SA-MP Plugin Invoke Function
By Peter Beverloo

This function demonstrates how you can call native pawn-functions using
plugins. The whole usage of the function is explained in the n_TestInvoke
function, which sends a message to all the clients connected to the server.
The function itself might be complicated and messy, however, the usage
is simple. Each function you use has to be defined as a PAWN_FUNCTION
structure, which contains three elements;

struct PAWN_FUNCTION
{
	int ParamCnt;		// Number of parameters for the function
	char Function[ 33 ];	// Name of the function, ex. "GetPlayerPos"
	char Params[ 18 ];	// Parameters for the function; i f v p s
};

The first entry is obvious, the number of parameters the pawn function
expects. The second one is the name of the function, "GetPlayerName" for
example. As the pawn-limit for functionnames is 32 characters, this doesn't
need to be any bigger. The third variable, Params, explains the way
parameters are handled. There are five possible options:

 Parameters:
   i = integer
   f = float value
   s = string
   v = variable
   p = string var (GetPlayerName etc.)

While the first three might be clear, the other two might need some
explaining. A variable is what is used in GetPlayerPos, where the floats
get returned in their respective variables. You would use it like this;

float fPosX, fPosY, fPosZ;
const PAWN_FUNCTION GetPlayerPos = { 4,  "GetPlayerPos",  "ivvv" };
PawnCommand( &GetPlayerPos, playerid, &fPosX, &fPosY, &fPosZ );

The player's position will be stored in the three float values. The "p"
parameter-type is used for strings which get returned, as is the case
with GetPlayerIp and GetPlayerName. Usage of those functions is like
this;

char szPlayerName[ 25 ];
PawnCommand( &GetPlayerName, playerid, szPlayerName, 24 );

That's pretty much all there is to say. Again, the code's quite messy
but it works on both Linux as Windows, I'm using it myself. Keep in
mind that AMX is SINGLE THREADED, meaning you cannot have multiple
threads which both execute pawn-functions.

Peter