Java example source code file (LinuxUserDefinedFileAttributeView.java)
The LinuxUserDefinedFileAttributeView.java Java example source code
/*
* Copyright (c) 2008, 2013, 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
* questions.
*/
package sun.nio.fs;
import java.nio.file.*;
import java.nio.ByteBuffer;
import java.io.IOException;
import java.util.*;
import sun.misc.Unsafe;
import static sun.nio.fs.UnixConstants.*;
import static sun.nio.fs.LinuxNativeDispatcher.*;
/**
* Linux implementation of UserDefinedFileAttributeView using extended attributes.
*/
class LinuxUserDefinedFileAttributeView
extends AbstractUserDefinedFileAttributeView
{
private static final Unsafe unsafe = Unsafe.getUnsafe();
// namespace for extended user attributes
private static final String USER_NAMESPACE = "user.";
// maximum bytes in extended attribute name (includes namespace)
private static final int XATTR_NAME_MAX = 255;
private byte[] nameAsBytes(UnixPath file, String name) throws IOException {
if (name == null)
throw new NullPointerException("'name' is null");
name = USER_NAMESPACE + name;
byte[] bytes = Util.toBytes(name);
if (bytes.length > XATTR_NAME_MAX) {
throw new FileSystemException(file.getPathForExceptionMessage(),
null, "'" + name + "' is too big");
}
return bytes;
}
// Parses buffer as array of NULL-terminated C strings.
private List<String> asList(long address, int size) {
List<String> list = new ArrayList<>();
int start = 0;
int pos = 0;
while (pos < size) {
if (unsafe.getByte(address + pos) == 0) {
int len = pos - start;
byte[] value = new byte[len];
unsafe.copyMemory(null, address+start, value,
Unsafe.ARRAY_BYTE_BASE_OFFSET, len);
String s = Util.toString(value);
if (s.startsWith(USER_NAMESPACE)) {
s = s.substring(USER_NAMESPACE.length());
list.add(s);
}
start = pos + 1;
}
pos++;
}
return list;
}
private final UnixPath file;
private final boolean followLinks;
LinuxUserDefinedFileAttributeView(UnixPath file, boolean followLinks) {
this.file = file;
this.followLinks = followLinks;
}
@Override
public List<String> list() throws IOException {
if (System.getSecurityManager() != null)
checkAccess(file.getPathForPermissionCheck(), true, false);
int fd = file.openForAttributeAccess(followLinks);
NativeBuffer buffer = null;
try {
int size = 1024;
buffer = NativeBuffers.getNativeBuffer(size);
for (;;) {
try {
int n = flistxattr(fd, buffer.address(), size);
List<String> list = asList(buffer.address(), n);
return Collections.unmodifiableList(list);
} catch (UnixException x) {
// allocate larger buffer if required
if (x.errno() == ERANGE && size < 32*1024) {
buffer.release();
size *= 2;
buffer = null;
buffer = NativeBuffers.getNativeBuffer(size);
continue;
}
throw new FileSystemException(file.getPathForExceptionMessage(),
null, "Unable to get list of extended attributes: " +
x.getMessage());
}
}
} finally {
if (buffer != null)
buffer.release();
close(fd);
}
}
@Override
public int size(String name) throws IOException {
if (System.getSecurityManager() != null)
checkAccess(file.getPathForPermissionCheck(), true, false);
int fd = file.openForAttributeAccess(followLinks);
try {
// fgetxattr returns size if called with size==0
return fgetxattr(fd, nameAsBytes(file,name), 0L, 0);
} catch (UnixException x) {
throw new FileSystemException(file.getPathForExceptionMessage(),
null, "Unable to get size of extended attribute '" + name +
"': " + x.getMessage());
} finally {
close(fd);
}
}
@Override
public int read(String name, ByteBuffer dst) throws IOException {
if (System.getSecurityManager() != null)
checkAccess(file.getPathForPermissionCheck(), true, false);
if (dst.isReadOnly())
throw new IllegalArgumentException("Read-only buffer");
int pos = dst.position();
int lim = dst.limit();
assert (pos <= lim);
int rem = (pos <= lim ? lim - pos : 0);
NativeBuffer nb;
long address;
if (dst instanceof sun.nio.ch.DirectBuffer) {
nb = null;
address = ((sun.nio.ch.DirectBuffer)dst).address() + pos;
} else {
// substitute with native buffer
nb = NativeBuffers.getNativeBuffer(rem);
address = nb.address();
}
int fd = file.openForAttributeAccess(followLinks);
try {
try {
int n = fgetxattr(fd, nameAsBytes(file,name), address, rem);
// if remaining is zero then fgetxattr returns the size
if (rem == 0) {
if (n > 0)
throw new UnixException(ERANGE);
return 0;
}
// copy from buffer into backing array if necessary
if (nb != null) {
int off = dst.arrayOffset() + pos + Unsafe.ARRAY_BYTE_BASE_OFFSET;
unsafe.copyMemory(null, address, dst.array(), off, n);
}
dst.position(pos + n);
return n;
} catch (UnixException x) {
String msg = (x.errno() == ERANGE) ?
