vfs: add IO read/write methods that accept ByteBuffer

Motivation:
The use of ByteBuffer for IO operations adds more flexibility as ByteBuffers
can be sliced, shared and passed directly to various channels. Moreover, any
byte array can be easily wrapped into ByteBuffer, if needed.

Modification:
added vfs#read and vfs#write methods with default implementation falling
back to byte array based methods to maintain backward compatibility. Updated
OperationREAD and OperationWRITE to use the new methods. Deprecate byte
array based methods.

Result:
more flexibility with same functionality.

Acked-by: Paul Millar
Target: master

core/src/main/java/org/dcache/nfs/v4/OperationREAD.java

@@ -73,18 +73,12 @@ public void process(CompoundContext context, nfs_resop4 result) throws IOExcepti
 
         ByteBuffer buf = ByteBuffer.allocate(count);
 
-        int bytesReaded = context.getFs().read(context.currentInode(),
-                buf.array(), offset, count);
+        int bytesReaded = context.getFs().read(context.currentInode(), buf, offset);
         if (bytesReaded < 0) {
             throw new NfsIoException("IO not allowd");
         }
 
-        /*
-         * As we have written directly into back-end byte array tell the byte
-         * buffer where the limit is.
-         */
-        buf.limit(bytesReaded);
-
+        buf.flip();
         res.status = nfsstat.NFS_OK;
         res.resok4 = new READ4resok();
 

core/src/main/java/org/dcache/nfs/v4/OperationWRITE.java

@@ -75,12 +75,8 @@ public void process(CompoundContext context, nfs_resop4 result) throws ChimeraNF
         }
 
         long offset = _args.opwrite.offset.value;
-        int count = _args.opwrite.data.remaining();
-        byte[] data = new byte[count];
-        _args.opwrite.data.get(data);
-
         VirtualFileSystem.WriteResult writeResult = context.getFs().write(context.currentInode(),
-                data, offset, count, VirtualFileSystem.StabilityLevel.fromStableHow(_args.opwrite.stable));
+                _args.opwrite.data, offset, VirtualFileSystem.StabilityLevel.fromStableHow(_args.opwrite.stable));
 
         if (writeResult.getBytesWritten() < 0) {
             throw new NfsIoException("IO not allowed");

core/src/main/java/org/dcache/nfs/vfs/ForwardingFileSystem.java

@@ -20,6 +20,7 @@
 package org.dcache.nfs.vfs;
 
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import javax.security.auth.Subject;
 import org.dcache.nfs.v4.NfsIdMapping;
 import org.dcache.nfs.v4.xdr.nfsace4;
@@ -95,6 +96,11 @@ public int read(Inode inode, byte[] data, long offset, int count) throws IOExcep
         return delegate().read(inode, data, offset, count);
     }
 
+    @Override
+    public int read(Inode inode, ByteBuffer data, long offset) throws IOException {
+        return delegate().read(inode, data, offset);
+    }
+
     @Override
     public String readlink(Inode inode) throws IOException {
         return delegate().readlink(inode);
@@ -115,6 +121,11 @@ public WriteResult write(Inode inode, byte[] data, long offset, int count, Stabi
         return delegate().write(inode, data, offset, count, stabilityLevel);
     }
 
+    @Override
+    public WriteResult write(Inode inode, ByteBuffer data, long offset, StabilityLevel stabilityLevel) throws IOException {
+        return delegate().write(inode, data, offset, stabilityLevel);
+    }
+
     @Override
     public void commit(Inode inode, long offset, int count) throws IOException {
         delegate().commit(inode, offset, count);

core/src/main/java/org/dcache/nfs/vfs/PseudoFs.java

@@ -22,6 +22,7 @@
 import com.google.common.base.Splitter;
 import java.io.IOException;
 import java.net.InetAddress;
+import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashSet;
@@ -281,6 +282,12 @@ public int read(Inode inode, byte[] data, long offset, int count) throws IOExcep
         return _inner.read(inode, data, offset, count);
     }
 
+    @Override
+    public int read(Inode inode, ByteBuffer data, long offset) throws IOException {
+        checkAccess(inode, ACE4_READ_DATA);
+        return _inner.read(inode, data, offset);
+    }
+
     @Override
     public String readlink(Inode inode) throws IOException {
         checkAccess(inode, ACE4_READ_DATA);
@@ -318,6 +325,12 @@ public WriteResult write(Inode inode, byte[] data, long offset, int count, Stabi
         return _inner.write(inode, data, offset, count, stabilityLevel);
     }
 
+    @Override
+    public WriteResult write(Inode inode, ByteBuffer data, long offset, StabilityLevel stabilityLevel) throws IOException {
+        checkAccess(inode, ACE4_WRITE_DATA);
+        return _inner.write(inode, data, offset, stabilityLevel);
+    }
+
     @Override
     public Stat getattr(Inode inode) throws IOException {
         checkAccess(inode, ACE4_READ_ATTRIBUTES);

core/src/main/java/org/dcache/nfs/vfs/VirtualFileSystem.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009 - 2019 Deutsches Elektronen-Synchroton,
+ * Copyright (c) 2009 - 2020 Deutsches Elektronen-Synchroton,
  * Member of the Helmholtz Association, (DESY), HAMBURG, GERMANY
  *
  * This library is free software; you can redistribute it and/or modify
@@ -20,6 +20,7 @@
 package org.dcache.nfs.vfs;
 
