json_pointer.h File Reference

JSON Pointer (RFC 6901) implementation for retrieving objects from a json-c object tree. More...

Functions
int	json_pointer_get (struct json_object *obj, const char *path, struct json_object **res)
int	json_pointer_getf (struct json_object *obj, struct json_object **res, const char *path_fmt,...)
int	json_pointer_set (struct json_object **obj, const char *path, struct json_object *value)
int	json_pointer_setf (struct json_object **obj, struct json_object *value, const char *path_fmt,...)

Detailed Description

JSON Pointer (RFC 6901) implementation for retrieving objects from a json-c object tree.

Function Documentation

json_pointer_get()

int json_pointer_get	(	struct json_object *	obj,
		const char *	path,
		struct json_object **	res
	)

Retrieves a JSON sub-object from inside another JSON object using the JSON pointer notation as defined in RFC 6901 https://tools.ietf.org/html/rfc6901

The returned JSON sub-object is equivalent to parsing manually the 'obj' JSON tree ; i.e. it's not a new object that is created, but rather a pointer inside the JSON tree.

Internally, this is equivalent to doing a series of 'json_object_object_get()' and 'json_object_array_get_idx()' along the given 'path'.

Note that the 'path' string supports 'printf()' type arguments, so, whatever is added after the 'res' param will be treated as an argument for 'path' Example: json_pointer_get(obj, "/foo/%d/%s", &res, 0, bar) This means, that you need to escape '' with '%' (just like in printf())

Parameters

obj	the json_object instance/tree from where to retrieve sub-objects
path	a (RFC6901) string notation for the sub-object to retrieve
res	a pointer where to store a reference to the json_object associated with the given path

Returns

negative if an error (or not found), or 0 if succeeded

json_pointer_getf()

int json_pointer_getf	(	struct json_object *	obj,
		struct json_object **	res,
		const char *	path_fmt,
			...
	)

This is a variant of 'json_pointer_get()' that supports printf() style arguments.

Example: json_pointer_getf(obj, res, "/foo/%d/%s", 0, bak) This also means that you need to escape '' with '%' (just like in printf())

Please take into consideration all recommended 'printf()' format security aspects when using this function.

Parameters

obj	the json_object instance/tree to which to add a sub-object
res	a pointer where to store a reference to the json_object associated with the given path
path_fmt	a printf() style format for the path

Returns

negative if an error (or not found), or 0 if succeeded

json_pointer_set()

int json_pointer_set	(	struct json_object **	obj,
		const char *	path,
		struct json_object *	value
	)

Sets JSON object 'value' in the 'obj' tree at the location specified by the 'path'. 'path' is JSON pointer notation as defined in RFC 6901 https://tools.ietf.org/html/rfc6901

Note that 'obj' is a double pointer, mostly for the "" (empty string) case, where the entire JSON object would be replaced by 'value'. In the case of the "" path, the object at '*obj' will have it's refcount decremented with 'json_object_put()' and the 'value' object will be assigned to it.

For other cases (JSON sub-objects) ownership of 'value' will be transferred into '*obj' via 'json_object_object_add()' & 'json_object_array_put_idx()', so the only time the refcount should be decremented for 'value' is when the return value of 'json_pointer_set()' is negative (meaning the 'value' object did not get set into '*obj').

That also implies that 'json_pointer_set()' does not do any refcount incrementing. (Just that single decrement that was mentioned above).

Note that the 'path' string supports 'printf()' type arguments, so, whatever is added after the 'value' param will be treated as an argument for 'path' Example: json_pointer_set(obj, "/foo/%d/%s", value, 0, bak) This means, that you need to escape '' with '%' (just like in printf())

Parameters

obj	the json_object instance/tree to which to add a sub-object
path	a (RFC6901) string notation for the sub-object to set in the tree
value	object to set at path

Returns

negative if an error (or not found), or 0 if succeeded

json_pointer_setf()

int json_pointer_setf	(	struct json_object **	obj,
		struct json_object *	value,
		const char *	path_fmt,
			...
	)

This is a variant of 'json_pointer_set()' that supports printf() style arguments.

Example: json_pointer_setf(obj, value, "/foo/%d/%s", 0, bak) This also means that you need to escape '' with '%' (just like in printf())

Please take into consideration all recommended 'printf()' format security aspects when using this function.

Parameters

obj	the json_object instance/tree to which to add a sub-object
value	object to set at path
path_fmt	a printf() style format for the path

Returns

negative if an error (or not found), or 0 if succeeded