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