--- /dev/null
+/*
+ * Copyright (c) 2016 Alexandru Ardelean.
+ *
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the MIT license. See COPYING for details.
+ *
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <ctype.h>
+
+#include "json_pointer.h"
+
+/**
+ * JavaScript Object Notation (JSON) Pointer
+ * RFC 6901 - https://tools.ietf.org/html/rfc6901
+ */
+
+static void string_replace_all_occurrences_with_char(char *s, const char *occur, char repl_char)
+{
+ int slen = strlen(s);
+ int skip = strlen(occur) - 1; /* length of the occurence, minus the char we're replacing */
+ char *p = s;
+ while ((p = strstr(p, occur))) {
+ *p = repl_char;
+ p++;
+ slen -= skip;
+ memcpy(p, (p + skip), slen - (p - s) + 1); /* includes null char too */
+ }
+}
+
+static int is_valid_index(struct json_object *jo, const char *path, int32_t *idx)
+{
+ int i, len = strlen(path);
+ /* this code-path optimizes a bit, for when we reference the 0-9 index range in a JSON array
+ and because leading zeros not allowed */
+ if (len == 1) {
+ if (isdigit(path[0])) {
+ *idx = (path[0] - '0');
+ goto check_oob;
+ }
+ errno = EINVAL;
+ return 0;
+ }
+ /* leading zeros not allowed per RFC */
+ if (path[0] == '0') {
+ errno = EINVAL;
+ return 0;
+ }
+ /* RFC states base-10 decimals */
+ for (i = 0; i < len; i++) {
+ if (!isdigit(path[i])) {
+ errno = EINVAL;
+ return 0;
+ }
+ }
+
+ *idx = strtol(path, NULL, 10);
+ if (*idx < 0) {
+ errno = EINVAL;
+ return 0;
+ }
+check_oob:
+ len = json_object_array_length(jo);
+ if (*idx >= len) {
+ errno = ENOENT;
+ return 0;
+ }
+
+ return 1;
+}
+
+static int json_pointer_get_single_path(struct json_object *obj, char *path, struct json_object **value)
+{
+ if (json_object_is_type(obj, json_type_array)) {
+ int32_t idx;
+ if (!is_valid_index(obj, path, &idx))
+ return -1;
+ obj = json_object_array_get_idx(obj, idx);
+ if (obj) {
+ if (value)
+ *value = obj;
+ return 0;
+ }
+ /* Entry not found */
+ errno = ENOENT;
+ return -1;
+ }
+
+ /* RFC states that we first must eval all ~1 then all ~0 */
+ string_replace_all_occurrences_with_char(path, "~1", '/');
+ string_replace_all_occurrences_with_char(path, "~0", '~');
+
+ if (!json_object_object_get_ex(obj, path, value)) {
+ errno = ENOENT;
+ return -1;
+ }
+
+ return 0;
+}
+
+static int json_pointer_set_single_path(
+ struct json_object *parent,
+ const char *path,
+ struct json_object *value)
+{
+ if (json_object_is_type(parent, json_type_array)) {
+ int32_t idx;
+ /* RFC (Chapter 4) states that '-' may be used to add new elements to an array */
+ if (path[0] == '-' && path[1] == '\0')
+ return json_object_array_add(parent, value);
+ if (!is_valid_index(parent, path, &idx))
+ return -1;
+ return json_object_array_put_idx(parent, idx, value);
+ }
+
+ /* path replacements should have been done in json_pointer_get_single_path(),
+ and we should still be good here */
+ if (json_object_is_type(parent, json_type_object))
+ return json_object_object_add(parent, path, value);
+
+ /* Getting here means that we tried to "dereference" a primitive JSON type (like string, int, bool).
