json-c: json_object.h File Reference

json-c 0.19

Macros | Typedefs | Functions | Variables
json_object.h File Reference

Core json-c API. Start here, or with json_tokener.h. More...

## Macros
#define | JSON_C_CONST_FUNCTION(func) func
#define | JSON_OBJECT_DEF_HASH_ENTRIES 16
#define | JSON_C_TO_STRING_PLAIN 0
#define | JSON_C_TO_STRING_SPACED (1 << 0)
#define | JSON_C_TO_STRING_PRETTY (1 << 1)
#define | JSON_C_TO_STRING_PRETTY_TAB (1 << 3)
#define | JSON_C_TO_STRING_NOZERO (1 << 2)
#define | JSON_C_TO_STRING_NOSLASHESCAPE (1 << 4)
#define | JSON_C_TO_STRING_COLOR (1 << 5)
#define | JSON_C_OBJECT_ADD_KEY_IS_NEW (1 << 1)
#define | JSON_C_OBJECT_ADD_CONSTANT_KEY (1 << 2)
#define | JSON_C_OBJECT_KEY_IS_CONSTANT JSON_C_OBJECT_ADD_CONSTANT_KEY
#define | JSON_C_OPTION_GLOBAL (0)
#define | JSON_C_OPTION_THREAD (1)
#define | json_object_object_foreach(obj, key, val)
#define | json_object_object_foreachC(obj, iter)

## Typedefs
typedef int() | json_c_shallow_copy_fn(json_object *src, json_object *parent, const char *key, size_t index, json_object **dst)

## Functions
JSON_EXPORT struct json_object * | json_object_get (struct json_object *obj)
JSON_EXPORT int | json_object_put (struct json_object *obj)
JSON_EXPORT int | json_object_is_type (const struct json_object *obj, enum json_type type)
JSON_EXPORT enum json_type | json_object_get_type (const struct json_object *obj)
JSON_EXPORT const char * | json_object_to_json_string (struct json_object *obj)
JSON_EXPORT const char * | json_object_to_json_string_ext (struct json_object *obj, int flags)
JSON_EXPORT const char * | json_object_to_json_string_length (struct json_object *obj, int flags, size_t *length)
JSON_EXPORT void * | json_object_get_userdata (json_object *jso)
JSON_EXPORT void | json_object_set_userdata (json_object *jso, void *userdata, json_object_delete_fn *user_delete)
JSON_EXPORT void | json_object_set_serializer (json_object *jso, json_object_to_json_string_fn *to_string_func, void *userdata, json_object_delete_fn *user_delete)
JSON_EXPORT struct json_object * | json_object_new_object (void)
JSON_EXPORT struct lh_table * | json_object_get_object (const struct json_object *obj)
JSON_EXPORT int | json_object_object_length (const struct json_object *obj)
JSON_EXPORT size_t | json_c_object_sizeof (void)
JSON_EXPORT int | json_object_object_add (struct json_object *obj, const char *key, struct json_object *val)
JSON_EXPORT int | json_object_object_add_ex (struct json_object *obj, const char *const key, struct json_object *const val, const unsigned opts)
JSON_EXPORT struct json_object * | json_object_object_get (const struct json_object *obj, const char *key)
JSON_EXPORT int | json_object_object_get_ex (const struct json_object *obj, const char *key, struct json_object **value)
JSON_EXPORT void | json_object_object_del (struct json_object *obj, const char *key)
JSON_EXPORT struct json_object * | json_object_new_array (void)
JSON_EXPORT struct json_object * | json_object_new_array_ext (int initial_size)
JSON_EXPORT struct array_list * | json_object_get_array (const struct json_object *obj)
JSON_EXPORT size_t | json_object_array_length (const struct json_object *obj)
JSON_EXPORT void | json_object_array_sort (struct json_object *jso, int(*sort_fn)(const void *, const void *))
JSON_EXPORT struct json_object * | json_object_array_bsearch (const struct json_object *key, const struct json_object *jso, int(*sort_fn)(const void *, const void *))
JSON_EXPORT int | json_object_array_add (struct json_object *obj, struct json_object *val)
JSON_EXPORT int | json_object_array_put_idx (struct json_object *obj, size_t idx, struct json_object *val)
JSON_EXPORT int | json_object_array_insert_idx (struct json_object *obj, size_t idx, struct json_object *val)
JSON_EXPORT struct json_object * | json_object_array_get_idx (const struct json_object *obj, size_t idx)
JSON_EXPORT int | json_object_array_del_idx (struct json_object *obj, size_t idx, size_t count)
JSON_EXPORT int | json_object_array_shrink (struct json_object *jso, int empty_slots)
JSON_EXPORT struct json_object * | json_object_new_boolean (json_bool b)
JSON_EXPORT json_bool | json_object_get_boolean (const struct json_object *obj)
JSON_EXPORT int | json_object_set_boolean (struct json_object *obj, json_bool new_value)
JSON_EXPORT struct json_object * | json_object_new_int (int32_t i)
JSON_EXPORT struct json_object * | json_object_new_int64 (int64_t i)
JSON_EXPORT struct json_object * | json_object_new_uint64 (uint64_t i)
JSON_EXPORT int32_t | json_object_get_int (const struct json_object *obj)
JSON_EXPORT int | json_object_set_int (struct json_object *obj, int new_value)
JSON_EXPORT int | json_object_int_inc (struct json_object *obj, int64_t val)
JSON_EXPORT int64_t | json_object_get_int64 (const struct json_object *obj)
JSON_EXPORT uint64_t | json_object_get_uint64 (const struct json_object *obj)
JSON_EXPORT int | json_object_set_int64 (struct json_object *obj, int64_t new_value)
JSON_EXPORT int | json_object_set_uint64 (struct json_object *obj, uint64_t new_value)
JSON_EXPORT struct json_object * | json_object_new_double (double d)
JSON_EXPORT struct json_object * | json_object_new_double_s (double d, const char *ds)
JSON_EXPORT int | json_c_set_serialization_double_format (const char *double_format, int global_or_thread)
JSON_EXPORT int | json_object_double_to_json_string (struct json_object *jso, struct printbuf *pb, int level, int flags)
JSON_EXPORT double | json_object_get_double (const struct json_object *obj)
JSON_EXPORT int | json_object_set_double (struct json_object *obj, double new_value)
JSON_EXPORT struct json_object * | json_object_new_string (const char *s)
JSON_EXPORT struct json_object * | json_object_new_string_len (const char *s, const int len)
JSON_EXPORT const char * | json_object_get_string (struct json_object *obj)
JSON_EXPORT int | json_object_get_string_len (const struct json_object *obj)
JSON_EXPORT int | json_object_set_string (json_object *obj, const char *new_value)
JSON_EXPORT int | json_object_set_string_len (json_object *obj, const char *new_value, int len)
JSON_EXPORT struct json_object * | json_object_new_null (void)
JSON_EXPORT int | json_object_equal (struct json_object *obj1, struct json_object *obj2)
JSON_EXPORT int | json_object_deep_copy (struct json_object *src, struct json_object **dst, json_c_shallow_copy_fn *shallow_copy)

