12 All declarations are in :file:`jansson.h`, so it's enough to
20 All constants are prefixed ``JSON_`` and other identifiers with
21 ``json_``. Type names are suffixed with ``_t`` and ``typedef``\ 'd so
22 that the ``struct`` keyword need not be used.
28 The JSON specification (:rfc:`4627`) defines the following data types:
29 *object*, *array*, *string*, *number*, *boolean*, and *null*. JSON
30 types are used dynamically; arrays and objects can hold any other data
31 type, including themselves. For this reason, Jansson's type system is
32 also dynamic in nature. There's one C type to represent all JSON
33 values, and this structure knows the type of the JSON value it holds.
37 This data structure is used throughout the library to represent all
38 JSON values. It always contains the type of the JSON value it holds
39 and the value's reference count. The rest depends on the type of the
42 Objects of :ctype:`json_t` are always used through a pointer. There
43 are APIs for querying the type, manipulating the reference count, and
44 for constructing and manipulating values of different types.
46 Unless noted otherwise, all API functions return an error value if an
47 error occurs. Depending on the function's signature, the error value
48 is either *NULL* or -1. Invalid arguments or invalid input are
49 apparent sources for errors. Memory allocation and I/O operations may
56 The type of a JSON value is queried and tested using the following
59 .. ctype:: enum json_type
61 The type of a JSON value. The following members are defined:
63 +-------------------------+
64 | :const:`JSON_OBJECT` |
65 +-------------------------+
66 | :const:`JSON_ARRAY` |
67 +-------------------------+
68 | :const:`JSON_STRING` |
69 +-------------------------+
70 | :const:`JSON_INTEGER` |
71 +-------------------------+
72 | :const:`JSON_REAL` |
73 +-------------------------+
74 | :const:`JSON_TRUE` |
75 +-------------------------+
76 | :const:`JSON_FALSE` |
77 +-------------------------+
78 | :const:`JSON_NULL` |
79 +-------------------------+
81 These correspond to JSON object, array, string, number, boolean and
82 null. A number is represented by either a value of the type
83 :const:`JSON_INTEGER` or of the type :const:`JSON_REAL`. A true
84 boolean value is represented by a value of the type
85 :const:`JSON_TRUE` and false by a value of the type
88 .. cfunction:: int json_typeof(const json_t *json)
90 Return the type of the JSON value (a :ctype:`json_type` cast to
91 :ctype:`int`). *json* MUST NOT be *NULL*. This function is actually
92 implemented as a macro for speed.
94 .. cfunction:: json_is_object(const json_t *json)
95 json_is_array(const json_t *json)
96 json_is_string(const json_t *json)
97 json_is_integer(const json_t *json)
98 json_is_real(const json_t *json)
99 json_is_true(const json_t *json)
100 json_is_false(const json_t *json)
101 json_is_null(const json_t *json)
103 These functions (actually macros) return true (non-zero) for values
104 of the given type, and false (zero) for values of other types and
107 .. cfunction:: json_is_number(const json_t *json)
109 Returns true for values of types :const:`JSON_INTEGER` and
110 :const:`JSON_REAL`, and false for other types and for *NULL*.
112 .. cfunction:: json_is_boolean(const json_t *json)
114 Returns true for types :const:`JSON_TRUE` and :const:`JSON_FALSE`,
115 and false for values of other types and for *NULL*.
118 .. _apiref-reference-count:
123 The reference count is used to track whether a value is still in use
124 or not. When a value is created, it's reference count is set to 1. If
125 a reference to a value is kept (e.g. a value is stored somewhere for
126 later use), its reference count is incremented, and when the value is
127 no longer needed, the reference count is decremented. When the
128 reference count drops to zero, there are no references left, and the
129 value can be destroyed.
131 The following functions are used to manipulate the reference count.
133 .. cfunction:: json_t *json_incref(json_t *json)
135 Increment the reference count of *json* if it's not non-*NULL*.
138 .. cfunction:: void json_decref(json_t *json)
140 Decrement the reference count of *json*. As soon as a call to
141 :cfunc:`json_decref()` drops the reference count to zero, the value
142 is destroyed and it can no longer be used.