+ i.e. add a sub-object to it */
+ errno = ENOENT;
+ return -1;
+}
+
+static int json_pointer_get_recursive(
+ struct json_object *obj,
+ char *path,
+ struct json_object **value)
+{
+ char *endp;
+ int rc;
+
+ /* All paths (on each recursion level must have a leading '/' */
+ if (path[0] != '/') {
+ errno = EINVAL;
+ return -1;
+ }
+ path++;
+
+ endp = strchr(path, '/');
+ if (endp)
+ *endp = '\0';
+
+ /* If we err-ed here, return here */
+ if ((rc = json_pointer_get_single_path(obj, path, &obj)))
+ return rc;
+
+ if (endp) {
+ *endp = '/'; /* Put the slash back, so that the sanity check passes on next recursion level */
+ return json_pointer_get_recursive(obj, endp, value);
+ }
+
+ /* We should be at the end of the recursion here */
+ if (value)
+ *value = obj;
+
+ return 0;
+}
+
+int json_pointer_get(struct json_object *obj, const char *path, struct json_object **res)
+{
+ char *path_copy = NULL;
+ int rc;
+
+ if (!obj || !path) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ if (path[0] == '\0') {
+ if (res)
+ *res = obj;
+ return 0;
+ }
+
+ /* pass a working copy to the recursive call */
+ if (!(path_copy = strdup(path))) {
+ errno = ENOMEM;
+ return -1;
+ }
+ rc = json_pointer_get_recursive(obj, path_copy, res);
+ free(path_copy);
+
+ return rc;
+}
+
+int json_pointer_set(struct json_object **obj, const char *path, struct json_object *value)
+{
+ const char *endp;
+ char *path_copy = NULL;
+ struct json_object *set = NULL;
+ int rc;
+
+ if (!obj || !path) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ if (path[0] == '\0') {
+ json_object_put(*obj);
+ *obj = value;
+ return 0;
+ }
+
+ if (path[0] != '/') {
+ errno = EINVAL;
+ return -1;
+ }
+
+ /* If there's only 1 level to set, stop here */
+ if ((endp = strrchr(path, '/')) == path) {
+ path++;
+ return json_pointer_set_single_path(*obj, path, value);
+ }
+
+ /* pass a working copy to the recursive call */
+ if (!(path_copy = strdup(path))) {
+ errno = ENOMEM;
+ return -1;
+ }
+ path_copy[endp - path] = '\0';
+ rc = json_pointer_get_recursive(*obj, path_copy, &set);
+ free(path_copy);
+
+ if (rc)
+ return rc;
+
+ endp++;
+ return json_pointer_set_single_path(set, endp, value);
+}
+
--- /dev/null
+/*
+ * Copyright (c) 2016 Alexadru Ardelean.
+ *
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the MIT license. See COPYING for details.
+ *
+ */
+
+#ifndef _json_pointer_h_
+#define _json_pointer_h_
+
+#include "json_object.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Retrieves a JSON sub-object from inside another JSON object
+ * using the JSON pointer notation as defined in RFC 6901
+ * https://tools.ietf.org/html/rfc6901
+ *
+ * The returned JSON sub-object is equivalent to parsing manually the
+ * 'obj' JSON tree ; i.e. it's not a new object that is created, but rather
+ * a pointer inside the JSON tree.
+ *
+ * Internally, this is equivalent to doing a series of 'json_object_object_get()'
+ * and 'json_object_array_get_idx()' along the given 'path'.
+ *
+ * @param obj the json_object instance/tree from where to retrieve sub-objects
+ * @param path a (RFC6901) string notation for the sub-object to retrieve
+ * @param res a pointer where to store a reference to the json_object
+ * associated with the given path
+ *
+ * @return negative if an error (or not found), or 0 if succeeded
+ */
+int json_pointer_get(struct json_object *obj, const char *path, struct json_object **res);
+
+/**
+ * Sets JSON object 'value' in the 'obj' tree at the location specified
+ * by the 'path'. 'path' is JSON pointer notation as defined in RFC 6901
+ * https://tools.ietf.org/html/rfc6901
+ *
+ * Note that 'obj' is a double pointer, mostly for the "" (empty string)
+ * case, where the entire JSON object would be replaced by 'value'.
+ * In the case of the "" path, the object at '*obj' will have it's refcount
+ * decremented with 'json_object_put()' and the 'value' object will be assigned to it.
+ *
+ * For other cases (JSON sub-objects) ownership of 'value' will be transferred into
+ * '*obj' via 'json_object_object_add()' & 'json_object_array_put_idx()', so the
+ * only time the refcount should be decremented for 'value' is when the return value of
+ * 'json_pointer_set()' is negative (meaning the 'value' object did not get set into '*obj').
+ *
+ * That also implies that 'json_pointer_set()' does not do any refcount incrementing.
+ * (Just that single decrement that was mentioned above).
+ *
+ * @param obj the json_object instance/tree to which to add a sub-object
+ * @param path a (RFC6901) string notation for the sub-object to set in the tree
+ * @param value object to set at path
+ *
+ * @return negative if an error (or not found), or 0 if succeeded
+ */
+int json_pointer_set(struct json_object **obj, const char *path, struct json_object *value);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
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