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cf2a88a773
fpc/docs/ipc.tex
michael cf2a88a773 Initial implementation of IPC docs
1999-01-14 15:43:52 +00:00

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%
% $Id$
% This file is part of the FPC documentation.
% Copyright (C) 1998, by Michael Van Canneyt
%
% The FPC documentation is free text; you can redistribute it and/or
% modify it under the terms of the GNU Library General Public License as
% published by the Free Software Foundation; either version 2 of the
% License, or (at your option) any later version.
%
% The FPC Documentation is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
% Library General Public License for more details.
%
% You should have received a copy of the GNU Library General Public
% License along with the FPC documentation; see the file COPYING.LIB. If not,
% write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
% Boston, MA 02111-1307, USA.
%
\chapter{The IPC unit.}
This chapter describes the IPC unit for Free Pascal. It was written for
\linux by Micha\"el Van Canneyt. It gives all the functionality of system V
Inter-Process Communication: shared memory, semaphores and messages.
The chapter is divided in 2 sections:
\begin{itemize}
\item The first section lists types, constants and variables from the
interface part of the unit.
\item The second section describes the functions defined in the unit.
\end{itemize}
\section {Types, Constants and variables : }
\subsection{Variables}
\begin{verbatim}
Var
IPCerror : longint;
\end{verbatim}
The \var{IPCerror} variable is used to report errors, by all calls.
\subsection{Constants}
\begin{verbatim}
Const
IPC_CREAT = 1 shl 9; { create if key is nonexistent }
IPC_EXCL = 2 shl 9; { fail if key exists }
IPC_NOWAIT = 4 shl 9; { return error on wait }
\end{verbatim}
These constants are used in the various \var{xxxget} calls.
\begin{verbatim}
IPC_RMID = 0; { remove resource }
IPC_SET = 1; { set ipc_perm options }
IPC_STAT = 2; { get ipc_perm options }
IPC_INFO = 3; { see ipcs }
\end{verbatim}
These constants can be passed to the various \var{xxxctl} calls.
\begin{verbatim}
const
MSG_NOERROR = 1 shl 12;
MSG_EXCEPT = 2 shl 12;
MSGMNI = 128;
MSGMAX = 4056;
MSGMNB = 16384;
\end{verbatim}
These constants are used in the messaging system, they are not for use by
the programmer.
\begin{verbatim}
const
SEM_UNDO = $1000;
GETPID = 11;
GETVAL = 12;
GETALL = 13;
GETNCNT = 14;
GETZCNT = 15;
SETVAL = 16;
SETALL = 17;
\end{verbatim}
These constants call be specified in the \seef{semop} call.
\begin{verbatim}
SEMMNI = 128;
SEMMSL = 32;
SEMMNS = (SEMMNI * SEMMSL);
SEMOPM = 32;
SEMVMX = 32767;
\end{verbatim}
These constanst are used internally by the semaphore system, they should not
be used by the programmer.
\begin{verbatim}
const
SHM_R = 4 shl 6;
SHM_W = 2 shl 6;
SHM_RDONLY = 1 shl 12;
SHM_RND = 2 shl 12;
SHM_REMAP = 4 shl 12;
SHM_LOCK = 11;
SHM_UNLOCK = 12;
\end{verbatim}
These constants are used in the \seef{shmctl} call.
\subsection{Types}
\begin{verbatim}
Type
TKey = Longint;
\end{verbatim}
\var{TKey} is the type returned by the \seef{ftok} key generating function.
\begin{verbatim}
type
PIPC_Perm = ^TIPC_Perm;
TIPC_Perm = record
key : TKey;
uid,
gid,
cuid,
cgid,
mode,
seq : Word;
end;
\end{verbatim}
The \var{TIPC\_Perm} structure is used in all IPC systems to specify the
permissions.
