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xpc_dictionary_create(3) BSD Library Functions Manual xpc_dictionary_create(3)


NAME

     xpc_dictionary_create -- creation and management of XPC messages


SYNOPSIS

     #include <xpc/xpc.h>

     xpc_object_t
     xpc_dictionary_create(const char * const *keys,
         const xpc_object_t *values, size_t count);

     xpc_object_t
     xpc_dictionary_create_reply(xpc_object_t original);

     void
     xpc_dictionary_set_value(xpc_object_t dictionary, const char *key,
         xpc_object_t value);

     xpc_object_t
     xpc_dictionary_get_value(xpc_object_t dictionary, const char *key);

     size_t
     xpc_dictionary_get_count(xpc_object_t dictionary);

     bool
     xpc_dictionary_apply(xpc_object_t dictionary,
         xpc_dictionary_applier_t applier);

     xpc_connection_t
     xpc_dictionary_get_remote_connection(xpc_object_t dictionary);

     void
     xpc_dictionary_set_bool(xpc_object_t dictionary, const char *key,
         bool value);

     void
     xpc_dictionary_set_int64(xpc_object_t dictionary, const char *key,
         int64_t value);

     void
     xpc_dictionary_set_uint64(xpc_object_t dictionary, const char *key,
         uint64_t value);

     void
     xpc_dictionary_set_double(xpc_object_t dictionary, const char *key,
         double value);

     void
     xpc_dictionary_set_date(xpc_object_t dictionary, const char *key,
         int64_t value);

     void
     xpc_dictionary_set_data(xpc_object_t dictionary, const char *key,
         const void *value, size_t length);

     void
     xpc_dictionary_set_string(xpc_object_t dictionary, const char *key,
         const char *value);

     void
     xpc_dictionary_set_uuid(xpc_object_t dictionary, const char *key,
         const uuid_t value);

     void
     xpc_dictionary_set_fd(xpc_object_t dictionary, const char *key,
         int value);

     void
     xpc_dictionary_set_connection(xpc_object_t dictionary, const char *key,
         xpc_connection_t connection);

     bool
     xpc_dictionary_get_bool(xpc_object_t dictionary, const char *key);

     int64_t
     xpc_dictionary_get_int64(xpc_object_t dictionary, const char *key);

     uint64_t
     xpc_dictionary_get_uint64(xpc_object_t dictionary, const char *key);

     double
     xpc_dictionary_get_double(xpc_object_t dictionary, const char *key);

     int64_t
     xpc_dictionary_get_date(xpc_object_t dictionary, const char *key);

     const void *
     xpc_dictionary_get_data(xpc_object_t dictionary, const char *key,
         size_t *length);

     const uint8_t *
     xpc_dictionary_get_uuid(xpc_object_t dictionary, const char *key);

     const char *
     xpc_dictionary_get_string(xpc_object_t dictionary, const char *key);

     int
     xpc_dictionary_dup_fd(xpc_object_t dictionary, const char *key);

     xpc_connection_t
     xpc_dictionary_get_connection(xpc_object_t dictionary, const char *key);


DICTIONARIES

     XPC dictionaries are collections of XPC objects that map keys (expressed
     as C strings) to values.

     Objects of dictionary collection type are mutable and will automatically
     expand to accommodate new keys and values that are inserted into the dic-
     tionary.

   CREATION
     The xpc_dictionary_create() function returns a newly created dictionary.
     The caller may optionally provide corresponding C arrays of keys and
     values to initialize the dictionary.  All values must be XPC objects and
     are automatically retained by the XPC framework as they are inserted into
     the dictionary.  The count is used to specify the size of the C arrays.
     Both arrays must be of the same size. The behavior when count is greater
     than the number of elements in either of the C arrays is undefined.
     These arguments are optional and NULL may be passed to both keys and
     values with a count of zero, resulting in an empty dictionary.

   GETTING AND SETTING VALUES
     The xpc_dictionary_set_value() function may be used to insert or replace
     the value of a specified key in a dictionary.  The XPC framework will
     retain a reference to the value while it is present in the dictionary,
     and will release the reference when it is removed.  The value provided
     may be NULL, in which case the key will be removed from the dictionary.

     The value of a specific key in the dictionary may be retrieved using the
     xpc_dictionary_get_value() function. This function returns the value for
     the specified key if it exists or NULL if it does not.

   PRIMITIVE GET AND SET FUNCTIONS
     Various functions exist for retrieving primitive C and operating system
     types directly from a dictionary without the need for an intermediate
     boxed object.  See xpc_object(3) for more information.

   ITERATION
     The xpc_dictionary_apply() function may be used to iterate the key and
     value pairs of a dictionary using an applier callback block. The callback
     block is invoked for each pair and must return a bool indicating whether
     the iteration should continue (true if it should continue, false if it
     should not).  The xpc_dictionary_apply() function will return true if the
     applier block was called for all pairs, or false if it was not (i.e. the
     applier returned false during the iteration).

     Note that the C language does not require an explicit return type to be
     declared for a block when the return expression is unambigous. Therefore
     the formal block declaration

           (void)xpc_dictionary_apply(dictionary, ^ bool (const char *key, xpc_object_t value) {
                   // Do iteration.
                   return true;
           });

     may instead be written as follows (omitting the declared return type, and
     explicitly casting the return value to the desired type):

           (void)xpc_dictionary_apply(dictionary, ^(const char *key, xpc_object_t value) {
                   // Do iteration.
                   return (bool)true;
           });

     Important: the behavior of modifying the contents of an XPC dictionary
     during iteration is undefined.


DICTIONARIES AS MESSAGES

     All messages sent and received by XPC connections are dictionaries. As a
     result, several functions are available to assist with the use of dictio-
     naries as XPC messages.

     The xpc_dictionary_get_remote_connection() function may be used to return
     the underlying XPC connection through which a message was received.

     When a client sends a message using the
     xpc_connection_send_message_with_reply(3) function, a specific reply mes-
     sage must be created with xpc_dictionary_create_reply().  This function
     returns a new dictionary which shares the underlying remote connection as
     the original message. A reply dictionary may be used the same as any
     other dictionary, but it must be sent to the connection returned by
     xpc_dictionary_get_remote_connection(), at which point the sender's reply
     block will be invoked when the reply message is received.


DICTIONARIES AS ERRORS

     Errors encountered by the XPC framework are delivered to the event han-
     dler of a connection as a dictionary of type XPC_TYPE_ERROR.  See
     xpc_get_type(3) for more information about XPC object types.  These error
     dictionaries may be directly compared against the following constants:
           o   XPC_ERROR_CONNECTION_INTERRUPTED
           o   XPC_ERROR_CONNECTION_INVALID
           o   XPC_ERROR_CONNECTION_TERMINATION_IMMINENT

     Important: these dictionaries are constant singletons and must not be
     modified.

     Error dictionaries contain a single XPC_ERROR_KEY_DESCRIPTION key. The
     value of this key is a string object which encapsulates a human-readable
     description of the error condition. This value is guaranteed to be a
     string type and it is safe to use the xpc_dictionary_get_string() func-
     tion directly to obtain a C string representation of the description.
     The contents of this string is intended for diagnostic use and is subject
     to change in future releases.

     Additional keys and values may be added to the error dictionaries over
     time.


SEE ALSO

     xpc_object(3), xpc_objects(3), xpc_connection_create(3),
     xpc_array_create(3)

Darwin                           1 July, 2011                           Darwin

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