Add functions json_object_iter_{at,set,set_new}

[jansson.git] / doc / apiref.rst

diff --git a/doc/apiref.rst b/doc/apiref.rst
index c70c0bc..0a96999 100644 (file)
--- a/doc/apiref.rst
+++ b/doc/apiref.rst
@@ -1,3 +1,5 @@
+.. _apiref:
+

 *************
 API Reference
 *************
 *************
 API Reference
 *************


@@ -41,6 +43,12 @@ Objects of :ctype:`json_t` are always used through a pointer. There
 are APIs for querying the type, manipulating the reference count, and
 for constructing and manipulating values of different types.
 
 are APIs for querying the type, manipulating the reference count, and
 for constructing and manipulating values of different types.
 

+Unless noted otherwise, all API functions return an error value if an
+error occurs. Depending on the function's signature, the error value
+is either *NULL* or -1. Invalid arguments or invalid input are
+apparent sources for errors. Memory allocation and I/O operations may
+also cause errors.
+

 
 Type
 ----
 
 Type
 ----


@@ -80,8 +88,8 @@ functions:
 .. cfunction:: int json_typeof(const json_t *json)
 
    Return the type of the JSON value (a :ctype:`json_type` cast to
 .. cfunction:: int json_typeof(const json_t *json)
 
    Return the type of the JSON value (a :ctype:`json_type` cast to

-   :ctype:`int`). This function is actually implemented as a macro for
-   speed.
+   :ctype:`int`). *json* MUST NOT be *NULL*. This function is actually
+   implemented as a macro for speed.

 
 .. cfunction:: json_is_object(const json_t *json)
                json_is_array(const json_t *json)
 
 .. cfunction:: json_is_object(const json_t *json)
                json_is_array(const json_t *json)


@@ -93,19 +101,22 @@ functions:
                json_is_null(const json_t *json)
 
    These functions (actually macros) return true (non-zero) for values
                json_is_null(const json_t *json)
 
    These functions (actually macros) return true (non-zero) for values

-   of the given type, and false (zero) for values of other types.
+   of the given type, and false (zero) for values of other types and
+   for *NULL*.

 
 .. cfunction:: json_is_number(const json_t *json)
 
    Returns true for values of types :const:`JSON_INTEGER` and
 
 .. cfunction:: json_is_number(const json_t *json)
 
    Returns true for values of types :const:`JSON_INTEGER` and

-   :const:`JSON_REAL`, and false for other types.
+   :const:`JSON_REAL`, and false for other types and for *NULL*.

 
 .. cfunction:: json_is_boolean(const json_t *json)
 
    Returns true for types :const:`JSON_TRUE` and :const:`JSON_FALSE`,
 
 .. cfunction:: json_is_boolean(const json_t *json)
 
    Returns true for types :const:`JSON_TRUE` and :const:`JSON_FALSE`,

-   and false for values of other types.
+   and false for values of other types and for *NULL*.

 
 
 
 

+.. _apiref-reference-count:
+

 Reference Count
 ---------------
 
 Reference Count
 ---------------
 


@@ -121,7 +132,8 @@ The following functions are used to manipulate the reference count.
 
 .. cfunction:: json_t *json_incref(json_t *json)
 
 
 .. cfunction:: json_t *json_incref(json_t *json)
 

-   Increment the reference count of *json*.
+   Increment the reference count of *json* if it's not non-*NULL*.
+   Returns *json*.

 
 .. cfunction:: void json_decref(json_t *json)
 
 
 .. cfunction:: void json_decref(json_t *json)
 


@@ -151,29 +163,60 @@ will return a new or borrowed reference or steal a reference to its
 argument.
 
 
 argument.
 
 

+Circular References
+-------------------
+
+A circular reference is created when an object or an array is,
+directly or indirectly, inserted inside itself. The direct case is
+simple::
+
+  json_t *obj = json_object();
+  json_object_set(obj, "foo", obj);
+
+Jansson will refuse to do this, and :cfunc:`json_object_set()` (and
+all the other such functions for objects and arrays) will return with
+an error status. The indirect case is the dangerous one::
+
+  json_t *arr1 = json_array(), *arr2 = json_array();
+  json_array_append(arr1, arr2);
+  json_array_append(arr2, arr1);
+
+In this example, the array ``arr2`` is contained in the array
+``arr1``, and vice versa. Jansson cannot check for this kind of
+indirect circular references without a performance hit, so it's up to
+the user to avoid them.
+
+If a circular reference is created, the memory consumed by the values
+cannot be freed by :cfunc:`json_decref()`. The reference counts never
+drops to zero because the values are keeping the circular reference to
+themselves. Moreover, trying to encode the values with any of the
+encoding functions will fail. The encoder detects circular references
+and returns an error status.
+
+