## Variables
JSON_EXPORT json_object_delete_fn | json_object_free_userdata
JSON_EXPORT json_object_to_json_string_fn | json_object_userdata_to_json_string
JSON_EXPORT json_c_shallow_copy_fn | json_c_shallow_copy_default

## Detailed Description

Core json-c API. Start here, or with json_tokener.h.

## Macro Definition Documentation

## ◆ JSON_C_CONST_FUNCTION

#define JSON_C_CONST_FUNCTION | ( |  | func | ) | func

## ◆ JSON_C_OBJECT_ADD_CONSTANT_KEY

#define JSON_C_OBJECT_ADD_CONSTANT_KEY (1 << 2)

A flag for the json_object_object_add_ex function which flags the key as being constant memory. This means that the key will NOT be copied via strdup(), resulting in a potentially huge performance win (malloc, strdup and free are usually performance hogs). It is acceptable to use this flag for keys in non-constant memory blocks if the caller ensure that the memory holding the key lives longer than the corresponding json object. However, this is somewhat dangerous and should only be done if really justified. The general use-case for this flag is cases where the key is given as a real constant value in the function call, e.g. as in json_object_object_add_ex(obj, "ip", json, JSON_C_OBJECT_ADD_CONSTANT_KEY);

## ◆ JSON_C_OBJECT_ADD_KEY_IS_NEW

#define JSON_C_OBJECT_ADD_KEY_IS_NEW (1 << 1)

A flag for the json_object_object_add_ex function which causes the value to be added without a check if it already exists. Note: it is the responsibility of the caller to ensure that no key is added multiple times. If this is done, results are unpredictable. While this option is somewhat dangerous, it permits potentially large performance savings in code that knows for sure the key values are unique (e.g. because the code adds a well-known set of constant key values).

## ◆ JSON_C_OBJECT_KEY_IS_CONSTANT

#define JSON_C_OBJECT_KEY_IS_CONSTANT JSON_C_OBJECT_ADD_CONSTANT_KEY

This flag is an alias to JSON_C_OBJECT_ADD_CONSTANT_KEY. Historically, this flag was used first and the new name JSON_C_OBJECT_ADD_CONSTANT_KEY was introduced for version 0.16.00 in order to have regular naming. Use of this flag is now legacy.

## ◆ JSON_C_OPTION_GLOBAL

#define JSON_C_OPTION_GLOBAL (0)

Set the global value of an option, which will apply to all current and future threads that have not set a thread-local value.

See also
  json_c_set_serialization_double_format

## ◆ JSON_C_OPTION_THREAD

#define JSON_C_OPTION_THREAD (1)

Set a thread-local value of an option, overriding the global value. This will fail if json-c is not compiled with threading enabled, and with the __thread specifier (or equivalent) available.

See also
  json_c_set_serialization_double_format

## ◆ JSON_C_TO_STRING_COLOR

#define JSON_C_TO_STRING_COLOR (1 << 5)

A flag for the json_object_to_json_string_ext() and json_object_to_file_ext() functions which causes the output to be formatted.

Use color for printing json.

## ◆ JSON_C_TO_STRING_NOSLASHESCAPE

#define JSON_C_TO_STRING_NOSLASHESCAPE (1 << 4)

Don't escape forward slashes.

## ◆ JSON_C_TO_STRING_NOZERO

#define JSON_C_TO_STRING_NOZERO (1 << 2)

A flag to drop trailing zero for float values

## ◆ JSON_C_TO_STRING_PLAIN

#define JSON_C_TO_STRING_PLAIN 0

A flag for the json_object_to_json_string_ext() and json_object_to_file_ext() functions which causes the output to have no extra whitespace or formatting applied.

## ◆ JSON_C_TO_STRING_PRETTY

#define JSON_C_TO_STRING_PRETTY (1 << 1)

A flag for the json_object_to_json_string_ext() and json_object_to_file_ext() functions which causes the output to be formatted.

See the "Two Space Tab" option at https://jsonformatter.curiousconcept.com/ for an example of the format.

## ◆ JSON_C_TO_STRING_PRETTY_TAB

#define JSON_C_TO_STRING_PRETTY_TAB (1 << 3)

A flag for the json_object_to_json_string_ext() and json_object_to_file_ext() functions which causes the output to be formatted.

Instead of a "Two Space Tab" this gives a single tab character.

## ◆ JSON_C_TO_STRING_SPACED

#define JSON_C_TO_STRING_SPACED (1 << 0)

A flag for the json_object_to_json_string_ext() and json_object_to_file_ext() functions which causes the output to have minimal whitespace inserted to make things slightly more readable.