144 Functions creating new JSON values set the reference count to 1. These
145 functions are said to return a **new reference**. Other functions
146 returning (existing) JSON values do not normally increase the
147 reference count. These functions are said to return a **borrowed
148 reference**. So, if the user will hold a reference to a value returned
149 as a borrowed reference, he must call :cfunc:`json_incref`. As soon as
150 the value is no longer needed, :cfunc:`json_decref` should be called
151 to release the reference.
153 Normally, all functions accepting a JSON value as an argument will
154 manage the reference, i.e. increase and decrease the reference count
155 as needed. However, some functions **steal** the reference, i.e. they
156 have the same result as if the user called :cfunc:`json_decref()` on
157 the argument right after calling the function. These functions are
158 suffixed with ``_new`` or have ``_new_`` somewhere in their name.
160 For example, the following code creates a new JSON array and appends
163 json_t *array, *integer;
165 array = json_array();
166 integer = json_integer(42);
168 json_array_append(array, integer);
169 json_decref(integer);
171 Note how the caller has to release the reference to the integer value
172 by calling :cfunc:`json_decref()`. By using a reference stealing
173 function :cfunc:`json_array_append_new()` instead of
174 :cfunc:`json_array_append()`, the code becomes much simpler::
176 json_t *array = json_array();
177 json_array_append_new(array, json_integer(42));
179 In this case, the user doesn't have to explicitly release the
180 reference to the integer value, as :cfunc:`json_array_append_new()`
181 steals the reference when appending the value to the array.
183 In the following sections it is clearly documented whether a function
184 will return a new or borrowed reference or steal a reference to its
191 A circular reference is created when an object or an array is,
192 directly or indirectly, inserted inside itself. The direct case is
195 json_t *obj = json_object();
196 json_object_set(obj, "foo", obj);
198 Jansson will refuse to do this, and :cfunc:`json_object_set()` (and
199 all the other such functions for objects and arrays) will return with
200 an error status. The indirect case is the dangerous one::
202 json_t *arr1 = json_array(), *arr2 = json_array();
203 json_array_append(arr1, arr2);
204 json_array_append(arr2, arr1);
206 In this example, the array ``arr2`` is contained in the array
207 ``arr1``, and vice versa. Jansson cannot check for this kind of
208 indirect circular references without a performance hit, so it's up to
209 the user to avoid them.
211 If a circular reference is created, the memory consumed by the values
212 cannot be freed by :cfunc:`json_decref()`. The reference counts never
213 drops to zero because the values are keeping the references to each
214 other. Moreover, trying to encode the values with any of the encoding
215 functions will fail. The encoder detects circular references and
216 returns an error status.
222 These values are implemented as singletons, so each of these functions
223 returns the same value each time.
225 .. cfunction:: json_t *json_true(void)
229 Returns the JSON true value.
231 .. cfunction:: json_t *json_false(void)
235 Returns the JSON false value.
237 .. cfunction:: json_t *json_null(void)
241 Returns the JSON null value.
247 Jansson uses UTF-8 as the character encoding. All JSON strings must be
248 valid UTF-8 (or ASCII, as it's a subset of UTF-8). Normal null
249 terminated C strings are used, so JSON strings may not contain
250 embedded null characters. All other Unicode codepoints U+0001 through
251 U+10FFFF are allowed.
253 .. cfunction:: json_t *json_string(const char *value)
257 Returns a new JSON string, or *NULL* on error. *value* must be a
258 valid UTF-8 encoded Unicode string.
260 .. cfunction:: json_t *json_string_nocheck(const char *value)
264 Like :cfunc:`json_string`, but doesn't check that *value* is valid
265 UTF-8. Use this function only if you are certain that this really
266 is the case (e.g. you have already checked it by other means).
268 .. versionadded:: 1.2
270 .. cfunction:: const char *json_string_value(const json_t *string)
272 Returns the associated value of *string* as a null terminated UTF-8
273 encoded string, or *NULL* if *string* is not a JSON string.
275 .. cfunction:: int json_string_set(const json_t *string, const char *value)
277 Sets the associated value of *string* to *value*. *value* must be a
278 valid UTF-8 encoded Unicode string. Returns 0 on success and -1 on
281 .. versionadded:: 1.1
283 .. cfunction:: int json_string_set_nocheck(const json_t *string, const char *value)
285 Like :cfunc:`json_string_set`, but doesn't check that *value* is
286 valid UTF-8. Use this function only if you are certain that this
287 really is the case (e.g. you have already checked it by other
290 .. versionadded:: 1.2
296 The JSON specification only contains one numeric type, "number". The C
297 programming language has distinct types for integer and floating-point
298 numbers, so for practical reasons Jansson also has distinct types for
299 the two. They are called "integer" and "real", respectively. For more
300 information, see :ref:`rfc-conformance`.
