/*
* Copyright (c) 2000, 2006, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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 General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
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*/
package sun.nio.ch;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.RandomAccessFile;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.*;
import java.nio.channels.spi.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Iterator;
import java.util.concurrent.ConcurrentHashMap;
import java.lang.ref.WeakReference;
import java.lang.ref.ReferenceQueue;
import java.lang.reflect.Field;
import java.security.AccessController;
import java.security.PrivilegedAction;
import sun.misc.Cleaner;
import sun.security.action.GetPropertyAction;
public class FileChannelImpl
extends FileChannel
{
// Used to make native read and write calls
private static NativeDispatcher nd;
// Memory allocation size for mapping buffers
private static long allocationGranularity;
// Cached field for MappedByteBuffer.isAMappedBuffer
private static Field isAMappedBufferField;
// File descriptor
private FileDescriptor fd;
// File access mode (immutable)
private boolean writable;
private boolean readable;
private boolean appending;
// Required to prevent finalization of creating stream (immutable)
private Object parent;
// Thread-safe set of IDs of native threads, for signalling
private NativeThreadSet threads = new NativeThreadSet(2);
// Lock for operations involving position and size
private Object positionLock = new Object();
private FileChannelImpl(FileDescriptor fd, boolean readable,
boolean writable, Object parent, boolean append)
{
this.fd = fd;
this.readable = readable;
this.writable = writable;
this.parent = parent;
this.appending = append;
}
// Invoked by getChannel() methods
// of java.io.File{Input,Output}Stream and RandomAccessFile
//
public static FileChannel open(FileDescriptor fd,
boolean readable, boolean writable,
Object parent)
{
return new FileChannelImpl(fd, readable, writable, parent, false);
}
public static FileChannel open(FileDescriptor fd,
boolean readable, boolean writable,
Object parent, boolean append)
{
return new FileChannelImpl(fd, readable, writable, parent, append);
}
private void ensureOpen() throws IOException {
if (!isOpen())
throw new ClosedChannelException();
}
// -- Standard channel operations --
protected void implCloseChannel() throws IOException {
nd.preClose(fd);
threads.signal();
// Invalidate and release any locks that we still hold
if (fileLockTable != null) {
fileLockTable.removeAll( new FileLockTable.Releaser() {
public void release(FileLock fl) throws IOException {
((FileLockImpl)fl).invalidate();
release0(fd, fl.position(), fl.size());
}
});
}
if (parent != null) {
// Close the fd via the parent stream's close method. The parent
// will reinvoke our close method, which is defined in the
// superclass AbstractInterruptibleChannel, but the isOpen logic in
// that method will prevent this method from being reinvoked.
//
if (parent instanceof FileInputStream)
((FileInputStream)parent).close();
else if (parent instanceof FileOutputStream)
((FileOutputStream)parent).close();
else if (parent instanceof RandomAccessFile)
((RandomAccessFile)parent).close();
else
assert false;
} else {
nd.close(fd);
}
}
public int read(ByteBuffer dst) throws IOException {
ensureOpen();
if (!readable)
throw new NonReadableChannelException();
synchronized (positionLock) {
int n = 0;
int ti = -1;
try {
begin();
if (!isOpen())
return 0;
ti = threads.add();
do {
n = IOUtil.read(fd, dst, -1, nd, positionLock);
} while ((n == IOStatus.INTERRUPTED) && isOpen());
return IOStatus.normalize(n);
} finally {
threads.remove(ti);
end(n > 0);
assert IOStatus.check(n);
}
}
}