## ◆ JSON_OBJECT_DEF_HASH_ENTRIES

#define JSON_OBJECT_DEF_HASH_ENTRIES 16

## ◆ json_object_object_foreach

#define json_object_object_foreach | ( |  | obj,
|  |  | key,
|  |  | val
| ) |  |

Value:
char *key = NULL; \
struct json_object *val = NULL; \
struct lh_entry *entry##key; \
struct lh_entry *entry_next##key = NULL; \
for (entry##key = lh_table_head(json_object_get_object(obj)); \
(entry##key ? (key = (char *)lh_entry_k(entry##key), \
val = (struct json_object *)lh_entry_v(entry##key), \
entry_next##key = lh_entry_next(entry##key), entry##key) \
: 0); \
entry##key = entry_next##key)
json_object_get_object
JSON_EXPORT struct lh_table * json_object_get_object(const struct json_object *obj)
json_object
struct json_object json_object
The core type for all type of JSON objects handled by json-c.
Definition json_types.h:47
lh_entry_k
static void * lh_entry_k(const struct lh_entry *e)
Definition linkhash.h:398
lh_table_head
static struct lh_entry * lh_table_head(const lh_table *t)
Definition linkhash.h:360
lh_entry_next
static struct lh_entry * lh_entry_next(const struct lh_entry *e)
Definition linkhash.h:438
lh_entry_v
static void * lh_entry_v(const struct lh_entry *e)
Definition linkhash.h:419
lh_entry
Definition linkhash.h:86

Iterate through all keys and values of an object.

Adding keys to the object while iterating is NOT allowed.

Deleting an existing key, or replacing an existing key with a new value IS allowed.

Parameters

  obj | the json_object instance
  key | the local name for the char* key variable defined in the body
  val | the local name for the json_object* object variable defined in the body

## ◆ json_object_object_foreachC

#define json_object_object_foreachC | ( |  | obj,
|  |  | iter
| ) |  |

Value:
for (iter.entry = lh_table_head(json_object_get_object(obj)); \
(iter.entry ? (iter.key = (char *)lh_entry_k(iter.entry), \
iter.val = (struct json_object *)lh_entry_v(iter.entry), iter.entry) \
: 0); \
iter.entry = lh_entry_next(iter.entry))

Iterate through all keys and values of an object (ANSI C Safe)

Parameters

  obj | the json_object instance
  iter | the object iterator, use type json_object_iter

## Typedef Documentation

## ◆ json_c_shallow_copy_fn

typedef int() json_c_shallow_copy_fn(json_object *src, json_object *parent, const char *key, size_t index, json_object **dst)

Perform a shallow copy of src into *dst as part of an overall json_object_deep_copy().

If src is part of a containing object or array, parent will be non-NULL, and key or index will be provided. When shallow_copy is called *dst will be NULL, and must be non-NULL when it returns. src will never be NULL.

If shallow_copy sets the serializer on an object, return 2 to indicate to json_object_deep_copy that it should not attempt to use the standard userdata copy function.

Returns
  On success 1 or 2, -1 on errors

## Function Documentation

## ◆ json_c_object_sizeof()

JSON_EXPORT size_t json_c_object_sizeof | ( | void |  | ) |

Get the sizeof (struct json_object).

Returns
  a size_t with the sizeof (struct json_object)

## ◆ json_c_set_serialization_double_format()

JSON_EXPORT int json_c_set_serialization_double_format | ( | const char * | double_format,
|  | int | global_or_thread
| ) |  |

Set a global or thread-local json-c option, depending on whether JSON_C_OPTION_GLOBAL or JSON_C_OPTION_THREAD is passed. Thread-local options default to undefined, and inherit from the global value, even if the global value is changed after the thread is created. Attempting to set thread-local options when threading is not compiled in will result in an error. Be sure to check the return value.

double_format is a "%g" printf format, such as "%.20g"

Returns
  -1 on errors, 0 on success.

## ◆ json_object_array_add()

JSON_EXPORT int json_object_array_add | ( | struct json_object * | obj,
|  | struct json_object * | val
| ) |  |

Add an element to the end of a json_object of type json_type_array

The reference count will not be incremented. This is to make adding fields to objects in code more compact. If you want to retain a reference to an added object you must wrap the passed object with json_object_get

Parameters

  obj | the json_object instance
  val | the json_object to be added

## ◆ json_object_array_bsearch()

JSON_EXPORT struct json_object * json_object_array_bsearch | ( | const struct json_object * | key,
|  | const struct json_object * | jso,
|  | int(*)(const void *, const void *) | sort_fn
| ) |  |

Binary search a sorted array for a specified key object.

It depends on your compare function what's sufficient as a key. Usually you create some dummy object with the parameter compared in it, to identify the right item you're actually looking for.

See also
  json_object_array_sort() for hints on the compare function.

Parameters

  key | a dummy json_object with the right key
  jso | the array object we're searching
  sort_fn | the sort/compare function

Returns
  the wanted json_object instance

## ◆ json_object_array_del_idx()

JSON_EXPORT int json_object_array_del_idx | ( | struct json_object * | obj,
|  | size_t | idx,
|  | size_t | count
| ) |  |

Delete an elements from a specified index in an array (a json_object of type json_type_array)

The reference count will be decremented for each of the deleted objects. If there are no more owners of an element that is being deleted, then the value is freed. Otherwise, the reference to the value will remain in memory.

Parameters

  obj | the json_object instance
  idx | the index to start deleting elements at
  count | the number of elements to delete

Returns
  0 if the elements were successfully deleted

## ◆ json_object_array_get_idx()

JSON_EXPORT struct json_object * json_object_array_get_idx | ( | const struct json_object * | obj,
|  | size_t | idx
| ) |  |

Get the element at specified index of array `obj` (which must be a json_object of type json_type_array)

No reference counts will be changed, and ownership of the returned object remains with `obj`. See json_object_object_get() for additional implications of this behavior.

Calling this with anything other than a json_type_array will trigger an assert.

