Citadel Server Extension API Documentation --------------------------------------------- This is a VERY INCOMPLETE documentation of the API for extending the Citadel server using dynamically loaded modules. It really isn't an API at all, but rather a list of some of the functions available in the server which are likely to be of use to module writers. The current trend is to move as much stuff as possible out of the server proper and into loadable modules. This makes the code much easier to read and understand. Expect this document to become more complete over time, as both the API and the person documenting it have a chance to mature a bit. :) USER RELATED FUNCTIONS ---------------------- The fundamental user data is stored in "struct ctdluser" which is defined in citadel.h. The following functions are available: int getuser(struct ctdluser *usbuf, char name[]) Given the name of a requested user and a buffer to store the user record in, getuser() will search the userlog for the named user and load its data into the buffer. getuser() returns 0 upon success or a nonzero error code if the requested operation could not be performed. void putuser(struct ctdluser *usbuf, char *name) After reading in a user record with getuser() and perhaps modifying the data in some way, a program may use putuser() to write it back to disk. int lgetuser(struct ctdluser *usbuf, char *name) void lputuser(struct ctdluser *usbuf, char *name) If critical-section operation is required, this pair of calls may be used. They function the same as getuser() and putuser(), except that lgetuser() locks the user file immediately after retrieving the record and lputuser() unlocks it. This will guarantee that no other threads manipulate the same user record at the same time. NOTE: do NOT attempt to combine the locking lgetuser/lputuser calls with any other locking calls in this API. Attempting to obtain concurrent locks on multiple files may result in a deadlock condition which would freeze the entire server. void ForEachUser(void (*CallBack)(struct ctdluser *EachUser)) This allows a user-supplied function to be called once for each user on the system. The user-supplied function will be called with a pointer to a user structure as its only argument. int getuserbynumber(struct ctdluser *usbuf, long int number) getuserbynumber() functions similarly to getuser(), except that it is supplied with a user number rather than a name. Calling this function results in a sequential search of the user file, so use it sparingly if at all. int purge_user(char *pname) This function deletes the named user off the system and erases all related objects: bio, photo, etc. It returns 0 upon success or a nonzero error code if the requested operation could not be performed. HOW TO REGISTER FUNCTION HOOKS ------------------------------ The truly powerful part of the Citadel API is the ability for extensions to register "hooks" -- user-supplied functions will be called while the server is performing various tasks. Here are the API calls to register hooks: void CtdlRegisterProtoHook(void (*handler)(char *), char *cmd, char *desc) void CtdlUnregisterProtoHook(void (*handler)(char *), char *cmd) CtdlRegisterProtoHook() adds a new server command to the system. The handler function should accept a single string parameter, which will be set to a string containing any parameters the client software sent along with the server command. "cmd" should be the four-character mnemonic the server command is known by, and "desc" is a description of the new command. CtdlUnregisterProtoHook() removes a server command from the system. It must be called with the same handler and cmd which were previously registered. void CtdlRegisterCleanupHook(void *fcn_ptr) void CtdlUnregisterCleanupHook(void *fcn_ptr) CtdlRegisterCleanupHook() registers a new function to be called whenever the server is shutting down. Cleanup functions accept no parameters. CtdlUnregsiterCleanupHook() removes a cleanup function from the system. It must be called with the same fcn_ptr which was previously registered. void CtdlRegisterSessionHook(void *fcn_ptr, int EventType) void CtdlUnregisterSessionHook(void *fcn_ptr, int EventType) CtdlRegisterSessionHook() registers a session hook. Session hooks accept no parameters. There are multiple types of session hooks; the server extension registers which one it is interested in by setting the value of EventType. The available session hook types are: #define EVT_STOP 0 /* Session is terminating */ #define EVT_START 1 /* Session is starting */ #define EVT_LOGIN 2 /* A user is logging in */ #define EVT_NEWROOM 3 /* Changing rooms */ #define EVT_LOGOUT 4 /* A user is logging out */ #define EVT_SETPASS 5 /* Setting or changing password */ #define EVT_CMD 6 /* Called after each server command */ #define EVT_RWHO 7 /* An RWHO command is being executed */ #define EVT_ASYNC 8 /* Doing asynchronous message */ #define EVT_TIMER 50 /* Timer events are called once per minute */ #define EVT_HOUSE 51 /* Housekeeping event */ CtdlUnregisterSessionHook() removes a session hook. It must be called with the same fcn_ptr and EventTYpe which were previously registered. void CtdlRegisterUserHook(void *fcn_ptr, int EventType) void CtdlUnregisterUserHook(void *fcn_ptr, int EventType) CtdlRegisterUserHook() registers a user hook. User hooks accept two parameters: a string pointer containing the user name, and a long which *may* contain a user number (only applicable for certain types of hooks). The available user hook types are: #define EVT_PURGEUSER 100 /* Deleting a user */ #define EVT_OUTPUTMSG 101 /* Outputting a message */ CtdlUnregisterUserHook() removes a user hook from the system. It must be called with the same fcn_ptr and EventType which were previously registered. void CtdlRegisterLogHook(void (*fcn_ptr) (char *), int loglevel) void CtdlUnregisterLogHook(void (*fcn_ptr) (char *), int loglevel) CtdlRegisterLogHook() adds