private long read0(ByteBuffer[] dsts) throws IOException {
ensureOpen();
if (!readable)
throw new NonReadableChannelException();
synchronized (positionLock) {
long n = 0;
int ti = -1;
try {
begin();
if (!isOpen())
return 0;
ti = threads.add();
do {
n = IOUtil.read(fd, dsts, nd);
} while ((n == IOStatus.INTERRUPTED) && isOpen());
return IOStatus.normalize(n);
} finally {
threads.remove(ti);
end(n > 0);
assert IOStatus.check(n);
}
}
}
public long read(ByteBuffer[] dsts, int offset, int length)
throws IOException
{
if ((offset < 0) || (length < 0) || (offset > dsts.length - length))
throw new IndexOutOfBoundsException();
// ## Fix IOUtil.write so that we can avoid this array copy
return read0(Util.subsequence(dsts, offset, length));
}
public int write(ByteBuffer src) throws IOException {
ensureOpen();
if (!writable)
throw new NonWritableChannelException();
synchronized (positionLock) {
int n = 0;
int ti = -1;
try {
begin();
if (!isOpen())
return 0;
ti = threads.add();
if (appending)
position(size());
do {
n = IOUtil.write(fd, src, -1, nd, positionLock);
} while ((n == IOStatus.INTERRUPTED) && isOpen());
return IOStatus.normalize(n);
} finally {
threads.remove(ti);
end(n > 0);
assert IOStatus.check(n);
}
}
}
private long write0(ByteBuffer[] srcs) throws IOException {
ensureOpen();
if (!writable)
throw new NonWritableChannelException();
synchronized (positionLock) {
long n = 0;
int ti = -1;
try {
begin();
if (!isOpen())
return 0;
ti = threads.add();
if (appending)
position(size());
do {
n = IOUtil.write(fd, srcs, nd);
} while ((n == IOStatus.INTERRUPTED) && isOpen());
return IOStatus.normalize(n);
} finally {
threads.remove(ti);
end(n > 0);
assert IOStatus.check(n);
}
}
}
public long write(ByteBuffer[] srcs, int offset, int length)
throws IOException
{
if ((offset < 0) || (length < 0) || (offset > srcs.length - length))
throw new IndexOutOfBoundsException();
// ## Fix IOUtil.write so that we can avoid this array copy
return write0(Util.subsequence(srcs, offset, length));
}
// -- Other operations --
public long position() throws IOException {
ensureOpen();
synchronized (positionLock) {
long p = -1;
int ti = -1;
try {
begin();
if (!isOpen())
return 0;
ti = threads.add();
do {
p = position0(fd, -1);
} while ((p == IOStatus.INTERRUPTED) && isOpen());
return IOStatus.normalize(p);
} finally {
threads.remove(ti);
end(p > -1);
assert IOStatus.check(p);
}
}
}
public FileChannel position(long newPosition) throws IOException {
ensureOpen();
if (newPosition < 0)
throw new IllegalArgumentException();
synchronized (positionLock) {
long p = -1;
int ti = -1;
try {
begin();
if (!isOpen())
return null;
ti = threads.add();
do {
p = position0(fd, newPosition);
} while ((p == IOStatus.INTERRUPTED) && isOpen());
return this;
} finally {
threads.remove(ti);
end(p > -1);
assert IOStatus.check(p);
}
}
}
public long size() throws IOException {
ensureOpen();
synchronized (positionLock) {
long s = -1;
int ti = -1;
try {
begin();
if (!isOpen())
return -1;
ti = threads.add();
do {
s = size0(fd);
} while ((s == IOStatus.INTERRUPTED) && isOpen());
return IOStatus.normalize(s);
} finally {
threads.remove(ti);
end(s > -1);
assert IOStatus.check(s);
}
}
}
public FileChannel truncate(long size) throws IOException {
ensureOpen();
if (size < 0)
throw new IllegalArgumentException();
if (size > size())
return this;
if (!writable)
throw new NonWritableChannelException();
synchronized (positionLock) {
int rv = -1;
long p = -1;
int ti = -1;
try {
begin();
if (!isOpen())
return null;
ti = threads.add();
// get current position
do {
p = position0(fd, -1);
} while ((p == IOStatus.INTERRUPTED) && isOpen());
if (!isOpen())
return null;
assert p >= 0;
// truncate file
do {
rv = truncate0(fd, size);
} while ((rv == IOStatus.INTERRUPTED) && isOpen());
if (!isOpen())
return null;
