DBusMessage implementation details
[D-Bus secret internal implementation details]

DBusMessage private implementation details. More...

Data Structures

struct  DBusMessageLoader
 Implementation details of DBusMessageLoader. More...
struct  DBusMessage
 Internals of DBusMessage. More...
struct  DBusMessageRealIter
 Internals of DBusMessageIter. More...

Defines

#define CHANGED_STAMP_BITS   21
 How many bits are in the changed_stamp used to validate iterators.
#define ensure_byte_order(message)
 byte-swap the message if it doesn't match our byte order.
#define MAX_MESSAGE_SIZE_TO_CACHE   10 * _DBUS_ONE_KILOBYTE
 Avoid caching huge messages.
#define MAX_MESSAGE_CACHE_SIZE   5
 Avoid caching too many messages.
#define INITIAL_LOADER_DATA_LEN   32
 The initial buffer size of the message loader.

Typedefs

typedef DBusMessageRealIter DBusMessageRealIter
 typedef for internals of message iterator
typedef DBusMessageLoader DBusMessageLoader
 The DBusMessageLoader object encapsulates the process of converting a byte stream into a series of DBusMessage.

Enumerations

enum  { DBUS_MESSAGE_ITER_TYPE_READER = 3, DBUS_MESSAGE_ITER_TYPE_WRITER = 7 }

Functions

dbus_bool_t _dbus_message_iter_get_args_valist (DBusMessageIter *iter, DBusError *error, int first_arg_type, va_list var_args)
 Implementation of the varargs arg-getting functions.
 _DBUS_STRING_DEFINE_STATIC (_dbus_empty_signature_str,"")
 An static string representing an empty signature.
void _dbus_message_get_network_data (DBusMessage *message, const DBusString **header, const DBusString **body)
 Gets the data to be sent over the network for this message.
void _dbus_message_set_serial (DBusMessage *message, dbus_uint32_t serial)
 Sets the serial number of a message.
void _dbus_message_add_size_counter_link (DBusMessage *message, DBusList *link)
 Adds a counter to be incremented immediately with the size of this message, and decremented by the size of this message when this message if finalized.
dbus_bool_t _dbus_message_add_size_counter (DBusMessage *message, DBusCounter *counter)
 Adds a counter to be incremented immediately with the size of this message, and decremented by the size of this message when this message if finalized.
void _dbus_message_remove_size_counter (DBusMessage *message, DBusCounter *counter, DBusList **link_return)
 Removes a counter tracking the size of this message, and decrements the counter by the size of this message.
void _dbus_message_lock (DBusMessage *message)
 Locks a message.
DBusMessageLoader_dbus_message_loader_new (void)
 Creates a new message loader.
DBusMessageLoader_dbus_message_loader_ref (DBusMessageLoader *loader)
 Increments the reference count of the loader.
void _dbus_message_loader_unref (DBusMessageLoader *loader)
 Decrements the reference count of the loader and finalizes the loader when the count reaches zero.
void _dbus_message_loader_get_buffer (DBusMessageLoader *loader, DBusString **buffer)
 Gets the buffer to use for reading data from the network.
void _dbus_message_loader_return_buffer (DBusMessageLoader *loader, DBusString *buffer, int bytes_read)
 Returns a buffer obtained from _dbus_message_loader_get_buffer(), indicating to the loader how many bytes of the buffer were filled in.
dbus_bool_t _dbus_message_loader_queue_messages (DBusMessageLoader *loader)
 Converts buffered data into messages, if we have enough data.
DBusMessage_dbus_message_loader_peek_message (DBusMessageLoader *loader)
 Peeks at first loaded message, returns NULL if no messages have been queued.
DBusMessage_dbus_message_loader_pop_message (DBusMessageLoader *loader)
 Pops a loaded message (passing ownership of the message to the caller).
DBusList_dbus_message_loader_pop_message_link (DBusMessageLoader *loader)
 Pops a loaded message inside a list link (passing ownership of the message and link to the caller).
void _dbus_message_loader_putback_message_link (DBusMessageLoader *loader, DBusList *link)
 Returns a popped message link, used to undo a pop.
dbus_bool_t _dbus_message_loader_get_is_corrupted (DBusMessageLoader *loader)
 Checks whether the loader is confused due to bad data.
void _dbus_message_loader_set_max_message_size (DBusMessageLoader *loader, long size)
 Sets the maximum size message we allow.
long _dbus_message_loader_get_max_message_size (DBusMessageLoader *loader)
 Gets the maximum allowed message size in bytes.
dbus_bool_t dbus_message_allocate_data_slot (dbus_int32_t *slot_p)
 Allocates an integer ID to be used for storing application-specific data on any DBusMessage.
void dbus_message_free_data_slot (dbus_int32_t *slot_p)
 Deallocates a global ID for message data slots.
dbus_bool_t dbus_message_set_data (DBusMessage *message, dbus_int32_t slot, void *data, DBusFreeFunction free_data_func)
 Stores a pointer on a DBusMessage, along with an optional function to be used for freeing the data when the data is set again, or when the message is finalized.
void * dbus_message_get_data (DBusMessage *message, dbus_int32_t slot)
 Retrieves data previously set with dbus_message_set_data().
int dbus_message_type_from_string (const char *type_str)
 Utility function to convert a machine-readable (not translated) string into a D-Bus message type.
const char * dbus_message_type_to_string (int type)
 Utility function to convert a D-Bus message type into a machine-readable string (not translated).
dbus_bool_t dbus_message_marshal (DBusMessage *msg, char **marshalled_data_p, int *len_p)
 Turn a DBusMessage into the marshalled form as described in the D-Bus specification.
DBusMessagedbus_message_demarshal (const char *str, int len, DBusError *error)
 Demarshal a D-Bus message from the format described in the D-Bus specification.

