Keith Derrick | ded667a | 2012-04-23 15:34:44 -0700 | [diff] [blame^] | 1 | /** |
Keith Derrick | bcfd1f5 | 2012-04-12 09:54:21 -0700 | [diff] [blame] | 2 | ******************************************************************************* |
Keith Derrick | ded667a | 2012-04-23 15:34:44 -0700 | [diff] [blame^] | 3 | * @file json_object_iterator.c |
| 4 | * |
| 5 | * Copyright (c) 2009-2012 Hewlett-Packard Development Company, L.P. |
Keith Derrick | bcfd1f5 | 2012-04-12 09:54:21 -0700 | [diff] [blame] | 6 | * |
| 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. |
| 9 | * |
Keith Derrick | ded667a | 2012-04-23 15:34:44 -0700 | [diff] [blame^] | 10 | * @brief json-c forces clients to use its private data |
Keith Derrick | bcfd1f5 | 2012-04-12 09:54:21 -0700 | [diff] [blame] | 11 | * structures for JSON Object iteration. This API |
| 12 | * implementation corrects that by abstracting the |
Keith Derrick | ded667a | 2012-04-23 15:34:44 -0700 | [diff] [blame^] | 13 | * private json-c details. |
| 14 | * |
Keith Derrick | bcfd1f5 | 2012-04-12 09:54:21 -0700 | [diff] [blame] | 15 | ******************************************************************************* |
| 16 | */ |
| 17 | |
| 18 | #include <stddef.h> |
| 19 | #include <stdbool.h> |
| 20 | |
| 21 | #include "json.h" |
| 22 | #include "json_object_private.h" |
| 23 | |
| 24 | #include "json_object_iterator.h" |
| 25 | |
| 26 | /** |
| 27 | * How It Works |
Keith Derrick | ded667a | 2012-04-23 15:34:44 -0700 | [diff] [blame^] | 28 | * |
| 29 | * For each JSON Object, json-c maintains a linked list of zero |
Keith Derrick | bcfd1f5 | 2012-04-12 09:54:21 -0700 | [diff] [blame] | 30 | * or more lh_entry (link-hash entry) structures inside the |
| 31 | * Object's link-hash table (lh_table). |
Keith Derrick | ded667a | 2012-04-23 15:34:44 -0700 | [diff] [blame^] | 32 | * |
Keith Derrick | bcfd1f5 | 2012-04-12 09:54:21 -0700 | [diff] [blame] | 33 | * Each lh_entry structure on the JSON Object's linked list |
| 34 | * represents a single name/value pair. The "next" field of the |
| 35 | * last lh_entry in the list is set to NULL, which terminates |
| 36 | * the list. |
Keith Derrick | ded667a | 2012-04-23 15:34:44 -0700 | [diff] [blame^] | 37 | * |
Keith Derrick | bcfd1f5 | 2012-04-12 09:54:21 -0700 | [diff] [blame] | 38 | * We represent a valid iterator that refers to an actual |
| 39 | * name/value pair via a pointer to the pair's lh_entry |
| 40 | * structure set as the iterator's opaque_ field. |
Keith Derrick | ded667a | 2012-04-23 15:34:44 -0700 | [diff] [blame^] | 41 | * |
| 42 | * We follow json-c's current pair list representation by |
Keith Derrick | bcfd1f5 | 2012-04-12 09:54:21 -0700 | [diff] [blame] | 43 | * representing a valid "end" iterator (one that refers past the |
| 44 | * last pair) with a NULL value in the iterator's opaque_ field. |
Keith Derrick | ded667a | 2012-04-23 15:34:44 -0700 | [diff] [blame^] | 45 | * |
Keith Derrick | bcfd1f5 | 2012-04-12 09:54:21 -0700 | [diff] [blame] | 46 | * A JSON Object without any pairs in it will have the "head" |
| 47 | * field of its lh_table structure set to NULL. For such an |
| 48 | * object, json_object_iter_begin will return an iterator with |
| 49 | * the opaque_ field set to NULL, which is equivalent to the |
| 50 | * "end" iterator. |
Keith Derrick | ded667a | 2012-04-23 15:34:44 -0700 | [diff] [blame^] | 51 | * |
Keith Derrick | bcfd1f5 | 2012-04-12 09:54:21 -0700 | [diff] [blame] | 52 | * When iterating, we simply update the iterator's opaque_ field |
| 53 | * to point to the next lh_entry structure in the linked list. |
| 54 | * opaque_ will become NULL once we iterate past the last pair |
| 55 | * in the list, which makes the iterator equivalent to the "end" |
| 56 | * iterator. |
| 57 | */ |