Parameters

  obj | the json_object instance
  idx | the index to get the element at

Returns
  the json_object at the specified index (or NULL)

## ◆ json_object_array_insert_idx()

JSON_EXPORT int json_object_array_insert_idx | ( | struct json_object * | obj,
|  | size_t | idx,
|  | struct json_object * | val
| ) |  |

Insert an element at a specified index in an array (a json_object of type json_type_array)

The reference count will not be incremented. This is to make adding fields to objects in code more compact. If you want to retain a reference to an added object you must wrap the passed object with json_object_get

The array size will be automatically be expanded to the size of the index if the index is larger than the current size. If the index is within the existing array limits, then the element will be inserted and all elements will be shifted. This is the only difference between this function and json_object_array_put_idx().

Parameters

  obj | the json_object instance
  idx | the index to insert the element at
  val | the json_object to be added

## ◆ json_object_array_length()

JSON_EXPORT size_t json_object_array_length | ( | const struct json_object * | obj | ) |

Get the length of a json_object of type json_type_array

Parameters

  obj | the json_object instance

Returns
  the length of the array

## ◆ json_object_array_put_idx()

JSON_EXPORT int json_object_array_put_idx | ( | struct json_object * | obj,
|  | size_t | idx,
|  | struct json_object * | val
| ) |  |

Insert or replace an element at a specified index in an array (a json_object of type json_type_array)

The reference count will not be incremented. This is to make adding fields to objects in code more compact. If you want to retain a reference to an added object you must wrap the passed object with json_object_get

The reference count of a replaced object will be decremented.

The array size will be automatically be expanded to the size of the index if the index is larger than the current size.

Parameters

  obj | the json_object instance
  idx | the index to insert the element at
  val | the json_object to be added

## ◆ json_object_array_shrink()

JSON_EXPORT int json_object_array_shrink | ( | struct json_object * | jso,
|  | int | empty_slots
| ) |  |

Shrink the internal memory allocation of the array to just enough to fit the number of elements in it, plus empty_slots.

Parameters

  jso | the json_object instance, must be json_type_array
  empty_slots | the number of empty slots to leave allocated

## ◆ json_object_array_sort()

JSON_EXPORT void json_object_array_sort | ( | struct json_object * | jso,
|  | int(*)(const void *, const void *) | sort_fn
| ) |  |

Sorts the elements of jso of type json_type_array

Pointers to the json_object pointers will be passed as the two arguments to sort_fn

Parameters

  jso | the json_object instance
  sort_fn | a sorting function

## ◆ json_object_deep_copy()

JSON_EXPORT int json_object_deep_copy | ( | struct json_object * | src,
|  | struct json_object ** | dst,
|  | json_c_shallow_copy_fn * | shallow_copy
| ) |  |

Copy the contents of the JSON object. The destination object must be initialized to NULL, to make sure this function won't overwrite an existing JSON object.

This does roughly the same thing as `json_tokener_parse(json_object_get_string(src))`.

Parameters

  src | source JSON object whose contents will be copied
  dst | pointer to the destination object where the contents of `src`; make sure this pointer is initialized to NULL
  shallow_copy | an optional function to copy individual objects, needed when custom serializers are in use. See also json_object set_serializer.

Returns
  0 if the copy went well, -1 if an error occurred during copy or if the destination pointer is non-NULL

## ◆ json_object_double_to_json_string()

JSON_EXPORT int json_object_double_to_json_string | ( | struct json_object * | jso,
|  | struct printbuf * | pb,
|  | int | level,
|  | int | flags
| ) |  |

Serialize a json_object of type json_type_double to a string.

This function isn't meant to be called directly. Instead, you can set a custom format string for the serialization of this double using the following call (where "%.17g" actually is the default):

jso = json_object_new_double(d);
json_object_set_serializer(jso, json_object_double_to_json_string,
"%.17g", NULL);
json_object_set_serializer
JSON_EXPORT void json_object_set_serializer(json_object *jso, json_object_to_json_string_fn *to_string_func, void *userdata, json_object_delete_fn *user_delete)
json_object_new_double
JSON_EXPORT struct json_object * json_object_new_double(double d)
json_object_double_to_json_string
JSON_EXPORT int json_object_double_to_json_string(struct json_object *jso, struct printbuf *pb, int level, int flags)

See also
  printf(3) man page for format strings

Parameters

  jso | The json_type_double object that is serialized.
  pb | The destination buffer.
  level | Ignored.
  flags | Ignored.

## ◆ json_object_equal()

JSON_EXPORT int json_object_equal | ( | struct json_object * | obj1,
|  | struct json_object * | obj2
| ) |  |

Check if two json_object's are equal

If the passed objects are equal 1 will be returned. Equality is defined as follows:

- json_objects of different types are never equal
- json_objects of the same primitive type are equal if the c-representation of their value is equal
- json-arrays are considered equal if all values at the same indices are equal (same order)
- Complex json_objects are considered equal if all contained objects referenced by their key are equal, regardless their order.

Parameters

  obj1 | the first json_object instance
  obj2 | the second json_object instance

Returns
  1 if both objects are equal, 0 otherwise

## ◆ json_object_get()

JSON_EXPORT struct json_object * json_object_get | ( | struct json_object * | obj | ) |

Increment the reference count of json_object, thereby taking ownership of it.

Cases where you might need to increase the refcount include:

- Using an object field or array index (retrieved through `json_object_object_get()` or `json_object_array_get_idx()`) beyond the lifetime of the parent object.
- Detaching an object field or array index from its parent object (using `json_object_object_del()` or `json_object_array_del_idx()`)
- Sharing a json_object with multiple (not necessarily parallel) threads of execution that all expect to free it (with `json_object_put()`) when they're done.

Parameters

  obj | the json_object instance

See also
  json_object_put()
  json_object_object_get()
  json_object_array_get_idx()

## ◆ json_object_get_array()

JSON_EXPORT struct array_list * json_object_get_array | ( | const struct json_object * | obj | ) |

Get the arraylist of a json_object of type json_type_array

Parameters

  obj | the json_object instance

Returns
  an arraylist

## ◆ json_object_get_boolean()

JSON_EXPORT json_bool json_object_get_boolean | ( | const struct json_object * | obj | ) |

Get the json_bool value of a json_object

The type is coerced to a json_bool if the passed object is not a json_bool. integer and double objects will return 0 if there value is zero or 1 otherwise. If the passed object is a string it will return 1 if it has a non zero length. If any other object type is passed 0 will be returned, even non-empty json_type_array and json_type_object objects.

