This code is distributed under the GNU Library General Public License
This library is free software; 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.
This library 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 this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ public class SharedMem extends IPC { private CPtr cptr; /** Attach an existing shared memory segment. */ public SharedMem(int key,int flag) throws IPCException { this(key,0,flag); } /** Attach or create a shared memory segment. @param key IPC key or IPC_PRIVATE @param size size of shared memory @param flag options */ public SharedMem(int key,int size,int flag) throws IPCException { id = shmget(key,size,flag); if (id < 0) throw new IPCException("shmget, key=0x" + Integer.toHexString(key)); if (false) { // done by attach() size = getStatus().shm_segsz; long addr = shmat(id,0,0); if (addr == -1L) throw new IPCException("shmat"); cptr = new CPtr(addr,size); } owner = (flag & IPC_CREAT) != 0 || key == IPC_PRIVATE; } public SharedMem(String path,int type) throws IPCException { this(ftok(path,type),0); } static final int SHM_SIZE = 6; // change the size of a segment static final int SHM_RDONLY = 010000; // attach read-only (else read-write) static final int SHM_RND = 020000; // round attach address to SHMLBA /** The modulus for attaching shared memory by logical address. This is system dependent and therefore computed by the class initializer. While attaching shared memory to a specific address is somewhat system dependent, it is easily handled by configuration or property settings. */ public static final long SHMLBA = getLBA(); public static class shmid_ds extends IPC.Perm { shmid_ds(int id) throws IPCException { // only we can create super(id); int rc = shmctl(id,IPC_STAT,this); if (rc != 0) throw new IPCException(String.format("shmctl(%d,IPC_STAT)",id),rc); } public int shm_segsz; /* segment size */ public int shm_lpid; /* pid of last shmop */ public int shm_cpid; /* pid of creator */ public int shm_nattch; /* current # attached */ public int shm_cnattch; /* in memory # attached */ public long shm_atime; /* last shmat time */ public long shm_dtime; /* last shmdt time */ public long shm_ctime; /* last change time */ } private static native long getLBA(); private static native int shmctl(int id,int cmd,shmid_ds buf); private static native long shmat(int id,long addr,int flag); private static native int shmdt(long addr); private static native int shmget(int key,int size,int flag); public shmid_ds getStatus() throws IPCException { int id = this.id; if (id < 0) return null; return new shmid_ds(id); } /** Set the user, group, mode for this IPC data structure. */ public void setPerm(Perm st) throws IPCException { if (!(st instanceof shmid_ds) || st.id != this.id) throw new IllegalArgumentException("Current shmid_ds required."); int rc = shmctl(id,IPC_SET,(shmid_ds)st); if (rc < 0) throw new IPCException("shmctl",rc & 0x7fffffff); } public synchronized CPtr attach() throws IPCException { if (cptr == null) { int size = getStatus().shm_segsz; long addr = shmat(id,0,0); if (addr == -1L) throw new IPCException("shmat"); cptr = new CPtr(addr,size); } return cptr; } public void remove() { if (id >= 0) { shmctl(id,IPC_RMID,null); id = -1; } } public synchronized void dispose() { if (id >= 0) { if (cptr != null) { cptr.size = 0; // prevent further access through cptr shmdt(cptr.addr); cptr.addr = CPtr.NULL; cptr = null; } super.dispose(); } } }