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import javax.security.auth.Subject;
 import org.dcache.nfs.status.NotSuppException;
 import org.dcache.nfs.v4.NfsIdMapping;
@@ -177,9 +178,31 @@ public interface VirtualFileSystem {
      * @return number of bytes read from the file, possibly zero. -1 if EOF is
      * reached.
      * @throws IOException
+     * @deprecated instead use the {@code read(Inode inode, ByteBuffer data, long offset)}
      */
+    @Deprecated
     int read(Inode inode, byte[] data, long offset, int count) throws IOException;
 
+    /**
+     * Read data from file with a given inode into {@code data}.
+     *
+     * @param inode inode of the file to read from.
+     * @param data byte array for writing.
+     * @param offset file's position to read from.
+     * @return number of bytes read from the file, possibly zero. -1 if EOF is
+     * reached.
+     * @throws IOException
+     */
+    default int read(Inode inode, ByteBuffer data, long offset) throws IOException {
+        ByteBuffer buf = ByteBuffer.allocate(data.remaining());
+        int n = read(inode, buf.array(), offset, buf.remaining());
+        if (n > 0) {
+            buf.limit(n);
+            data.put(buf);
+        }
+        return n;
+    }
+
     /**
      * Get value of a symbolic link object.
      *
@@ -222,12 +245,31 @@ public interface VirtualFileSystem {
      * @param stabilityLevel data stability level.
      * @return write result.
      * @throws IOException
+     * @deprecated instead use the {@code write(Inode inode, ByteBuffer data, long offset, StabilityLevel stabilityLevel)}
      */
+    @Deprecated
     WriteResult write(Inode inode, byte[] data, long offset, int count, StabilityLevel stabilityLevel) throws IOException;
 
+    /**
+     * Write provided {@code data} into inode with a given stability level.
+     *
+     * @param inode inode of the file to write.
+     * @param data data to be written.
+     * @param offset the file position to begin writing at.
+     * @param stabilityLevel data stability level.
+     * @return write result.
+     * @throws IOException
+     */
+    default WriteResult write(Inode inode, ByteBuffer data, long offset, StabilityLevel stabilityLevel) throws IOException {
+        int count = data.remaining();
+        byte[] bytes = new byte[count];
+        data.get(bytes);
+        return write(inode, bytes, offset, count, stabilityLevel);
+    }
+
     /**
      * Flush data in {@code dirty} state to the stable storage. Typically
-     * follows {@link #write()} operation.
+     * follows {@link #write(Inode, ByteBuffer, long, StabilityLevel)} operation.
      *
      * @param inode inode of the file to commit.
      * @param offset the file position to start commit at.

core/src/test/java/org/dcache/nfs/v4/OperationWRITETest.java

@@ -54,7 +54,7 @@ public void testLeaseUpdateForV40Client() throws UnknownHostException, ChimeraNF
         NFSv4StateHandler stateHandler = mock(NFSv4StateHandler.class);
 
         when(vfs.getattr(any())).thenReturn(fileStat);
-        when(vfs.write(any(), any(), anyLong(), anyInt(), any()))
+        when(vfs.write(any(), any(), anyLong(), any()))
                 .thenReturn(new VirtualFileSystem.WriteResult(VirtualFileSystem.StabilityLevel.UNSTABLE, 1));
 
         COMPOUND4args writeArgs = new CompoundBuilder()
@@ -80,7 +80,7 @@ public void testNoLeaseUpdateForV41Client() throws UnknownHostException, Chimera
         NFSv4StateHandler stateHandler = mock(NFSv4StateHandler.class);
 
         when(vfs.getattr(any())).thenReturn(fileStat);
-        when(vfs.write(any(), any(), anyLong(), anyInt(), any()))
+        when(vfs.write(any(), any(), anyLong(), any()))
                 .thenReturn(new VirtualFileSystem.WriteResult(VirtualFileSystem.StabilityLevel.UNSTABLE, 1));
 
         COMPOUND4args writeArgs = new CompoundBuilder()
@@ -107,7 +107,7 @@ public void testReturnWriteVerifier() throws UnknownHostException, ChimeraNFSExc
         verifier4 verifier = mock(verifier4.class);
 
         when(vfs.getattr(any())).thenReturn(fileStat);
-        when(vfs.write(any(), any(), anyLong(), anyInt(), any()))
+        when(vfs.write(any(), any(), anyLong(), any()))
                 .thenReturn(new VirtualFileSystem.WriteResult(VirtualFileSystem.StabilityLevel.UNSTABLE, 1));
 
         COMPOUND4args writeArgs = new CompoundBuilder()