// set position to size if greater than size
if (p > size)
p = size;
do {
rv = (int)position0(fd, p);
} while ((rv == IOStatus.INTERRUPTED) && isOpen());
return this;
} finally {
threads.remove(ti);
end(rv > -1);
assert IOStatus.check(rv);
}
}
}
public void force(boolean metaData) throws IOException {
ensureOpen();
int rv = -1;
int ti = -1;
try {
begin();
if (!isOpen())
return;
ti = threads.add();
do {
rv = force0(fd, metaData);
} while ((rv == IOStatus.INTERRUPTED) && isOpen());
} finally {
threads.remove(ti);
end(rv > -1);
assert IOStatus.check(rv);
}
}
// Assume at first that the underlying kernel supports sendfile();
// set this to false if we find out later that it doesn't
//
private static volatile boolean transferSupported = true;
// Assume that the underlying kernel sendfile() will work if the target
// fd is a pipe; set this to false if we find out later that it doesn't
//
private static volatile boolean pipeSupported = true;
// Assume that the underlying kernel sendfile() will work if the target
// fd is a file; set this to false if we find out later that it doesn't
//
private static volatile boolean fileSupported = true;
private long transferToDirectly(long position, int icount,
WritableByteChannel target)
throws IOException
{
if (!transferSupported)
return IOStatus.UNSUPPORTED;
FileDescriptor targetFD = null;
if (target instanceof FileChannelImpl) {
if (!fileSupported)
return IOStatus.UNSUPPORTED_CASE;
targetFD = ((FileChannelImpl)target).fd;
} else if (target instanceof SelChImpl) {
// Direct transfer to pipe causes EINVAL on some configurations
if ((target instanceof SinkChannelImpl) && !pipeSupported)
return IOStatus.UNSUPPORTED_CASE;
targetFD = ((SelChImpl)target).getFD();
}
if (targetFD == null)
return IOStatus.UNSUPPORTED;
int thisFDVal = IOUtil.fdVal(fd);
int targetFDVal = IOUtil.fdVal(targetFD);
if (thisFDVal == targetFDVal) // Not supported on some configurations
return IOStatus.UNSUPPORTED;
long n = -1;
int ti = -1;
try {
begin();
if (!isOpen())
return -1;
ti = threads.add();
do {
n = transferTo0(thisFDVal, position, icount, targetFDVal);
} while ((n == IOStatus.INTERRUPTED) && isOpen());
if (n == IOStatus.UNSUPPORTED_CASE) {
if (target instanceof SinkChannelImpl)
pipeSupported = false;
if (target instanceof FileChannelImpl)
fileSupported = false;
return IOStatus.UNSUPPORTED_CASE;
}
if (n == IOStatus.UNSUPPORTED) {
// Don't bother trying again
transferSupported = false;
return IOStatus.UNSUPPORTED;
}
return IOStatus.normalize(n);
} finally {
threads.remove(ti);
end (n > -1);
}
}
private long transferToTrustedChannel(long position, int icount,
WritableByteChannel target)
throws IOException
{
if ( !((target instanceof FileChannelImpl)
|| (target instanceof SelChImpl)))
return IOStatus.UNSUPPORTED;
// Trusted target: Use a mapped buffer
MappedByteBuffer dbb = null;
try {
dbb = map(MapMode.READ_ONLY, position, icount);
// ## Bug: Closing this channel will not terminate the write
return target.write(dbb);
} finally {
if (dbb != null)
unmap(dbb);
}
}
private long transferToArbitraryChannel(long position, int icount,
WritableByteChannel target)
throws IOException
{
// Untrusted target: Use a newly-erased buffer
int c = Math.min(icount, TRANSFER_SIZE);
ByteBuffer bb = Util.getTemporaryDirectBuffer(c);
long tw = 0; // Total bytes written
long pos = position;
try {
Util.erase(bb);
while (tw < icount) {
bb.limit(Math.min((int)(icount - tw), TRANSFER_SIZE));
int nr = read(bb, pos);
if (nr <= 0)
break;
bb.flip();
// ## Bug: Will block writing target if this channel
// ## is asynchronously closed
int nw = target.write(bb);
tw += nw;
if (nw != nr)
break;
pos += nw;
bb.clear();
}
return tw;
} catch (IOException x) {
if (tw > 0)
return tw;
throw x;
} finally {
Util.releaseTemporaryDirectBuffer(bb);
}
}
public long transferTo(long position, long count,
