Message bus APIs
[D-BUS low-level public API]

Functions for communicating with the message bus. More...

Functions

DBusConnectiondbus_bus_get (DBusBusType type, DBusError *error)
 Connects to a bus daemon and registers the client with it.
DBusConnectiondbus_bus_get_private (DBusBusType type, DBusError *error)
 Connects to a bus daemon and registers the client with it.
dbus_bool_t dbus_bus_register (DBusConnection *connection, DBusError *error)
 Registers a connection with the bus.
dbus_bool_t dbus_bus_set_unique_name (DBusConnection *connection, const char *unique_name)
 Sets the unique name of the connection.
const char * dbus_bus_get_unique_name (DBusConnection *connection)
 Gets the unique name of the connection.
unsigned long dbus_bus_get_unix_user (DBusConnection *connection, const char *name, DBusError *error)
 Asks the bus to return the uid of the named connection.
int dbus_bus_request_name (DBusConnection *connection, const char *name, unsigned int flags, DBusError *error)
 Asks the bus to assign the given name to this connection by invoking the RequestName method on the bus.
int dbus_bus_release_name (DBusConnection *connection, const char *name, DBusError *error)
dbus_bool_t dbus_bus_name_has_owner (DBusConnection *connection, const char *name, DBusError *error)
 Checks whether a certain name has an owner.
dbus_bool_t dbus_bus_start_service_by_name (DBusConnection *connection, const char *name, dbus_uint32_t flags, dbus_uint32_t *result, DBusError *error)
 Starts a service that will request ownership of the given name.
void dbus_bus_add_match (DBusConnection *connection, const char *rule, DBusError *error)
 Adds a match rule to match messages going through the message bus.
void dbus_bus_remove_match (DBusConnection *connection, const char *rule, DBusError *error)
 Removes a previously-added match rule "by value" (the most recently-added identical rule gets removed).
const char * dbus_bus_connection_get_unique_name (DBusConnection *connection)

Detailed Description

Functions for communicating with the message bus.

Todo:
right now the default address of the system bus is hardcoded, so if you change it in the global config file suddenly you have to set DBUS_SYSTEM_BUS_ADDRESS env variable. Might be nice if the client lib somehow read the config file, or if the bus on startup somehow wrote out its address to a well-known spot, but might also not be worth it.

Function Documentation

void dbus_bus_add_match DBusConnection connection,
const char *  rule,
DBusError error
 

Adds a match rule to match messages going through the message bus.

The "rule" argument is the string form of a match rule.

If you pass NULL for the error, this function will not block; the match thus won't be added until you flush the connection, and if there's an error adding the match (only possible error is lack of resources in the bus), you won't find out about it.

If you pass non-NULL for the error this function will block until it gets a reply.

Normal API conventions would have the function return a boolean value indicating whether the error was set, but that would require blocking always to determine the return value.

Parameters:
connection connection to the message bus
rule textual form of match rule
error location to store any errors

Definition at line 1029 of file dbus-bus.c.

References dbus_message_append_args(), dbus_message_new_method_call(), dbus_message_unref(), and NULL.

DBusConnection* dbus_bus_get DBusBusType  type,
DBusError error
 

Connects to a bus daemon and registers the client with it.

If a connection to the bus already exists, then that connection is returned. Caller owns a reference to the bus.

Todo:
alex thinks we should nullify the connection when we get a disconnect-message.
Parameters:
type bus type
error address where an error can be returned.
Returns:
a DBusConnection with new ref

Definition at line 419 of file dbus-bus.c.

References FALSE.

Referenced by dbus_g_bus_get().

DBusConnection* dbus_bus_get_private DBusBusType  type,
DBusError error
 

Connects to a bus daemon and registers the client with it.

Unlike dbus_bus_get(), always creates a new connection. This connection will not be saved or recycled by libdbus. Caller owns a reference to the bus.

Parameters:
type bus type
error address where an error can be returned.
Returns:
a DBusConnection with new ref

Definition at line 435 of file dbus-bus.c.

References TRUE.

const char* dbus_bus_get_unique_name DBusConnection connection  ) 
 

Gets the unique name of the connection.

Only possible after the connection has been registered with the message bus.

The name remains valid for the duration of the connection and should not be freed by the caller.

Parameters:
connection the connection
Returns:
the unique name or NULL on error

Definition at line 563 of file dbus-bus.c.

References NULL, and BusData::unique_name.

unsigned long dbus_bus_get_unix_user DBusConnection connection,
const char *  name,
DBusError error
 

Asks the bus to return the uid of the named connection.

Parameters:
connection the connection
name a name owned by the connection
error location to store the error
Returns:
a result code, -1 if error is set

Definition at line 586 of file dbus-bus.c.

References dbus_connection_send_with_reply_and_block(), dbus_message_append_args(), dbus_message_get_args(), dbus_message_new_method_call(), dbus_message_unref(), dbus_set_error_from_message(), and NULL.

dbus_bool_t dbus_bus_name_has_owner DBusConnection connection,
const char *  name,
DBusError error
 

Checks whether a certain name has an owner.

Parameters:
connection the connection
name the name
error location to store any errors
Returns:
TRUE if the name exists, FALSE if not or on error

Definition at line 855 of file dbus-bus.c.

References dbus_connection_send_with_reply_and_block(), dbus_message_append_args(), dbus_message_get_args(), dbus_message_new_method_call(), dbus_message_unref(), FALSE, and NULL.

dbus_bool_t dbus_bus_register DBusConnection connection,
DBusError error
 

Registers a connection with the bus.

This must be the first thing an application does when connecting to the message bus. If registration succeeds, the unique name will be set, and can be obtained using dbus_bus_get_unique_name().