a new logging function to the system. The handler function should accept a single string as a parameter. Logging functions can be used to implement additional logging facilities in addition to the Citadel trace file, which is output on stderr, or redirected to a file with the -t command line option. The handler function will be called if the loglevel is greater than or equal to loglevel. Security considerations: Logs may contain plain text passwords and other sensitive information. It is your responsibility to ensure that your logs have appropriate access protection. The Citadel trace file is readable only by the superuser when the -t option is used. CtdlUnregisterLogHook() removes a logging function from the system. It must be called with the same fcn_ptr and loglevel which were previously registered. void CtdlRegisterMessageHook(int (*handler) (struct CtdlMessage *), int EventType) void CtdlUnregisterMessageHook(int (*handler) (struct CtdlMessage *), int EventType) CtdlRegisterMessageHook() registers a function with the message handling subsystem. This function will be called with one parameter, a pointer to a CtdlMessage structure, when the message triggers an event of type EventType. The registered function should return non zero if it has handled the event to prevent other hook functions from also processing the event. CtdlUnregisterMessageHook() removes a function from the list of registered message handlers. To successfully remove a function registered with CtdlRegisterMessageHook() CtdlUnregisterMessageHook() must be called with the same parameters. Possible values for EventType are: EVT_BEFOREREAD Called after a message is loaded from disk but before it is presented for reading. EVT_BEFORESAVE Called before the message is saved to disk. returning non zero for this event will prevent the message being saved to disk in the normal manner. EVT_AFTERSAVE Called after the message is saved to disk but before any IGnet spooling is carried out. EVT_SMTPSCAN Called during the SMTP reception of a message after the message is received and before the response is sent to the sender. This is intended for spam filters and virus checkers. A positive return code will cause the message to be rejected by the SMTP server. void CtdlRegisterRoomHook(int (*fcn_ptr) (char *)) void CtdlUnregisterRoomHook(int (*fcn_ptr) (char *)) Register or remove a function with the room processing system. Registered functions are called in the order they are registered when a message is added to a room. This allows modules such as Sieve to process new messages appearing in a room. void CtdlRegisterXmsgHook(int (*fcn_ptr) (char *, char *, char *), int order) void CtdlUnregisterXmsgHook(int (*fcn_ptr) (char *, char *, char *), int order) Please write documentation for me! void CtdlRegisterServiceHook(int tcp_port, char *sockpath, void (*h_greeting_function) (void), void (*h_command_function) (void)) void CtdlUnregisterServiceHook(int tcp_port, char *sockpath, void (*h_greeting_function) (void), void (*h_command_function) (void)) Please write documentation for me! FUNCTIONS WHICH MANIPULATE USER/ROOM RELATIONSHIPS void CtdlGetRelationship(struct visit *vbuf, struct ctdluser *rel_user, struct ctdlroom *rel_room); void CtdlSetRelationship(struct visit *newvisit, struct ctdluser *rel_user, struct ctdlroom *rel_room); These functions get/set a "struct visit" structure which may contain information about the relationship between a user and a room. Specifically: struct visit { char v_roomname[20]; long v_generation; long v_lastseen; unsigned int v_flags; }; #define V_FORGET 1 /* User has zapped this room */ #define V_LOCKOUT 2 /* User is locked out of this room */ #define V_ACCESS 4 /* Access is granted to this room */ Don't change v_roomname or v_generation; they're used to identify the room being referred to. A room is unique to the system by its combination of room name and generation number. If a new room is created with the same name as a recently deleted room, it will have a new generation number, and therefore stale "visit" records will not be applied (and will eventually be purged). v_lastseen contains the number of the newest message the user has read in this room. Any existing messages higher than this number can be considered as "new messages." v_flags contains information regarding access to the room. int CtdlRoomAccess(struct ctdlroom *roombuf, struct ctdluser *userbuf) This is a convenience function which uses CtdlGetRelationship() to determine whether a user has access to a room. It returns a bucket of bits which may contain: #define UA_INUSE 1 /* Room exists */ #define UA_KNOWN 2 /* Room is in user's Known list */ #define UA_GOTOALLOWED 4 /* User may <.G>oto this room */ #define UA_HASNEWMSGS 8 /* Room contains new messages */ #define UA_ZAPPED 16 /* User has forgotten this room */ ROOM RELATED FUNCTIONS ---------------------- unsigned create_room(char *new_room_name, int new_room_type, char *new_room_pass, int new_room_floor, int really_create) This function is used to create a new room. new_room_name should be set to the desired name for the new room. new_room_type should be set to one of the following values: 0 = public room 1 = guess-name room 2 = passworded room 3 = invitation-only room 4 = personal (mailbox) room 5 = personal (mailbox) room, and new_room_name already contains the namespace prefix (use with caution!) new_room_pass should be set to the desired password for the room (obviously this is only valid for passworded rooms). If the room is really to be created, set really_create to 1. Otherwise, the caller may merely check to see if it's possible to create the room without actually creating it by setting really_create to 0. create_room() returns the flags associated with the new room (as in the data structure item room.QRflags). If the room cannot be created (for example, a room with the name already exists), it returns 0.