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/* cygserver_ipc.h
Copyright 2002 Red Hat, Inc.
Originally written by Conrad Scott <conrad.scott@dsl.pipex.com>
This file is part of Cygwin.
This software is a copyrighted work licensed under the terms of the
Cygwin license. Please consult the file "CYGWIN_LICENSE" for
details. */
#ifndef __CYGSERVER_IPC_H__
#define __CYGSERVER_IPC_H__
#include <assert.h>
#include <limits.h> /* For OPEN_MAX. */
/*
* The sysv ipc id's (msgid, semid, shmid) are integers arranged such
* that they no subsystem will generate the same id as some other
* subsystem; nor do these ids overlap file descriptors (the other
* common integer ids). Since Cygwin can allocate more than OPEN_MAX
* file descriptors, it can't be guaranteed not to overlap, but it
* should help catch some errors.
*
* msgid's: OPEN_MAX, OPEN_MAX + 3, OPEN_MAX + 6, . . .
* semid's: OPEN_MAX + 1, OPEN_MAX + 4, OPEN_MAX + 7, . . .
* shmid's: OPEN_MAX + 2, OPEN_MAX + 5, OPEN_MAX + 8, . . .
*
* To further ensure that ids are unique, if ipc objects are created
* and destroyed and then re-created, they are given new ids by
* munging the basic id (as above) with a sequence number.
*
* Internal ipc id's, which are 0, 1, ... within each subsystem (and
* not munged with a sequence number), are used solely by the ipcs(8)
* interface.
*/
enum ipc_subsys_t
{
IPC_MSGOP = 0,
IPC_SEMOP = 1,
IPC_SHMOP = 2,
IPC_SUBSYS_COUNT
};
/*
* IPCMNI - The absolute maximum number of simultaneous ipc ids for
* any one subsystem.
*/
enum
{
IPCMNI = 0x10000 // Must be a power of two.
};
inline int
ipc_int2ext (const int intid, const ipc_subsys_t subsys, long & sequence)
{
assert (0 <= intid && intid < IPCMNI);
const long tmp = InterlockedIncrement (&sequence);
return (((tmp & 0x7fff) << 16)
| (OPEN_MAX + (intid * IPC_SUBSYS_COUNT) + subsys));
}
inline int
ipc_ext2int_subsys (const int extid)
{
return ((extid & (IPCMNI - 1)) - OPEN_MAX) % IPC_SUBSYS_COUNT;
}
inline int
ipc_ext2int (const int extid, const ipc_subsys_t subsys)
{
if (ipc_ext2int_subsys (extid) != subsys)
return -1;
else
return ((extid & (IPCMNI - 1)) - OPEN_MAX) / IPC_SUBSYS_COUNT;
}
#endif /* __CYGSERVER_IPC_H__ */
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