WritableByteChannel target)
throws IOException
{
ensureOpen();
if (!target.isOpen())
throw new ClosedChannelException();
if (!readable)
throw new NonReadableChannelException();
if (target instanceof FileChannelImpl &&
!((FileChannelImpl)target).writable)
throw new NonWritableChannelException();
if ((position < 0) || (count < 0))
throw new IllegalArgumentException();
long sz = size();
if (position > sz)
return 0;
int icount = (int)Math.min(count, Integer.MAX_VALUE);
if ((sz - position) < icount)
icount = (int)(sz - position);
long n;
// Attempt a direct transfer, if the kernel supports it
if ((n = transferToDirectly(position, icount, target)) >= 0)
return n;
// Attempt a mapped transfer, but only to trusted channel types
if ((n = transferToTrustedChannel(position, icount, target)) >= 0)
return n;
// Slow path for untrusted targets
return transferToArbitraryChannel(position, icount, target);
}
private long transferFromFileChannel(FileChannelImpl src,
long position, long count)
throws IOException
{
// Note we could loop here to accumulate more at once
synchronized (src.positionLock) {
long p = src.position();
int icount = (int)Math.min(Math.min(count, Integer.MAX_VALUE),
src.size() - p);
// ## Bug: Closing this channel will not terminate the write
MappedByteBuffer bb = src.map(MapMode.READ_ONLY, p, icount);
try {
long n = write(bb, position);
src.position(p + n);
return n;
} finally {
unmap(bb);
}
}
}
private static final int TRANSFER_SIZE = 8192;
private long transferFromArbitraryChannel(ReadableByteChannel src,
long position, long count)
throws IOException
{
// Untrusted target: Use a newly-erased buffer
int c = (int)Math.min(count, TRANSFER_SIZE);
ByteBuffer bb = Util.getTemporaryDirectBuffer(c);
long tw = 0; // Total bytes written
long pos = position;
try {
Util.erase(bb);
while (tw < count) {
bb.limit((int)Math.min((count - tw), (long)TRANSFER_SIZE));
// ## Bug: Will block reading src if this channel
// ## is asynchronously closed
int nr = src.read(bb);
if (nr <= 0)
break;
bb.flip();
int nw = write(bb, pos);
tw += nw;
if (nw != nr)
break;
pos += nw;
bb.clear();
}
return tw;
} catch (IOException x) {
if (tw > 0)
return tw;
throw x;
} finally {
Util.releaseTemporaryDirectBuffer(bb);
}
}
public long transferFrom(ReadableByteChannel src,
long position, long count)
throws IOException
{
ensureOpen();
if (!src.isOpen())
throw new ClosedChannelException();
if (!writable)
throw new NonWritableChannelException();
if ((position < 0) || (count < 0))
throw new IllegalArgumentException();
if (position > size())
return 0;
if (src instanceof FileChannelImpl)
return transferFromFileChannel((FileChannelImpl)src,
position, count);
return transferFromArbitraryChannel(src, position, count);
}
public int read(ByteBuffer dst, long position) throws IOException {
if (dst == null)
throw new NullPointerException();
if (position < 0)
throw new IllegalArgumentException("Negative position");
if (!readable)
throw new NonReadableChannelException();
ensureOpen();
int n = 0;
int ti = -1;
try {
begin();
if (!isOpen())
return -1;
ti = threads.add();
do {
n = IOUtil.read(fd, dst, position, nd, positionLock);
} while ((n == IOStatus.INTERRUPTED) && isOpen());
return IOStatus.normalize(n);
} finally {
threads.remove(ti);
end(n > 0);
assert IOStatus.check(n);
}
}
public int write(ByteBuffer src, long position) throws IOException {
if (src == null)
throw new NullPointerException();
if (position < 0)
throw new IllegalArgumentException("Negative position");
if (!writable)
throw new NonWritableChannelException();
ensureOpen();
int n = 0;
int ti = -1;
try {
begin();
if (!isOpen())
return -1;
ti = threads.add();
do {
n = IOUtil.write(fd, src, position, nd, positionLock);
} while ((n == IOStatus.INTERRUPTED) && isOpen());
return IOStatus.normalize(n);
