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==============================================================================
Description of C API bindings
==============================================================================
This file contains information specific to the C bindings. Refer to the generic
API documentation for information that is not specific to C bindings. See also
C-HOWTO.txt .
Data types
==========
C allows only a limited set of data types. Types from the abstract API that
are not available in C are used as follows:
bool - int with values 1 for true and 0 for false
string - char* NUL-terminated string; calls that return char* allocate it dynamically
and the caller must deallocate it by calling free()
arrays ( int[], string[] ) - intarr, stringarr (see below)
windowinfo - DapiWindowInfo (see below)
DapiConnection
--------------
Opaque data type that contains all internal data. Most calls require it
as the first argument.
DapiWindowInfo
--------------
Some call require information about a window related to the call. This structure
holds data about such window. Call dapi_windowInfoInitWindow() to fill in the info
or use the convenience _Window functions.
void dapi_windowInfoInitWindow( DapiWindowInfo* winfo, long window )
--------------------------------------------------------------------
Initializes DapiWindowInfo with data about given window.
winfo: DapiWindowInfo data structure to initialize
window: Window handle (as used with X Window System)
void dapi_freeWindowInfo( DapiWindowInfo winfo )
------------------------------------------------
Frees DapiWindowInfo structure data.
winfo: DapiWindowInfo data structure to free data from.
intarr
------
A structure representing an integer array.
typedef struct
{
int count;
int* data;
} intarr;
'count' is number of elements, 'data' is array of elements.
void dapi_freeintarr( intarr arr )
----------------------------------
Convenience function that frees dynamically allocated data from intarr.
All DAPI functions that return intarr allocate the data dynamically
and the caller must free it.
stringarr
---------
A structure representing a string array.
typedef struct
{
int count;
char** data;
} stringarr;
'count' is number of elements, 'data' is array of char* strings.
void dapi_freestringarr( stringarr arr )
----------------------------------------
Convenience function that frees dynamically allocated data from stringarr.
All DAPI functions that return stringarr allocate the data dynamically
and the caller must free it.
Utility functions
=================
DapiConnection* dapi_connect( void )
------------------------------------
Tries to connect to a running backend daemon.
Returns: NULL if failed, opaque connection handle if success.
DapiConnection* dapi_connectAndInit( void )
-------------------------------------------
Convenience function that calls dapi_connect() and if successful
also performs initialization by calling dapi_Init() (see later).
void dapi_close( DapiConnection* conn )
---------------------------------------
Closes a connection to a backend daemon.
conn: Opaque connection handle.
int dapi_socket( DapiConnection* conn )
---------------------------------------
Returns a file descriptor that can be used with system functions such as select()
to watch activity.
conn: Opaque connection handle.
Returns: file descriptor
void dapi_processData( DapiConnection* conn )
---------------------------------------------
Processes pending incoming data on the connection socket.
conn: Opaque connection handle.
int dapi_readCommand( DapiConnection* conn, int* comm, int* seq )
-----------------------------------------------------------------
Reads a command header of the next incoming command request/reply.
conn: Opaque connection handle.
comm: Id number of the incomming command.
seq: Sequence number of the incoming command.
Returns: 1 if successful, 0 if failure
TBD:
typedef void (*DapiGenericCallback)( DapiConnection* conn, int command, int seq );
DapiGenericCallback dapi_setGenericCallback( DapiConnection* conn, DapiGenericCallback callback );
void dapi_genericCallback( DapiConnection* conn, int command, int seq );
Calls functions
===============
There are several ways to invoke the API calls. For call XYZ there is:
- lowlevel dapi_writeCommandXYZ(), dapi_readReplyXYZ() calls that write a command
request resp. read a command reply.
dapi_writeCommandXYZ() writes a command header and all command arguments and
returns either 0 if failure or sequence number of the command. Each command request
has a specific sequence number assigned and is used to identify replies.
dapi_readCommandXYZ() reads all reply arguments. It doesn't read command header,
dapi_readCommand() must be called first to identify a command. Returns 1 if success
or 0 if failure.
Include file dapi/comm_generated.h contains all function prototypes.
- blocking dapi_XYZ() call that writes a command request and waits for a reply.
Include file dapi/calls_generated.h contains all function prototypes.
- non-blocking dapi_callbackXYZ() call that writes a command and invokes the passed
callback when a reply comes.
dapi_callbackXYZ() returns a sequence number if success or 0 if failure
Include file dapi/callbacks_generated.h contains all function prototypes.
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