
		if (o->keys[i] != NULL && o->keys[i]->type == JSON_STRING) {
			if (strcmp(o->keys[i]->string, s) == 0) {
				return o->values[i];
			}
		}
	}

	return NULL;
}

static int peek(FILE *f) {
	int c = getc(f);
	ungetc(c, f);
	return c;
}

struct string {
	char *buf;
	int n;
	int nalloc;
};

static void string_init(struct string *s) {
	s->nalloc = 500;
	s->buf = malloc(s->nalloc);
	s->n = 0;
	s->buf[0] = '\0';
}

static void string_append(struct string *s, char c) {
	if (s->n + 2 >= s->nalloc) {
		s->nalloc += 500;
		s->buf = realloc(s->buf, s->nalloc);
	}

	s->buf[s->n++] = c;
	s->buf[s->n] = '\0';
}

static void string_free(struct string *s) {
	free(s->buf);
}

json_object *json_parse(FILE *f, json_object *current, char **error) {
	int current_is = 0;
	int c;
again:
	/////////////////////////// Whitespace

	do {
		c = getc(f);
		if (c == EOF) {
			if (current != NULL) {
				*error = "Reached EOF without all containers being closed";
			}

			return NULL;
		}
	} while (c == ' ' || c == '\t' || c == '\r' || c == '\n');

	/////////////////////////// Arrays

	if (c == '[') {
		current = add_object(JSON_ARRAY, current, error);
		if (current == NULL) {
			return NULL;
		}
		current_is = '[';
		goto again;
	} else if (c == ']') {
		if (current == NULL) {
			*error = "Found ] at top level";
			return NULL;
		}

		if (current_is == '[') { // Empty array
			return current;
		} else if (current_is) {
			*error = "Found ] without final element";
			return NULL;
		}

		if (current->parent == NULL || current->parent->type != JSON_ARRAY) {
			*error = "Found ] without matching [";
			return NULL;
		}

		return current->parent;
	}

	/////////////////////////// Hashes

	if (c == '{') {
		current = add_object(JSON_HASH, current, error);
		if (current == NULL) {
			return NULL;
		}
		current_is = '{';
		goto again;
	} else if (c == '}') {
		if (current == NULL) {
			*error = "Found } at top level";
			return NULL;
		}

		if (current_is == '{') { // Empty hash
			return current;
		} else if (current_is) {
			*error = "Found } without final element";
			return NULL;
		}

		if (current->parent == NULL || current->parent->type != JSON_HASH) {
			*error = "Found } without matching {";
			return NULL;
		}
		if (current->parent->length != 0 && current->parent->values[current->parent->length - 1] == NULL) {
			*error = "Found hash key without value";
			return NULL;
		}

		return current->parent;
	}

	/////////////////////////// Null

	if (c == 'n') {
		if (getc(f) != 'u' || getc(f) != 'l' || getc(f) != 'l') {
			*error = "Found misspelling of null";
			return NULL;
		}

		return add_object(JSON_NULL, current, error);
	}

	/////////////////////////// True

	if (c == 't') {
		if (getc(f) != 'r' || getc(f) != 'u' || getc(f) != 'e') {
			*error = "Found misspelling of true";
			return NULL;
		}

		return add_object(JSON_TRUE, current, error);
	}

	/////////////////////////// False

	if (c == 'f') {
		if (getc(f) != 'a' || getc(f) != 'l' || getc(f) != 's' || getc(f) != 'e') {
			*error = "Found misspelling of false";
			return NULL;
		}

		return add_object(JSON_FALSE, current, error);
	}

	/////////////////////////// Comma

	if (c == ',') {
		if (current == NULL) {
			*error = "Found comma at top level";
			return NULL;
		}

		if (current->parent == NULL || (current->parent->type != JSON_ARRAY && current->parent->type != JSON_HASH)) {
			*error = "Found comma outside of array or hash";
			return NULL;
		}

