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8303260: (fc) FileChannel::transferFrom should support position > size()
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Reviewed-by: alanb
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Brian Burkhalter committed Apr 4, 2023
1 parent 3ef834f commit 7baccd9
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Showing 3 changed files with 176 additions and 13 deletions.
26 changes: 15 additions & 11 deletions src/java.base/share/classes/java/nio/channels/FileChannel.java
Original file line number Diff line number Diff line change
Expand Up @@ -633,10 +633,10 @@ public final long write(ByteBuffer[] srcs) throws IOException {
* bytes free in its output buffer.
*
* <p> This method does not modify this channel's position. If the given
* position is greater than or equal to the file's current size then no bytes are
* transferred. If the target channel has a position then bytes are
* written starting at that position and then the position is incremented
* by the number of bytes written.
* position is greater than or equal to the file's current size then no
* bytes are transferred. If the target channel has a position then bytes
* are written starting at that position and then the position
* is incremented by the number of bytes written.
*
* <p> This method is potentially much more efficient than a simple loop
* that reads from this channel and writes to the target channel. Many
Expand Down Expand Up @@ -701,8 +701,10 @@ public abstract long transferTo(long position, long count,
* source has reached end-of-stream.
*
* <p> This method does not modify this channel's position. If the given
* position is greater than the file's current size then no bytes are
* transferred. If the source channel has a position then bytes are read
* position is greater than or equal to the file's current size then the
* file will be grown to accommodate the new bytes; the values of any bytes
* between the previous end-of-file and the newly-written bytes are
* unspecified. If the source channel has a position then bytes are read
* starting at that position and then the position is incremented by the
* number of bytes read.
*
Expand All @@ -715,7 +717,7 @@ public abstract long transferTo(long position, long count,
* The source channel
*
* @param position
* The position within the file at which the transfer is to begin;
* The file position at which the transfer is to begin;
* must be non-negative
*
* @param count
Expand Down Expand Up @@ -761,7 +763,8 @@ public abstract long transferFrom(ReadableByteChannel src,
* #read(ByteBuffer)} method, except that bytes are read starting at the
* given file position rather than at the channel's current position. This
* method does not modify this channel's position. If the given position
* is greater than or equal to the file's current size then no bytes are read. </p>
* is greater than or equal to the file's current size then no bytes are
* read. </p>
*
* @param dst
* The buffer into which bytes are to be transferred
Expand Down Expand Up @@ -806,9 +809,10 @@ public abstract long transferFrom(ReadableByteChannel src,
* #write(ByteBuffer)} method, except that bytes are written starting at
* the given file position rather than at the channel's current position.
* This method does not modify this channel's position. If the given
* position is greater than or equal to the file's current size then the file will be
* grown to accommodate the new bytes; the values of any bytes between the
* previous end-of-file and the newly-written bytes are unspecified. </p>
* position is greater than or equal to the file's current size then the
* file will be grown to accommodate the new bytes; the values of any bytes
* between the previous end-of-file and the newly-written bytes are
* unspecified. </p>
*
* <p> If the file is open in <a href="#append-mode">append mode</a>, then
* the effect of invoking this method is unspecified.
Expand Down
2 changes: 0 additions & 2 deletions src/java.base/share/classes/sun/nio/ch/FileChannelImpl.java
Original file line number Diff line number Diff line change
Expand Up @@ -935,8 +935,6 @@ public long transferFrom(ReadableByteChannel src,
throw new NonWritableChannelException();
if ((position < 0) || (count < 0))
throw new IllegalArgumentException();
if (position > size())
return 0;

// System calls supporting fast transfers might not work on files
// which advertise zero size such as those in Linux /proc
Expand Down
161 changes: 161 additions & 0 deletions test/jdk/java/nio/channels/FileChannel/TransferFromExtend.java
Original file line number Diff line number Diff line change
@@ -0,0 +1,161 @@
/*
* Copyright (c) 2023, 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.
*
* 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.
*/