302 .. ctype:: json_int_t
304 This is the C type that is used to store JSON integer values. It
305 represents the widest integer type available on your system. In
306 practice it's just a typedef of ``long long`` if your compiler
307 supports it, otherwise ``long``.
309 Usually, you can safely use plain ``int`` in place of
310 ``json_int_t``, and the implicit C integer conversion handles the
311 rest. Only when you know that you need the full 64-bit range, you
312 should use ``json_int_t`` explicitly.
314 ``JSON_INTEGER_IS_LONG_LONG``
316 This is a preprocessor variable that holds the value 1 if
317 :ctype:`json_int_t` is ``long long``, and 0 if it's ``long``. It
318 can be used as follows::
320 #if JSON_INTEGER_IS_LONG_LONG
321 /* Code specific for long long */
323 /* Code specific for long */
326 ``JSON_INTEGER_FORMAT``
328 This is a macro that expands to a :cfunc:`printf()` conversion
329 specifier that corresponds to :ctype:`json_int_t`, without the
330 leading ``%`` sign, i.e. either ``"lld"`` or ``"ld"``. This macro
331 is required because the actual type of :ctype:`json_int_t` can be
332 either ``long`` or ``long long``, and :cfunc:`printf()` reuiqres
333 different length modifiers for the two.
337 json_int_t x = 123123123;
338 printf("x is %" JSON_INTEGER_FORMAT "\n", x);
341 .. cfunction:: json_t *json_integer(json_int_t value)
345 Returns a new JSON integer, or *NULL* on error.
347 .. cfunction:: json_int_t json_integer_value(const json_t *integer)
349 Returns the associated value of *integer*, or 0 if *json* is not a
352 .. cfunction:: int json_integer_set(const json_t *integer, json_int_t value)
354 Sets the associated value of *integer* to *value*. Returns 0 on
355 success and -1 if *integer* is not a JSON integer.
357 .. versionadded:: 1.1
359 .. cfunction:: json_t *json_real(double value)
363 Returns a new JSON real, or *NULL* on error.
365 .. cfunction:: double json_real_value(const json_t *real)
367 Returns the associated value of *real*, or 0.0 if *real* is not a
370 .. cfunction:: int json_real_set(const json_t *real, double value)
372 Sets the associated value of *real* to *value*. Returns 0 on
373 success and -1 if *real* is not a JSON real.
375 .. versionadded:: 1.1
377 In addition to the functions above, there's a common query function
378 for integers and reals:
380 .. cfunction:: double json_number_value(const json_t *json)
382 Returns the associated value of the JSON integer or JSON real
383 *json*, cast to double regardless of the actual type. If *json* is
384 neither JSON real nor JSON integer, 0.0 is returned.
390 A JSON array is an ordered collection of other JSON values.
392 .. cfunction:: json_t *json_array(void)
396 Returns a new JSON array, or *NULL* on error. Initially, the array
399 .. cfunction:: size_t json_array_size(const json_t *array)
401 Returns the number of elements in *array*, or 0 if *array* is NULL
404 .. cfunction:: json_t *json_array_get(const json_t *array, size_t index)
406 .. refcounting:: borrow
408 Returns the element in *array* at position *index*. The valid range
409 for *index* is from 0 to the return value of
410 :cfunc:`json_array_size()` minus 1. If *array* is not a JSON array,
411 if *array* is *NULL*, or if *index* is out of range, *NULL* is
414 .. cfunction:: int json_array_set(json_t *array, size_t index, json_t *value)
416 Replaces the element in *array* at position *index* with *value*.
417 The valid range for *index* is from 0 to the return value of
418 :cfunc:`json_array_size()` minus 1. Returns 0 on success and -1 on
421 .. cfunction:: int json_array_set_new(json_t *array, size_t index, json_t *value)
423 Like :cfunc:`json_array_set()` but steals the reference to *value*.
424 This is useful when *value* is newly created and not used after
427 .. versionadded:: 1.1
429 .. cfunction:: int json_array_append(json_t *array, json_t *value)
431 Appends *value* to the end of *array*, growing the size of *array*
432 by 1. Returns 0 on success and -1 on error.