} finally {
threads.remove(ti);
end(n > 0);
assert IOStatus.check(n);
}
}
// -- Memory-mapped buffers --
private static class Unmapper
implements Runnable
{
private long address;
private long size;
private Unmapper(long address, long size) {
assert (address != 0);
this.address = address;
this.size = size;
}
public void run() {
if (address == 0)
return;
unmap0(address, size);
address = 0;
}
}
private static void unmap(MappedByteBuffer bb) {
Cleaner cl = ((DirectBuffer)bb).cleaner();
if (cl != null)
cl.clean();
}
private static final int MAP_RO = 0;
private static final int MAP_RW = 1;
private static final int MAP_PV = 2;
public MappedByteBuffer map(MapMode mode, long position, long size)
throws IOException
{
ensureOpen();
if (position < 0L)
throw new IllegalArgumentException("Negative position");
if (size < 0L)
throw new IllegalArgumentException("Negative size");
if (position + size < 0)
throw new IllegalArgumentException("Position + size overflow");
if (size > Integer.MAX_VALUE)
throw new IllegalArgumentException("Size exceeds Integer.MAX_VALUE");
int imode = -1;
if (mode == MapMode.READ_ONLY)
imode = MAP_RO;
else if (mode == MapMode.READ_WRITE)
imode = MAP_RW;
else if (mode == MapMode.PRIVATE)
imode = MAP_PV;
assert (imode >= 0);
if ((mode != MapMode.READ_ONLY) && !writable)
throw new NonWritableChannelException();
if (!readable)
throw new NonReadableChannelException();
long addr = -1;
int ti = -1;
try {
begin();
if (!isOpen())
return null;
ti = threads.add();
if (size() < position + size) { // Extend file size
if (!writable) {
throw new IOException("Channel not open for writing " +
"- cannot extend file to required size");
}
int rv;
do {
rv = truncate0(fd, position + size);
} while ((rv == IOStatus.INTERRUPTED) && isOpen());
}
if (size == 0) {
addr = 0;
if ((!writable) || (imode == MAP_RO))
return Util.newMappedByteBufferR(0, 0, null);
else
return Util.newMappedByteBuffer(0, 0, null);
}
int pagePosition = (int)(position % allocationGranularity);
long mapPosition = position - pagePosition;
long mapSize = size + pagePosition;
try {
// If no exception was thrown from map0, the address is valid
addr = map0(imode, mapPosition, mapSize);
} catch (OutOfMemoryError x) {
// An OutOfMemoryError may indicate that we've exhausted memory
// so force gc and re-attempt map
System.gc();
try {
Thread.sleep(100);
} catch (InterruptedException y) {
Thread.currentThread().interrupt();
}
try {
addr = map0(imode, mapPosition, mapSize);
} catch (OutOfMemoryError y) {
// After a second OOME, fail
throw new IOException("Map failed", y);
}
}
assert (IOStatus.checkAll(addr));
assert (addr % allocationGranularity == 0);
int isize = (int)size;
Unmapper um = new Unmapper(addr, size + pagePosition);
if ((!writable) || (imode == MAP_RO))
return Util.newMappedByteBufferR(isize, addr + pagePosition, um);
else
return Util.newMappedByteBuffer(isize, addr + pagePosition, um);
} finally {
threads.remove(ti);
end(IOStatus.checkAll(addr));
}
}
// -- Locks --
public static final int NO_LOCK = -1; // Failed to lock
public static final int LOCKED = 0; // Obtained requested lock
public static final int RET_EX_LOCK = 1; // Obtained exclusive lock
public static final int INTERRUPTED = 2; // Request interrupted
// keeps track of locks on this file
private volatile FileLockTable fileLockTable;
// indicates if file locks are maintained system-wide (as per spec)
private static boolean isSharedFileLockTable;
// indicates if the disableSystemWideOverlappingFileLockCheck property
// has been checked
private static volatile boolean propertyChecked;
// The lock list in J2SE 1.4/5.0 was local to each FileChannel instance so
// the overlap check wasn't system wide when there were multiple channels to
// the same file. This property is used to get 1.4/5.0 behavior if desired.