		if (current->parent->type == JSON_HASH) {
			if (current->parent->length == 0 || current->parent->values[current->parent->length - 1] == NULL) {
				*error = "Found comma in hash without a hash value";
				return NULL;
			}
		}

		current = current->parent;
		current_is = ',';
		goto again;
	}

	/////////////////////////// Colon

	if (c == ':') {
		if (current == NULL) {
			*error = "Found colon at top level";
			return NULL;
		}

		if (current->parent == NULL || current->parent->type != JSON_HASH) {
			*error = "Found colon outside of hash";
			return NULL;
		}
		if (current->parent->length == 0 || current->parent->keys[current->parent->length - 1] == NULL) {
			*error = "Found colon without a hash key";
			return NULL;
		}

		current = current->parent;
		current_is = ':';
		goto again;
	}

	/////////////////////////// Numbers

	if (c == '-' || (c >= '0' && c <= '9')) {
		struct string val;
		string_init(&val);

		if (c == '-') {
			string_append(&val, c);
			c = getc(f);
		}

		if (c == '0') {
			string_append(&val, c);
		} else if (c >= '1' && c <= '9') {
			string_append(&val, c);
			c = peek(f);

			while (c >= '0' && c <= '9') {
				string_append(&val, getc(f));
				c = peek(f);
			}
		}

		if (peek(f) == '.') {
			string_append(&val, getc(f));

			c = peek(f);
			while (c >= '0' && c <= '9') {
				string_append(&val, getc(f));
				c = peek(f);
			}
		}

		c = peek(f);
		if (c == 'e' || c == 'E') {
			string_append(&val, getc(f));

			c = peek(f);
			if (c == '+' || c == '-') {
				string_append(&val, getc(f));
			}

			c = peek(f);
			if (c < '0' || c > '9') {
				*error = "Exponent without digits";
				return NULL;
			}
			while (c >= '0' && c <= '9') {
				string_append(&val, getc(f));
				c = peek(f);
			}
		}

		json_object *n = add_object(JSON_NUMBER, current, error);
		if (n != NULL) {
			n->number = atof(val.buf);
			string_free(&val);
		}

		return n;
	}

	/////////////////////////// Strings

	if (c == '"') {
		struct string val;
		string_init(&val);

		while ((c = getc(f)) != EOF) {
			if (c == '"') {
				break;
			} else if (c == '\\') {
				c = getc(f);

				if (c == '"') {
					string_append(&val, '"');
				} else if (c == '\\') {
					string_append(&val, '\\');
				} else if (c == '/') {
					string_append(&val, '/');
				} else if (c == 'b') {
					string_append(&val, '\b');
				} else if (c == 'f') {
					string_append(&val, '\f');
				} else if (c == 'n') {
					string_append(&val, '\n');
				} else if (c == 'r') {
					string_append(&val, '\r');
				} else if (c == 't') {
					string_append(&val, '\t');
				} else if (c == 'u') {
					char hex[5] = "aaaa";
					int i;
					for (i = 0; i < 4; i++) {
						hex[i] = getc(f);
					}
					unsigned long ch = strtoul(hex, NULL, 16);
					if (ch <= 0x7F) {
						string_append(&val, ch);
					} else if (ch <= 0x7FF) {
						string_append(&val, 0xC0 | (ch >> 6));
						string_append(&val, 0x80 | (ch & 0x3F));
					} else {
						string_append(&val, 0xE0 | (ch >> 12));
						string_append(&val, 0x80 | ((ch >> 6) & 0x3F));
						string_append(&val, 0x80 | (ch & 0x3F));
					}
				} else {
					*error = "Found backslash followed by unknown character";
					return NULL;
				}
			} else {
				string_append(&val, c);
			}
		}

		json_object *s = add_object(JSON_STRING, current, error);
		if (s != NULL) {
			s->string = val.buf;
			s->length = val.n;
		}

		return s;
	}

	*error = "Found unexpected character";
	return NULL;
}