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| Dir : //usr/include/json-c/json_object_iterator.h |
/**
*******************************************************************************
* @file json_object_iterator.h
*
* Copyright (c) 2009-2012 Hewlett-Packard Development Company, L.P.
*
* This library is free software; you can redistribute it and/or modify
* it under the terms of the MIT license. See COPYING for details.
*
* @brief An API for iterating over json_type_object objects,
* styled to be familiar to C++ programmers.
* Unlike json_object_object_foreach() and
* json_object_object_foreachC(), this avoids the need to expose
* json-c internals like lh_entry.
*
* API attributes: <br>
* * Thread-safe: NO<br>
* * Reentrant: NO
*
*******************************************************************************
*/
#ifndef JSON_OBJECT_ITERATOR_H
#define JSON_OBJECT_ITERATOR_H
#include <stddef.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* Forward declaration for the opaque iterator information.
*/
struct json_object_iter_info_;
/**
* The opaque iterator that references a name/value pair within
* a JSON Object instance or the "end" iterator value.
*/
struct json_object_iterator {
const void* opaque_;
};
/**
* forward declaration of json-c's JSON value instance structure
*/
struct json_object;
/**
* Initializes an iterator structure to a "default" value that
* is convenient for initializing an iterator variable to a
* default state (e.g., initialization list in a class'
* constructor).
*
* @code
* struct json_object_iterator iter = json_object_iter_init_default();
* MyClass() : iter_(json_object_iter_init_default())
* @endcode
*
* @note The initialized value doesn't reference any specific
* pair, is considered an invalid iterator, and MUST NOT
* be passed to any json-c API that expects a valid
* iterator.
*
* @note User and internal code MUST NOT make any assumptions
* about and dependencies on the value of the "default"
* iterator value.
*
* @return json_object_iterator
*/
struct json_object_iterator
json_object_iter_init_default(void);
/** Retrieves an iterator to the first pair of the JSON Object.
*
* @warning Any modification of the underlying pair invalidates all
* iterators to that pair.
*
* @param obj JSON Object instance (MUST be of type json_object)
*
* @return json_object_iterator If the JSON Object has at
* least one pair, on return, the iterator refers
* to the first pair. If the JSON Object doesn't
* have any pairs, the returned iterator is
* equivalent to the "end" iterator for the same
* JSON Object instance.
*
* @code
* struct json_object_iterator it;
* struct json_object_iterator itEnd;
* struct json_object* obj;
*
* obj = json_tokener_parse("{'first':'george', 'age':100}");
* it = json_object_iter_begin(obj);
* itEnd = json_object_iter_end(obj);
*
* while (!json_object_iter_equal(&it, &itEnd)) {
* printf("%s\n",
* json_object_iter_peek_name(&it));
* json_object_iter_next(&it);
* }
*
* @endcode
*/
struct json_object_iterator
json_object_iter_begin(struct json_object* obj);
/** Retrieves the iterator that represents the position beyond the
* last pair of the given JSON Object instance.
*
* @warning Do NOT write code that assumes that the "end"
* iterator value is NULL, even if it is so in a
* particular instance of the implementation.
*
* @note The reason we do not (and MUST NOT) provide
* "json_object_iter_is_end(json_object_iterator* iter)"
* type of API is because it would limit the underlying
* representation of name/value containment (or force us
* to add additional, otherwise unnecessary, fields to
* the iterator structure). The "end" iterator and the
* equality test method, on the other hand, permit us to
* cleanly abstract pretty much any reasonable underlying
* representation without burdening the iterator
* structure with unnecessary data.
*
* @note For performance reasons, memorize the "end" iterator prior
* to any loop.
*
* @param obj JSON Object instance (MUST be of type json_object)
*
* @return json_object_iterator On return, the iterator refers
* to the "end" of the Object instance's pairs
* (i.e., NOT the last pair, but "beyond the last
* pair" value)
*/
struct json_object_iterator
json_object_iter_end(const struct json_object* obj);
/** Returns an iterator to the next pair, if any
*
* @warning Any modification of the underlying pair
* invalidates all iterators to that pair.
*
* @param iter [IN/OUT] Pointer to iterator that references a
* name/value pair; MUST be a valid, non-end iterator.
* WARNING: bad things will happen if invalid or "end"
* iterator is passed. Upon return will contain the
* reference to the next pair if there is one; if there
* are no more pairs, will contain the "end" iterator
* value, which may be compared against the return value
* of json_object_iter_end() for the same JSON Object
* instance.
*/
void
json_object_iter_next(struct json_object_iterator* iter);
/** Returns a const pointer to the name of the pair referenced
* by the given iterator.
*
* @param iter pointer to iterator that references a name/value
* pair; MUST be a valid, non-end iterator.
*
* @warning bad things will happen if an invalid or
* "end" iterator is passed.
*
* @return const char* Pointer to the name of the referenced
* name/value pair. The name memory belongs to the
* name/value pair, will be freed when the pair is
* deleted or modified, and MUST NOT be modified or
* freed by the user.
*/
const char*
json_object_iter_peek_name(const struct json_object_iterator* iter);
/** Returns a pointer to the json-c instance representing the
* value of the referenced name/value pair, without altering
* the instance's reference count.
*
* @param iter pointer to iterator that references a name/value
* pair; MUST be a valid, non-end iterator.
*
* @warning bad things will happen if invalid or
* "end" iterator is passed.
*
* @return struct json_object* Pointer to the json-c value
* instance of the referenced name/value pair; the
* value's reference count is not changed by this
* function: if you plan to hold on to this json-c node,
* take a look at json_object_get() and
* json_object_put(). IMPORTANT: json-c API represents
* the JSON Null value as a NULL json_object instance
* pointer.
*/
struct json_object*
json_object_iter_peek_value(const struct json_object_iterator* iter);
/** Tests two iterators for equality. Typically used to test
* for end of iteration by comparing an iterator to the
* corresponding "end" iterator (that was derived from the same
* JSON Object instance).
*
* @note The reason we do not (and MUST NOT) provide
* "json_object_iter_is_end(json_object_iterator* iter)"
* type of API is because it would limit the underlying
* representation of name/value containment (or force us
* to add additional, otherwise unnecessary, fields to
* the iterator structure). The equality test method, on
* the other hand, permits us to cleanly abstract pretty
* much any reasonable underlying representation.
*
* @param iter1 Pointer to first valid, non-NULL iterator
* @param iter2 POinter to second valid, non-NULL iterator
*
* @warning if a NULL iterator pointer or an uninitialized
* or invalid iterator, or iterators derived from
* different JSON Object instances are passed, bad things
* will happen!
*
* @return json_bool non-zero if iterators are equal (i.e., both
* reference the same name/value pair or are both at
* "end"); zero if they are not equal.
*/
json_bool
json_object_iter_equal(const struct json_object_iterator* iter1,
const struct json_object_iterator* iter2);
#ifdef __cplusplus
}
#endif
#endif /* JSON_OBJECT_ITERATOR_H */