private static boolean isSharedFileLockTable() {
if (!propertyChecked) {
synchronized (FileChannelImpl.class) {
if (!propertyChecked) {
String value = AccessController.doPrivileged(
new GetPropertyAction(
"sun.nio.ch.disableSystemWideOverlappingFileLockCheck"));
isSharedFileLockTable = ((value == null) || value.equals("false"));
propertyChecked = true;
}
}
}
return isSharedFileLockTable;
}
private FileLockTable fileLockTable() {
if (fileLockTable == null) {
synchronized (this) {
if (fileLockTable == null) {
fileLockTable = isSharedFileLockTable() ?
new SharedFileLockTable(this) : new SimpleFileLockTable();
}
}
}
return fileLockTable;
}
public FileLock lock(long position, long size, boolean shared)
throws IOException
{
ensureOpen();
if (shared && !readable)
throw new NonReadableChannelException();
if (!shared && !writable)
throw new NonWritableChannelException();
FileLockImpl fli = new FileLockImpl(this, position, size, shared);
FileLockTable flt = fileLockTable();
flt.add(fli);
boolean i = true;
int ti = -1;
try {
begin();
if (!isOpen())
return null;
ti = threads.add();
int result = lock0(fd, true, position, size, shared);
if (result == RET_EX_LOCK) {
assert shared;
FileLockImpl fli2 = new FileLockImpl(this, position, size,
false);
flt.replace(fli, fli2);
return fli2;
}
if (result == INTERRUPTED || result == NO_LOCK) {
flt.remove(fli);
i = false;
}
} catch (IOException e) {
flt.remove(fli);
throw e;
} finally {
threads.remove(ti);
try {
end(i);
} catch (ClosedByInterruptException e) {
throw new FileLockInterruptionException();
}
}
return fli;
}
public FileLock tryLock(long position, long size, boolean shared)
throws IOException
{
ensureOpen();
if (shared && !readable)
throw new NonReadableChannelException();
if (!shared && !writable)
throw new NonWritableChannelException();
FileLockImpl fli = new FileLockImpl(this, position, size, shared);
FileLockTable flt = fileLockTable();
flt.add(fli);
int result = lock0(fd, false, position, size, shared);
if (result == NO_LOCK) {
flt.remove(fli);
return null;
}
if (result == RET_EX_LOCK) {
assert shared;
FileLockImpl fli2 = new FileLockImpl(this, position, size,
false);
flt.replace(fli, fli2);
return fli2;
}
return fli;
}
void release(FileLockImpl fli) throws IOException {
ensureOpen();
release0(fd, fli.position(), fli.size());
assert fileLockTable != null;
fileLockTable.remove(fli);
}
// -- File lock support --
/**
* A table of FileLocks.
*/
private interface FileLockTable {
/**
* Adds a file lock to the table.
*
* @throws OverlappingFileLockException if the file lock overlaps
* with an existing file lock in the table
*/
void add(FileLock fl) throws OverlappingFileLockException;
/**
* Remove an existing file lock from the table.