 True, False and Null
 ====================
 
 True, False and Null
 ====================
 

+These values are implemented as singletons, so each of these functions
+returns the same value each time.
+

 .. cfunction:: json_t *json_true(void)
 
    .. refcounting:: new
 
 .. cfunction:: json_t *json_true(void)
 
    .. refcounting:: new
 

-   Returns a value of the type :const:`JSON_TRUE`, or *NULL* on
-   error.
+   Returns the JSON true value.

 
 .. cfunction:: json_t *json_false(void)
 
    .. refcounting:: new
 
 
 .. cfunction:: json_t *json_false(void)
 
    .. refcounting:: new
 

-   Returns a value of the type :const:`JSON_FALSE`, or *NULL* on
-   error.
+   Returns the JSON false value.

 
 .. cfunction:: json_t *json_null(void)
 
    .. refcounting:: new
 
 
 .. cfunction:: json_t *json_null(void)
 
    .. refcounting:: new
 

-   Returns a value of the type :const:`JSON_NULL`, or *NULL* on
-   error.
+   Returns the JSON null value.

 
 
 String
 
 
 String


@@ -183,13 +226,40 @@ String
 
    .. refcounting:: new
 
 
    .. refcounting:: new
 

-   Returns a new value of the type :const:`JSON_STRING`, or *NULL* on
-   error. *value* must be a valid UTF-8 encoded Unicode string.
+   Returns a new JSON string, or *NULL* on error. *value* must be a
+   valid UTF-8 encoded Unicode string.
+
+.. cfunction:: json_t *json_string_nocheck(const char *value)
+
+   .. refcounting:: new
+
+   Like :cfunc:`json_string`, but doesn't check that *value* is valid
+   UTF-8. Use this function only if you are certain that this really
+   is the case (e.g. you have already checked it by other means).
+
+   .. versionadded:: 1.2
+
+.. cfunction:: const char *json_string_value(const json_t *string)
+
+   Returns the associated value of *string* as a null terminated UTF-8
+   encoded string, or *NULL* if *string* is not a JSON string.
+
+.. cfunction:: int json_string_set(const json_t *string, const char *value)
+
+   Sets the associated value of *string* to *value*. *value* must be a
+   valid UTF-8 encoded Unicode string. Returns 0 on success and -1 on
+   error.
+
+   .. versionadded:: 1.1
+
+.. cfunction:: int json_string_set_nocheck(const json_t *string, const char *value)

 
 

-.. cfunction:: const char *json_string_value(const json_t *json)
+   Like :cfunc:`json_string_set`, but doesn't check that *value* is
+   valid UTF-8. Use this function only if you are certain that this
+   really is the case (e.g. you have already checked it by other
+   means).

 
 

-   Returns the associated value of a :const:`JSON_STRING` value as a
-   null terminated UTF-8 encoded string.
+   .. versionadded:: 1.2

 
 
 Number
 
 
 Number


@@ -199,33 +269,46 @@ Number
 
    .. refcounting:: new
 
 
    .. refcounting:: new
 

-   Returns a new value of the type :const:`JSON_INTEGER`, or *NULL* on
-   error.
+   Returns a new JSON integer, or *NULL* on error.
+
+.. cfunction:: int json_integer_value(const json_t *integer)
+
+   Returns the associated value of *integer*, or 0 if *json* is not a
+   JSON integer.
+
+.. cfunction:: int json_integer_set(const json_t *integer, int value)

 
 

-.. cfunction:: int json_integer_value(const json_t *json)
+   Sets the associated value of *integer* to *value*. Returns 0 on
+   success and -1 if *integer* is not a JSON integer.

 
 

-   Returns the associated integer value of values of the type
-   :const:`JSON_INTEGER`, or 0 for values of other types.
+   .. versionadded:: 1.1

 
 .. cfunction:: json_t *json_real(double value)
 
    .. refcounting:: new
 
 
 .. cfunction:: json_t *json_real(double value)
 
    .. refcounting:: new
 

-   Returns a new value of the type :const:`JSON_REAL`, or *NULL* on
-   error.
+   Returns a new JSON real, or *NULL* on error.
+
+.. cfunction:: double json_real_value(const json_t *real)
+
+   Returns the associated value of *real*, or 0.0 if *real* is not a
+   JSON real.