| 58 | |
| 59 | /// Our current representation of the "end" iterator; |
Keith Derrick | ded667a | 2012-04-23 15:34:44 -0700 | [diff] [blame^] | 60 | /// |
Keith Derrick | bcfd1f5 | 2012-04-12 09:54:21 -0700 | [diff] [blame] | 61 | /// @note May not always be NULL |
| 62 | static const void* kObjectEndIterValue = NULL; |
| 63 | |
| 64 | /** |
| 65 | * **************************************************************************** |
| 66 | */ |
| 67 | struct json_object_iterator |
| 68 | json_object_iter_begin(struct json_object* obj) |
| 69 | { |
| 70 | struct json_object_iterator iter; |
| 71 | struct lh_table* pTable; |
| 72 | |
| 73 | /// @note json_object_get_object will return NULL if passed NULL |
| 74 | /// or a non-json_type_object instance |
| 75 | pTable = json_object_get_object(obj); |
| 76 | JASSERT(NULL != pTable); |
| 77 | |
| 78 | /// @note For a pair-less Object, head is NULL, which matches our |
| 79 | /// definition of the "end" iterator |
| 80 | iter.opaque_ = pTable->head; |
| 81 | return iter; |
| 82 | } |
| 83 | |
| 84 | /** |
| 85 | * **************************************************************************** |
| 86 | */ |
| 87 | struct json_object_iterator |
| 88 | json_object_iter_end(const struct json_object* obj) |
| 89 | { |
| 90 | struct json_object_iterator iter; |
| 91 | |
| 92 | JASSERT(NULL != obj); |
| 93 | JASSERT(json_object_is_type(obj, json_type_object)); |
| 94 | |
| 95 | iter.opaque_ = kObjectEndIterValue; |
| 96 | |
| 97 | return iter; |
| 98 | } |
| 99 | |
| 100 | /** |
| 101 | * **************************************************************************** |
| 102 | */ |
| 103 | void |
| 104 | json_object_iter_next(struct json_object_iterator* iter) |
| 105 | { |
| 106 | JASSERT(NULL != iter); |
| 107 | JASSERT(kObjectEndIterValue != iter->opaque_); |
| 108 | |
| 109 | iter->opaque_ = ((struct lh_entry *)iter->opaque_)->next; |
| 110 | } |
| 111 | |
| 112 | |
| 113 | /** |
| 114 | * **************************************************************************** |
| 115 | */ |
| 116 | const char* |
| 117 | json_object_iter_peek_name(const struct json_object_iterator* iter) |
| 118 | { |
| 119 | JASSERT(NULL != iter); |
| 120 | JASSERT(kObjectEndIterValue != iter->opaque_); |
| 121 | |
| 122 | return (const char*)(((struct lh_entry *)iter->opaque_)->k); |
| 123 | } |
| 124 | |
| 125 | |
| 126 | /** |
| 127 | * **************************************************************************** |
| 128 | */ |
| 129 | struct json_object* |
| 130 | json_object_iter_peek_value(const struct json_object_iterator* iter) |
| 131 | { |
| 132 | JASSERT(NULL != iter); |
| 133 | JASSERT(kObjectEndIterValue != iter->opaque_); |
| 134 | |
| 135 | return (struct json_object*)(((struct lh_entry *)iter->opaque_)->v); |
| 136 | } |
| 137 | |
| 138 | |
| 139 | /** |
| 140 | * **************************************************************************** |
| 141 | */ |
| 142 | bool |
| 143 | json_object_iter_equal(const struct json_object_iterator* iter1, |
| 144 | const struct json_object_iterator* iter2) |
| 145 | { |
| 146 | JASSERT(NULL != iter1); |
| 147 | JASSERT(NULL != iter2); |
| 148 | |
| 149 | return (iter1->opaque_ == iter2->opaque_); |
| 150 | } |
| 151 | |
| 152 | |
| 153 | /** |
| 154 | * **************************************************************************** |
| 155 | */ |
| 156 | struct json_object_iterator |
| 157 | json_object_iter_init_default(void) |
| 158 | { |
| 159 | struct json_object_iterator iter; |
| 160 | |
| 161 | /** |
| 162 | * @note Make this a negative, invalid value, such that |
| 163 | * accidental access to it would likely be trapped by the |
| 164 | * hardware as an invalid address. |
| 165 | */ |
| 166 | iter.opaque_ = NULL; |
| 167 | |
| 168 | return iter; |
| 169 | } |