X-Git-Url: http://www.project-moonshot.org/gitweb/?a=blobdiff_plain;f=doc%2Fapiref.rst;h=dcd401cedeb78e9d35db7524b26853852dbef7f5;hb=50031440a3b7ab2623e9468bd20e837250250cd9;hp=dc8252712f450c19973fabcc2012293e84c44d7d;hpb=057ba29a27c0aca5e6566a8037623c0cbdaea8d6;p=jansson.git diff --git a/doc/apiref.rst b/doc/apiref.rst index dc82527..dcd401c 100644 --- a/doc/apiref.rst +++ b/doc/apiref.rst @@ -1,3 +1,5 @@ +.. _apiref: + ************* API Reference ************* @@ -113,6 +115,8 @@ functions: and false for values of other types and for *NULL*. +.. _apiref-reference-count: + Reference Count --------------- @@ -147,7 +151,7 @@ the value is no longer needed, :cfunc:`json_decref` should be called to release the reference. Normally, all functions accepting a JSON value as an argument will -nmanage the reference, i.e. increase and decrease the reference count +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 @@ -159,6 +163,37 @@ will return a new or borrowed reference or steal a reference to its 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 ==================== @@ -194,11 +229,18 @@ String Returns a new JSON string, or *NULL* on error. *value* must be a valid UTF-8 encoded Unicode string. -.. cfunction:: const char *json_string_value(const json_t *json) +.. 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. - Returns the associated value of the JSON string *json* as a null - terminated UTF-8 encoded string, or *NULL* if *json* is not a JSON - string. + .. versionadded:: 1.1 Number @@ -210,10 +252,17 @@ Number Returns a new JSON integer, or *NULL* on error. -.. cfunction:: int json_integer_value(const json_t *json) +.. 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) - Returns the associated value the JSON integer *json*. If *json* is - *NULL* or not a JSON integer, 0 is returned. + Sets the associated value of *integer* to *value*. Returns 0 on + success and -1 if *integer* is not a JSON integer. + + .. versionadded:: 1.1 .. cfunction:: json_t *json_real(double value) @@ -221,10 +270,17 @@ Number Returns a new JSON real, or *NULL* on error. -.. cfunction:: double json_real_value(const json_t *json) +.. 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:: int json_real_set(const json_t *real, double value) - Returns the associated value of the JSON real *json*. If *json* is - *NULL* or not a JSON real, 0.0 is returned. + 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: @@ -291,6 +347,44 @@ A JSON array is an ordered collection of other JSON values. .. 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 ====== @@ -305,6 +399,13 @@ Unicode string and the value is any JSON value. 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) .. refcounting:: borrow @@ -333,6 +434,21 @@ Unicode string and the value is any JSON value. -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) @@ -378,32 +494,56 @@ 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. +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)`` - 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 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()`. -.. 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. + 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