Detailed Description

DBusMessage private implementation details.

The guts of DBusMessage and its methods.


Define Documentation

#define ensure_byte_order ( message   ) 

Value:

if (message->byte_order != DBUS_COMPILER_BYTE_ORDER)   \
   _dbus_message_byteswap (message)
byte-swap the message if it doesn't match our byte order.

Called only when we need the message in our own byte order, normally when reading arrays of integers or doubles. Otherwise should not be called since it would do needless work.

Definition at line 137 of file dbus-message.c.

#define INITIAL_LOADER_DATA_LEN   32

The initial buffer size of the message loader.

Todo:
this should be based on min header size plus some average body size, or something. Or rather, the min header size only, if we want to try to read only the header, store that in a DBusMessage, then read only the body and store that, etc., depends on how we optimize _dbus_message_loader_get_buffer() and what the exact message format is.

Definition at line 3295 of file dbus-message.c.

Referenced by _dbus_message_loader_new().


Typedef Documentation

DBusMessageLoader

The DBusMessageLoader object encapsulates the process of converting a byte stream into a series of DBusMessage.

It buffers the incoming bytes as efficiently as possible, and generates a queue of messages. DBusMessageLoader is typically used as part of a DBusTransport implementation. The DBusTransport then hands off the loaded messages to a DBusConnection, making the messages visible to the application.

Todo:
write tests for break-loader that a) randomly delete header fields and b) set string fields to zero-length and other funky values.

Definition at line 32 of file dbus-message-internal.h.


Function Documentation

dbus_bool_t _dbus_message_add_size_counter ( DBusMessage message,
DBusCounter counter 
)

Adds a counter to be incremented immediately with the size of this message, and decremented by the size of this message when this message if finalized.

Parameters:
message the message
counter the counter
Returns:
FALSE if no memory

Definition at line 229 of file dbus-message.c.

References _dbus_counter_ref(), _dbus_list_alloc_link(), _dbus_message_add_size_counter_link(), FALSE, NULL, and TRUE.

Referenced by _dbus_transport_queue_messages().

void _dbus_message_add_size_counter_link ( DBusMessage message,
DBusList link 
)

Adds a counter to be incremented immediately with the size of this message, and decremented by the size of this message when this message if finalized.

