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How to add Global Unique IDs to objects and characters

How to add Global Unique IDs to objects and characters

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Posted by Nick Gammon Australia (22,975 posts) bio Forum Administrator

Date Tue 23 Feb 2010 04:07 AM (UTC)

Message

As part of experimenting with improved client/server interaction, I have added GUIDs to characters and objects in SMAUG. In case anyone else wants to do it, this is how I did it...

Compile as C++

Edit the Makefile and force compilation to be C++ rather than C by adding "-x c++" to the line that does the compiles:


o/%.o: %.c
    echo "  Compiling $@....";
    $(CC) -x c++ -c $(C_FLAGS) $< -o $@

This should compile OK without any errors or warnings under SmaugFUSS 1.9.

Add some STL stuff to mud.h

There are some useful STL headers you can grab (Standard Template Library). Near the start of mud.h add:


#include <list>
#include <map>
#include <vector>
#include <string>
#include <algorithm>

Add typedef for GUID


// global unique IDs
typedef long long GUID;

Add guid field to char_data and obj_data


struct char_data
{

...

   GUID guid;   // unique ID - stored in guid_char_map
};

...

struct obj_data
{

...

   GUID guid;  // unique ID - stored in guid_object_map
};

Add function to make the GUID


GUID makeguid ();  // prototype in mud.h

... and in comm.c (or some file) add the function:


GUID makeguid ()  // get a new GUID
  {
  static GUID _guid = 0;
  return ++_guid;
  }

Add maps to map GUIDs to pointers


// in mud.h

extern std::map<GUID, OBJ_DATA *> guid_object_map;
extern std::map<GUID, CHAR_DATA *> guid_char_map;

Create GUIDs when things are created

In db.c add the actual declarations for the maps:


std::map<GUID,OBJ_DATA *> guid_object_map;
std::map<GUID, CHAR_DATA *> guid_char_map;

In create_object add the object to the map:


// after the CREATE line:

   obj->guid = makeguid ();
   guid_object_map [obj->guid] = obj;

And in clone_object do the same thing:


// after the CREATE line:

   clone->guid = makeguid ();
   guid_object_map [clone->guid] = clone;

And in create_mobile do the same for mobiles:


// after the CREATE line:

   mob->guid = makeguid ();
   guid_char_map [mob->guid] = mob;

And in save.c, function fread_obj:


// after the CREATE line:

   obj->guid = makeguid ();
   guid_object_map [obj->guid] = obj;

Also in save.c, in load_char_obj, do something similar:


// after the CREATE line:

   mob->guid = makeguid ();
   guid_char_map [mob->guid] = mob;

Remove object from map when removed from world

In handler.c, in extract_obj function, after the line:


  UNLINK( obj, first_object, last_object, next, prev );

Add:


   std::map<GUID,OBJ_DATA *>::iterator i = guid_object_map.find (obj->guid);
   if (i != guid_object_map.end ())
     guid_object_map.erase (i);

And in free_obj before the line:


DISPOSE( obj );

Add:


   std::map<GUID,OBJ_DATA *>::iterator i = guid_object_map.find (obj->guid);
   if (i != guid_object_map.end ())
     guid_object_map.erase (i);

(It may be overkill doing it twice, but I wanted to make sure that once the object is unlinked from the world's object list it was removed from the map).

In free_char do the same for mobs/characters ... before the line:


   DISPOSE( ch );

Do this:


   // get rid of it from GUID map
   std::map<GUID,CHAR_DATA *>::iterator i = guid_char_map.find (ch->guid);
   if (i != guid_char_map.end ())
     guid_char_map.erase (i);

Also in save.c if the object is created and then disposed we need to get rid of the map as well:

Before the line:


DISPOSE( obj );

Add:


   std::map<GUID,OBJ_DATA *>::iterator i = guid_object_map.find (obj->guid);
   if (i != guid_object_map.end ())
     guid_object_map.erase (i);

Now we can use the GUIDs

After this work, we can be pretty confident that, given a GUID we can get back the original pointer.

eg.


