8030048: (fs) Support UserDefinedFileAttributeView/extended attributes on OS X / HFS+

Reviewed-by: alanb

Author: overheadhunter

src/java.base/macosx/classes/sun/nio/fs/BsdFileStore.java

@@ -77,4 +77,56 @@ UnixMountEntry findMountEntry() throws IOException {
 
         throw new IOException("Mount point not found in fstab");
     }
+
+    // returns true if extended attributes enabled on file system where given
+    // file resides, returns false if disabled or unable to determine.
+    private 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");
+            BsdNativeDispatcher.fgetxattr(fd, name, 0L, 0);
+            return true;
+        } catch (UnixException e) {
+            // attribute does not exist
+            if (e.errno() == UnixConstants.ENOATTR)
+                return true;
+        } finally {
+            UnixNativeDispatcher.close(fd);
+        }
+        return false;
+    }
+
+    @Override
+    public boolean supportsFileAttributeView(Class<? extends FileAttributeView> type) {
+        // support UserDefinedAttributeView if extended attributes enabled
+        if (type == UserDefinedFileAttributeView.class) {
+            // lookup fstypes.properties
+            FeatureStatus status = checkIfFeaturePresent("user_xattr");
+            if (status == FeatureStatus.PRESENT)
+                return true;
+            if (status == FeatureStatus.NOT_PRESENT)
+                return false;
+
+            // typical macOS file system types that are known to support xattr
+            if (entry().fstype().equals("apfs")
+                || entry().fstype().equals("hfs")) {
+                return true;
+            }
+
+            // probe file system capabilities
+            UnixPath dir = new UnixPath(file().getFileSystem(), entry().dir());
+            return isExtendedAttributesEnabled(dir);
+        }
+        return super.supportsFileAttributeView(type);
+    }
+
+    @Override
+    public boolean supportsFileAttributeView(String name) {
+        if (name.equals("user"))
+            return supportsFileAttributeView(UserDefinedFileAttributeView.class);
+        return super.supportsFileAttributeView(name);
+    }
 }

src/java.base/macosx/classes/sun/nio/fs/BsdFileSystem.java

@@ -56,6 +56,8 @@ private static class SupportedFileFileAttributeViewsHolder {
         private static Set<String> supportedFileAttributeViews() {
             Set<String> result = new HashSet<String>();
             result.addAll(standardFileAttributeViews());
+            // additional BSD-specific views
+            result.add("user");
             return Collections.unmodifiableSet(result);
         }
     }

src/java.base/macosx/classes/sun/nio/fs/BsdFileSystemProvider.java

@@ -25,6 +25,8 @@
 
 package sun.nio.fs;
 
+import java.nio.file.*;
+import java.nio.file.attribute.*;
 import java.io.IOException;
 
 /**
@@ -45,4 +47,29 @@ BsdFileSystem newFileSystem(String dir) {
     BsdFileStore getFileStore(UnixPath path) throws IOException {
         return new BsdFileStore(path);
     }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public <V extends FileAttributeView> V getFileAttributeView(Path obj,
+                                                                Class<V> type,
+                                                                LinkOption... options)
+    {
+        if (type == UserDefinedFileAttributeView.class) {
+            return (V) new BsdUserDefinedFileAttributeView(UnixPath.toUnixPath(obj),
+                    Util.followLinks(options));
+        }
+        return super.getFileAttributeView(obj, type, options);
+    }
+
+    @Override
+    public DynamicFileAttributeView getFileAttributeView(Path obj,
+                                                         String name,
+                                                         LinkOption... options)
+    {
+        if (name.equals("user")) {
+            return new BsdUserDefinedFileAttributeView(UnixPath.toUnixPath(obj),
+                    Util.followLinks(options));
+        }
+        return super.getFileAttributeView(obj, name, options);
+    }
 }

src/java.base/macosx/classes/sun/nio/fs/BsdNativeDispatcher.java

@@ -65,6 +65,67 @@ static byte[] getmntonname(UnixPath path) throws UnixException {
     }
     static native byte[] getmntonname0(long pathAddress) throws UnixException;
 
+    /**
+     * ssize_t fgetxattr(int fd, const char *name, void *value, size_t size,
+     *  u_int32_t position, int options);
+     */
+    static int fgetxattr(int fd, byte[] name, long valueAddress,
+                         int valueLen) throws UnixException
+    {
+        NativeBuffer buffer = NativeBuffers.asNativeBuffer(name);
+        try {
+            return fgetxattr0(fd, buffer.address(), valueAddress, valueLen, 0L, 0);
+        } finally {
+            buffer.release();
+        }
+    }
+
+    private static native int fgetxattr0(int fd, long nameAddress,
+        long valueAddress, int valueLen, long position, int options) throws UnixException;
+
+    /**
+     * int fsetxattr(int fd, const char *name, void *value, size_t size,
+     *  u_int32_t position, int options);
+     */
+    static void fsetxattr(int fd, byte[] name, long valueAddress,
+                          int valueLen) throws UnixException
+    {
+        NativeBuffer buffer = NativeBuffers.asNativeBuffer(name);
+        try {
+            fsetxattr0(fd, buffer.address(), valueAddress, valueLen, 0L, 0);
+        } finally {
+            buffer.release();
+        }
+    }
+
+    private static native void fsetxattr0(int fd, long nameAddress,
+        long valueAddress, int valueLen, long position, int options) throws UnixException;
+
+    /**
+     * int fremovexattr(int fd, const char *name, int options);
+     */
+    static void fremovexattr(int fd, byte[] name) throws UnixException {
+        NativeBuffer buffer = NativeBuffers.asNativeBuffer(name);
+        try {
+            fremovexattr0(fd, buffer.address(), 0);
+        } finally {
+            buffer.release();
+        }
+    }
+
+    private static native void fremovexattr0(int fd, long nameAddress, int options)
+        throws UnixException;
+
+    /**
+     * ssize_t flistxattr(int fd, char *namebuf, size_t size, int options);
+     */
+    static int flistxattr(int fd, long nameBufAddress, int size) throws UnixException {
+        return flistxattr0(fd, nameBufAddress, size, 0);
+    }
+
+    private static native int flistxattr0(int fd, long nameBufAddress, int size,
+        int options) throws UnixException;
+
     // initialize field IDs
     private static native void initIDs();