*/
void remove(FileLock fl);
/**
* An implementation of this interface releases a given file lock.
* Used with removeAll.
*/
interface Releaser {
void release(FileLock fl) throws IOException;
}
/**
* Removes all file locks from the table.
* <p>
* The Releaser#release method is invoked for each file lock before
* it is removed.
*
* @throws IOException if the release method throws IOException
*/
void removeAll(Releaser r) throws IOException;
/**
* Replaces an existing file lock in the table.
*/
void replace(FileLock fl1, FileLock fl2);
}
/**
* A simple file lock table that maintains a list of FileLocks obtained by a
* FileChannel. Use to get 1.4/5.0 behaviour.
*/
private static class SimpleFileLockTable implements FileLockTable {
// synchronize on list for access
private List<FileLock> lockList = new ArrayList<FileLock>(2);
public SimpleFileLockTable() {
}
private void checkList(long position, long size)
throws OverlappingFileLockException
{
assert Thread.holdsLock(lockList);
for (FileLock fl: lockList) {
if (fl.overlaps(position, size)) {
throw new OverlappingFileLockException();
}
}
}
public void add(FileLock fl) throws OverlappingFileLockException {
synchronized (lockList) {
checkList(fl.position(), fl.size());
lockList.add(fl);
}
}
public void remove(FileLock fl) {
synchronized (lockList) {
lockList.remove(fl);
}
}
public void removeAll(Releaser releaser) throws IOException {
synchronized(lockList) {
Iterator<FileLock> i = lockList.iterator();
while (i.hasNext()) {
FileLock fl = i.next();
releaser.release(fl);
i.remove();
}
}
}
public void replace(FileLock fl1, FileLock fl2) {
synchronized (lockList) {
lockList.remove(fl1);
lockList.add(fl2);
}
}
}
/**
* A weak reference to a FileLock.
* <p>
* SharedFileLockTable uses a list of file lock references to avoid keeping the
* FileLock (and FileChannel) alive.
*/
private static class FileLockReference extends WeakReference<FileLock> {
private FileKey fileKey;
FileLockReference(FileLock referent,
ReferenceQueue queue,
FileKey key) {
super(referent, queue);
this.fileKey = key;
}
private FileKey fileKey() {
return fileKey;
}
}
/**
* A file lock table that is over a system-wide map of all file locks.
*/
private static class SharedFileLockTable implements FileLockTable {
// The system-wide map is a ConcurrentHashMap that is keyed on the FileKey.
// The map value is a list of file locks represented by FileLockReferences.
// All access to the list must be synchronized on the list.
private static ConcurrentHashMap<FileKey, ArrayList<FileLockReference>> lockMap =
new ConcurrentHashMap<FileKey, ArrayList<FileLockReference>>();
// reference queue for cleared refs
private static ReferenceQueue queue = new ReferenceQueue();
// the enclosing file channel
private FileChannelImpl fci;
// File key for the file that this channel is connected to
private FileKey fileKey;
public SharedFileLockTable(FileChannelImpl fci) {
this.fci = fci;
this.fileKey = FileKey.create(fci.fd);
}
public void add(FileLock fl) throws OverlappingFileLockException {
ArrayList<FileLockReference> list = lockMap.get(fileKey);
for (;;) {
// The key isn't in the map so we try to create it atomically
if (list == null) {
list = new ArrayList<FileLockReference>(2);
ArrayList<FileLockReference> prev;
synchronized (list) {
prev = lockMap.putIfAbsent(fileKey, list);
if (prev == null) {
// we successfully created the key so we add the file lock
list.add(new FileLockReference(fl, queue, fileKey));
break;
}
}
// someone else got there first
list = prev;
}
// There is already a key. It is possible that some other thread
// is removing it so we re-fetch the value from the map. If it
// hasn't changed then we check the list for overlapping locks
// and add the new lock to the list.
