android-35/java/nio/MappedByteBuffer.java - platform/prebuilts/fullsdk/sources - Git at Google

 /*
  * Copyright (C) 2014 The Android Open Source Project
  * Copyright (c) 2000, 2021, 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.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * 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.
  */

 package java.nio;

 import dalvik.annotation.codegen.CovariantReturnType;

 import java.io.FileDescriptor;
 import java.io.UncheckedIOException;
 import java.lang.ref.Reference;
 import java.util.Objects;

 import jdk.internal.misc.Unsafe;


 /**
  * A direct byte buffer whose content is a memory-mapped region of a file.
  *
  * <p> Mapped byte buffers are created via the {@link
  * java.nio.channels.FileChannel#map FileChannel.map} method.  This class
  * extends the {@link ByteBuffer} class with operations that are specific to
  * memory-mapped file regions.
  *
  * <p> A mapped byte buffer and the file mapping that it represents remain
  * valid until the buffer itself is garbage-collected.
  *
  * <p> The content of a mapped byte buffer can change at any time, for example
  * if the content of the corresponding region of the mapped file is changed by
  * this program or another.  Whether or not such changes occur, and when they
  * occur, is operating-system dependent and therefore unspecified.
  *
  * <a id="inaccess"></a><p> All or part of a mapped byte buffer may become
  * inaccessible at any time, for example if the mapped file is truncated.  An
  * attempt to access an inaccessible region of a mapped byte buffer will not
  * change the buffer's content and will cause an unspecified exception to be
  * thrown either at the time of the access or at some later time.  It is
  * therefore strongly recommended that appropriate precautions be taken to
  * avoid the manipulation of a mapped file by this program, or by a
  * concurrently running program, except to read or write the file's content.
  *
  * <p> Mapped byte buffers otherwise behave no differently than ordinary direct
  * byte buffers. </p>
  *
  *
  * @author Mark Reinhold
  * @author JSR-51 Expert Group
  * @since 1.4
  */

 public abstract class MappedByteBuffer
     extends ByteBuffer
 {

     // This is a little bit backwards: By rights MappedByteBuffer should be a
     // subclass of DirectByteBuffer, but to keep the spec clear and simple, and
     // for optimization purposes, it's easier to do it the other way around.
     // This works because DirectByteBuffer is a package-private class.

     // For mapped buffers, a FileDescriptor that may be used for mapping
     // operations if valid; null if the buffer is not mapped.
     private final FileDescriptor fd;

     // A flag true if this buffer is mapped against non-volatile
     // memory using one of the extended FileChannel.MapMode modes,
     // MapMode.READ_ONLY_SYNC or MapMode.READ_WRITE_SYNC and false if
     // it is mapped using any of the other modes. This flag only
     // determines the behavior of force operations.
     private final boolean isSync;

     // Android-removed: Remove unsupported scoped memory access.
     // static final ScopedMemoryAccess SCOPED_MEMORY_ACCESS = ScopedMemoryAccess.getScopedMemoryAccess();

     // This should only be invoked by the DirectByteBuffer constructors
     //
     // Android-removed: Removed MemorySegmentProxy to be supported yet./
     MappedByteBuffer(int mark, int pos, int lim, int cap, // package-private
                      FileDescriptor fd, boolean isSync) {
         super(mark, pos, lim, cap);
         this.fd = fd;
         this.isSync = isSync;
     }

     // Android-added: Additional constructor for use by Android's DirectByteBuffer.
     MappedByteBuffer(int mark, int pos, int lim, int cap, byte[] buf, int offset) {
         super(mark, pos, lim, cap, buf, offset);
         this.fd = null;
         isSync = false;
     }

     // Android-removed: Removed MemorySegmentProxy to be supported yet./
     MappedByteBuffer(int mark, int pos, int lim, int cap, // package-private
                      boolean isSync) {
         super(mark, pos, lim, cap);
         this.fd = null;
         this.isSync = isSync;
     }

     // Android-removed: Removed MemorySegmentProxy to be supported yet.
     MappedByteBuffer(int mark, int pos, int lim, int cap) { // package-private
         super(mark, pos, lim, cap);
         this.fd = null;
         this.isSync = false;
     }

     // Android-removed: Remove unsupported UnmapperProxy.
     /*
     UnmapperProxy unmapper() {
         return fd != null ?
                 new UnmapperProxy() {
                     @Override
                     public long address() {
                         return address;
                     }

                     @Override
                     public FileDescriptor fileDescriptor() {
                         return fd;
                     }

                     @Override
                     public boolean isSync() {
                         return isSync;
                     }

                     @Override
                     public void unmap() {
                         Unsafe.getUnsafe().invokeCleaner(MappedByteBuffer.this);
                     }
                 } : null;
     }
     */

     /**
      * Tells whether this buffer was mapped against a non-volatile
      * memory device by passing one of the sync map modes {@link
      * jdk.nio.mapmode.ExtendedMapMode#READ_ONLY_SYNC
      * ExtendedMapModeMapMode#READ_ONLY_SYNC} or {@link
      * jdk.nio.mapmode.ExtendedMapMode#READ_ONLY_SYNC
      * ExtendedMapMode#READ_WRITE_SYNC} in the call to {@link
      * java.nio.channels.FileChannel#map FileChannel.map} or was
      * mapped by passing one of the other map modes.
      *
      * @return true if the file was mapped using one of the sync map
      * modes, otherwise false.
      */
     final boolean isSync() { // package-private
         return isSync;
     }