Parameters

  obj | the json_object instance

Returns
  a json_bool

## ◆ json_object_get_double()

JSON_EXPORT double json_object_get_double | ( | const struct json_object * | obj | ) |

Get the double floating point value of a json_object

The type is coerced to a double if the passed object is not a double. integer objects will return their double conversion. Strings will be parsed as a double. If no conversion exists then 0.0 is returned and errno is set to EINVAL. null is equivalent to 0 (no error values set)

If the value is too big to fit in a double, then the value is set to the closest infinity with errno set to ERANGE. If strings cannot be converted to their double value, then EINVAL is set & NaN is returned.

Arrays of length 0 are interpreted as 0 (with no error flags set). Arrays of length 1 are effectively cast to the equivalent object and converted using the above rules. All other arrays set the error to EINVAL & return NaN.

NOTE: Set errno to 0 directly before a call to this function to determine whether or not conversion was successful (it does not clear the value for you).

Parameters

  obj | the json_object instance

Returns
  a double floating point number

## ◆ json_object_get_int()

JSON_EXPORT int32_t json_object_get_int | ( | const struct json_object * | obj | ) |

Get the int value of a json_object

The type is coerced to a int if the passed object is not a int. double objects will return their integer conversion except for NaN values which return INT32_MIN and the errno is set to EINVAL. Strings will be parsed as an integer. If no conversion exists then 0 is returned and errno is set to EINVAL. null is equivalent to 0 (no error values set). Sets errno to ERANGE if the value exceeds the range of int.

Note that integers are stored internally as 64-bit values. If the value of too big or too small to fit into 32-bit, INT32_MAX or INT32_MIN are returned, respectively.

Parameters

  obj | the json_object instance

Returns
  an int

## ◆ json_object_get_int64()

JSON_EXPORT int64_t json_object_get_int64 | ( | const struct json_object * | obj | ) |

Get the int value of a json_object

The type is coerced to a int64 if the passed object is not a int64. double objects will return their int64 conversion except for NaN values which return INT64_MIN and the errno is set to EINVAL. Strings will be parsed as an int64. If no conversion exists then 0 is returned and errno is set to EINVAL. null is equivalent to 0 (no error values set). Sets errno to ERANGE if the value exceeds the range of int64.

NOTE: Set errno to 0 directly before a call to this function to determine whether or not conversion was successful (it does not clear the value for you).

Parameters

  obj | the json_object instance

Returns
  an int64

## ◆ json_object_get_object()

JSON_EXPORT struct lh_table * json_object_get_object | ( | const struct json_object * | obj | ) |

Get the hashtable of a json_object of type json_type_object

Parameters

  obj | the json_object instance

Returns
  a linkhash

## ◆ json_object_get_string()

JSON_EXPORT const char * json_object_get_string | ( | struct json_object * | obj | ) |

Get the string value of a json_object

If the passed object is of type json_type_null (i.e. obj == NULL), NULL is returned.

If the passed object of type json_type_string, the string contents are returned.

Otherwise the JSON representation of the object is returned.

The returned string memory is managed by the json_object and will be freed when the reference count of the json_object drops to zero.

Parameters

  obj | the json_object instance

Returns
  a string or NULL

## ◆ json_object_get_string_len()

JSON_EXPORT int json_object_get_string_len | ( | const struct json_object * | obj | ) |

Get the string length of a json_object

If the passed object is not of type json_type_string then zero will be returned.

Parameters

  obj | the json_object instance

Returns
  int

## ◆ json_object_get_type()

JSON_EXPORT enum json_type json_object_get_type | ( | const struct json_object * | obj | ) |

Get the type of the json_object. See also json_type_to_name() to turn this into a string suitable, for instance, for logging.

Parameters

  obj | the json_object instance

Returns
  type being one of: json_type_null (i.e. obj == NULL), json_type_boolean, json_type_double, json_type_int, json_type_object, json_type_array, json_type_string

## ◆ json_object_get_uint64()

JSON_EXPORT uint64_t json_object_get_uint64 | ( | const struct json_object * | obj | ) |

Get the uint value of a json_object

The type is coerced to a uint64 if the passed object is not a uint64. double objects will return their uint64 conversion except for NaN values which return 0 and the errno is set to EINVAL. Strings will be parsed as an uint64. If no conversion exists then 0 is returned and errno is set to EINVAL. null is equivalent to 0 (no error values set). Sets errno to ERANGE if the value exceeds the range of uint64.

NOTE: Set errno to 0 directly before a call to this function to determine whether or not conversion was successful (it does not clear the value for you).

Parameters

  obj | the json_object instance

Returns
  an uint64

## ◆ json_object_get_userdata()

JSON_EXPORT void * json_object_get_userdata | ( | json_object * | jso | ) |

Returns the userdata set by json_object_set_userdata() or json_object_set_serializer()

Parameters

  jso | the object to return the userdata for

## ◆ json_object_int_inc()

JSON_EXPORT int json_object_int_inc | ( | struct json_object * | obj,
|  | int64_t | val
| ) |  |

Increment a json_type_int object by the given amount, which may be negative.

If the type of obj is not json_type_int then 0 is returned with no further action taken. If the addition would result in a overflow, the object value is set to INT64_MAX. If the addition would result in a underflow, the object value is set to INT64_MIN. Neither overflow nor underflow affect the return value.

Parameters

  obj | the json_object instance
  val | the value to add

Returns
  1 if the increment succeeded, 0 otherwise

## ◆ json_object_is_type()

JSON_EXPORT int json_object_is_type | ( | const struct json_object * | obj,
|  | enum json_type | type
| ) |  |

Check if the json_object is of a given type

Parameters

  obj | the json_object instance
  type | one of: json_type_null (i.e. obj == NULL), json_type_boolean, json_type_double, json_type_int, json_type_object, json_type_array, json_type_string

Returns
  1 if the object is of the specified type, 0 otherwise

## ◆ json_object_new_array()

JSON_EXPORT struct json_object * json_object_new_array | ( | void |  | ) |

Create a new empty json_object of type json_type_array with 32 slots allocated. If you know the array size you'll need ahead of time, use json_object_new_array_ext() instead.