// for some guid we know about:

  std::map<GUID,CHAR_DATA *>::iterator iter = guid_char_map.find (guid);
 
  if (iter != guid_char_map.end ())
    {
    CHAR_DATA * ch = iter->second;
    
    // play with character here
    }

And similarly for objects:


 std::map<GUID,OBJ_DATA *>::iterator iter = guid_object_map.find (guid);
 
  if (iter != guid_object_map.end ())
    {
    OBJ_DATA * obj = iter->second;

    // play with object here
    }

Allow players to use GUIDs

You can modify get_obj_list and get_obj_list_rev to allow players to use GUIDs in their commands, like this:


get <4587483>
examine <858756>

I did that by looking for <id> inside those functions (extra lines in bold):


/*
 * Find an obj in a list.
 */
OBJ_DATA *get_obj_list( CHAR_DATA * ch, char *argument, OBJ_DATA * list )
{
   char arg[MAX_INPUT_LENGTH];
   OBJ_DATA *obj;
   int number;
   int count;
   GUID guid;

   number = sscanf(argument, "<%Ld>", &guid );

   if (number == 1 && guid > 0)
     {
     for( obj = list; obj; obj = obj->next_content )
       if( can_see_obj( ch, obj ) && obj->guid == guid )
            return obj;

     return NULL;
     }

   number = number_argument( argument, arg );


/*
 * Find an obj in a list...going the other way          -Thoric
 */
OBJ_DATA *get_obj_list_rev( CHAR_DATA * ch, const char *argument, OBJ_DATA * list )
{
   char arg[MAX_INPUT_LENGTH];
   OBJ_DATA *obj;
   int number;
   int count;

   GUID guid;

   number = sscanf(argument, "<%Ld>", &guid );

   if (number == 1 && guid > 0)
     {
     for( obj = list; obj; obj = obj->prev_content )
       if( can_see_obj( ch, obj ) && obj->guid == guid )
            return obj;

     return NULL;
     }

   number = number_argument( argument, arg );

- Nick Gammon

www.gammon.com.au, www.mushclient.com

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Posted by

Nick Gammon Australia (22,975 posts)

bio Forum Administrator

Date

Reply #1 on Tue 23 Feb 2010 04:12 AM (UTC)

Amended on Tue 23 Feb 2010 04:18 AM (UTC) by Nick Gammon

Message

So what is the point of all this you ask?

Well, when working on scripted interactions between client and server, we need a precise way of defining things, and the old "get 2.sword" just doesn't cut it.

Let's imagine there are three swords on the ground, and two players try to pick up the second one (ie. "get 2.sword").

Well the server can only process one command at a time, so by the time the second player's command is processed 2.sword is gone, and the original 3.sword is now 2.sword.

There is also confusion if there are two types of swords and you inadvertently grab the wrong one.

All these problems go away if the server assigns every object a unique ID (the GUID). Then as part of server->client interaction (the subject of another thread) it can send down the GUIDs to positively identify things (like, in an inventory).

Now the client can send back "get <3487384>" to get an object, positively and uniquely identified by its own number, and not have confusion about some other object of a similar name. Ditto for mobs.

- Nick Gammon

www.gammon.com.au, www.mushclient.com

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Posted by

ThomasWatts USA (66 posts)

bio

Date

Reply #2 on Tue 23 Feb 2010 05:08 AM (UTC)

Amended on Tue 23 Feb 2010 05:11 AM (UTC) by ThomasWatts

Message

Quote:
Let's imagine there are three swords on the ground, and two players try to pick up the second one (ie. "get 2.sword").

Well the server can only process one command at a time, so by the time the second player's command is processed 2.sword is gone, and the original 3.sword is now 2.sword.

Or if you allow players to use more descriptive actions.
IE. 'get blue sword'

However, things having unique global identification can allow for anything to be cloned and then have temporary changes without having to create a physical(written to disk) copy.

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Posted by

Llarn (23 posts)

bio

Date

Reply #3 on Sun 20 Oct 2013 02:29 PM (UTC)

Amended on Sun 20 Oct 2013 02:31 PM (UTC) by Llarn

Message

Hi Nick,

I thought this concept is cool enough to give it a go.