\begin{verbatim}
Type
PShmid_DS = ^TShmid_ds;
TShmid_ds = record
shm_perm : TIPC_Perm;
shm_segsz : longint;
shm_atime : longint;
shm_dtime : longint;
shm_ctime : longint;
shm_cpid : word;
shm_lpid : word;
shm_nattch : integer;
shm_npages : word;
shm_pages : Pointer;
attaches : pointer;
end;
type
PSHMinfo = ^TSHMinfo;
TSHMinfo = record
shmmax : longint;
shmmin : longint;
shmmni : longint;
shmseg : longint;
shmall : longint;
end;
type
PMSG = ^TMSG;
TMSG = record
msg_next : PMSG;
msg_type : Longint;
msg_spot : PChar;
msg_stime : Longint;
msg_ts : Integer;
end;
type
PMSQid_ds = ^TMSQid_ds;
TMSQid_ds = record
msg_perm : TIPC_perm;
msg_first : PMsg;
msg_last : PMsg;
msg_stime : Longint;
msg_rtime : Longint;
msg_ctime : Longint;
wwait : Pointer;
rwait : pointer;
msg_cbytes : word;
msg_qnum : word;
msg_qbytes : word;
msg_lspid : word;
msg_lrpid : word;
end;
PMSGbuf = ^TMSGbuf;
TMSGbuf = record
mtype : longint;
mtext : array[0..0] of char;
end;
PMSGinfo = ^TMSGinfo;
TMSGinfo = record
msgpool : Longint;
msgmap : Longint;
msgmax : Longint;
msgmnb : Longint;
msgmni : Longint;
msgssz : Longint;
msgtql : Longint;
msgseg : Word;
end;
type
PSEMid_ds = ^PSEMid_ds;
TSEMid_ds = record
sem_perm : tipc_perm;
sem_otime : longint;
sem_ctime : longint;
sem_base : pointer;
sem_pending : pointer;
sem_pending_last : pointer;
undo : pointer;
sem_nsems : word;
end;
PSEMbuf = ^TSEMbuf;
TSEMbuf = record
sem_num : word;
sem_op : integer;
sem_flg : integer;
end;
PSEMinfo = ^TSEMinfo;
TSEMinfo = record
semmap : longint;
semmni : longint;
semmns : longint;
semmnu : longint;
semmsl : longint;
semopm : longint;
semume : longint;
semusz : longint;
semvmx : longint;
semaem : longint;
end;
PSEMun = ^TSEMun;
TSEMun = record
case longint of
0 : ( val : longint );
1 : ( buf : PSEMid_ds );
2 : ( arr : Pointer );
3 : ( padbuf : PSeminfo );
4 : ( padpad : pointer );
end;
\end{verbatim}
\section{Functions and procedures}
\begin{function}{ftok}
\Declaration
Function ftok (Path : String; ID : char) : TKey;
\Description
\Errors
\SeeAlso
\end{function}
\begin{function}{msgget}
\Declaration
Function msgget(key: TKey; msgflg:longint):longint;
\Description
\Errors
\SeeAlso
\end{function}
\begin{function}{msgsnd}
\Declaration
Function msgsnd(msqid:longint; msgp: PMSGBuf; msgsz: longint; msgflg:longint): Boolean;
\Description
\Errors
\SeeAlso
\end{function}
\begin{function}{msgrcv}
\Declaration
Function msgrcv(msqid:longint; msgp: PMSGBuf; msgsz: longint; msgtyp:longint; msgflg:longint): Boolean;
\Description
\Errors
\SeeAlso
\end{function}
\begin{function}{msgctl}
\Declaration
Function msgctl(msqid:longint; cmd: longint; buf: PMSQid\_ds): Boolean;
\Description
\Errors
\SeeAlso
\end{function}
\begin{function}{semget}
\Declaration
Function semget(key:Tkey; nsems:longint; semflg:longint): longint;
\Description
\Errors
\SeeAlso
\end{function}
\begin{function}{semop}
\Declaration
Function semop(semid:longint; sops: pointer; nsops: cardinal): Boolean;
\Description
\Errors
\SeeAlso
\end{function}
\begin{function}{semctl}
\Declaration
Function semctl(semid:longint; semnum:longint; cmd:longint; var arg: tsemun): longint;
\Description
\Errors
\SeeAlso
\end{function}
\begin{function}{shmget}
\Declaration
Function shmget(key: Tkey; size:longint; flag:longint):longint;
\Description
\Errors
\SeeAlso
\end{function}
\begin{function}{shmat}
\Declaration
Function shmat (shmid:longint; shmaddr:pchar; shmflg:longint):pchar;
\Description
\Errors
\SeeAlso
\end{function}
\begin{function}{shmdt}
\Declaration
Function shmdt (shmaddr:pchar):boolean;
\Description
\Errors
\SeeAlso
\end{function}
\begin{function}{shmctl}
\Declaration
Function shmctl(shmid:longint; cmd:longint; buf: pshmid\_ds): Boolean;
\Description
\Errors
\SeeAlso
\end{function}
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