The link contains a counter with its refcount already incremented, but the counter itself not incremented. Ownership of link and counter refcount is passed to the message.

Parameters:
message the message
link link with counter as data

Definition at line 193 of file dbus-message.c.

References _dbus_counter_adjust(), _dbus_list_append_link(), DBusMessage::body, DBusList::data, DBusHeader::data, DBusMessage::header, NULL, DBusMessage::size_counter_delta, and DBusMessage::size_counters.

Referenced by _dbus_message_add_size_counter().

void _dbus_message_get_network_data ( DBusMessage message,
const DBusString **  header,
const DBusString **  body 
)

Gets the data to be sent over the network for this message.

The header and then the body should be written out. This function is guaranteed to always return the same data once a message is locked (with _dbus_message_lock()).

Parameters:
message the message.
header return location for message header data.
body return location for message body data.

Definition at line 152 of file dbus-message.c.

References _dbus_assert, DBusMessage::body, DBusHeader::data, DBusMessage::header, and DBusMessage::locked.

dbus_bool_t _dbus_message_iter_get_args_valist ( DBusMessageIter iter,
DBusError error,
int  first_arg_type,
va_list  var_args 
)

Implementation of the varargs arg-getting functions.

dbus_message_get_args() is the place to go for complete documentation.

See also:
dbus_message_get_args
Parameters:
iter the message iter
error error to be filled in
first_arg_type type of the first argument
var_args return location for first argument, followed by list of type/location pairs
Returns:
FALSE if error was set

Definition at line 641 of file dbus-message.c.

References _dbus_assert, _dbus_strdup(), _dbus_type_reader_get_current_type(), _dbus_type_reader_get_element_type(), _dbus_type_reader_next(), _dbus_type_reader_read_basic(), _dbus_type_reader_read_fixed_multi(), _dbus_type_reader_recurse(), _dbus_type_to_string(), _dbus_warn(), DBUS_ERROR_INVALID_ARGS, dbus_free_string_array(), dbus_message_iter_get_arg_type(), dbus_new0, dbus_set_error(), DBUS_TYPE_ARRAY, DBUS_TYPE_INVALID, dbus_type_is_basic(), dbus_type_is_fixed(), DBUS_TYPE_OBJECT_PATH, DBUS_TYPE_SIGNATURE, DBUS_TYPE_STRING, FALSE, NULL, and TRUE.

Referenced by dbus_message_get_args_valist().

void _dbus_message_loader_get_buffer ( DBusMessageLoader loader,
DBusString **  buffer 
)

Gets the buffer to use for reading data from the network.

Network data is read directly into an allocated buffer, which is then used in the DBusMessage, to avoid as many extra memcpy's as possible. The buffer must always be returned immediately using _dbus_message_loader_return_buffer(), even if no bytes are successfully read.

Todo:
this function can be a lot more clever. For example it can probably always return a buffer size to read exactly the body of the next message, thus avoiding any memory wastage or reallocs.
Todo:
we need to enforce a max length on strings in header fields.
Parameters:
loader the message loader.
buffer the buffer

Definition at line 3387 of file dbus-message.c.

References _dbus_assert, DBusMessageLoader::buffer_outstanding, DBusMessageLoader::data, and TRUE.

Referenced by dbus_message_demarshal().

dbus_bool_t _dbus_message_loader_get_is_corrupted ( DBusMessageLoader loader  ) 

Checks whether the loader is confused due to bad data.

If messages are received that are invalid, the loader gets confused and gives up permanently. This state is called "corrupted."

Parameters:
loader the loader
Returns:
TRUE if the loader is hosed.

Definition at line 3717 of file dbus-message.c.

References _dbus_assert, DBusMessageLoader::corrupted, DBusMessageLoader::corruption_reason, and DBUS_VALID.

Referenced by _dbus_transport_queue_messages(), and dbus_message_demarshal().

long _dbus_message_loader_get_max_message_size ( DBusMessageLoader loader  ) 

Gets the maximum allowed message size in bytes.