See also
  json_object_new_array_ext()
  json_object_array_shrink()

Returns
  a json_object of type json_type_array

## ◆ json_object_new_array_ext()

JSON_EXPORT struct json_object * json_object_new_array_ext | ( | int | initial_size | ) |

Create a new empty json_object of type json_type_array with the desired number of slots allocated.

See also
  json_object_array_shrink()

Parameters

  initial_size | the number of slots to allocate

Returns
  a json_object of type json_type_array

## ◆ json_object_new_boolean()

JSON_EXPORT struct json_object * json_object_new_boolean | ( | json_bool | b | ) |

Create a new empty json_object of type json_type_boolean

Parameters

  b | a json_bool 1 or 0

Returns
  a json_object of type json_type_boolean

## ◆ json_object_new_double()

JSON_EXPORT struct json_object * json_object_new_double | ( | double | d | ) |

Create a new empty json_object of type json_type_double

See also
  json_object_double_to_json_string() for how to set a custom format string.

Parameters

  d | the double

Returns
  a json_object of type json_type_double

## ◆ json_object_new_double_s()

JSON_EXPORT struct json_object * json_object_new_double_s | ( | double | d,
|  | const char * | ds
| ) |  |

Create a new json_object of type json_type_double, using the exact serialized representation of the value.

This allows for numbers that would otherwise get displayed inefficiently (e.g. 12.3 => "12.300000000000001") to be serialized with the more convenient form.

Notes:

This is used by json_tokener_parse_ex() to allow for an exact re-serialization of a parsed object.

The userdata field is used to store the string representation, so it can't be used for other data if this function is used.

A roughly equivalent sequence of calls, with the difference being that the serialization function won't be reset by json_object_set_double(), is:

jso = json_object_new_double(d);
json_object_set_serializer(jso, json_object_userdata_to_json_string,
strdup(ds), json_object_free_userdata);
json_object_userdata_to_json_string
JSON_EXPORT json_object_to_json_string_fn json_object_userdata_to_json_string
Definition json_object.h:341
json_object_free_userdata
JSON_EXPORT json_object_delete_fn json_object_free_userdata
Definition json_object.h:330

Parameters

  d | the numeric value of the double.
  ds | the string representation of the double. This will be copied.

## ◆ json_object_new_int()

JSON_EXPORT struct json_object * json_object_new_int | ( | int32_t | i | ) |

Create a new empty json_object of type json_type_int Note that values are stored as 64-bit values internally. To ensure the full range is maintained, use json_object_new_int64 instead.

Parameters

  i | the integer

Returns
  a json_object of type json_type_int

## ◆ json_object_new_int64()

JSON_EXPORT struct json_object * json_object_new_int64 | ( | int64_t | i | ) |

Create a new empty json_object of type json_type_int

Parameters

  i | the integer

Returns
  a json_object of type json_type_int

## ◆ json_object_new_null()

JSON_EXPORT struct json_object * json_object_new_null | ( | void |  | ) |

This method exists only to provide a complementary function along the lines of the other json_object_new_* functions. It always returns NULL, and it is entirely acceptable to simply use NULL directly.

## ◆ json_object_new_object()

JSON_EXPORT struct json_object * json_object_new_object | ( | void |  | ) |

Create a new empty object with a reference count of 1. The caller of this object initially has sole ownership. Remember, when using json_object_object_add or json_object_array_put_idx, ownership will transfer to the object/array. Call json_object_get if you want to maintain shared ownership or also add this object as a child of multiple objects or arrays. Any ownerships you acquired but did not transfer must be released through json_object_put.

Returns
  a json_object of type json_type_object

## ◆ json_object_new_string()

JSON_EXPORT struct json_object * json_object_new_string | ( | const char * | s | ) |

Create a new empty json_object of type json_type_string

A copy of the string is made and the memory is managed by the json_object

Parameters

  s | the string

Returns
  a json_object of type json_type_string

See also
  json_object_new_string_len()

## ◆ json_object_new_string_len()

JSON_EXPORT struct json_object * json_object_new_string_len | ( | const char * | s,
|  | const int | len
| ) |  |

Create a new empty json_object of type json_type_string and allocate len characters for the new string.

A copy of the string is made and the memory is managed by the json_object

Parameters

  s | the string
  len | max length of the new string

Returns
  a json_object of type json_type_string

See also
  json_object_new_string()

## ◆ json_object_new_uint64()

JSON_EXPORT struct json_object * json_object_new_uint64 | ( | uint64_t | i | ) |

Create a new empty json_object of type json_type_uint

Parameters

  i | the integer

Returns
  a json_object of type json_type_uint

## ◆ json_object_object_add()

JSON_EXPORT int json_object_object_add | ( | struct json_object * | obj,
|  | const char * | key,
|  | struct json_object * | val
| ) |  |

Add an object field to a json_object of type json_type_object

The reference count of `val` will not be incremented, in effect transferring ownership that object to `obj`, and thus `val` will be freed when `obj` is. (i.e. through `json_object_put(obj)`)

If you want to retain a reference to the added object, independent of the lifetime of obj, you must increment the refcount with `json_object_get(val)` (and later release it with json_object_put()).

Since ownership transfers to `obj`, you must make sure that you do in fact have ownership over `val`. For instance, json_object_new_object() will give you ownership until you transfer it, whereas json_object_object_get() does not.

Any previous object stored under `key` in `obj` will have its refcount decremented, and be freed normally if that drops to zero.

Parameters

  obj | the json_object instance
  key | the object field name (a private copy will be duplicated)
  val | a json_object or NULL member to associate with the given field

Returns
  On success, `0` is returned. On error, a negative value is returned.

