http://poi.apache.org/: Apache POI - Java API To Access Microsoft Format Files
(Apache Software Foundation)
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package org.apache.poi.poifs.nio;
import org.apache.poi.util.SuppressForbidden;
import java.io.IOException;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.nio.ByteBuffer;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Objects;
import static java.lang.invoke.MethodHandles.constant;
import static java.lang.invoke.MethodHandles.dropArguments;
import static java.lang.invoke.MethodHandles.filterReturnValue;
import static java.lang.invoke.MethodHandles.guardWithTest;
import static java.lang.invoke.MethodType.methodType;
This is taken from Hadoop at https://issues.apache.org/jira/browse/HADOOP-12760 and
https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/CleanerUtil.java
Unfortunately this is not available in some general utility library yet, but hopefully will be at some point.
sun.misc.Cleaner has moved in OpenJDK 9 and
sun.misc.Unsafe#invokeCleaner(ByteBuffer) is the replacement.
This class is a hack to use sun.misc.Cleaner in Java 8 and
use the replacement in Java 9+.
This implementation is inspired by LUCENE-6989.
/**
* This is taken from Hadoop at https://issues.apache.org/jira/browse/HADOOP-12760 and
* https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/CleanerUtil.java
* Unfortunately this is not available in some general utility library yet, but hopefully will be at some point.
*
* sun.misc.Cleaner has moved in OpenJDK 9 and
* sun.misc.Unsafe#invokeCleaner(ByteBuffer) is the replacement.
* This class is a hack to use sun.misc.Cleaner in Java 8 and
* use the replacement in Java 9+.
* This implementation is inspired by LUCENE-6989.
*/
public final class CleanerUtil {
// Prevent instantiation
private CleanerUtil(){}
true, if this platform supports unmapping mmapped files.
/**
* <code>true</code>, if this platform supports unmapping mmapped files.
*/
public static final boolean UNMAP_SUPPORTED;
if UNMAP_SUPPORTED is false, this contains the reason why unmapping is not supported. /**
* if {@link #UNMAP_SUPPORTED} is {@code false}, this contains the reason
* why unmapping is not supported.
*/
public static final String UNMAP_NOT_SUPPORTED_REASON;
private static final BufferCleaner CLEANER;
Reference to a BufferCleaner that does unmapping.
Returns: null if not supported.
/**
* Reference to a BufferCleaner that does unmapping.
* @return {@code null} if not supported.
*/
public static BufferCleaner getCleaner() {
return CLEANER;
}
static {
final Object hack = AccessController.doPrivileged(
(PrivilegedAction<Object>) CleanerUtil::unmapHackImpl);
if (hack instanceof BufferCleaner) {
CLEANER = (BufferCleaner) hack;
UNMAP_SUPPORTED = true;
UNMAP_NOT_SUPPORTED_REASON = null;
} else {
CLEANER = null;
UNMAP_SUPPORTED = false;
UNMAP_NOT_SUPPORTED_REASON = hack.toString();
}
}
@SuppressForbidden("Java 9 Jigsaw whitelists access to sun.misc.Cleaner, so setAccessible works")
private static Object unmapHackImpl() {
final MethodHandles.Lookup lookup = MethodHandles.lookup();
try {
try {
// *** sun.misc.Unsafe unmapping (Java 9+) ***
final Class<?> unsafeClass = Class.forName("sun.misc.Unsafe");
// first check if Unsafe has the right method, otherwise we can
// give up without doing any security critical stuff:
final MethodHandle unmapper = lookup.findVirtual(unsafeClass,
"invokeCleaner", methodType(void.class, ByteBuffer.class));
// fetch the unsafe instance and bind it to the virtual MH:
final Field f = unsafeClass.getDeclaredField("theUnsafe");
f.setAccessible(true);
final Object theUnsafe = f.get(null);
return newBufferCleaner(ByteBuffer.class, unmapper.bindTo(theUnsafe));
} catch (SecurityException se) {
// rethrow to report errors correctly (we need to catch it here,
// as we also catch RuntimeException below!):
throw se;
} catch (ReflectiveOperationException | RuntimeException e) {
// *** sun.misc.Cleaner unmapping (Java 8) ***
final Class<?> directBufferClass =
Class.forName("java.nio.DirectByteBuffer");
final Method m = directBufferClass.getMethod("cleaner");
m.setAccessible(true);
final MethodHandle directBufferCleanerMethod = lookup.unreflect(m);
final Class<?> cleanerClass =
directBufferCleanerMethod.type().returnType();
/*
* "Compile" a MethodHandle that basically is equivalent
* to the following code:
*
* void unmapper(ByteBuffer byteBuffer) {
* sun.misc.Cleaner cleaner =
* ((java.nio.DirectByteBuffer) byteBuffer).cleaner();
* if (Objects.nonNull(cleaner)) {
* cleaner.clean();
* } else {
* // the noop is needed because MethodHandles#guardWithTest
* // always needs ELSE
* noop(cleaner);
* }
* }
*/
final MethodHandle cleanMethod = lookup.findVirtual(
cleanerClass, "clean", methodType(void.class));
final MethodHandle nonNullTest = lookup.findStatic(Objects.class,
"nonNull", methodType(boolean.class, Object.class))
.asType(methodType(boolean.class, cleanerClass));
final MethodHandle noop = dropArguments(
constant(Void.class, null).asType(methodType(void.class)),
0, cleanerClass);
final MethodHandle unmapper = filterReturnValue(
directBufferCleanerMethod,
guardWithTest(nonNullTest, cleanMethod, noop))
.asType(methodType(void.class, ByteBuffer.class));
return newBufferCleaner(directBufferClass, unmapper);
}
} catch (SecurityException se) {
return "Unmapping is not supported, because not all required " +
"permissions are given to the Hadoop JAR file: " + se +
" [Please grant at least the following permissions: " +
"RuntimePermission(\"accessClassInPackage.sun.misc\") " +
" and ReflectPermission(\"suppressAccessChecks\")]";
} catch (ReflectiveOperationException | RuntimeException e) {
return "Unmapping is not supported on this platform, " +
"because internal Java APIs are not compatible with " +
"this Hadoop version: " + e;
}
}
private static BufferCleaner newBufferCleaner(
final Class<?> unmappableBufferClass, final MethodHandle unmapper) {
assert Objects.equals(
methodType(void.class, ByteBuffer.class), unmapper.type());
return buffer -> {
if (!buffer.isDirect()) {
throw new IllegalArgumentException(
"unmapping only works with direct buffers");
}
if (!unmappableBufferClass.isInstance(buffer)) {
throw new IllegalArgumentException("buffer is not an instance of " +
unmappableBufferClass.getName());
}
final Throwable error = AccessController.doPrivileged(
(PrivilegedAction<Throwable>) () -> {
try {
unmapper.invokeExact(buffer);
return null;
} catch (Throwable t) {
return t;
}
});
if (error != null) {
throw new IOException("Unable to unmap the mapped buffer", error);
}
};
}
Pass in an implementation of this interface to cleanup ByteBuffers.
CleanerUtil implements this to allow unmapping of bytebuffers
with private Java APIs.
/**
* Pass in an implementation of this interface to cleanup ByteBuffers.
* CleanerUtil implements this to allow unmapping of bytebuffers
* with private Java APIs.
*/
@FunctionalInterface
public interface BufferCleaner {
void freeBuffer(ByteBuffer b) throws IOException;
}
}