synchronized (list) {
ArrayList<FileLockReference> current = lockMap.get(fileKey);
if (list == current) {
checkList(list, fl.position(), fl.size());
list.add(new FileLockReference(fl, queue, fileKey));
break;
}
list = current;
}
}
// process any stale entries pending in the reference queue
removeStaleEntries();
}
private void removeKeyIfEmpty(FileKey fk, ArrayList<FileLockReference> list) {
assert Thread.holdsLock(list);
assert lockMap.get(fk) == list;
if (list.isEmpty()) {
lockMap.remove(fk);
}
}
public void remove(FileLock fl) {
assert fl != null;
// the lock must exist so the list of locks must be present
ArrayList<FileLockReference> list = lockMap.get(fileKey);
assert list != null;
synchronized (list) {
int index = 0;
while (index < list.size()) {
FileLockReference ref = list.get(index);
FileLock lock = ref.get();
if (lock == fl) {
assert (lock != null) && (lock.channel() == fci);
ref.clear();
list.remove(index);
break;
}
index++;
}
}
}
public void removeAll(Releaser releaser) throws IOException {
ArrayList<FileLockReference> list = lockMap.get(fileKey);
if (list != null) {
synchronized (list) {
int index = 0;
while (index < list.size()) {
FileLockReference ref = list.get(index);
FileLock lock = ref.get();
// remove locks obtained by this channel
if (lock != null && lock.channel() == fci) {
// invoke the releaser to invalidate/release the lock
releaser.release(lock);
// remove the lock from the list
ref.clear();
list.remove(index);
} else {
index++;
}
}
// once the lock list is empty we remove it from the map
removeKeyIfEmpty(fileKey, list);
}
}
}
public void replace(FileLock fromLock, FileLock toLock) {
// the lock must exist so there must be a list
ArrayList<FileLockReference> list = lockMap.get(fileKey);
assert list != null;
synchronized (list) {
for (int index=0; index<list.size(); index++) {
FileLockReference ref = list.get(index);
FileLock lock = ref.get();
if (lock == fromLock) {
ref.clear();
list.set(index, new FileLockReference(toLock, queue, fileKey));
break;
}
}
}
}
// Check for overlapping file locks
private void checkList(List<FileLockReference> list, long position, long size)
throws OverlappingFileLockException
{
assert Thread.holdsLock(list);
for (FileLockReference ref: list) {
FileLock fl = ref.get();
if (fl != null && fl.overlaps(position, size))
throw new OverlappingFileLockException();
}
}
// Process the reference queue
private void removeStaleEntries() {
FileLockReference ref;
while ((ref = (FileLockReference)queue.poll()) != null) {
FileKey fk = ref.fileKey();
ArrayList<FileLockReference> list = lockMap.get(fk);
if (list != null) {
synchronized (list) {
list.remove(ref);
removeKeyIfEmpty(fk, list);
}
}
}
}
}
// -- Native methods --
// Grabs a file lock
native int lock0(FileDescriptor fd, boolean blocking, long pos, long size,
boolean shared) throws IOException;
// Releases a file lock
native void release0(FileDescriptor fd, long pos, long size)
throws IOException;
// Creates a new mapping
private native long map0(int prot, long position, long length)
throws IOException;
// Removes an existing mapping
private static native int unmap0(long address, long length);
// Forces output to device
private native int force0(FileDescriptor fd, boolean metaData);
// Truncates a file
private native int truncate0(FileDescriptor fd, long size);
// Transfers from src to dst, or returns -2 if kernel can't do that
private native long transferTo0(int src, long position, long count, int dst);
// Sets or reports this file's position
// If offset is -1, the current position is returned
// otherwise the position is set to offset
private native long position0(FileDescriptor fd, long offset);
// Reports this file's size
private native long size0(FileDescriptor fd);
// Caches fieldIDs
private static native long initIDs();
static {
Util.load();
allocationGranularity = initIDs();
nd = new FileDispatcher();
isAMappedBufferField = Reflect.lookupField("java.nio.MappedByteBuffer",
"isAMappedBuffer");
}
}