JSON to S-expr

json2sexpr.c

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <inttypes.h>
#include <unistd.h>

#include <json-c/json.h>

void json2sexp(struct json_object *jobj);
void json_array2sexp(struct json_object *jarray);
void json_obj2sexp(struct json_object *jobj);

void json_array2sexp(struct json_object *jarray)
{
	size_t array_len;
	
	array_len = json_object_array_length(jarray);
	if (array_len > 0) {
		json2sexp(json_object_array_get_idx(jarray, 0));
	}
	for (size_t i = 1; i < array_len; i++) {
		printf(" ");
		json2sexp(json_object_array_get_idx(jarray, i));
	}
}

void json_obj2sexp(struct json_object *jobj)
{
	struct json_object_iter iter;
	json_object_object_foreachC(jobj, iter) {
		printf("(%s ", iter.key);
		json2sexp(iter.val);
		printf(iter.entry->next ? ") " : ")");
	}
}

void json2sexp(struct json_object *jobj)
{
	switch (json_object_get_type(jobj)) {
	case json_type_null:
		printf("nil");
		break;
	case json_type_boolean:
		printf(json_object_get_boolean(jobj) ? "" : "nil");
		break;
	case json_type_double:
		printf("%lf", json_object_get_double(jobj));
		break;
	case json_type_int:
		printf("%" PRId64, json_object_get_int64(jobj));
		break;
	case json_type_string:
		printf("\"%s\"", json_object_get_string(jobj));
		break;
	case json_type_object:
		json_obj2sexp(jobj);
		break;
	case json_type_array:
		json_array2sexp(jobj);
		break;
	}
}

int main(void)
{
	char buf[65536];
	ssize_t nb_read;
	json_object *jobj;
	enum json_tokener_error jerr;
	struct json_tokener *jtok;
	
	jtok = json_tokener_new();
	while (1) {
		jerr = json_tokener_continue;
		while ((jerr == json_tokener_continue) &&
		       (nb_read = read(STDIN_FILENO, &buf, 65536)) > 0) {
			jobj = json_tokener_parse_ex(jtok, buf, nb_read);
			jerr = json_tokener_get_error(jtok);
		}
		
		if (nb_read < 0) {
			perror("read");
			exit(EXIT_FAILURE);
		}
		if (nb_read == 0) {
			fprintf(stderr, "EOF reached\n");
			exit(EXIT_SUCCESS);
		}
		
		if (jerr != json_tokener_success) {
			fprintf(stderr, "json error: %s\n", json_tokener_error_desc(jerr));
			exit(EXIT_FAILURE);
		}
		fprintf(stderr, "%s\n", json_object_to_json_string(jobj));
		json2sexp(jobj); putchar('\n');
	}
	
	return 0;
}