8260966: (fs) Consolidate Linux and macOS implementations of UserDefinedFileAttributeView

8260691: (fs) LinuxNativeDispatcher should link to xattr functions

Reviewed-by: alanb

src/java.base/unix/classes/sun/nio/fs/UnixConstants.java.template

@@ -117,9 +117,14 @@ class UnixConstants {
     static final int PREFIX_ENODATA = ENODATA;
 #endif
 
-#ifdef ENOATTR
-    // BSD uses ENOATTR instead of ENODATA during xattr calls
-    static final int PREFIX_ENOATTR = ENOATTR;
+// fgetxattr error codes for absent attributes depend on the OS:
+#ifdef _ALLBSD_SOURCE
+    static final int PREFIX_XATTR_NOT_FOUND = ENOATTR;
+#elif __linux__
+    static final int PREFIX_XATTR_NOT_FOUND = ENODATA;
+#else
+    // not supported (dummy values will not be used at runtime).
+    static final int PREFIX_XATTR_NOT_FOUND = 00;
 #endif
 
     static final int PREFIX_ERANGE = ERANGE;

src/java.base/unix/classes/sun/nio/fs/UnixFileStore.java

@@ -172,6 +172,31 @@ abstract class UnixFileStore
         throw new UnsupportedOperationException("'" + attribute + "' not recognized");
     }
 
+    /**
+     * Checks whether extended attributes are enabled on the file system where the given file resides.
+     *
+     * @param path A path pointing to an existing node, such as the file system's root
+     * @return <code>true</code> if enabled, <code>false</code> if disabled or unable to determine
+     */
+    protected boolean isExtendedAttributesEnabled(UnixPath path) {
+        int fd = -1;
+        try {
+            fd = path.openForAttributeAccess(false);
+
+            // fgetxattr returns size if called with size==0
+            byte[] name = Util.toBytes("user.java");
+            UnixNativeDispatcher.fgetxattr(fd, name, 0L, 0);
+            return true;
+        } catch (UnixException e) {
+            // attribute does not exist
+            if (e.errno() == UnixConstants.XATTR_NOT_FOUND)
+                return true;
+        } finally {
+            UnixNativeDispatcher.close(fd);
+        }
+        return false;
+    }
+
     @Override
     public boolean supportsFileAttributeView(Class<? extends FileAttributeView> type) {
         if (type == null)

src/java.base/unix/classes/sun/nio/fs/UnixNativeDispatcher.java

@@ -563,6 +563,52 @@ class UnixNativeDispatcher {
      */
     static native byte[] strerror(int errnum);
 
+    /**
+     * ssize_t fgetxattr(int filedes, const char *name, void *value, size_t size);
+     */
+    static int fgetxattr(int filedes, byte[] name, long valueAddress,
+                         int valueLen) throws UnixException
+    {
+        try (NativeBuffer buffer = NativeBuffers.asNativeBuffer(name)) {
+            return fgetxattr0(filedes, buffer.address(), valueAddress, valueLen);
+        }
+    }
+
+    private static native int fgetxattr0(int filedes, long nameAddress,
+        long valueAddress, int valueLen) throws UnixException;
+
+    /**
+     *  fsetxattr(int filedes, const char *name, const void *value, size_t size, int flags);
+     */
+    static void fsetxattr(int filedes, byte[] name, long valueAddress,
+                          int valueLen) throws UnixException
+    {
+        try (NativeBuffer buffer = NativeBuffers.asNativeBuffer(name)) {
+            fsetxattr0(filedes, buffer.address(), valueAddress, valueLen);
+        }
+    }
+
+    private static native void fsetxattr0(int filedes, long nameAddress,
+        long valueAddress, int valueLen) throws UnixException;
+
+    /**
+     * fremovexattr(int filedes, const char *name);
+     */
+    static void fremovexattr(int filedes, byte[] name) throws UnixException {
+        try (NativeBuffer buffer = NativeBuffers.asNativeBuffer(name)) {
+            fremovexattr0(filedes, buffer.address());
+        }
+    }
+
+    private static native void fremovexattr0(int filedes, long nameAddress)
+        throws UnixException;
+
+    /**
+     * size_t flistxattr(int filedes, const char *list, size_t size)
+     */
+    static native int flistxattr(int filedes, long listAddress, int size)
+        throws UnixException;
+
     /**
      * Capabilities
      */

src/java.base/unix/classes/sun/nio/fs/UnixUserDefinedFileAttributeView.java

@@ -0,0 +1,375 @@
+/*
+ * Copyright (c) 2008, 2015, 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 jdk.internal.misc.Unsafe;
+
+import static sun.nio.fs.UnixConstants.*;
+import static sun.nio.fs.UnixNativeDispatcher.*;
+
+/**
+ * Unix implementation of UserDefinedFileAttributeView using extended attributes.
+ */
+abstract class UnixUserDefinedFileAttributeView
+    extends AbstractUserDefinedFileAttributeView
+{
+    private static final Unsafe unsafe = Unsafe.getUnsafe();
+
+    // namespace for extended user attributes
+    private static final String USER_NAMESPACE = "user.";
+
+    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 > maxNameLength()) {
+            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;
+
+    UnixUserDefinedFileAttributeView(UnixPath file, boolean followLinks) {
+        this.file = file;
+        this.followLinks = followLinks;
+    }
+
+    /**
+     * @return the maximum supported length of xattr names (in bytes, including namespace)
+     */
+    protected abstract int maxNameLength();
+
+    @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();
+        }
+    }
+
+    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.
+     *
+     * @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();
+        }
+    }
+}