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package sun.nio.fs;

import java.nio.file.*;
import java.nio.ByteBuffer;
import java.io.IOException;
import java.util.*;
import jdk.internal.misc.Unsafe;

import static sun.nio.fs.UnixConstants.*;
import static sun.nio.fs.LinuxNativeDispatcher.*;

Linux implementation of UserDefinedFileAttributeView using extended attributes.
/** * 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 = -1; try { fd = file.openForAttributeAccess(followLinks); } catch (UnixException x) { x.rethrowAsIOException(file); } 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 = -1; try { fd = file.openForAttributeAccess(followLinks); } catch (UnixException x) { x.rethrowAsIOException(file); } 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 = -1; try { fd = file.openForAttributeAccess(followLinks); } catch (UnixException x) { x.rethrowAsIOException(file); } 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 = -1; try { fd = file.openForAttributeAccess(followLinks); } catch (UnixException x) { x.rethrowAsIOException(file); } 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 = -1; try { fd = file.openForAttributeAccess(followLinks); } catch (UnixException x) { x.rethrowAsIOException(file); } 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.
Params:
  • ofd – file descriptor for source file
  • nfd – file descriptor for target file
/** * 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(); } } }