434 .. cfunction:: int json_array_append_new(json_t *array, json_t *value)
436 Like :cfunc:`json_array_append()` but steals the reference to
437 *value*. This is useful when *value* is newly created and not used
440 .. versionadded:: 1.1
442 .. cfunction:: int json_array_insert(json_t *array, size_t index, json_t *value)
444 Inserts *value* to *array* at position *index*, shifting the
445 elements at *index* and after it one position towards the end of
446 the array. Returns 0 on success and -1 on error.
448 .. versionadded:: 1.1
450 .. cfunction:: int json_array_insert_new(json_t *array, size_t index, json_t *value)
452 Like :cfunc:`json_array_insert()` but steals the reference to
453 *value*. This is useful when *value* is newly created and not used
456 .. versionadded:: 1.1
458 .. cfunction:: int json_array_remove(json_t *array, size_t index)
460 Removes the element in *array* at position *index*, shifting the
461 elements after *index* one position towards the start of the array.
462 Returns 0 on success and -1 on error.
464 .. versionadded:: 1.1
466 .. cfunction:: int json_array_clear(json_t *array)
468 Removes all elements from *array*. Returns 0 on sucess and -1 on
471 .. versionadded:: 1.1
473 .. cfunction:: int json_array_extend(json_t *array, json_t *other_array)
475 Appends all elements in *other_array* to the end of *array*.
476 Returns 0 on success and -1 on error.
478 .. versionadded:: 1.1
484 A JSON object is a dictionary of key-value pairs, where the key is a
485 Unicode string and the value is any JSON value.
487 .. cfunction:: json_t *json_object(void)
491 Returns a new JSON object, or *NULL* on error. Initially, the
494 .. cfunction:: size_t json_object_size(const json_t *object)
496 Returns the number of elements in *object*, or 0 if *object* is not
499 .. versionadded:: 1.1
501 .. cfunction:: json_t *json_object_get(const json_t *object, const char *key)
503 .. refcounting:: borrow
505 Get a value corresponding to *key* from *object*. Returns *NULL* if
506 *key* is not found and on error.
508 .. cfunction:: int json_object_set(json_t *object, const char *key, json_t *value)
510 Set the value of *key* to *value* in *object*. *key* must be a
511 valid null terminated UTF-8 encoded Unicode string. If there
512 already is a value for *key*, it is replaced by the new value.
513 Returns 0 on success and -1 on error.
515 .. cfunction:: int json_object_set_nocheck(json_t *object, const char *key, json_t *value)
517 Like :cfunc:`json_object_set`, but doesn't check that *key* is
518 valid UTF-8. Use this function only if you are certain that this
519 really is the case (e.g. you have already checked it by other
522 .. versionadded:: 1.2
524 .. cfunction:: int json_object_set_new(json_t *object, const char *key, json_t *value)
526 Like :cfunc:`json_object_set()` but steals the reference to
527 *value*. This is useful when *value* is newly created and not used
530 .. versionadded:: 1.1
532 .. cfunction:: int json_object_set_new_nocheck(json_t *object, const char *key, json_t *value)
534 Like :cfunc:`json_object_set_new`, but doesn't check that *key* is
535 valid UTF-8. Use this function only if you are certain that this
536 really is the case (e.g. you have already checked it by other
539 .. versionadded:: 1.2
541 .. cfunction:: int json_object_del(json_t *object, const char *key)
543 Delete *key* from *object* if it exists. Returns 0 on success, or
544 -1 if *key* was not found.
547 .. cfunction:: int json_object_clear(json_t *object)
549 Remove all elements from *object*. Returns 0 on success and -1 if
550 *object* is not a JSON object.
552 .. versionadded:: 1.1
554 .. cfunction:: int json_object_update(json_t *object, json_t *other)
556 Update *object* with the key-value pairs from *other*, overwriting
557 existing keys. Returns 0 on success or -1 on error.
559 .. versionadded:: 1.1
562 The following functions implement an iteration protocol for objects:
564 .. cfunction:: void *json_object_iter(json_t *object)
566 Returns an opaque iterator which can be used to iterate over all
567 key-value pairs in *object*, or *NULL* if *object* is empty.