"Insufficient space in buffer" : x.getMessage();
throw new FileSystemException(file.getPathForExceptionMessage(),
null, "Error reading extended attribute '" + name + "': " + msg);
} finally {
close(fd);
}
} finally {
if (nb != null)
nb.release();
}
}
@Override
public int write(String name, ByteBuffer src) throws IOException {
if (System.getSecurityManager() != null)
checkAccess(file.getPathForPermissionCheck(), false, true);
int pos = src.position();
int lim = src.limit();
assert (pos <= lim);
int rem = (pos <= lim ? lim - pos : 0);
NativeBuffer nb;
long address;
if (src instanceof sun.nio.ch.DirectBuffer) {
nb = null;
address = ((sun.nio.ch.DirectBuffer)src).address() + pos;
} else {
// substitute with native buffer
nb = NativeBuffers.getNativeBuffer(rem);
address = nb.address();
if (src.hasArray()) {
// copy from backing array into buffer
int off = src.arrayOffset() + pos + Unsafe.ARRAY_BYTE_BASE_OFFSET;
unsafe.copyMemory(src.array(), off, null, address, rem);
} else {
// backing array not accessible so transfer via temporary array
byte[] tmp = new byte[rem];
src.get(tmp);
src.position(pos); // reset position as write may fail
unsafe.copyMemory(tmp, Unsafe.ARRAY_BYTE_BASE_OFFSET, null,
address, rem);
}
}
int fd = file.openForAttributeAccess(followLinks);
try {
try {
fsetxattr(fd, nameAsBytes(file,name), address, rem);
src.position(pos + rem);
return rem;
} catch (UnixException x) {
throw new FileSystemException(file.getPathForExceptionMessage(),
null, "Error writing extended attribute '" + name + "': " +
x.getMessage());
} finally {
close(fd);
}
} finally {
if (nb != null)
nb.release();
}
}
@Override
public void delete(String name) throws IOException {
if (System.getSecurityManager() != null)
checkAccess(file.getPathForPermissionCheck(), false, true);
int fd = file.openForAttributeAccess(followLinks);
try {
fremovexattr(fd, nameAsBytes(file,name));
} catch (UnixException x) {
throw new FileSystemException(file.getPathForExceptionMessage(),
null, "Unable to delete extended attribute '" + name + "': " + x.getMessage());
} finally {
close(fd);
}
}
/**
* Used by copyTo/moveTo to copy extended attributes from source to target.
*
* @param ofd
* file descriptor for source file
* @param nfd
* file descriptor for target file
*/
static void copyExtendedAttributes(int ofd, int nfd) {
NativeBuffer buffer = null;
try {
// call flistxattr to get list of extended attributes.
int size = 1024;
buffer = NativeBuffers.getNativeBuffer(size);
for (;;) {
try {
size = flistxattr(ofd, buffer.address(), size);
break;
} catch (UnixException x) {
// allocate larger buffer if required
if (x.errno() == ERANGE && size < 32*1024) {
buffer.release();
size *= 2;
buffer = null;
buffer = NativeBuffers.getNativeBuffer(size);
continue;
}
// unable to get list of attributes
return;
}
}
// parse buffer as array of NULL-terminated C strings.
long address = buffer.address();
int start = 0;
int pos = 0;
while (pos < size) {
if (unsafe.getByte(address + pos) == 0) {
// extract attribute name and copy attribute to target.
// FIXME: We can avoid needless copying by using address+pos
// as the address of the name.
int len = pos - start;
byte[] name = new byte[len];
unsafe.copyMemory(null, address+start, name,
Unsafe.ARRAY_BYTE_BASE_OFFSET, len);
try {
copyExtendedAttribute(ofd, name, nfd);
} catch (UnixException ignore) {
// ignore
}
start = pos + 1;
}
pos++;
}
} finally {
if (buffer != null)
buffer.release();
}
}
private static void copyExtendedAttribute(int ofd, byte[] name, int nfd)
throws UnixException
{
int size = fgetxattr(ofd, name, 0L, 0);
NativeBuffer buffer = NativeBuffers.getNativeBuffer(size);
try {
long address = buffer.address();
size = fgetxattr(ofd, name, address, size);
fsetxattr(nfd, name, address, size);
} finally {
buffer.release();
}
}
}
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