/* @test
* @bug 8303260
* @summary Test transferFrom to a position greater than the file size
* @library .. /test/lib
* @build jdk.test.lib.RandomFactory
* @run junit TransferFromExtend
* @key randomness
*/

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Random;
import java.util.stream.Stream;

import static java.nio.file.StandardOpenOption.*;

import jdk.test.lib.RandomFactory;

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.Arguments;
import org.junit.jupiter.params.provider.MethodSource;

import static org.junit.jupiter.api.Assertions.*;

public class TransferFromExtend {
private static final Random RND = RandomFactory.getRandom();

private static final Path DIR = Path.of(System.getProperty("test.dir", "."));

private static Stream<Arguments> paramProvider(int transferSizeMin,
int transferSizeMax) {
List<Arguments> list = new ArrayList<Arguments>();
int sizeDelta = transferSizeMax - transferSizeMin;
for (int i = 0; i < 10; i++) {
Arguments args =
Arguments.of(RND.nextInt(1024),
transferSizeMin + RND.nextInt(sizeDelta),
1 + RND.nextInt(2047));
list.add(args);
}
return list.stream();
}

//
// transfer size must be greater than the threshold
// sun.nio.ch.FileChannelImpl::MAPPED_TRANSFER_THRESHOLD (16K)
// for a mapped transfer to be used when direct is unavailable
//
private static Stream<Arguments> fastParamProvider() {
return paramProvider(16*1024 + 1, 500*1024);
}

private static Stream<Arguments> readingByteChannelParamProvider() {
return paramProvider(1, 64*1024);
}

/*
* This method tests the optimized path for transferring from a file
* source to a file destination.
*/
@ParameterizedTest
@MethodSource("fastParamProvider")
void fromFileChannel(long initialPosition, int bufSize, long offset)
throws IOException
{
Path file = Files.createTempFile(DIR, "foo", "bar");
try (FileChannel src = FileChannel.open(file, DELETE_ON_CLOSE,
READ, WRITE)) {
byte[] bytes = new byte[bufSize];
RND.nextBytes(bytes);
ByteBuffer buf = ByteBuffer.wrap(bytes);
int total = 0;
while (total < bufSize) {
int n = src.write(ByteBuffer.wrap(bytes), 0);
assertTrue(n >= 0, n + " < " + 0);
total += n;
}
testTransferFrom(src, src.size(), initialPosition, offset, bytes);
}
}

//
// Test the arbitrary source path. This method tests the
// generic path on all platforms.
//
@ParameterizedTest
@MethodSource("readingByteChannelParamProvider")
void fromReadingByteChannel(long initialPosition, int bufSize, long offset)
throws IOException
{
byte[] bytes = new byte[bufSize];
RND.nextBytes(bytes);
ByteArrayInputStream bais = new ByteArrayInputStream(bytes);
try (ReadableByteChannel src = Channels.newChannel(bais)) {
testTransferFrom(src, bufSize, initialPosition, offset, bytes);
}
}

/**
* Tests transferring bytes to a FileChannel from a ReadableByteChannel.
*
* @param src the source of the bytes to transfer
* @param count the number of bytes to transfer
* @param initialPos the position of the target channel before the transfer
* @param offset the offset beyong the end of the target channel
* @param bytes the bytes expected to be transferred
*/
private static void testTransferFrom(ReadableByteChannel src, long count,
long initialPos, long offset,
byte[] bytes)
throws IOException
{
Path file = Files.createTempFile(DIR, "foo", "bar");
try (FileChannel target = FileChannel.open(file, DELETE_ON_CLOSE,
READ, WRITE)) {
target.position(initialPos);
assertEquals(1, target.write(ByteBuffer.wrap(new byte[] {(byte)42})));

long position = target.size() + offset;
long transferred = target.transferFrom(src, position, count);
assertTrue(transferred >= 0, "transferFrom returned negative");
assertFalse(count < transferred, count + " < " + transferred);
ByteBuffer buf = ByteBuffer.allocate((int)transferred);
target.read(buf, position);
assertArrayEquals(Arrays.copyOf(bytes, (int)transferred),
buf.array(), "arrays unequal");
}
}
}

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