569 .. cfunction:: void *json_object_iter_at(json_t *object, const char *key)
571 Like :cfunc:`json_object_iter()`, but returns an iterator to the
572 key-value pair in *object* whose key is equal to *key*, or NULL if
573 *key* is not found in *object*. Iterating forward to the end of
574 *object* only yields all key-value pairs of the object if *key*
575 happens to be the first key in the underlying hash table.
577 .. versionadded:: 1.3
579 .. cfunction:: void *json_object_iter_next(json_t *object, void *iter)
581 Returns an iterator pointing to the next key-value pair in *object*
582 after *iter*, or *NULL* if the whole object has been iterated
585 .. cfunction:: const char *json_object_iter_key(void *iter)
587 Extract the associated key from *iter*.
589 .. cfunction:: json_t *json_object_iter_value(void *iter)
591 .. refcounting:: borrow
593 Extract the associated value from *iter*.
595 .. cfunction:: int json_object_iter_set(json_t *object, void *iter, json_t *value)
597 Set the value of the key-value pair in *object*, that is pointed to
598 by *iter*, to *value*.
600 .. versionadded:: 1.3
602 .. cfunction:: int json_object_iter_set_new(json_t *object, void *iter, json_t *value)
604 Like :cfunc:`json_object_iter_set()`, but steals the reference to
605 *value*. This is useful when *value* is newly created and not used
608 .. versionadded:: 1.3
610 The iteration protocol can be used for example as follows::
612 /* obj is a JSON object */
615 void *iter = json_object_iter(obj);
618 key = json_object_iter_key(iter);
619 value = json_object_iter_value(iter);
620 /* use key and value ... */
621 iter = json_object_iter_next(obj, iter);
628 This sections describes the functions that can be used to encode
629 values to JSON. Only objects and arrays can be encoded, since they are
630 the only valid "root" values of a JSON text.
632 By default, the output has no newlines, and spaces are used between
633 array and object elements for a readable output. This behavior can be
634 altered by using the ``JSON_INDENT`` and ``JSON_COMPACT`` flags
635 described below. A newline is never appended to the end of the encoded
638 Each function takes a *flags* parameter that controls some aspects of
639 how the data is encoded. Its default value is 0. The following macros
640 can be ORed together to obtain *flags*.
643 Pretty-print the result, using newlines between array and object
644 items, and indenting with *n* spaces. The valid range for *n* is
645 between 0 and 32, other values result in an undefined output. If
646 ``JSON_INDENT`` is not used or *n* is 0, no newlines are inserted
647 between array and object items.
650 This flag enables a compact representation, i.e. sets the separator
651 between array and object items to ``","`` and between object keys
652 and values to ``":"``. Without this flag, the corresponding
653 separators are ``", "`` and ``": "`` for more readable output.
655 .. versionadded:: 1.2
657 ``JSON_ENSURE_ASCII``
658 If this flag is used, the output is guaranteed to consist only of
659 ASCII characters. This is achived by escaping all Unicode
660 characters outside the ASCII range.
662 .. versionadded:: 1.2
665 If this flag is used, all the objects in output are sorted by key.
666 This is useful e.g. if two JSON texts are diffed or visually
669 .. versionadded:: 1.2
671 ``JSON_PRESERVE_ORDER``
672 If this flag is used, object keys in the output are sorted into the
673 same order in which they were first inserted to the object. For
674 example, decoding a JSON text and then encoding with this flag
675 preserves the order of object keys.
677 .. versionadded:: 1.3
679 The following functions perform the actual JSON encoding. The result
682 .. cfunction:: char *json_dumps(const json_t *root, size_t flags)
684 Returns the JSON representation of *root* as a string, or *NULL* on
685 error. *flags* is described above. The return value must be freed
686 by the caller using :cfunc:`free()`.
688 .. cfunction:: int json_dumpf(const json_t *root, FILE *output, size_t flags)
690 Write the JSON representation of *root* to the stream *output*.
691 *flags* is described above. Returns 0 on success and -1 on error.
692 If an error occurs, something may have already been written to
693 *output*. In this case, the output is undefined and most likely not
696 .. cfunction:: int json_dump_file(const json_t *json, const char *path, size_t flags)
698 Write the JSON representation of *root* to the file *path*. If
699 *path* already exists, it is overwritten. *flags* is described
700 above. Returns 0 on success and -1 on error.
706 This sections describes the functions that can be used to decode JSON
707 text to the Jansson representation of JSON data. The JSON
708 specification requires that a JSON text is either a serialized array
709 or object, and this requirement is also enforced with the following
710 functions. In other words, the top level value in the JSON text being
711 decoded must be either array or object.
