CONCEPT
driver modes / native driver mode
DESCRIPTION
During the evolution of LPMud there has been a hiatus as the
old driver became too restricting for the demands of modern
muds: it did a lot of things the mudlib could do better or
completely different. Removing these things from the driver
weren't a problem, but to keep compatible with the existing
mudlibs (namely the well-known 2.4.5 lib), it was possible to
undo these changes. First by setting a runtime option, then
by compiling the driver either in 'compat' or in 'native'
mode.
Starting with 3.2.1, the distinction between compat and native
mode is more and more transferred into the mudlib, with the
future goal of having a modeless driver. Starting with 3.2.7,
native mode no longer exists as such.
The main mode of the driver is determined at compile time
by preprocessor symbols to be defined/undefined in config.h:
COMPAT_MODE: when defined, the compat mode specifics are activated.
Additional modifications can be achieved by the specification
of commandline arguments (most of them have a default setting
entry in config.h as well):
strict-euids: when active, euid usage is enforced.
Following is the description of the changes (de) activated by
these defines. A shorthand notation is used: 'compat' means
'if COMPAT_MODE is defined' and '!compat' means 'if
COMPAT_MODE is not defined', etc.
Predefined Preprocessor Symbols
If compat, the symbols COMPAT_FLAG and __COMPAT_MODE__ are
defined for all LPC programs.
If strict-euids, the symbol __STRICT_EUIDS__ is defined
for all LPC programs.
For compatibility reasons, the symbol __EUIDS__ is defined
for all LPC programs all the time.
Preloading Of Objects
The driver has the possibility to preload objects before the
game is actually opened to the world. This is done by
calling master->epilog(), which has to return 0 or an array.
If its an array, its elements (as long as they are strings)
are given one by one as argument to master->preload() which
may now preload the objects (or do anything else).
Up to 3.2, compat mode used a different scheme: the file
INIT_FILE (defined in config.h) was read and each line
interpreted as filename of an object to preload. After this
was done, master->epilog() was called. This was dumped in
3.2.1 as it can be simulated by the master.
Initialisation Of Objects
Since 3.2.1, it is task of the mudlib (through the driver
hooks) to call the initialisation lfuns in newly created
objects, so the following table applies only up to 3.2:
mode : init call : reset call
--------------------------------------------
!compat & !native : create() : reset(1)
!compat & native : create() : reset()
compat & !native : reset(0) : reset(1)
compat & native : reset(0) : reset(1)
If INITIALIZATION_BY___INIT was defined, the lfun __INIT()
is called first on creation to initialize the objects
variables.
Movement Of Objects
Since 3.2.1, the efun move_object() is implemented in the
mudlib through driver hooks and the set_environment() efun.
move_object() itself exists just for convenience and
compatibility.
Before 3.2.1, move_object() could applied only to this_object() as
the object to move if in native mode, and called the lfun
exit() in the old environment if in compat mode. As a side
effect, the lfun exit() may not be target of add_action()s
in compat mode.
In !native mode, objects may be moved using the transfer()
efun. It does make assumptions about the design of the
mudlib, though, as it calls the lfuns query_weight(),
can_put_and_get(), get(), prevent_insert() and add_weight().
Efuns In General
creator(), transfer()
These exist only in compat mode (creator() is
identical with getuid() from !compat mode).
getuid()
Exists only in !compat mode (getuid() is identical with
creator()).
file_name(),function_exists()
In !compat mode, the returned filenames start with a
leading '/', in compat mode they don't.
parse_command()
This command exists in two versions: the old is used with
compat, the new with !compat. However,
SUPPLY_PARSE_COMMAND must be defined in config.h in both
cases (this efun is not very useful at all).
process_string()
If this_object() doesn't exist, it defaults to this_player()
and receives the backbone uid (returned by master->get_bb_uid())
as euid. If strict-euids, this uid must not be 0.
snoop()
Besides that the call is verified with a call to
master->verify_snoop(), up to 3.2 the snooper has to have
a non-zero euid.
Userids and Effective Userids
This is probably the most important difference between the
modes.
LPMud always had userids (uids) attributing the objects,
though they were called 'creator names' in compat mode.
Internally, the compat mode uses the 'creator names' as
(e)uid.