Parameters:
loader the loader
Returns:
max size in bytes

Definition at line 3750 of file dbus-message.c.

References DBusMessageLoader::max_message_size.

Referenced by _dbus_transport_get_max_message_size().

DBusMessageLoader* _dbus_message_loader_new ( void   ) 

Creates a new message loader.

Returns NULL if memory can't be allocated.

Returns:
new loader, or NULL.

Definition at line 3304 of file dbus-message.c.

References _dbus_string_init(), _dbus_string_set_length(), DBusMessageLoader::corrupted, DBusMessageLoader::corruption_reason, DBusMessageLoader::data, dbus_free(), DBUS_MAXIMUM_MESSAGE_LENGTH, dbus_new0, DBUS_VALID, FALSE, INITIAL_LOADER_DATA_LEN, DBusMessageLoader::max_message_size, NULL, and DBusMessageLoader::refcount.

Referenced by _dbus_transport_init_base(), and dbus_message_demarshal().

DBusMessage* _dbus_message_loader_peek_message ( DBusMessageLoader loader  ) 

Peeks at first loaded message, returns NULL if no messages have been queued.

Parameters:
loader the loader.
Returns:
the next message, or NULL if none.

Definition at line 3658 of file dbus-message.c.

References DBusList::data, DBusMessageLoader::messages, and NULL.

Referenced by _dbus_transport_get_dispatch_status().

DBusMessage* _dbus_message_loader_pop_message ( DBusMessageLoader loader  ) 

Pops a loaded message (passing ownership of the message to the caller).

Returns NULL if no messages have been queued.

Parameters:
loader the loader.
Returns:
the next message, or NULL if none.

Definition at line 3675 of file dbus-message.c.

References _dbus_list_pop_first(), and DBusMessageLoader::messages.

Referenced by dbus_message_demarshal().

DBusList* _dbus_message_loader_pop_message_link ( DBusMessageLoader loader  ) 

Pops a loaded message inside a list link (passing ownership of the message and link to the caller).

Returns NULL if no messages have been loaded.

Parameters:
loader the loader.
Returns:
the next message link, or NULL if none.

Definition at line 3689 of file dbus-message.c.

References _dbus_list_pop_first_link(), and DBusMessageLoader::messages.

Referenced by _dbus_transport_queue_messages().

void _dbus_message_loader_putback_message_link ( DBusMessageLoader loader,
DBusList link 
)

Returns a popped message link, used to undo a pop.

Parameters:
loader the loader
link the link with a message in it

Definition at line 3701 of file dbus-message.c.

References _dbus_list_prepend_link(), and DBusMessageLoader::messages.

Referenced by _dbus_transport_queue_messages().

dbus_bool_t _dbus_message_loader_queue_messages ( DBusMessageLoader loader  ) 

Converts buffered data into messages, if we have enough data.

If we don't have enough data, does nothing.

Todo:
we need to check that the proper named header fields exist for each message type.
Todo:
If a message has unknown type, we should probably eat it right here rather than passing it out to applications. However it's not an error to see messages of unknown type.
Parameters:
loader the loader.
Returns:
TRUE if we had enough memory to finish.

Definition at line 3595 of file dbus-message.c.

References _dbus_assert, _dbus_header_have_message_untrusted(), _dbus_list_find_last(), DBusMessageLoader::corrupted, DBusMessageLoader::corruption_reason, DBusMessageLoader::data, dbus_message_unref(), DBUS_MINIMUM_HEADER_SIZE, DBUS_VALID, FALSE, DBusMessageLoader::max_message_size, NULL, and TRUE.

Referenced by _dbus_transport_get_dispatch_status(), and dbus_message_demarshal().

DBusMessageLoader* _dbus_message_loader_ref ( DBusMessageLoader loader  ) 

Increments the reference count of the loader.

Parameters:
loader the loader.
Returns:
the loader

Definition at line 3340 of file dbus-message.c.

