2 *******************************************************************************
3 * @file json_object_iterator.c
5 * Copyright (c) 2009-2012 Hewlett-Packard Development Company, L.P.
7 * This library is free software; you can redistribute it and/or modify
8 * it under the terms of the MIT license. See COPYING for details.
10 * @brief json-c forces clients to use its private data
11 * structures for JSON Object iteration. This API
12 * implementation corrects that by abstracting the
13 * private json-c details.
15 *******************************************************************************
21 #include "json_object_private.h"
23 #include "json_object_iterator.h"
28 * For each JSON Object, json-c maintains a linked list of zero
29 * or more lh_entry (link-hash entry) structures inside the
30 * Object's link-hash table (lh_table).
32 * Each lh_entry structure on the JSON Object's linked list
33 * represents a single name/value pair. The "next" field of the
34 * last lh_entry in the list is set to NULL, which terminates
37 * We represent a valid iterator that refers to an actual
38 * name/value pair via a pointer to the pair's lh_entry
39 * structure set as the iterator's opaque_ field.
41 * We follow json-c's current pair list representation by
42 * representing a valid "end" iterator (one that refers past the
43 * last pair) with a NULL value in the iterator's opaque_ field.
45 * A JSON Object without any pairs in it will have the "head"
46 * field of its lh_table structure set to NULL. For such an
47 * object, json_object_iter_begin will return an iterator with
48 * the opaque_ field set to NULL, which is equivalent to the
51 * When iterating, we simply update the iterator's opaque_ field
52 * to point to the next lh_entry structure in the linked list.
53 * opaque_ will become NULL once we iterate past the last pair
54 * in the list, which makes the iterator equivalent to the "end"
58 /// Our current representation of the "end" iterator;
60 /// @note May not always be NULL
61 static const void* kObjectEndIterValue
= NULL
;
64 * ****************************************************************************
66 struct json_object_iterator
67 json_object_iter_begin(struct json_object
* obj
)
69 struct json_object_iterator iter
;
70 struct lh_table
* pTable
;
72 /// @note json_object_get_object will return NULL if passed NULL
73 /// or a non-json_type_object instance
74 pTable
= json_object_get_object(obj
);
75 JASSERT(NULL
!= pTable
);
77 /// @note For a pair-less Object, head is NULL, which matches our
78 /// definition of the "end" iterator
79 iter
.opaque_
= pTable
->head
;
84 * ****************************************************************************
86 struct json_object_iterator
87 json_object_iter_end(const struct json_object
* obj
)
89 struct json_object_iterator iter
;
92 JASSERT(json_object_is_type(obj
, json_type_object
));
94 iter
.opaque_
= kObjectEndIterValue
;
100 * ****************************************************************************
103 json_object_iter_next(struct json_object_iterator
* iter
)
105 JASSERT(NULL
!= iter
);
106 JASSERT(kObjectEndIterValue
!= iter
->opaque_
);
108 iter
->opaque_
= ((struct lh_entry
*)iter
->opaque_
)->next
;
113 * ****************************************************************************
116 json_object_iter_peek_name(const struct json_object_iterator
* iter
)
118 JASSERT(NULL
!= iter
);
119 JASSERT(kObjectEndIterValue
!= iter
->opaque_
);
121 return (const char*)(((struct lh_entry
*)iter
->opaque_
)->k
);
126 * ****************************************************************************
129 json_object_iter_peek_value(const struct json_object_iterator
* iter
)
131 JASSERT(NULL
!= iter
);
132 JASSERT(kObjectEndIterValue
!= iter
->opaque_
);
134 return (struct json_object
*)(((struct lh_entry
*)iter
->opaque_
)->v
);
139 * ****************************************************************************
142 json_object_iter_equal(const struct json_object_iterator
* iter1
,
143 const struct json_object_iterator
* iter2
)
145 JASSERT(NULL
!= iter1
);
146 JASSERT(NULL
!= iter2
);
148 return (iter1
->opaque_
== iter2
->opaque_
);
153 * ****************************************************************************
155 struct json_object_iterator
156 json_object_iter_init_default(void)
158 struct json_object_iterator iter
;
161 * @note Make this a negative, invalid value, such that
162 * accidental access to it would likely be trapped by the
163 * hardware as an invalid address.