## ◆ json_object_object_add_ex()

JSON_EXPORT int json_object_object_add_ex | ( | struct json_object * | obj,
|  | const char *const | key,
|  | struct json_object *const | val,
|  | const unsigned | opts
| ) |  |

Add an object field to a json_object of type json_type_object

The semantics are identical to json_object_object_add, except that an additional flag fields gives you more control over some detail aspects of processing. See the description of JSON_C_OBJECT_ADD_* flags for more details.

Parameters

  obj | the json_object instance
  key | the object field name (a private copy will be duplicated)
  val | a json_object or NULL member to associate with the given field
  opts | process-modifying options. To specify multiple options, use (OPT1|OPT2)

## ◆ json_object_object_del()

JSON_EXPORT void json_object_object_del | ( | struct json_object * | obj,
|  | const char * | key
| ) |  |

Delete the given json_object field

The reference count will be decremented for the deleted object. If there are no more owners of the value represented by this key, then the value is freed. Otherwise, the reference to the value will remain in memory.

Parameters

  obj | the json_object instance
  key | the object field name

## ◆ json_object_object_get()

JSON_EXPORT struct json_object * json_object_object_get | ( | const struct json_object * | obj,
|  | const char * | key
| ) |  |

Get the json_object associate with a given object field. Deprecated/discouraged: used json_object_object_get_ex instead.

This returns NULL if the field is found but its value is null, or if the field is not found, or if obj is not a json_type_object. If you need to distinguish between these cases, use json_object_object_get_ex().

No reference counts will be changed. There is no need to manually adjust reference counts through the json_object_put/json_object_get methods unless you need to have the child (value) reference maintain a different lifetime than the owning parent (obj). Ownership of the returned value is retained by obj (do not do json_object_put unless you have done a json_object_get). If you delete the value from obj (json_object_object_del) and wish to access the returned reference afterwards, make sure you have first gotten shared ownership through json_object_get (& don't forget to do a json_object_put or transfer ownership to prevent a memory leak).

Parameters

  obj | the json_object instance
  key | the object field name

Returns
  the json_object associated with the given field name

## ◆ json_object_object_get_ex()

JSON_EXPORT int json_object_object_get_ex | ( | const struct json_object * | obj,
|  | const char * | key,
|  | struct json_object ** | value
| ) |  |

Get the json_object associated with a given object field.

This returns true if the key is found, false in all other cases (including if obj isn't a json_type_object).

No reference counts will be changed. There is no need to manually adjust reference counts through the json_object_put/json_object_get methods unless you need to have the child (value) reference maintain a different lifetime than the owning parent (obj). Ownership of value is retained by obj.

Parameters

  obj | the json_object instance
  key | the object field name
  value | a pointer where to store a reference to the json_object associated with the given field name.

It is safe to pass a NULL value.

Returns
  1 if the key exists, 0 otherwise

## ◆ json_object_object_length()

JSON_EXPORT int json_object_object_length | ( | const struct json_object * | obj | ) |

Get the size of an object in terms of the number of fields it has.

Parameters

  obj | the json_object whose length to return

## ◆ json_object_put()

JSON_EXPORT int json_object_put | ( | struct json_object * | obj | ) |

Decrement the reference count of json_object and free if it reaches zero.

You must have ownership of obj prior to doing this or you will cause an imbalance in the reference count, leading to a classic use-after-free bug. In particular, you normally do not need to call `json_object_put()` on the json_object returned by `json_object_object_get()` or `json_object_array_get_idx()`.

Just like after calling `free()` on a block of memory, you must not use `obj` after calling `json_object_put()` on it or any object that it is a member of (unless you know you've called `json_object_get(obj)` to explicitly increment the refcount).

NULL may be passed, in which case this is a no-op.

Parameters

  obj | the json_object instance

Returns
  1 if the object was freed, 0 if only the refcount was decremented

See also
  json_object_get()

## ◆ json_object_set_boolean()

JSON_EXPORT int json_object_set_boolean | ( | struct json_object * | obj,
|  | json_bool | new_value
| ) |  |

Set the json_bool value of a json_object

The type of obj is checked to be a json_type_boolean and 0 is returned if it is not without any further actions. If type of obj is json_type_boolean the object value is changed to new_value

Parameters

  obj | the json_object instance
  new_value | the value to be set

Returns
  1 if value is set correctly, 0 otherwise

## ◆ json_object_set_double()

JSON_EXPORT int json_object_set_double | ( | struct json_object * | obj,
|  | double | new_value
| ) |  |

Set the double value of a json_object

The type of obj is checked to be a json_type_double and 0 is returned if it is not without any further actions. If type of obj is json_type_double the object value is changed to new_value

If the object was created with json_object_new_double_s(), the serialization function is reset to the default and the cached serialized value is cleared.

Parameters

  obj | the json_object instance
  new_value | the value to be set

Returns
  1 if value is set correctly, 0 otherwise

## ◆ json_object_set_int()

JSON_EXPORT int json_object_set_int | ( | struct json_object * | obj,
|  | int | new_value
| ) |  |

Set the int value of a json_object

The type of obj is checked to be a json_type_int and 0 is returned if it is not without any further actions. If type of obj is json_type_int the object value is changed to new_value

Parameters

  obj | the json_object instance
  new_value | the value to be set

Returns
  1 if value is set correctly, 0 otherwise

## ◆ json_object_set_int64()

JSON_EXPORT int json_object_set_int64 | ( | struct json_object * | obj,
|  | int64_t | new_value
| ) |  |

Set the int64_t value of a json_object

The type of obj is checked to be a json_type_int and 0 is returned if it is not without any further actions. If type of obj is json_type_int the object value is changed to new_value

Parameters

  obj | the json_object instance
  new_value | the value to be set

Returns
  1 if value is set correctly, 0 otherwise

## ◆ json_object_set_serializer()

JSON_EXPORT void json_object_set_serializer | ( | json_object * | jso,
|  | json_object_to_json_string_fn * | to_string_func,
|  | void * | userdata,
|  | json_object_delete_fn * | user_delete
| ) |  |

Set a custom serialization function to be used when this particular object is converted to a string by json_object_to_json_string.