References DBusMessageLoader::refcount.

void _dbus_message_loader_return_buffer ( DBusMessageLoader loader,
DBusString buffer,
int  bytes_read 
)

Returns a buffer obtained from _dbus_message_loader_get_buffer(), indicating to the loader how many bytes of the buffer were filled in.

This function must always be called, even if no bytes were successfully read.

Parameters:
loader the loader.
buffer the buffer.
bytes_read number of bytes that were read into the buffer.

Definition at line 3408 of file dbus-message.c.

References _dbus_assert, DBusMessageLoader::buffer_outstanding, DBusMessageLoader::data, and FALSE.

Referenced by dbus_message_demarshal().

void _dbus_message_loader_set_max_message_size ( DBusMessageLoader loader,
long  size 
)

Sets the maximum size message we allow.

Parameters:
loader the loader
size the max message size in bytes

Definition at line 3731 of file dbus-message.c.

References DBUS_MAXIMUM_MESSAGE_LENGTH, and DBusMessageLoader::max_message_size.

Referenced by _dbus_transport_set_max_message_size().

void _dbus_message_loader_unref ( DBusMessageLoader loader  ) 

Decrements the reference count of the loader and finalizes the loader when the count reaches zero.

Parameters:
loader the loader.

Definition at line 3354 of file dbus-message.c.

References _dbus_list_clear(), _dbus_list_foreach(), _dbus_string_free(), DBusMessageLoader::data, dbus_free(), dbus_message_unref(), DBusMessageLoader::messages, NULL, and DBusMessageLoader::refcount.

Referenced by _dbus_transport_finalize_base(), _dbus_transport_init_base(), and dbus_message_demarshal().

void _dbus_message_lock ( DBusMessage message  ) 

Locks a message.

Allows checking that applications don't keep a reference to a message in the outgoing queue and change it underneath us. Messages are locked when they enter the outgoing queue (dbus_connection_send_message()), and the library complains if the message is modified while locked.

Parameters:
message the message to lock.

Definition at line 285 of file dbus-message.c.

References _dbus_assert, _dbus_header_update_lengths(), DBusMessage::body, dbus_message_get_signature(), DBusMessage::header, DBusMessage::locked, NULL, and TRUE.

void _dbus_message_remove_size_counter ( DBusMessage message,
DBusCounter counter,
DBusList **  link_return 
)

Removes a counter tracking the size of this message, and decrements the counter by the size of this message.

Parameters:
message the message
link_return return the link used
counter the counter

Definition at line 253 of file dbus-message.c.

References _dbus_assert, _dbus_counter_adjust(), _dbus_counter_unref(), _dbus_list_find_last(), _dbus_list_free_link(), _dbus_list_unlink(), NULL, DBusMessage::size_counter_delta, and DBusMessage::size_counters.

Referenced by _dbus_connection_message_sent().

void _dbus_message_set_serial ( DBusMessage message,
dbus_uint32_t  serial 
)

Sets the serial number of a message.

This can only be done once on a message.

Parameters:
message the message
serial the serial

Definition at line 170 of file dbus-message.c.

References _dbus_assert, _dbus_header_set_serial(), dbus_message_get_serial(), DBusMessage::locked, and NULL.

Referenced by dbus_connection_send_with_reply().

dbus_bool_t dbus_message_allocate_data_slot ( dbus_int32_t slot_p  ) 

Allocates an integer ID to be used for storing application-specific data on any DBusMessage.

The allocated ID may then be used with dbus_message_set_data() and dbus_message_get_data(). The passed-in slot must be initialized to -1, and is filled in with the slot ID. If the passed-in slot is not -1, it's assumed to be already allocated, and its refcount is incremented.

The allocated slot is global, i.e. all DBusMessage objects will have a slot with the given integer ID reserved.

Parameters:
slot_p address of a global variable storing the slot
Returns:
FALSE on failure (no memory)

Definition at line 3773 of file dbus-message.c.

References _dbus_data_slot_allocator_alloc(), and _DBUS_LOCK_NAME.

DBusMessage* dbus_message_demarshal ( const char *  str,
int  len,
DBusError error 
)

Demarshal a D-Bus message from the format described in the D-Bus specification.

