interface

uses SDLh;

type TIPCMessage = record

                   str: shortstring;

                   len: Longword;

                   buf: Pointer

               end;

var msgFrontend, msgEngine: TIPCMessage;

    mutFrontend, mutEngine: PSDL_mutex;

    condFrontend, condEngine: PSDL_cond;

procedure initIPC;

procedure freeIPC;

procedure ipcToEngine(s: shortstring);

function  ipcReadFromEngine: shortstring;

function  ipcCheckFromEngine: boolean;

procedure ipcToEngine(s: shortstring);

begin

    SDL_LockMutex(mutEngine);

    while (msgEngine.str[0] > #0) or (msgEngine.buf <> nil) do

        SDL_CondWait(condEngine, mutEngine);

    msgEngine.str:= s;

    SDL_CondSignal(condEngine);

    SDL_UnlockMutex(mutEngine)

end;

function ipcReadFromEngine: shortstring;

begin

    SDL_LockMutex(mutFrontend);

    while (msgFrontend.str[0] = #0) and (msgFrontend.buf = nil) do

        SDL_CondWait(condFrontend, mutFrontend);

    ipcReadFromEngine:= msgFrontend.str;

    msgFrontend.str[0]:= #0;

    if msgFrontend.buf <> nil then

    begin

        FreeMem(msgFrontend.buf, msgFrontend.len);

        msgFrontend.buf:= nil

    end;

    SDL_CondSignal(condFrontend);

    SDL_UnlockMutex(mutFrontend)

end;

function ipcCheckFromEngine: boolean;

begin

    SDL_LockMutex(mutFrontend);

    ipcCheckFromEngine:= (msgFrontend.str[0] > #0) or (msgFrontend.buf <> nil);

    SDL_UnlockMutex(mutFrontend)

end;

procedure initIPC;

begin

    msgFrontend.str:= '';

    msgFrontend.buf:= nil;

    msgEngine.str:= '';

    msgEngine.buf:= nil;

    mutFrontend:= SDL_CreateMutex;

    mutEngine:= SDL_CreateMutex;

    condFrontend:= SDL_CreateCond;

    condEngine:= SDL_CreateCond;

end;

procedure freeIPC;

begin

    SDL_DestroyMutex(mutFrontend);

    SDL_DestroyMutex(mutEngine);

    SDL_DestroyCond(condFrontend);

    SDL_DestroyCond(condEngine);

end;