 
 

-.. cfunction:: double json_real_value(const json_t *json)
+.. cfunction:: int json_real_set(const json_t *real, double value)

 
 

-   Returns the associated real value of values of the type
-   :const:`JSON_INTEGER`, or 0 for values of other types.
+   Sets the associated value of *real* to *value*. Returns 0 on
+   success and -1 if *real* is not a JSON real.
+
+   .. versionadded:: 1.1

 
 In addition to the functions above, there's a common query function
 for integers and reals:
 
 .. cfunction:: double json_number_value(const json_t *json)
 
 
 In addition to the functions above, there's a common query function
 for integers and reals:
 
 .. cfunction:: double json_number_value(const json_t *json)
 

-   Returns the value of either ``JSON_INTEGER`` or ``JSON_REAL``, cast
-   to double regardless of the actual type.
+   Returns the associated value of the JSON integer or JSON real
+   *json*, cast to double regardless of the actual type. If *json* is
+   neither JSON real nor JSON integer, 0.0 is returned.

 
 
 Array
 
 
 Array


@@ -237,27 +320,30 @@ A JSON array is an ordered collection of other JSON values.
 
    .. refcounting:: new
 
 
    .. refcounting:: new
 

-   Returns a new value of the type :const:`JSON_ARRAY`, or *NULL* on
-   error. Initially, the array is empty.
+   Returns a new JSON array, or *NULL* on error. Initially, the array
+   is empty.

 
 .. cfunction:: unsigned int json_array_size(const json_t *array)
 
 
 .. cfunction:: unsigned int json_array_size(const json_t *array)
 

-   Returns the number of elements in *array*.
+   Returns the number of elements in *array*, or 0 if *array* is NULL
+   or not a JSON array.

 
 .. cfunction:: json_t *json_array_get(const json_t *array, unsigned int index)
 
    .. refcounting:: borrow
 
 
 .. cfunction:: json_t *json_array_get(const json_t *array, unsigned int index)
 
    .. refcounting:: borrow
 

-   Returns the element in *array* at position *index*, or *NULL* if
-   *index* is out of range. The valid range for *index* is from 0 to
-   the return value of :cfunc:`json_array_size()` minus 1.
+   Returns the element in *array* at position *index*. The valid range
+   for *index* is from 0 to the return value of
+   :cfunc:`json_array_size()` minus 1. If *array* is not a JSON array,
+   if *array* is *NULL*, or if *index* is out of range, *NULL* is
+   returned.

 
 .. cfunction:: int json_array_set(json_t *array, unsigned int index, json_t *value)
 
    Replaces the element in *array* at position *index* with *value*.
 
 .. cfunction:: int json_array_set(json_t *array, unsigned int index, json_t *value)
 
    Replaces the element in *array* at position *index* with *value*.

-   Returns 0 on success, or -1 if *index* is out of range. The valid
-   range for *index* is from 0 to the return value of
-   :cfunc:`json_array_size()` minus 1.
+   The valid range for *index* is from 0 to the return value of
+   :cfunc:`json_array_size()` minus 1. Returns 0 on success and -1 on
+   error.

 
 .. cfunction:: int json_array_set_new(json_t *array, unsigned int index, json_t *value)
 
 
 .. cfunction:: int json_array_set_new(json_t *array, unsigned int index, json_t *value)
 


@@ -280,6 +366,44 @@ A JSON array is an ordered collection of other JSON values.
 
    .. versionadded:: 1.1
 
 
    .. versionadded:: 1.1
 

+.. cfunction:: int json_array_insert(json_t *array, unsigned int index, json_t *value)
+
+   Inserts *value* to *array* at position *index*, shifting the
+   elements at *index* and after it one position towards the end of
+   the array. Returns 0 on success and -1 on error.
+
+   .. versionadded:: 1.1
+
+.. cfunction:: int json_array_insert_new(json_t *array, unsigned int index, json_t *value)
+
+   Like :cfunc:`json_array_insert()` but steals the reference to
+   *value*. This is useful when *value* is newly created and not used
+   after the call.
+
+   .. versionadded:: 1.1
+
+.. cfunction:: int json_array_remove(json_t *array, unsigned int index)
+
+   Removes the element in *array* at position *index*, shifting the
+   elements after *index* one position towards the start of the array.
+   Returns 0 on success and -1 on error.
+
+   .. versionadded:: 1.1
+
+.. cfunction:: int json_array_clear(json_t *array)
+
+   Removes all elements from *array*. Returns 0 on sucess and -1 on
+   error.
+
+   .. versionadded:: 1.1
+
+.. cfunction:: int json_array_extend(json_t *array, json_t *other_array)
+
+   Appends all elements in *other_array* to the end of *array*.
+   Returns 0 on success and -1 on error.
+
+   .. versionadded:: 1.1
+