Generally, this function is only useful for encapsulating D-Bus messages in a different protocol.

Parameters:
str the marshalled DBusMessage
len the length of str
error the location to save errors to
Returns:
NULL if there was an error

Definition at line 3982 of file dbus-message.c.

References _dbus_message_loader_get_buffer(), _dbus_message_loader_get_is_corrupted(), _dbus_message_loader_new(), _dbus_message_loader_pop_message(), _dbus_message_loader_queue_messages(), _dbus_message_loader_return_buffer(), _dbus_message_loader_unref(), _dbus_string_append_len(), DBUS_ERROR_INVALID_ARGS, dbus_set_error(), and NULL.

void dbus_message_free_data_slot ( dbus_int32_t slot_p  ) 

Deallocates a global ID for message data slots.

dbus_message_get_data() and dbus_message_set_data() may no longer be used with this slot. Existing data stored on existing DBusMessage objects will be freed when the message is finalized, but may not be retrieved (and may only be replaced if someone else reallocates the slot). When the refcount on the passed-in slot reaches 0, it is set to -1.

Parameters:
slot_p address storing the slot to deallocate

Definition at line 3792 of file dbus-message.c.

References _dbus_data_slot_allocator_free().

void* dbus_message_get_data ( DBusMessage message,
dbus_int32_t  slot 
)

Retrieves data previously set with dbus_message_set_data().

The slot must still be allocated (must not have been freed).

Parameters:
message the message
slot the slot to get data from
Returns:
the data, or NULL if not found

Definition at line 3849 of file dbus-message.c.

References _dbus_data_slot_list_get(), NULL, and DBusMessage::slot_list.

dbus_bool_t dbus_message_marshal ( DBusMessage msg,
char **  marshalled_data_p,
int *  len_p 
)

Turn a DBusMessage into the marshalled form as described in the D-Bus specification.

Generally, this function is only useful for encapsulating D-Bus messages in a different protocol.

Parameters:
msg the DBusMessage
marshalled_data_p the location to save the marshalled form to
len_p the location to save the length of the marshalled form to
Returns:
FALSE if there was not enough memory

Definition at line 3935 of file dbus-message.c.

References _dbus_string_copy(), _dbus_string_free(), _dbus_string_init(), _dbus_string_steal_data(), DBusMessage::body, DBusHeader::data, FALSE, DBusMessage::header, NULL, and TRUE.

dbus_bool_t dbus_message_set_data ( DBusMessage message,
dbus_int32_t  slot,
void *  data,
DBusFreeFunction  free_data_func 
)

Stores a pointer on a DBusMessage, along with an optional function to be used for freeing the data when the data is set again, or when the message is finalized.

The slot number must have been allocated with dbus_message_allocate_data_slot().

Parameters:
message the message
slot the slot number
data the data to store
free_data_func finalizer function for the data
Returns:
TRUE if there was enough memory to store the data

Definition at line 3813 of file dbus-message.c.

References _dbus_data_slot_list_set(), FALSE, NULL, and DBusMessage::slot_list.

int dbus_message_type_from_string ( const char *  type_str  ) 

Utility function to convert a machine-readable (not translated) string into a D-Bus message type.

Definition at line 3877 of file dbus-message.c.

References DBUS_MESSAGE_TYPE_ERROR, DBUS_MESSAGE_TYPE_INVALID, DBUS_MESSAGE_TYPE_METHOD_CALL, DBUS_MESSAGE_TYPE_METHOD_RETURN, and DBUS_MESSAGE_TYPE_SIGNAL.

const char* dbus_message_type_to_string ( int  type  ) 

Utility function to convert a D-Bus message type into a machine-readable string (not translated).

Definition at line 3905 of file dbus-message.c.

References DBUS_MESSAGE_TYPE_ERROR, DBUS_MESSAGE_TYPE_METHOD_CALL, DBUS_MESSAGE_TYPE_METHOD_RETURN, and DBUS_MESSAGE_TYPE_SIGNAL.


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