The following preprocessor constants specify the current version of
the library:
-``JANSSON_VERSION_MAJOR``, ``JANSSON_VERSION_MINOR``, ``JANSSON_VERSION_MICRO``
+``JANSSON_MAJOR_VERSION``, ``JANSSON_MINOR_VERSION``, ``JANSSON_MICRO_VERSION``
Integers specifying the major, minor and micro versions,
respectively.
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.
+ Returns 0 on success and -1 on error. The reference count of the
+ removed value is decremented.
.. function:: int json_array_clear(json_t *array)
Removes all elements from *array*. Returns 0 on sucess and -1 on
- error.
+ error. The reference count of all removed values are decremented.
.. function:: int json_array_extend(json_t *array, json_t *other_array)
.. function:: 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.
-
+ -1 if *key* was not found. The reference count of the removed value
+ is decremented.
.. function:: 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.
+ *object* is not a JSON object. The reference count of all removed
+ values are decremented.
.. function:: 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.
+.. function:: int json_object_update_existing(json_t *object, json_t *other)
+
+ Like :func:`json_object_update()`, but only the values of existing
+ keys are updated. No new keys are created. Returns 0 on success or
+ -1 on error.
+
+ .. versionadded:: 2.3
+
+.. function:: int json_object_update_missing(json_t *object, json_t *other)
+
+ Like :func:`json_object_update()`, but only new keys are created.
+ The value of any existing key is not changed. Returns 0 on success
+ or -1 on error.
+
+ .. versionadded:: 2.3
+
+The following macro can be used to iterate through all key-value pairs
+in an object.
+
+.. function:: json_object_foreach(object, key, value)
+
+ Iterate over every key-value pair of ``object``, running the block
+ of code that follows each time with the proper values set to
+ variables ``key`` and ``value``, of types :type:`const char *` and
+ :type:`json_t *` respectively. Example::
+
+ /* obj is a JSON object */
+ const char *key;
+ json_t *value;
+
+ json_object_foreach(obj, key, value) {
+ /* block of code that uses key and value */
+ }
+
+ The items are not returned in any particular order.
+
+ This macro expands to an ordinary ``for`` statement upon
+ preprocessing, so its performance is equivalent to that of
+ hand-written iteration code using the object iteration protocol
+ (see below). The main advantage of this macro is that it abstracts
+ away the complexity behind iteration, and makes for shorter, more
+ concise code.
+
+ .. versionadded:: 2.3
+
The following functions implement an iteration protocol for objects,
allowing to iterate through all key-value pairs in an object. The
items are not returned in any particular order, as this would require
-sorting due to the internal object representation.
+sorting due to the internal hashtable implementation.
.. function:: void *json_object_iter(json_t *object)
*value*. This is useful when *value* is newly created and not used
after the call.
+.. function:: void *json_object_key_to_iter(const char *key)
+
+ Like :func:`json_object_iter_at()`, but much faster. Only works for
+ values returned by :func:`json_object_iter_key()`. Using other keys
+ will lead to segfaults. This function is used internally to
+ implement :func:`json_object_foreach`.
+
+ .. versionadded:: 2.3
+
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)
{
}
Also note that if the call succeeded (``json != NULL`` in the above
-example), the contents of ``error`` are unspecified.
+example), the contents of ``error`` are generally left unspecified.
+The decoding functions write to the ``position`` member also on
+success. See :ref:`apiref-decoding` for more info.
All functions also accept *NULL* as the :type:`json_error_t` pointer,
in which case no error information is returned to the caller.
``JSON_INDENT(n)``
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 32, 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.
+ between 0 and 31 (inclusive), 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
**Note:** Encoding any value may be useful in some scenarios, but
it's generally discouraged as it violates strict compatiblity with
:rfc:`4627`. If you use this flag, don't expect interoperatibility
- with other JSON systems. Even Jansson itself doesn't have any means
- to decode JSON texts whose root value is not object or array.
+ with other JSON systems.
.. versionadded:: 2.1
*path* already exists, it is overwritten. *flags* is described
above. Returns 0 on success and -1 on error.
+.. type:: json_dump_callback_t
+
+ A typedef for a function that's called by
+ :func:`json_dump_callback()`::
+
+ typedef int (*json_dump_callback_t)(const char *buffer, size_t size, void *data);
+
+ *buffer* points to a buffer containing a chunk of output, *size* is
+ the length of the buffer, and *data* is the corresponding
+ :func:`json_dump_callback()` argument passed through.
+
+ On error, the function should return -1 to stop the encoding
+ process. On success, it should return 0.
