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8227609: (fs) Files.newInputStream(...).skip(n) should allow skipping…
… beyond file size

Backport-of: 3155cd8
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Larry-N authored and Yuri Nesterenko committed May 17, 2021
1 parent afdd824 commit 32036b2b5c31dff8d124f9a5e37c0ceb979ee777
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Showing 3 changed files with 142 additions and 47 deletions.
@@ -119,20 +119,21 @@ public int available() throws IOException {

public synchronized long skip(long n) throws IOException {
// special case where the channel is to a file
if (ch instanceof SeekableByteChannel && n > 0) {
if (ch instanceof SeekableByteChannel) {
SeekableByteChannel sbc = (SeekableByteChannel)ch;
try {
long pos = sbc.position();
long pos = sbc.position();
long newPos;
if (n > 0) {
newPos = pos + n;
long size = sbc.size();
if (pos >= size) {
return 0L;
if (newPos < 0 || newPos > size) {
newPos = size;
}
n = Math.min(n, size - pos);
sbc.position(pos + n);
return sbc.position() - pos;
} catch (ClosedChannelException cce) {
throw new IOException(cce);
} else {
newPos = Long.max(pos + n, 0);
}
sbc.position(newPos);
return newPos - pos;
}
return super.skip(n);
}
@@ -0,0 +1,130 @@
/*
* Copyright (c) 2019, 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 8227609
* @summary Test of InputStream and OutputStream created by java.nio.file.Files
* @library ..
*/

import java.io.InputStream;
import java.io.OutputStream;
import java.nio.channels.ClosedChannelException;
import java.nio.file.*;
import static java.nio.file.Files.*;
import static java.nio.file.LinkOption.*;
import java.nio.file.attribute.*;
import java.io.IOException;
import java.util.*;

public class InputStreamTest {

public static void main(String[] args) throws IOException {
Path dir = TestUtil.createTemporaryDirectory();
try {
testSkip(dir);
} finally {
TestUtil.removeAll(dir);
}
}

/**
* Tests Files.newInputStream(Path).skip().
*/
static void testSkip(Path tmpdir) throws IOException {
Path file = createFile(tmpdir.resolve("foo"));
try (OutputStream out = Files.newOutputStream(file)) {
final int size = 512;
byte[] blah = new byte[size];
for (int i = 0; i < size; i++) {
blah[i] = (byte)(i % 128);
}
out.write(blah);
out.close();

try (InputStream in = Files.newInputStream(file)) {
assertTrue(in.available() == size);
assertTrue(in.skip(size/4) == size/4); // 0.25
assertTrue(in.available() == 3*size/4);

int b = in.read();
assertTrue(b == blah[size/4]);
assertTrue(in.available() == 3*size/4 - 1);
assertTrue(in.skip(-1) == -1); // 0.25
assertTrue(in.available() == 3*size/4);

assertTrue(in.skip(-size/2) == -size/4); // 0
assertTrue(in.available() == size);

assertTrue(in.skip(5*size/4) == size); // 1.0
assertTrue(in.available() == 0);

assertTrue(in.skip(-3*size/4) == -3*size/4); // 0.25
assertTrue(in.available() == 3*size/4);

byte[] buf = new byte[16];
in.read(buf, 2, 12);
assertTrue(Arrays.equals(buf, 2, 14,
blah, size/4, size/4 + 12));
assertTrue(in.skip(-12) == -12); // 0.25

assertTrue(in.skip(3*size/4) == 3*size/4); // 1.0
assertTrue(in.available() == 0);

assertTrue(in.skip(-size/2) == -size/2); // 0.5
assertTrue(in.available() == size/2);

assertTrue(in.skip(-size) == -size/2); // 0
assertTrue(in.available() == size);

assertTrue(in.skip(size/2) == size/2); // 0.5
assertTrue(in.available() == size/2);

assertTrue(in.skip(Long.MIN_VALUE) == -size/2); // 0
assertTrue(in.available() == size);

assertTrue(in.skip(size/2) == size/2); // 0.5
assertTrue(in.available() == size/2);

assertTrue(in.skip(Long.MAX_VALUE - size/4) == size/2);
assertTrue(in.available() == 0);

in.close();
try {
in.skip(1);
throw new RuntimeException("skip() did not fail");
} catch (IOException ioe) {
if (!(ioe instanceof ClosedChannelException)) {
throw new RuntimeException
("IOException is not a ClosedChannelException");
}
}
}
}
}

static void assertTrue(boolean okay) {
if (!okay)
throw new RuntimeException("Assertion Failed");
}
}
@@ -22,14 +22,11 @@
*/

/* @test
* @bug 4313887 6838333 8005566 8032220 8215467 8227080
* @bug 4313887 6838333 8005566 8032220 8215467
* @summary Unit test for miscellenous methods in java.nio.file.Files
* @library ..
*/

import java.io.InputStream;
import java.io.OutputStream;
import java.nio.channels.ClosedChannelException;
import java.nio.file.*;
import static java.nio.file.Files.*;
import static java.nio.file.LinkOption.*;
@@ -47,7 +44,6 @@ public static void main(String[] args) throws IOException {
testIsSameFile(dir);
testFileTypeMethods(dir);
testAccessMethods(dir);
testSkip(dir);
} finally {
TestUtil.removeAll(dir);
}
@@ -376,38 +372,6 @@ static void testAccessMethods(Path tmpdir) throws IOException {
}
}

/**
* Tests Files.newInputStream(Path).skip().
*/
static void testSkip(Path tmpdir) throws IOException {
Path file = createFile(tmpdir.resolve("foo"));
try (OutputStream out = Files.newOutputStream(file)) {
byte[] blah = new byte[8192];
Arrays.fill(blah, (byte)42);
out.write(blah);
out.close();
try (InputStream in = Files.newInputStream(file)) {
assertTrue(in.skip(-1) == 0);
assertTrue(in.skip(0) == 0);
assertTrue(in.skip(blah.length/4) == blah.length/4);
assertTrue(in.skip(blah.length/2) == blah.length/2);
assertTrue(in.skip(Long.MAX_VALUE) == blah.length/4);
in.close();
try {
long n = in.skip(1);
throw new RuntimeException("skip() did not fail");
} catch (IOException ioe) {
if (!(ioe.getCause() instanceof ClosedChannelException)) {
throw new RuntimeException
("IOException not caused by ClosedChannelException");
}
}
}
} finally {
delete(file);
}
}

static void assertTrue(boolean okay) {
if (!okay)
throw new RuntimeException("Assertion Failed");

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