manage the reference, i.e. increase and decrease the reference count
as needed. However, some functions **steal** the reference, i.e. they
have the same result as if the user called :cfunc:`json_decref()` on
-the argument right after calling the function. These are usually
-convenience functions for adding new references to containers and not
-to worry about the reference count.
+the argument right after calling the function. These functions are
+suffixed with ``_new`` or have ``_new_`` somewhere in their name.
+
+For example, the following code creates a new JSON array and appends
+an integer to it::
+
+ json_t *array, *integer;
+
+ array = json_array();
+ integer = json_integer(42);
+
+ json_array_append(array, integer);
+ json_decref(integer);
+
+Note how the caller has to release the reference to the integer value
+by calling :cfunc:`json_decref()`. By using a reference stealing
+function :cfunc:`json_array_append_new()` instead of
+:cfunc:`json_array_append()`, the code becomes much simpler::
+
+ json_t *array = json_array();
+ json_array_append_new(array, json_integer(42));
+
+In this case, the user doesn't have to explicitly release the
+reference to the integer value, as :cfunc:`json_array_append_new()`
+steals the reference when appending the value to the array.
In the following sections it is clearly documented whether a function
will return a new or borrowed reference or steal a reference to its
String
======
+Jansson uses UTF-8 as the character encoding. All JSON strings must be
+valid UTF-8 (or ASCII, as it's a subset of UTF-8). Normal null
+terminated C strings are used, so JSON strings may not contain
+embedded null characters. All other Unicode codepoints U+0001 through
+U+10FFFF are allowed.
+
.. cfunction:: json_t *json_string(const char *value)
.. refcounting:: new
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
.. versionadded:: 1.1
+.. cfunction:: int json_string_set_nocheck(const json_t *string, const char *value)
+
+ 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).
+
+ .. versionadded:: 1.2
+
Number
======
+The JSON specification only contains one numeric type, "number". The C
+programming language has distinct types for integer and floating-point
+numbers, so for practical reasons Jansson also has distinct types for
+the two. They are called "integer" and "real", respectively. For more
+information, see :ref:`rfc-conformance`.
+
.. cfunction:: json_t *json_integer(int value)
.. refcounting:: new
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)
Like :cfunc:`json_object_set()` but steals the reference to
.. 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
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*
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 */
.. 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
+
+``JSON_PRESERVE_ORDER``
+ If this flag is used, object keys in the output are sorted into the
+ same order in which they were first inserted to the object. For
+ example, decoding a JSON text and then encoding with this flag
+ preserves the order of object keys.
+
+ .. versionadded:: 1.3
+
The following functions perform the actual JSON encoding. The result
is in UTF-8.
text to the Jansson representation of JSON data. The JSON
specification requires that a JSON text is either a serialized array
or object, and this requirement is also enforced with the following
-functions.
+functions. In other words, the top level value in the JSON text being
+decoded must be either array or object.
-The only supported character encoding is UTF-8 (which ASCII is a
-subset of).
+See :ref:`rfc-conformance` for a discussion on Jansson's conformance
+to the JSON specification. It explains many design decisions that
+affect especially the behavior of the decoder.
.. ctype:: json_error_t
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,
+ byte by byte. Unicode comparison algorithms are not implemented.
+
+* 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
projects / jansson.git / blobdiff