Re: static world

From: Erwin S. Andreasen (erwin@PIP.DKNET.DK)
Date: 01/13/98

On Tue, 13 Jan 1998, Daniel W. Burke wrote:

> I've been trying to talk
> myself into for a while now is to make the world static, so something like
> this is pratical... and also save things like who's grouped, fighting, etc...
> Have many people done such a static world?  I'm curious of implementation
> methods...

You could use shared memory, but it is quite complicated. The following is
based on my correspondation with M.C. Lewis.

The idea is that you write your own memory manager that allocates memory
using shared memory. No malloc, no strdup, everything has to be allocated

The memory manager should also allow for registration of some global
variables, e.g. foo_list and retrieval of those.

The code will look something like this:

// Starting up. Get foo from shared memory

if ((foo_list = getSharedVariable("foo_list")))
        // Foo_list was stored in the shared memory segment and has the same
        // Foos are not in the shared memory
        // We need to load them from the file

If the MUD crashes, the shared memory still exist. When you start the MUD
up again, you just attach to that shared memory again.

If you want to reload the code, you just reload the code. No data has to
be read from files, so this can happen instantly.


- If you corrupt your data, they'll stay corrupted
- If you add new fields to data, you'll have to find a mechanism to
  convert the old data to new

The latter can be done using a list of variable-size data structures
attached to each object. Basically, have a structure like this:

typedef enum { auxEmail, auxSomethingElse } aux_t;

#define COMMON aux_t type; \
                Auxillary *next

struct Auxillary

struct Email
        char *email;

struct SomethingElse
        char *some_Data;
        char *some_more_data;

The idea is that you have a pointer to an Auxillary in your char_data for
example. When you add a character's email, you allocate an Email object,
which has the same two first fields as an Auxillary. You the type to
auxEmail and insert it into the list

When you need to retrieve the Email data, you run through the list,
looking for type == auxEmail, then cast that to an Email*.

The advantage is that you can add new fields without changing the size of
the structure you are adding the fields. The disadvantages are that it
takes some time to run through the list, and that there is some overhead.
Plus, it's not very confirming ANSI C.

Erwin Andreasen   Herlev, Denmark <>  UNIX System Programmer
<URL:>     <*>         (not speaking for) DDE

     | Ensure that you have read the CircleMUD Mailing List FAQ:  |
     | |

This archive was generated by hypermail 2b30 : 12/15/00 PST