With the introduction of native mode, additionally
'effective userids' (euids) were introduced to improve
security handling (which was only a partial success).
The hardcoded handling of euids and uids was quite complex
and too mudlib-insensitive, so most of it got moved from the
driver into the mudlib with 3.2.1.
In strict-euids mode, only objects with a non-zero euid may load
or create new objects.
--- 3.2.1 and after ---
Userids of the Master
The masters (e)uid is determined by a call to
master->get_master_uid().
In strict-euids mode, the result has to be a string,
otherwise the driver won't start up at all. If the result is
valid it is set as the masters uid and euid.
In !strict-euids mode, the result may be any value: 0 or a
string are treated as the uid to set, a non-zero integer
leads to the use of the uid set in the default 'global'
wizlist entry, and any other value defaults to 0.
The euid is either set to the returned string (if any),
or to 0.
The masters uid is determined only on startup this way,
at runtime the uids of a reloaded master determined as
for every object by a call to the appropriate driver
hooks.
Userids of New Objects
To determine the (e)uids for a new object (loaded or
inherited, or cloned), the appropriate driver hook is
evaluated (H_LOAD_UIDS, H_CLONE_UIDS) and the result set
as (e)uid. The result may be a single value, in which case the
euid is set to 0, or an array ({ uid, euid }).
In strict-euids mode, both uid and euid must be 0 or a string,
any other value causes the load/clone to fail.
In !strict-euids mode, the uid (however returned) may also be
a non-zero integer to use the uid of the global
wizlist entry as uid. The euid is then
set to either 0 or the second entry of the returned
array if it's a string.
--- 3.2 ---
LPMud <= 3.2 in !compat mode has the algorithm deciding _which_
(e)uid to set hardcoded into the driver. For this it
features two builtin uids: the root uid (queried by a call
to master->get_root_uid()) and the backbone uid
(master->get_bb_uid()). Both uids should be a string: if
not, the driver in native mode will terminate, else print
a warning to stderr. The backbone uid is queried just once
at startup.
Userids of the Master
In compat mode, the master's (e)uid is the (e)uid as
determined for every other object as well. The following
therefore applies only to !compat mode.
The initial (e)uid is those determined using the normal
algorithm for newly created objects (see below).
After the master being loaded, master->get_root_uid() is
called to query the (e)uid to use for real. If the
result is a string, it is used as real (e)uid, else the
default setting. In native mode, get_root_uid() must
return a string, else the driver will terminate.
Userids of New Objects
If an object has been newly created, it is equipped with
a default uid: 0 in !native mode, "NONAME" in native
mode. The default euid (if needed) is equal to the uid,
or 0 if no master object exists.
The basic idea is simple: the master is asked, which (e)uid
the new object should have.
Objects loaded by the game, in compat model, or by an
object of the same creator will get the suggested e/uid.
Backbone objects will get the euid of the loader.
Other objects will get 0 as euid.
The details are a bit more complicated...:
Then master->creator_file() is asked for the 'creator
uid' (cuid) of this object. If the lfun doesn't exist,
the new object is destructed.
The cuid must be a string, the number 0 or an array of
two elements, !native mode also allows other non-array
values. If the cuid is non of these (native mode
restricts this further to the string or array), the
object is destructed again.
If the cuid is an array of two elements ({ uid, euid }),
these are set as e/uid (non-strings are treated as 0).
If the cuid is neither string, array or the number 0,
the object gets 0 as e/uid (!native mode only).
If the cuid is a string (all other cases are treated
above) is it always set as the objects uid. The objects
euid needs further treatment. If all following cases
(checked in the order listed here) fail, it is set to 0.
In compat mode, the euid is set to the uid.
In !native mode, if the object is loaded (not cloned) or
the loader has as 0 uid, the euid is set to the cuid.
Also in !native mode, if the loader has a 0 euid, the
objects euid is set to 0.
If the cuid is equal to the loaders uid, the objects
euid is set to the cuid == uid.
If the cuid is the backbone uid (and in !native mode the
loader has a non-zero euid), the objects e/uid are both
set to the loaders euid.
------
SEE ALSO
hooks(C), uids(C), move_object(E), initialisation(LPC)