Parameters:
connection the connection
error place to store errors
Returns:
TRUE on success

Definition at line 451 of file dbus-bus.c.

References _dbus_strdup(), _dbus_warn(), dbus_connection_send_with_reply_and_block(), dbus_message_get_args(), dbus_message_new_method_call(), dbus_message_unref(), dbus_set_error_from_message(), FALSE, NULL, TRUE, and BusData::unique_name.

void dbus_bus_remove_match DBusConnection connection,
const char *  rule,
DBusError error
 

Removes a previously-added match rule "by value" (the most recently-added identical rule gets removed).

The "rule" argument is the string form of a match rule.

If you pass NULL for the error, this function will not block; otherwise it will. See detailed explanation in docs for dbus_bus_add_match().

Parameters:
connection connection to the message bus
rule textual form of match rule
error location to store any errors

Definition at line 1075 of file dbus-bus.c.

References dbus_message_append_args(), dbus_message_new_method_call(), dbus_message_unref(), and NULL.

int dbus_bus_request_name DBusConnection connection,
const char *  name,
unsigned int  flags,
DBusError error
 

Asks the bus to assign the given name to this connection by invoking the RequestName method on the bus.

This method is fully documented in the D-BUS specification. For quick reference, the flags and result codes are discussed here, but the specification is the canonical version of this information.

The DBUS_NAME_FLAG_ALLOW_REPLACEMENT flag indicates that the caller will allow other services to take over the name from the current owner.

The DBUS_NAME_FLAG_REPLACE_EXISTING flag indicates that the caller would like to take over the name from the current owner. If the current name owner did not use DBUS_NAME_FLAG_ALLOW_REPLACEMENT then this flag indicates that the caller would like to be placed in the queue to own the name when the current owner lets go.

If no flags are given, an application will receive the requested name only if the name is currently unowned; it will NOT give up the name if another application asks to take it over using DBUS_NAME_FLAG_REPLACE_EXISTING.

This function returns a result code. The possible result codes are as follows.

DBUS_REQUEST_NAME_REPLY_PRIMARY_OWNER means that the name had no existing owner, and the caller is now the primary owner; or that the name had an owner, and the caller specified DBUS_NAME_FLAG_REPLACE_EXISTING, and the current owner specified DBUS_NAME_FLAG_ALLOW_REPLACEMENT.

DBUS_REQUEST_NAME_REPLY_IN_QUEUE happens only if the caller does NOT specify DBUS_NAME_FLAG_DO_NOT_QUEUE and either the current owner did NOT specify DBUS_NAME_FLAG_ALLOW_REPLACEMENT or the caller did NOT specify DBUS_NAME_FLAG_REPLACE_EXISTING. In this case the caller ends up in a queue to own the name after the current owner gives it up.

DBUS_REQUEST_NAME_REPLY_EXISTS happens if the name has an owner already and the caller specifies DBUS_NAME_FLAG_DO_NOT_QUEUE and either the current owner has NOT specified DBUS_NAME_FLAG_ALLOW_REPLACEMENT or the caller did NOT specify DBUS_NAME_FLAG_REPLACE_EXISTING.

DBUS_REQUEST_NAME_REPLY_ALREADY_OWNER happens if an application requests a name it already owns.

When a service represents an application, say "text editor," then it should specify DBUS_NAME_FLAG_ALLOW_REPLACEMENT if it wants the last editor started to be the user's editor vs. the first one started. Then any editor that can be the user's editor should specify DBUS_NAME_FLAG_REPLACE_EXISTING to either take over (last-started-wins) or be queued up (first-started-wins) according to whether DBUS_NAME_FLAG_ALLOW_REPLACEMENT was given.

Todo:
this all seems sort of broken. Shouldn't the flags be a property of the name, not the app requesting the name? What are the use-cases other than the "text editor" thing and how are we supporting them?
Parameters:
connection the connection
name the name to request
flags flags
error location to store the error
Returns:
a result code, -1 if error is set

Definition at line 715 of file dbus-bus.c.

References dbus_connection_send_with_reply_and_block(), dbus_message_append_args(), dbus_message_get_args(), dbus_message_new_method_call(), dbus_message_unref(), dbus_set_error_from_message(), and NULL.

dbus_bool_t dbus_bus_set_unique_name DBusConnection connection,
const char *  unique_name
 

Sets the unique name of the connection.

Can only be used if you registered with the bus manually (i.e. if you did not call dbus_bus_register()). Can only be called once per connection.

Parameters:
connection the connection
unique_name the unique name
Returns:
FALSE if not enough memory

Definition at line 534 of file dbus-bus.c.

References _dbus_assert, _dbus_strdup(), FALSE, NULL, and BusData::unique_name.

dbus_bool_t dbus_bus_start_service_by_name DBusConnection connection,
const char *  name,
dbus_uint32_t  flags,
dbus_uint32_t result,
DBusError error
 

Starts a service that will request ownership of the given name.

The returned result will be one of be one of DBUS_START_REPLY_SUCCESS or DBUS_START_REPLY_ALREADY_RUNNING if successful. Pass NULL if you don't care about the result.

The flags parameter is for future expansion, currently you should specify 0.

Parameters:
connection the connection
name the name we want the new service to request
flags the flags (should always be 0 for now)
result a place to store the result or NULL
error location to store any errors
Returns:
TRUE if the activation succeeded, FALSE if not

Definition at line 925 of file dbus-bus.c.

References dbus_connection_send_with_reply_and_block(), dbus_message_append_args(), dbus_message_get_args(), dbus_message_new_method_call(), dbus_message_unref(), dbus_set_error_from_message(), FALSE, NULL, and TRUE.


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