unit uFLIPC;

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;

function  ipcReadFromEngine: shortstring;

function  ipcCheckFromEngine: boolean;

procedure ipcToFrontend(s: shortstring);

function ipcReadFromFrontend: shortstring;

function ipcCheckFromFrontend: boolean;

implementation

procedure ipcSend(var s: shortstring; var msg: TIPCMessage; mut: PSDL_mutex; cond: PSDL_cond);

begin

    SDL_LockMutex(mut);

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

        SDL_CondWait(cond, mut);

    msg.str:= s;

    SDL_CondSignal(cond);

end;

function ipcRead(var msg: TIPCMessage; mut: PSDL_mutex; cond: PSDL_cond): shortstring;

begin

    SDL_LockMutex(mut);

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

        SDL_CondWait(cond, mut);

    ipcRead:= msg.str;

    msg.str[0]:= #0;

    if msg.buf <> nil then

    begin

        FreeMem(msg.buf, msg.len);

        msg.buf:= nil

    end;

    SDL_CondSignal(cond);

    SDL_UnlockMutex(mut)

end;

function ipcCheck(var msg: TIPCMessage; mut: PSDL_mutex): boolean;

begin

    SDL_LockMutex(mut);

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

    SDL_UnlockMutex(mut)

end;

begin

    ipcSend(s, msgEngine, mutEngine, condEngine)

end;

procedure ipcToFrontend(s: shortstring);

begin

    ipcSend(s, msgFrontend, mutFrontend, condFrontend)

end;

function ipcReadFromEngine: shortstring;

begin

    ipcReadFromEngine:= ipcRead(msgFrontend, mutFrontend, condFrontend)

end;

function ipcReadFromFrontend: shortstring;

begin

    ipcReadFromFrontend:= ipcRead(msgEngine, mutEngine, condEngine)

end;

function ipcCheckFromEngine: boolean;

begin

    ipcCheckFromEngine:= ipcCheck(msgFrontend, mutFrontend)

end;

function ipcCheckFromFrontend: boolean;

begin

    ipcCheckFromFrontend:= ipcCheck(msgEngine, mutEngine)

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;

end.