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8293502: (fc) FileChannel::transfer methods fail to copy /proc files …
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…on Linux

Reviewed-by: alanb
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Brian Burkhalter committed Sep 19, 2022
1 parent 1f9ff41 commit 6e23b43
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Showing 2 changed files with 206 additions and 14 deletions.
42 changes: 28 additions & 14 deletions src/java.base/share/classes/sun/nio/ch/FileChannelImpl.java
Original file line number Diff line number Diff line change
Expand Up @@ -761,23 +761,33 @@ public long transferTo(long position, long count,
throw new NonWritableChannelException();
if ((position < 0) || (count < 0))
throw new IllegalArgumentException();
long sz = size();
final long sz = size();
if (position > sz)
return 0;

if ((sz - position) < count)
count = sz - position;

// Attempt a direct transfer, if the kernel supports it, limiting
// the number of bytes according to which platform
int icount = (int)Math.min(count, MAX_DIRECT_TRANSFER_SIZE);
long n;
if ((n = transferToDirectly(position, icount, target)) >= 0)
return n;
// Now position <= sz so remaining >= 0 and
// remaining == 0 if and only if sz == 0
long remaining = sz - position;

// Adjust count only if remaining > 0, i.e.,
// sz > position which means sz > 0
if (remaining > 0 && remaining < count)
count = remaining;

// System calls supporting fast transfers might not work on files
// which advertise zero size such as those in Linux /proc
if (sz > 0) {
// Attempt a direct transfer, if the kernel supports it, limiting
// the number of bytes according to which platform
int icount = (int)Math.min(count, MAX_DIRECT_TRANSFER_SIZE);
long n;
if ((n = transferToDirectly(position, icount, target)) >= 0)
return n;

// Attempt a mapped transfer, but only to trusted channel types
if ((n = transferToTrustedChannel(position, count, target)) >= 0)
return n;
// Attempt a mapped transfer, but only to trusted channel types
if ((n = transferToTrustedChannel(position, count, target)) >= 0)
return n;
}

// Slow path for untrusted targets
return transferToArbitraryChannel(position, count, target);
Expand Down Expand Up @@ -925,14 +935,18 @@ public long transferFrom(ReadableByteChannel src,
ensureOpen();
if (!src.isOpen())
throw new ClosedChannelException();
if (src instanceof FileChannelImpl fci && !fci.readable)
throw new NonReadableChannelException();
if (!writable)
throw new NonWritableChannelException();
if ((position < 0) || (count < 0))
throw new IllegalArgumentException();
if (position > size())
return 0;

if (src instanceof FileChannelImpl fci) {
// System calls supporting fast transfers might not work on files
// which advertise zero size such as those in Linux /proc
if (src instanceof FileChannelImpl fci && fci.size() > 0) {
long n;
if ((n = transferFromDirectly(fci, position, count)) >= 0)
return n;
Expand Down
178 changes: 178 additions & 0 deletions test/jdk/java/nio/file/Files/CopyProcFile.java
Original file line number Diff line number Diff line change
@@ -0,0 +1,178 @@
/*
* Copyright (c) 2022, 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.
*/

import java.io.IOException;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UncheckedIOException;
import java.nio.channels.FileChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.List;
import java.util.function.ToLongBiFunction;
import static java.nio.file.StandardOpenOption.*;

import org.testng.Assert;
import org.testng.annotations.AfterTest;
import org.testng.annotations.BeforeTest;
import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;

/*
* @test
* @bug 8293502
* @requires (os.family == "linux")
* @summary Ensure that copying from a file in /proc works
* @run testng/othervm CopyProcFile
*/
public class CopyProcFile {
static final String SOURCE = "/proc/cpuinfo";
static final String BUFFERED_COPY = "bufferedCopy";
static final String TARGET = "target";

static final int BUF_SIZE = 8192;

static long theSize;

// copy src to dst via Java buffers
static long bufferedCopy(String src, String dst) {
try (InputStream in = new FileInputStream(src);
OutputStream out = new FileOutputStream(dst)) {
byte[] b = new byte[BUF_SIZE];
long total = 0;
int n;
while ((n = in.read(b)) > 0) {
out.write(b, 0, n);
total += n;
}
return total;
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}

// copy src to dst using Files::copy
static long copy(String src, String dst) {
try {
Path target = Files.copy(Path.of(src), Path.of(dst));
return Files.size(target);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}

// copy src to dst using InputStream::transferTo
static long transferToIO(String src, String dst) {
try (InputStream in = new FileInputStream(src);
OutputStream out = new FileOutputStream(dst)) {
return in.transferTo(out);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}

// copy src to dst using FileChannel::transferTo
static long transferToNIO(String src, String dst) {
try (FileChannel fci = FileChannel.open(Path.of(src), READ);
FileChannel fco = FileChannel.open(Path.of(dst), CREATE_NEW, WRITE);) {
return fci.transferTo(0, Long.MAX_VALUE, fco);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}

// copy src to dst using FileChannel::transferFrom
static long transferFrom(String src, String dst) {
try (FileChannel fci = FileChannel.open(Path.of(src), READ);
FileChannel fco = FileChannel.open(Path.of(dst), CREATE_NEW, WRITE);) {
return fco.transferFrom(fci, 0, Long.MAX_VALUE);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}

@BeforeTest(alwaysRun=true)
public void createBufferedCopy() {
System.out.printf("Using source file \"%s\"%n", SOURCE);
try {
theSize = bufferedCopy(SOURCE, BUFFERED_COPY);
System.out.printf("Copied %d bytes from %s%n", theSize, SOURCE);
if (Files.mismatch(Path.of(BUFFERED_COPY), Path.of(SOURCE)) != -1)
throw new RuntimeException("Copy does not match source");
} catch (Exception e) {
try {
Files.delete(Path.of(BUFFERED_COPY));
} catch (IOException ignore) {}
}
}

@AfterTest(alwaysRun=true)
public void deleteBufferedCopy() {
try {
Files.delete(Path.of(BUFFERED_COPY));
} catch (IOException ignore) {}
}

static class FHolder {
ToLongBiFunction<String,String> f;

FHolder(ToLongBiFunction<String,String> f) {
this.f = f;
}

long apply(String src, String dst) {
return f.applyAsLong(src, dst);
}
}

@DataProvider
static Object[][] functions() throws IOException {
List<Object[]> funcs = new ArrayList<>();
funcs.add(new Object[] {new FHolder((s, d) -> copy(s, d))});
funcs.add(new Object[] {new FHolder((s, d) -> transferToIO(s, d))});
funcs.add(new Object[] {new FHolder((s, d) -> transferToNIO(s, d))});
funcs.add(new Object[] {new FHolder((s, d) -> transferFrom(s, d))});
return funcs.toArray(Object[][]::new);
}

@Test(dataProvider = "functions")
public static void testCopyAndTransfer(FHolder f) throws IOException {
try {
long size = f.apply(SOURCE, TARGET);
if (size != theSize)
throw new RuntimeException("Size: expected " + theSize +
"; actual: " + size);
long mismatch = Files.mismatch(Path.of(BUFFERED_COPY),
Path.of(TARGET));
if (mismatch != -1)
throw new RuntimeException("Target does not match copy");
} finally {
try {
Files.delete(Path.of(TARGET));
} catch (IOException ignore) {}
}
}
}

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