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/*
* Copyright (C) 2015-2020 "IoT.bzh"
* Author José Bollo <jose.bollo@iot.bzh>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* This simple program expands the object { "$ref": "#/path/to/a/target" }
*
* For example:
*
* {
* "type":{
* "a": "int",
* "b": { "$ref": "#/type/a" }
* }
* }
*
* will be exapanded to
*
* {
* "type":{
* "a": "int",
* "b": "int"
* }
* }
*
* Invocation: program [file|-]...
*
* without arguments, it reads the input.
*/
#define _GNU_SOURCE
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <json-c/json.h>
/**
* records path to the expanded node
*/
struct path
{
struct json_object *object; /**< node being expanded */
struct path *upper; /**< link to upper expanded nodes */
};
/**
* root of the JSON being parsed
*/
struct json_object *root;
/**
* Search for a reference of type "#/a/b/c" int the
* parsed JSON object
*/
struct json_object *search(const char *path)
{
char *d;
struct json_object *i;
/* does it match #/ at the beginning? */
if (path[0] != '#' || (path[0] && path[1] != '/'))
return NULL;
/* search from root to target */
i = root;
d = strdupa(path+2);
d = strtok(d, "/");
while(i && d) {
if (!json_object_object_get_ex(i, d, &i))
return NULL;
d = strtok(NULL, "/");
}
return i;
}
/**
* Expands the node designated by path and returns its expanded form
*/
struct json_object *expand(struct path path)
{
struct path *p;
struct json_object *o, *x;
int n, i;
struct json_object_iterator ji, jn;
/* expansion depends of the type of the node */
switch (json_object_get_type(path.object)) {
case json_type_object:
/* for object, look if it contains a property "$ref" */
if (json_object_object_get_ex(path.object, "$ref", &o)) {
/* yes, reference, try to substitute its target */
if (!json_object_is_type(o, json_type_string)) {
fprintf(stderr, "found a $ref not being string. Is: %s\n", json_object_get_string(o));
exit(1);
}
x = search(json_object_get_string(o));
if (!x) {
fprintf(stderr, "$ref not found. Was: %s\n", json_object_get_string(o));
exit(1);
}
p = &path;
while(p) {
if (x == p->object) {
fprintf(stderr, "$ref recursive. Was: %s\n", json_object_get_string(o));
exit(1);
}
p = p->upper;
}
/* cool found, return a new instance of the target */
return json_object_get(x);
}
/* no, expand the values */
ji = json_object_iter_begin(path.object);
jn = json_object_iter_end(path.object);
while (!json_object_iter_equal(&ji, &jn)) {
o = json_object_iter_peek_value(&ji);
x = expand((struct path){ .object = o, .upper = &path });
if (x != o)
json_object_object_add(path.object, json_object_iter_peek_name(&ji), x);
json_object_iter_next(&ji);
}
break;
case json_type_array:
/* expand the values of arrays */
i = 0;
n = (int)json_object_array_length(path.object);
while (i != n) {
o = json_object_array_get_idx(path.object, i);
x = expand((struct path){ .object = o, .upper = &path });
if (x != o)
json_object_array_put_idx(path.object, i, x);
i++;
}
break;
default:
/* otherwise no expansion */
break;
}
/* return the given node */
return path.object;
}
/**
* process a file and prints its expansion on stdout
*/
void process(char *filename)
{
/* translate - */
if (!strcmp(filename, "-"))
filename = "/dev/stdin";
/* check access */
if (access(filename, R_OK)) {
fprintf(stderr, "can't access file %s\n", filename);
exit(1);
}
/* read the file */
root = json_object_from_file(filename);
if (!root) {
fprintf(stderr, "reading file %s produced null\n", filename);
exit(1);
}
/* expand */
root = expand((struct path){ .object = root, .upper = NULL });
/* print the result */
json_object_to_file_ext ("/dev/stdout", root, JSON_C_TO_STRING_PRETTY);
/* clean up */
json_object_put(root);
}
/** process the list of files or stdin if none */
int main(int ac, char **av)
{
if (!*++av)
process("-");
else {
do { process(*av); } while(*++av);
}
return 0;
}
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