 
 Object
 ======
 
 Object
 ======


@@ -291,8 +415,15 @@ Unicode string and the value is any JSON value.
 
    .. refcounting:: new
 
 
    .. refcounting:: new
 

-   Returns a new value of the type :const:`JSON_OBJECT`, or *NULL* on
-   error. Initially, the object is empty.
+   Returns a new JSON object, or *NULL* on error. Initially, the
+   object is empty.
+
+.. cfunction:: unsigned int json_object_size(const json_t *object)
+
+   Returns the number of elements in *object*, or 0 if *object* is not
+   a JSON object.
+
+   .. versionadded:: 1.1

 
 .. cfunction:: json_t *json_object_get(const json_t *object, const char *key)
 
 
 .. cfunction:: json_t *json_object_get(const json_t *object, const char *key)
 


@@ -304,9 +435,18 @@ Unicode string and the value is any JSON value.
 .. cfunction:: int json_object_set(json_t *object, const char *key, json_t *value)
 
    Set the value of *key* to *value* in *object*. *key* must be a
 .. cfunction:: int json_object_set(json_t *object, const char *key, json_t *value)
 
    Set the value of *key* to *value* in *object*. *key* must be a

-   valid terminated UTF-8 encoded Unicode string. If there already is
-   a value for *key*, it is replaced by the new value. Returns 0 on
-   success and -1 on error.
+   valid null terminated UTF-8 encoded Unicode string. If there
+   already is a value for *key*, it is replaced by the new value.
+   Returns 0 on success and -1 on error.
+
+.. cfunction:: int json_object_set_nocheck(json_t *object, const char *key, json_t *value)
+
+   Like :cfunc:`json_object_set`, but doesn't check that *key* is
+   valid UTF-8. Use this function only if you are certain that this
+   really is the case (e.g. you have already checked it by other
+   means).
+
+   .. versionadded:: 1.2

 
 .. cfunction:: int json_object_set_new(json_t *object, const char *key, json_t *value)
 
 
 .. cfunction:: int json_object_set_new(json_t *object, const char *key, json_t *value)
 


@@ -316,12 +456,36 @@ Unicode string and the value is any JSON value.
 
    .. versionadded:: 1.1
 
 
    .. versionadded:: 1.1
 

+.. cfunction:: int json_object_set_new_nocheck(json_t *object, const char *key, json_t *value)
+
+   Like :cfunc:`json_object_set_new`, but doesn't check that *key* is
+   valid UTF-8. Use this function only if you are certain that this
+   really is the case (e.g. you have already checked it by other
+   means).
+
+   .. versionadded:: 1.2
+

 .. cfunction:: int json_object_del(json_t *object, const char *key)
 
    Delete *key* from *object* if it exists. Returns 0 on success, or
    -1 if *key* was not found.
 
 
 .. cfunction:: int json_object_del(json_t *object, const char *key)
 
    Delete *key* from *object* if it exists. Returns 0 on success, or
    -1 if *key* was not found.
 
 

+.. cfunction:: int json_object_clear(json_t *object)
+
+   Remove all elements from *object*. Returns 0 on success and -1 if
+   *object* is not a JSON object.
+
+   .. versionadded:: 1.1
+
+.. cfunction:: int json_object_update(json_t *object, json_t *other)
+
+   Update *object* with the key-value pairs from *other*, overwriting
+   existing keys. Returns 0 on success or -1 on error.
+
+   .. versionadded:: 1.1
+
+

 The following functions implement an iteration protocol for objects:
 
 .. cfunction:: void *json_object_iter(json_t *object)
 The following functions implement an iteration protocol for objects:
 
 .. cfunction:: void *json_object_iter(json_t *object)


@@ -329,6 +493,16 @@ The following functions implement an iteration protocol for objects:
    Returns an opaque iterator which can be used to iterate over all
    key-value pairs in *object*, or *NULL* if *object* is empty.
 