+
+ .. versionadded:: 2.2
+
+.. function:: int json_dump_callback(const json_t *json, json_dump_callback_t callback, void *data, size_t flags)
+
+ Call *callback* repeatedly, passing a chunk of the JSON
+ representation of *root* each time. *flags* is described above.
+ Returns 0 on success and -1 on error.
+
+ .. versionadded:: 2.2
+
.. _apiref-decoding:
specification requires that a JSON text is either a serialized array
or object, and this requirement is also enforced with the following
functions. In other words, the top level value in the JSON text being
-decoded must be either array or object.
+decoded must be either array or object. To decode any JSON value, use
+the ``JSON_DECODE_ANY`` flag (see below).
See :ref:`rfc-conformance` for a discussion on Jansson's conformance
to the JSON specification. It explains many design decisions that
.. versionadded:: 2.1
+``JSON_DECODE_ANY``
+ By default, the decoder expects an array or object as the input.
+ With this flag enabled, the decoder accepts any valid JSON value.
+
+ **Note:** Decoding any value may be useful in some scenarios, but
+ it's generally discouraged as it violates strict compatiblity with
+ :rfc:`4627`. If you use this flag, don't expect interoperatibility
+ with other JSON systems.
+
+ .. versionadded:: 2.3
+
+``JSON_DISABLE_EOF_CHECK``
+ By default, the decoder expects that its whole input constitutes a
+ valid JSON text, and issues an error if there's extra data after
+ the otherwise valid JSON input. With this flag enabled, the decoder
+ stops after decoding a valid JSON array or object, and thus allows
+ extra data after the JSON text.
+
+ Normally, reading will stop when the last ``]`` or ``}`` in the
+ JSON input is encountered. If both ``JSON_DISABLE_EOF_CHECK`` and
+ ``JSON_DECODE_ANY`` flags are used, the decoder may read one extra
+ UTF-8 code unit (up to 4 bytes of input). For example, decoding
+ ``4true`` correctly decodes the integer 4, but also reads the
+ ``t``. For this reason, if reading multiple consecutive values that
+ are not arrays or objects, they should be separated by at least one
+ whitespace character.
+
+ .. versionadded:: 2.1
+
+Each function also takes an optional :type:`json_error_t` parameter
+that is filled with error information if decoding fails. It's also
+updated on success; the number of bytes of input read is written to
+its ``position`` field. This is especially useful when using
+``JSON_DISABLE_EOF_CHECK`` to read multiple consecutive JSON texts.
+
+.. versionadded:: 2.3
+ Number of bytes of input read is written to the ``position`` field
+ of the :type:`json_error_t` structure.
+
+If no error or position information is needed, you can pass *NULL*.
+
The following functions perform the actual JSON decoding.
.. function:: json_t *json_loads(const char *input, size_t flags, json_error_t *error)
filled with information about the error. *flags* is described
above.
+ This function will start reading the input from whatever position
+ the input file was, without attempting to seek first. If an error
+ occurs, the file position will be left indeterminate. On success,
+ the file position will be at EOF, unless ``JSON_DISABLE_EOF_CHECK``
+ flag was used. In this case, the file position will be at the first
+ character after the last ``]`` or ``}`` in the JSON input. This
+ allows calling :func:`json_loadf()` on the same ``FILE`` object
+ multiple times, if the input consists of consecutive JSON texts,
+ possibly separated by whitespace.
+
.. function:: json_t *json_load_file(const char *path, size_t flags, json_error_t *error)
.. refcounting:: new
filled with information about the error. *flags* is described
above.
+.. type:: json_load_callback_t
+
+ A typedef for a function that's called by
+ :func:`json_load_callback()` to read a chunk of input data::
+
+ typedef size_t (*json_load_callback_t)(void *buffer, size_t buflen, void *data);
+
+ *buffer* points to a buffer of *buflen* bytes, and *data* is the
+ corresponding :func:`json_load_callback()` argument passed through.
+
+ On error, the function should return ``(size_t)-1`` to abort the
+ decoding process. When there's no data left, it should return 0 to
+ report that the end of input has been reached.
+
+ .. versionadded:: 2.4
+
+.. function:: json_t *json_load_callback(json_load_callback_t callback, void *data, size_t flags, json_error_t *error)
+
+ .. refcounting:: new
+
+ Decodes the JSON text produced by repeated calls to *callback*, and
+ returns the array or object it contains, or *NULL* on error, in
+ which case *error* is filled with information about the error.
