How does INVALID_PLAYER_ID actually work?

How does INVALID_PLAYER_ID actually work? - Printable Version

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+--- Thread: How does INVALID_PLAYER_ID actually work? (/showthread.php?tid=560283)

How does INVALID_PLAYER_ID actually work? - Puppy - 27.01.2015

Now, this may seem a bit silly but I am basically curious about how INVALID_PLAYER_ID works. Let's start with this example:

pawn Код:

public OnPlayerUpdate(playerid)
{
     if(playerid != INVALID_PLAYER_ID)
     {
            .///
     }
     return 1;
}

This would allow the code to go through if the player is connected. But my question is what exactly is INVALID_PLAYER_ID? A function? If it's a constant value then this would make zero sense.

This is what the compiler sees this as:

if(0 !=

So, playerID obviously can be anything, but what about INVALID_PLAYER_ID? If it's a constant then it certainly can't be 0,1,2,3,4,5,6... How does this work?

Is it basically just a marco for a native function like IsPlayerConnected?

Thanks.

EDIT: In a_samp it's defined as

pawn Код:

#define INVALID_PLAYER_ID                       (0xFFFF)

This makes zero sense, is this like a memory address? Or is it basically something to do with bits?

Re: How does INVALID_PLAYER_ID actually work? - DRIFT_HUNTER - 27.01.2015

Its a simple define, from code you can see its defined as hexadecimal number

0xFFFF - FFFF is 65535 in decimal whitch is maximum signed integer for 32bit

65535 as player id is invalid for sure and thats why its used as invalid player id

Re: How does INVALID_PLAYER_ID actually work? - Puppy - 27.01.2015

That doesn't answer my question. Let's say no one is using playerID 0. And when I run a global timer(which I wouldn't but you get the point) to check if player 0 is online every 5 minutes...

pawn Код:

if(0 == 65535)
{
   // player is offline
}

This doesn't make any sense. This is not equal(0 doesn't equal 65535 that'd be crazy!), so how does the compiler actually process this information?

Re: How does INVALID_PLAYER_ID actually work? - Vince - 27.01.2015

Quote:

Originally Posted by DRIFT_HUNTER

65535 in decimal whitch is maximum signed integer for 32bit

16 bit. Also some callbacks use this value, namely OnPlayerDeath.

Quote:

Originally Posted by Puppy

That doesn't answer my question. Let's say no one is using playerID 0. And when I run a global timer(which I wouldn't but you get the point) to check if player 0 is online every 5 minutes...

pawn Код:

if(0 == 65535)
{
   // player is offline
}

This doesn't make any sense. This is not equal(0 doesn't equal 65535 that'd be crazy!), so how does the compiler actually process this information?

Don't confuse it with IsPlayerConnected, because for the most part they can't be used interchangeably.

Re: How does INVALID_PLAYER_ID actually work? - Ada32 - 27.01.2015

Quote:

Originally Posted by Puppy

This makes zero sense, is this like a memory address?

nope

Quote:

Originally Posted by Puppy

Or is it basically something to do with bits?

yup

Quote:

Originally Posted by DRIFT_HUNTER

0xFFFF - FFFF is 65535 in decimal whitch is maximum signed integer for 32bit

16*

Quote:

Originally Posted by DRIFT_HUNTER

65535 as player id is invalid for sure and thats why its used as invalid player id

so is -1..

just the max val of 2 byte int (samp got 1000p on the linux server..cool)

Re: How does INVALID_PLAYER_ID actually work? - DRIFT_HUNTER - 27.01.2015

Quote:

Originally Posted by Vince

16 bit. Also some callbacks use this value, namely OnPlayerDeath.

Don't confuse it with IsPlayerConnected, because for the most part they can't be used interchangeably.

16bit unsigned, 32bit signed :P

Re: How does INVALID_PLAYER_ID actually work? - Ada32 - 27.01.2015

Quote:

Originally Posted by DRIFT_HUNTER

16bit unsigned, 32bit signed :P

uh..no

Re: How does INVALID_PLAYER_ID actually work? - DRIFT_HUNTER - 27.01.2015

Quote:

Originally Posted by Ada32

uh..no

Oooopsss.... my bad

Anyway 65535 is maximum unsigned in 16 bits, and C/C++ integer is 2 bytes (2*8 = 16bits)

Re: How does INVALID_PLAYER_ID actually work? - ikkentim - 27.01.2015

Used to indicate that no player matches the description

E.g. The killerid on suicide.
https://sampwiki.blast.hk/wiki/OnPlayerDeath

Re: How does INVALID_PLAYER_ID actually work? - Puppy - 28.01.2015

I know what it does, it's just I am stumped upon the fact of how it works anyways thanks for the help so far, can someone explain this in layman(simple) terms?