    Returns an opaque iterator which can be used to iterate over all
    key-value pairs in *object*, or *NULL* if *object* is empty.
 

+.. cfunction:: void *json_object_iter_at(json_t *object, const char *key)
+
+   Like :cfunc:`json_object_iter()`, but returns an iterator to the
+   key-value pair in *object* whose key is equal to *key*, or NULL if
+   *key* is not found in *object*. Iterating forward to the end of
+   *object* only yields all key-value pairs of the object if *key*
+   happens to be the first key in the underlying hash table.
+
+   .. versionadded:: 1.3
+

 .. cfunction:: void *json_object_iter_next(json_t *object, void *iter)
 
    Returns an iterator pointing to the next key-value pair in *object*
 .. cfunction:: void *json_object_iter_next(json_t *object, void *iter)
 
    Returns an iterator pointing to the next key-value pair in *object*


@@ -345,6 +519,35 @@ The following functions implement an iteration protocol for objects:
 
    Extract the associated value from *iter*.
 
 
    Extract the associated value from *iter*.
 

+.. cfunction:: int json_object_iter_set(json_t *object, void *iter, json_t *value)
+
+   Set the value of the key-value pair in *object*, that is pointed to
+   by *iter*, to *value*.
+
+   .. versionadded:: 1.3
+
+.. cfunction:: int json_object_iter_set_new(json_t *object, void *iter, json_t *value)
+
+   Like :cfunc:`json_object_iter_set()`, but steals the reference to
+   *value*. This is useful when *value* is newly created and not used
+   after the call.
+
+   .. versionadded:: 1.3
+
+The iteration protocol can be used for example as follows::
+
+   /* obj is a JSON object */
+   const char *key;
+   json_t *value;
+   void *iter = json_object_iter(obj);
+   while(iter)
+   {
+       key = json_object_iter_key(iter);
+       value = json_object_iter_value(iter);
+       /* use key and value ... */
+       iter = json_object_iter_next(obj, iter);
+   }
+

 
 Encoding
 ========
 
 Encoding
 ========


@@ -353,32 +556,63 @@ This sections describes the functions that can be used to encode
 values to JSON. Only objects and arrays can be encoded, since they are
 the only valid "root" values of a JSON text.
 
 values to JSON. Only objects and arrays can be encoded, since they are
 the only valid "root" values of a JSON text.
 

+By default, the output has no newlines, and spaces are used between
+array and object elements for a readable output. This behavior can be
+altered by using the ``JSON_INDENT`` and ``JSON_COMPACT`` flags
+described below. A newline is never appended to the end of the encoded
+JSON data.
+

 Each function takes a *flags* parameter that controls some aspects of
 how the data is encoded. Its default value is 0. The following macros
 can be ORed together to obtain *flags*.
 
 ``JSON_INDENT(n)``
 Each function takes a *flags* parameter that controls some aspects of
 how the data is encoded. Its default value is 0. The following macros
 can be ORed together to obtain *flags*.
 
 ``JSON_INDENT(n)``

-   Pretty-print the result, indenting arrays and objects by *n*
-   spaces. The valid range for *n* is between 0 and 255, other values
-   result in an undefined output. If ``JSON_INDENT`` is not used or
-   *n* is 0, no pretty-printing is done and the result is a compact
-   representation.
+   Pretty-print the result, using newlines between array and object
+   items, and indenting with *n* spaces. The valid range for *n* is
+   between 0 and 255, other values result in an undefined output. If
+   ``JSON_INDENT`` is not used or *n* is 0, no newlines are inserted
+   between array and object items.
+
+``JSON_COMPACT``
+   This flag enables a compact representation, i.e. sets the separator
+   between array and object items to ``","`` and between object keys
+   and values to ``":"``. Without this flag, the corresponding
+   separators are ``", "`` and ``": "`` for more readable output.
+
+   .. versionadded:: 1.2
+
+``JSON_ENSURE_ASCII``
+   If this flag is used, the output is guaranteed to consist only of
+   ASCII characters. This is achived by escaping all Unicode
+   characters outside the ASCII range.
+
+   .. versionadded:: 1.2
+
+``JSON_SORT_KEYS``
+   If this flag is used, all the objects in output are sorted by key.
+   This is useful e.g. if two JSON texts are diffed or visually
+   compared.
+
+   .. versionadded:: 1.2

 
 The following functions perform the actual JSON encoding. The result
 is in UTF-8.
 
