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,
only 'plain' (quasi a superset of 'native' and 'compat')
and 'compat' mode, and since 3.2.9 the mode selection can be
made via commandline option.
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
by default.
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.
compat: when active, the compat mode is used.
Following is the description of the changes (de) activated by
these defines. A shorthand notation is used: 'compat' means
'if compat mode is active' and '!compat' means 'if
compat mode is not active', 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).
Initialisation Of Objects
It is task of the mudlib (through the driver hooks) to call
the initialisation lfuns in newly created objects. The
following table shows the traditional calls:
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
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.
In original native mode, move_object() could applied only to
this_object() as the object to move, and it 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 compat 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()).
object_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.
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/plain 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.
--- In Detail ---
Userids of the Master
The master's (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 master's 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 master's 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.
--- ---
SEE ALSO
hooks(C), uids(C), move_object(E), initialisation(LPC)
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