+ *data* is passed through to *callback* on each call. *flags* is
+ described above.
+
+ .. versionadded:: 2.4
+
.. _apiref-pack:
Building Values
===============
-This sectinon describes functions that help to create, or *pack*,
+This section describes functions that help to create, or *pack*,
complex JSON values, especially nested objects and arrays. Value
building is based on a *format string* that is used to tell the
functions about the expected arguments.
For example, the format string ``"i"`` specifies a single integer
value, while the format string ``"[ssb]"`` or the equivalent ``"[s, s,
-b]"`` specifies an array value with two integers and a boolean as its
+b]"`` specifies an array value with two strings and a boolean as its
items::
/* Create the JSON integer 42 */
``o`` (any value) [json_t \*]
Output any given JSON value as-is. If the value is added to an
array or object, the reference to the value passed to ``o`` is
- stealed by the container.
+ stolen by the container.
``O`` (any value) [json_t \*]
Like ``o``, but the argument's reference count is incremented.
fourth, etc. format character represent a value. Any value may be
an object or array, i.e. recursive value building is supported.
+Whitespace, ``:`` and ``,`` are ignored.
+
The following functions compose the value building API:
.. function:: json_t *json_pack(const char *fmt, ...)
json_pack("{}");
/* Build the JSON object {"foo": 42, "bar": 7} */
- json_pack("{sisb}", "foo", 42, "bar", 7);
+ json_pack("{sisi}", "foo", 42, "bar", 7);
/* Like above, ':', ',' and whitespace are ignored */
- json_pack("{s:i, s:b}", "foo", 42, "bar", 7);
+ json_pack("{s:i, s:i}", "foo", 42, "bar", 7);
/* Build the JSON array [[1, 2], {"cool": true}] */
- json_pack("[[i,i],{s:b]]", 1, 2, "cool", 1);
+ json_pack("[[i,i],{s:b}]", 1, 2, "cool", 1);
.. _apiref-unpack:
``s`` (string) [const char \*]
Convert a JSON string to a pointer to a NULL terminated UTF-8
- string.
+ string. The resulting string is extracted by using
+ :func:`json_string_value()` internally, so it exists as long as
+ there are still references to the corresponding JSON string.
``n`` (null)
Expect a JSON null value. Nothing is extracted.
``fmt`` may contain objects and arrays as values, i.e. recursive
value extraction is supporetd.
+ .. versionadded:: 2.3
+ Any ``s`` representing a key may be suffixed with a ``?`` to
+ make the key optional. If the key is not found, nothing is
+ extracted. See below for an example.
+
``!``
This special format character is used to enable the check that
all object and array items are accessed, on a per-value basis. It
or object as the last format character before the closing bracket
or brace.
+Whitespace, ``:`` and ``,`` are ignored.
+
The following functions compose the parsing and validation API:
.. function:: int json_unpack(json_t *root, const char *fmt, ...)
behaviour of the unpacker, see below for the flags. Returns 0 on
success and -1 on failure.
+.. note::
+
+ The first argument of all unpack functions is ``json_t *root``
+ instead of ``const json_t *root``, because the use of ``O`` format
+ character causes the reference count of ``root``, or some value
+ reachable from ``root``, to be increased. Furthermore, the ``o``
+ format character may be used to extract a value as-is, which allows
+ modifying the structure or contents of a value reachable from
+ ``root``.
+
+ If the ``O`` and ``o`` format character are not used, it's
+ perfectly safe to cast a ``const json_t *`` variable to plain
+ ``json_t *`` when used with these functions.
+
The following unpacking flags are available:
``JSON_STRICT``
json_unpack(root, "[ii!]", &myint1, &myint2);
/* returns -1 for failed validation */
+ /* root is an empty JSON object */
+ int myint = 0, myint2 = 0;
+ json_unpack(root, "{s?i, s?[ii]}",
+ "foo", &myint1,
+ "bar", &myint2, &myint3);
+ /* myint1, myint2 or myint3 is no touched as "foo" and "bar" don't exist */
+
Equality
========
Returns a deep copy of *value*, or *NULL* on error.
+.. _apiref-custom-memory-allocation:
+
Custom Memory Allocation
========================
For more information about the issues of storing sensitive data in
memory, see
http://www.dwheeler.com/secure-programs/Secure-Programs-HOWTO/protect-secrets.html.
-The page also examplains the :func:`guaranteed_memset()` function used
+The page also explains the :func:`guaranteed_memset()` function used
in the example and gives a sample implementation for it.
projects / jansson.git / blobdiff