 
 The following functions perform the actual JSON encoding. The result
 is in UTF-8.
 

-.. cfunction:: char *json_dumps(const json_t *root, uint32_t flags)
+.. cfunction:: char *json_dumps(const json_t *root, unsigned long flags)

 
    Returns the JSON representation of *root* as a string, or *NULL* on
    error. *flags* is described above. The return value must be freed
    by the caller using :cfunc:`free()`.
 
 
    Returns the JSON representation of *root* as a string, or *NULL* on
    error. *flags* is described above. The return value must be freed
    by the caller using :cfunc:`free()`.
 

-.. cfunction:: int json_dumpf(const json_t *root, FILE *output, uint32_t flags)
+.. cfunction:: int json_dumpf(const json_t *root, FILE *output, unsigned long flags)

 
    Write the JSON representation of *root* to the stream *output*.
    *flags* is described above. Returns 0 on success and -1 on error.
 
    Write the JSON representation of *root* to the stream *output*.
    *flags* is described above. Returns 0 on success and -1 on error.

+   If an error occurs, something may have already been written to
+   *output*. In this case, the output is undefined and most likely not
+   valid JSON.

 
 

-.. cfunction:: int json_dump_file(const json_t *json, const char *path, uint32_t flags)
+.. cfunction:: int json_dump_file(const json_t *json, const char *path, unsigned long flags)

 
    Write the JSON representation of *root* to the file *path*. If
    *path* already exists, it is overwritten. *flags* is described
 
    Write the JSON representation of *root* to the file *path*. If
    *path* already exists, it is overwritten. *flags* is described


@@ -464,3 +698,75 @@ The following functions perform the actual JSON decoding.
    object it contains, or *NULL* on error, in which case *error* is
    filled with information about the error. See above for discussion
    on the *error* parameter.
    object it contains, or *NULL* on error, in which case *error* is
    filled with information about the error. See above for discussion
    on the *error* parameter.

+
+
+Equality
+========
+
+Testing for equality of two JSON values cannot, in general, be
+achieved using the ``==`` operator. Equality in the terms of the
+``==`` operator states that the two :ctype:`json_t` pointers point to
+exactly the same JSON value. However, two JSON values can be equal not
+only if they are exactly the same value, but also if they have equal
+"contents":
+
+* Two integer or real values are equal if their contained numeric
+  values are equal. An integer value is never equal to a real value,
+  though.
+
+* Two strings are equal if their contained UTF-8 strings are equal.
+
+* Two arrays are equal if they have the same number of elements and
+  each element in the first array is equal to the corresponding
+  element in the second array.
+
+* Two objects are equal if they have exactly the same keys and the
+  value for each key in the first object is equal to the value of the
+  corresponding key in the second object.
+
+* Two true, false or null values have no "contents", so they are equal
+  if their types are equal. (Because these values are singletons,
+  their equality can actually be tested with ``==``.)
+
+The following function can be used to test whether two JSON values are
+equal.
+
+.. cfunction:: int json_equal(json_t *value1, json_t *value2)
+
+   Returns 1 if *value1* and *value2* are equal, as defined above.
+   Returns 0 if they are inequal or one or both of the pointers are
+   *NULL*.
+
+   .. versionadded:: 1.2
+
+
+Copying
+=======
+
+Because of reference counting, passing JSON values around doesn't
+require copying them. But sometimes a fresh copy of a JSON value is
+needed. For example, if you need to modify an array, but still want to
+use the original afterwards, you should take a copy of it first.
+
+Jansson supports two kinds of copying: shallow and deep. There is a
+difference between these methods only for arrays and objects. Shallow
+copying only copies the first level value (array or object) and uses
+the same child values in the copied value. Deep copying makes a fresh
+copy of the child values, too. Moreover, all the child values are deep
+copied in a recursive fashion.
+
+.. cfunction:: json_t *json_copy(json_t *value)
+
+   .. refcounting:: new
+
+   Returns a shallow copy of *value*, or *NULL* on error.
+
+   .. versionadded:: 1.2
+
+.. cfunction:: json_t *json_deep_copy(json_t *value)
+
+   .. refcounting:: new
+
+   Returns a deep copy of *value*, or *NULL* on error.
+
+   .. versionadded:: 1.2