713 See :ref:`rfc-conformance` for a discussion on Jansson's conformance
714 to the JSON specification. It explains many design decisions that
715 affect especially the behavior of the decoder.
717 .. ctype:: json_error_t
719 This data structure is used to return information on decoding
720 errors from the decoding functions. Its definition is repeated
723 #define JSON_ERROR_TEXT_LENGTH 160
726 char text[JSON_ERROR_TEXT_LENGTH];
730 *line* is the line number on which the error occurred, or -1 if
731 this information is not available. *text* contains the error
732 message (in UTF-8), or an empty string if a message is not
735 The normal usef of :ctype:`json_error_t` is to allocate it normally
736 on the stack, and pass a pointer to a decoding function. Example::
742 json = json_load_file("/path/to/file.json", 0, &error);
744 /* the error variable contains error information */
749 Also note that if the decoding succeeded (``json != NULL`` in the
750 above example), the contents of ``error`` are unspecified.
752 All decoding functions also accept *NULL* as the
753 :ctype:`json_error_t` pointer, in which case no error information
754 is returned to the caller.
756 The following functions perform the actual JSON decoding.
758 .. cfunction:: json_t *json_loads(const char *input, size_t flags, json_error_t *error)
762 Decodes the JSON string *input* and returns the array or object it
763 contains, or *NULL* on error, in which case *error* is filled with
764 information about the error. See above for discussion on the
765 *error* parameter. *flags* is currently unused, and should be set
768 .. cfunction:: json_t *json_loadf(FILE *input, size_t flags, json_error_t *error)
772 Decodes the JSON text in stream *input* and returns the array or
773 object it contains, or *NULL* on error, in which case *error* is
774 filled with information about the error. See above for discussion
775 on the *error* parameter. *flags* is currently unused, and should
778 .. cfunction:: json_t *json_load_file(const char *path, size_t flags, json_error_t *error)
782 Decodes the JSON text in file *path* and returns the array or
783 object it contains, or *NULL* on error, in which case *error* is
784 filled with information about the error. See above for discussion
785 on the *error* parameter. *flags* is currently unused, and should
792 Testing for equality of two JSON values cannot, in general, be
793 achieved using the ``==`` operator. Equality in the terms of the
794 ``==`` operator states that the two :ctype:`json_t` pointers point to
795 exactly the same JSON value. However, two JSON values can be equal not
796 only if they are exactly the same value, but also if they have equal
799 * Two integer or real values are equal if their contained numeric
800 values are equal. An integer value is never equal to a real value,
803 * Two strings are equal if their contained UTF-8 strings are equal,
804 byte by byte. Unicode comparison algorithms are not implemented.
806 * Two arrays are equal if they have the same number of elements and
807 each element in the first array is equal to the corresponding
808 element in the second array.
810 * Two objects are equal if they have exactly the same keys and the
811 value for each key in the first object is equal to the value of the
812 corresponding key in the second object.
814 * Two true, false or null values have no "contents", so they are equal
815 if their types are equal. (Because these values are singletons,
816 their equality can actually be tested with ``==``.)
818 The following function can be used to test whether two JSON values are
821 .. cfunction:: int json_equal(json_t *value1, json_t *value2)
823 Returns 1 if *value1* and *value2* are equal, as defined above.
824 Returns 0 if they are inequal or one or both of the pointers are
827 .. versionadded:: 1.2
833 Because of reference counting, passing JSON values around doesn't
834 require copying them. But sometimes a fresh copy of a JSON value is
835 needed. For example, if you need to modify an array, but still want to
836 use the original afterwards, you should take a copy of it first.
838 Jansson supports two kinds of copying: shallow and deep. There is a
839 difference between these methods only for arrays and objects. Shallow
840 copying only copies the first level value (array or object) and uses
841 the same child values in the copied value. Deep copying makes a fresh
842 copy of the child values, too. Moreover, all the child values are deep
843 copied in a recursive fashion.
845 .. cfunction:: json_t *json_copy(json_t *value)
849 Returns a shallow copy of *value*, or *NULL* on error.
851 .. versionadded:: 1.2
853 .. cfunction:: json_t *json_deep_copy(json_t *value)
857 Returns a deep copy of *value*, or *NULL* on error.
859 .. versionadded:: 1.2