If custom userdata is already set on this object, any existing user_delete function is called before the new one is set.

If to_string_func is NULL the default behaviour is reset (but the userdata and user_delete fields are still set).

The userdata parameter is optional and may be passed as NULL. It can be used to provide additional data for to_string_func to use. This parameter may be NULL even if user_delete is non-NULL.

The user_delete parameter is optional and may be passed as NULL, even if the userdata parameter is non-NULL. It will be called just before the json_object is deleted, after it's reference count goes to zero (see json_object_put()). If this is not provided, it is up to the caller to free the userdata at an appropriate time. (i.e. after the json_object is deleted)

Note that the userdata is the same as set by json_object_set_userdata(), so care must be taken not to overwrite the value when both a custom serializer and json_object_set_userdata() are used.

Parameters

  jso | the object to customize
  to_string_func | the custom serialization function
  userdata | an optional opaque cookie
  user_delete | an optional function from freeing userdata

## ◆ json_object_set_string()

JSON_EXPORT int json_object_set_string | ( | json_object * | obj,
|  | const char * | new_value
| ) |  |

Set the string value of a json_object with zero terminated strings equivalent to json_object_set_string_len (obj, new_value, strlen(new_value))

Returns
  1 if value is set correctly, 0 otherwise

## ◆ json_object_set_string_len()

JSON_EXPORT int json_object_set_string_len | ( | json_object * | obj,
|  | const char * | new_value,
|  | int | len
| ) |  |

Set the string value of a json_object str

The type of obj is checked to be a json_type_string and 0 is returned if it is not without any further actions. If type of obj is json_type_string the object value is changed to new_value

Parameters

  obj | the json_object instance
  new_value | the value to be set; Since string length is given in len this need not be zero terminated
  len | the length of new_value

Returns
  1 if value is set correctly, 0 otherwise

## ◆ json_object_set_uint64()

JSON_EXPORT int json_object_set_uint64 | ( | struct json_object * | obj,
|  | uint64_t | new_value
| ) |  |

Set the uint64_t value of a json_object

The type of obj is checked to be a json_type_uint and 0 is returned if it is not without any further actions. If type of obj is json_type_uint the object value is changed to new_value

Parameters

  obj | the json_object instance
  new_value | the value to be set

Returns
  1 if value is set correctly, 0 otherwise

## ◆ json_object_set_userdata()

JSON_EXPORT void json_object_set_userdata | ( | json_object * | jso,
|  | void * | userdata,
|  | json_object_delete_fn * | user_delete
| ) |  |

Set an opaque userdata value for an object

The userdata can be retrieved using json_object_get_userdata().

If custom userdata is already set on this object, any existing user_delete function is called before the new one is set.

The user_delete parameter is optional and may be passed as NULL, even if the userdata parameter is non-NULL. It will be called just before the json_object is deleted, after it's reference count goes to zero (see json_object_put()). If this is not provided, it is up to the caller to free the userdata at an appropriate time. (i.e. after the json_object is deleted)

Note: Objects created by parsing strings may have custom serializers set which expect the userdata to contain specific data (due to use of json_object_new_double_s()). In this case, json_object_set_serialiser() with NULL as to_string_func should be used instead to set the userdata and reset the serializer to its default value.

Parameters

  jso | the object to set the userdata for
  userdata | an optional opaque cookie
  user_delete | an optional function from freeing userdata

## ◆ json_object_to_json_string()

JSON_EXPORT const char * json_object_to_json_string | ( | struct json_object * | obj | ) |

Stringify object to json format. Equivalent to json_object_to_json_string_ext(obj, JSON_C_TO_STRING_SPACED) The pointer you get is an internal of your json object. You don't have to free it, later use of json_object_put() should be sufficient. If you can not ensure there's no concurrent access to *obj use strdup().

Parameters

  obj | the json_object instance

Returns
  a string in JSON format

## ◆ json_object_to_json_string_ext()

JSON_EXPORT const char * json_object_to_json_string_ext | ( | struct json_object * | obj,
|  | int | flags
| ) |  |

Stringify object to json format

See also
  json_object_to_json_string() for details on how to free string.

Parameters

  obj | the json_object instance
  flags | formatting options, see JSON_C_TO_STRING_PRETTY and other constants

Returns
  a string in JSON format

## ◆ json_object_to_json_string_length()

JSON_EXPORT const char * json_object_to_json_string_length | ( | struct json_object * | obj,
|  | int | flags,
|  | size_t * | length
| ) |  |

Stringify object to json format

See also
  json_object_to_json_string() for details on how to free string.

Parameters

  obj | the json_object instance
  flags | formatting options, see JSON_C_TO_STRING_PRETTY and other constants
  length | a pointer where, if not NULL, the length (without null) is stored

Returns
  a string in JSON format and the length if not NULL

## Variable Documentation

## ◆ json_c_shallow_copy_default

JSON_EXPORT json_c_shallow_copy_fn json_c_shallow_copy_default

The default shallow copy implementation for use with json_object_deep_copy(). This simply calls the appropriate json_object_new_<type>() function and copies over the serializer function (_to_json_string internal field of the json_object structure) but not any _userdata or _user_delete values.

If you're writing a custom shallow_copy function, perhaps because you're using your own custom serializer, you can call this first to create the new object before customizing it with json_object_set_serializer().

Returns
  1 on success, -1 on errors, but never 2.

## ◆ json_object_free_userdata

JSON_EXPORT json_object_delete_fn json_object_free_userdata

Simply call free on the userdata pointer. Can be used with json_object_set_serializer().

Parameters

  jso | unused
  userdata | the pointer that is passed to free().

## ◆ json_object_userdata_to_json_string

JSON_EXPORT json_object_to_json_string_fn json_object_userdata_to_json_string

Copy the jso->_userdata string over to pb as-is. Can be used with json_object_set_serializer().

Parameters

  jso | The object whose _userdata is used.
  pb | The destination buffer.
  level | Ignored.
  flags | Ignored.