Once I installed it though, my compiler does not like GUID used in mud.h for
In file included from act_comm.c:16:0:
h/mud.h:2226:5: error: ‘GUID’ does not name a type
h/mud.h:2741:5: error: ‘GUID’ does not name a type

These lines .....
GUID guid;

Instead it wants something like
it wants something like long guid I think.

I have gcc 4.6.3

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Posted by Nick Gammon Australia (22,975 posts) bio Forum Administrator

Date Reply #4 on Sun 20 Oct 2013 10:26 PM (UTC)

Message

Try this:


typedef struct _GUID {          // size is 16
    DWORD Data1;
    WORD   Data2;
    WORD   Data3;
    BYTE  Data4[8];
} GUID;

- Nick Gammon

www.gammon.com.au, www.mushclient.com

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Posted by Llarn (23 posts) bio

Date

Reply #5 on Mon 21 Oct 2013 01:14 AM (UTC)

Amended on Mon 21 Oct 2013 01:42 AM (UTC) by Llarn

Message

Adding that gives me this.

In file included from act_comm.c:16:0:
h/mud.h:2748:5: error: ‘GUID’ does not name a type
make[2]: *** [o/act_comm.o] Error 1

This is how my mud.h looks


extern std::map<GUID, OBJ_DATA *> guid_object_map;

GUID makeguid ();  // prototype in mud.h

// global unique IDs
// typedef long long GUID;

typedef struct _GUID {          // size is 16
    DWORD  Data1;
    WORD   Data2;
    WORD   Data3;
    BYTE   Data4[8];
} GUID;

And further down in the obj structure at line 2748
    
GUID                    guid;  // unique ID - stored in guid_object_map 
};

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Posted by

Nick Gammon Australia (22,975 posts)

bio Forum Administrator

Date

Reply #6 on Mon 21 Oct 2013 11:10 PM (UTC)

Message

Well, you have to have the typedef before you use it.

- Nick Gammon

www.gammon.com.au, www.mushclient.com

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Posted by Llarn (23 posts) bio

Date Reply #7 on Mon 21 Oct 2013 11:52 PM (UTC)

Message

you mean like this right?


typedef long long GUID;


typedef struct _GUID {          // size is 16
    DWORD  Data1;
    WORD   Data2;
    WORD   Data3;
    BYTE   Data4[8];
} GUID;



extern std::map<GUID, OBJ_DATA *> guid_object_map;



GUID makeguid ();  // prototype in mud.h

Doing this gives me

Compiling o/act_comm.o
In file included from act_comm.c:16:0:
h/mud.h:2745:5: error: ‘GUID’ does not name a type
make[1]: *** [o/act_comm.o] Error 1

Sorry if I am misunderstanding what I need to do.

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Posted by Nick Gammon Australia (22,975 posts) bio Forum Administrator

Date Reply #8 on Tue 22 Oct 2013 09:39 AM (UTC)

Message

On my Linux machine this compiles with no errors:


#include <map>

typedef long DWORD;
typedef int WORD;
typedef unsigned char BYTE;

typedef struct _GUID {          // size is 16
    DWORD  Data1;
    WORD   Data2;
    WORD   Data3;
    BYTE   Data4[8];
} GUID;

extern std::map<GUID, int> guid_object_map;

GUID makeguid ();  // prototype in mud.h

int main ()
 {
 return 0;
 }

- Nick Gammon

www.gammon.com.au, www.mushclient.com

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Posted by

Llarn (23 posts)

bio

Date

Reply #9 on Tue 22 Oct 2013 10:38 AM (UTC)

Message

Yeah, it has me baffled. I am using gcc 4.6.3 though.

My Makefile looks like
o/%.o: %.c $(H_FILES)
echo " Compiling $@";
$(CC) -x c++ -c $(C_FLAGS) $< -o $@
# $(CC) -c $(C_FLAGS) $< -o $@

So pretty sure I have the c++ gcc compile.

My mud.h looks identical to what you have now, and it still gives me that error in obj data structure unless I change the GUID to a int guid;

But that then errors out in comm.c in makeguid function
comm.c:3702:1: error: ‘GUID’ does not name a type
make[2]: *** [o/comm.o] Error 1

Thanks for trying Nick.

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