     /**
      * Returns the {@code FileDescriptor} associated with this
      * {@code MappedByteBuffer}.
      *
      * @return the buffer's file descriptor; may be {@code null}
      */
     final FileDescriptor fileDescriptor() { // package-private
         return fd;
     }

     // Android-added: Added the unused field to avoid compiler optimization in load();
     private static byte unused;
     // Android-added: Added checkMapped as Android doesn't allow null fd in DirectByteBuffer.
     private void checkMapped() {
         if (fd == null)
             // Can only happen if a user explicitly casts a direct byte buffer
             throw new UnsupportedOperationException();
     }

     // BEGIN Android-added: Additional fields / methods for removing unsupported scoped memory.
     // Returns the distance (in bytes) of the buffer from the page aligned address
     // of the mapping. Computed each time to avoid storing in every direct buffer.
     private long mappingOffset() {
         return mappingOffset(address);
     }

     private static long mappingOffset(long addr) {
         int ps = Bits.pageSize();
         long offset = addr % ps;
         return (offset >= 0) ? offset : (ps + offset);
     }

     private long mappingAddress(long mappingOffset) {
         return address - mappingOffset;
     }

     private static long mappingAddress(long addr, long mappingOffset) {
         return addr - mappingOffset;
     }

     private long mappingLength(long mappingOffset) {
         return mappingLength(capacity(), mappingOffset);
     }

     private long mappingLength(long length, long mappingOffset) {
         return length + mappingOffset;
     }
     // END Android-added: Additional fields / methods for removing unsupported scoped memory.


     /**
      * Tells whether or not this buffer's content is resident in physical
      * memory.
      *
      * <p> A return value of {@code true} implies that it is highly likely
      * that all of the data in this buffer is resident in physical memory and
      * may therefore be accessed without incurring any virtual-memory page
      * faults or I/O operations.  A return value of {@code false} does not
      * necessarily imply that the buffer's content is not resident in physical
      * memory.
      *
      * <p> The returned value is a hint, rather than a guarantee, because the
      * underlying operating system may have paged out some of the buffer's data
      * by the time that an invocation of this method returns.  </p>
      *
      * @return  {@code true} if it is likely that this buffer's content
      *          is resident in physical memory
      */
     public final boolean isLoaded() {
         // Android-added: Android throws UOE for memory-backed direct byte buffer.
         // if (fd == null) {
         //     return true;
         // }
         checkMapped();
         // Android-changed: Remove unsupported scoped memory access.
         // return SCOPED_MEMORY_ACCESS.isLoaded(scope(), address, isSync, capacity());
         if ((address == 0) || (capacity() == 0))
             return true;
         long offset = mappingOffset();
         long length = mappingLength(offset);
         return isLoaded0(mappingAddress(offset), length, Bits.pageCount(length));
     }

     /**
      * Loads this buffer's content into physical memory.
      *
      * <p> This method makes a best effort to ensure that, when it returns,
      * this buffer's content is resident in physical memory.  Invoking this
      * method may cause some number of page faults and I/O operations to
      * occur. </p>
      *
      * @return  This buffer
      */
     public final MappedByteBuffer load() {
         // Android-added: Android throws UOE for memory-backed direct byte buffer.
         // if (fd == null) {
         //     return this;
         // }
         checkMapped();
         // Android-changed: Remove unsupported scoped memory access.
         /*
         try {
             SCOPED_MEMORY_ACCESS.load(scope(), address, isSync, capacity());
         } finally {
             Reference.reachabilityFence(this);
         }
         */
         if ((address == 0) || (capacity() == 0))
             return this;
         long offset = mappingOffset();
         long length = mappingLength(offset);
         load0(mappingAddress(offset), length);

         // Read a byte from each page to bring it into memory. A checksum
         // is computed as we go along to prevent the compiler from otherwise
         // considering the loop as dead code.
         Unsafe unsafe = Unsafe.getUnsafe();
         int ps = Bits.pageSize();
         long count = Bits.pageCount(length);
         long a = mappingAddress(offset);
         byte x = 0;
         for (int i=0; i<count; i++) {
             x ^= unsafe.getByte(a);
             a += ps;
         }
         if (unused != 0)
             unused = x;

         return this;
     }

     /**
      * Forces any changes made to this buffer's content to be written to the
      * storage device containing the mapped file.  The region starts at index
      * zero in this buffer and is {@code capacity()} bytes.
      *
      * <p> If the file mapped into this buffer resides on a local storage
      * device then when this method returns it is guaranteed that all changes
      * made to the buffer since it was created, or since this method was last
      * invoked, will have been written to that device.
      *
      * <p> If the file does not reside on a local device then no such guarantee
      * is made.
      *
      * <p> If this buffer was not mapped in read/write mode ({@link
      * java.nio.channels.FileChannel.MapMode#READ_WRITE}) then
      * invoking this method may have no effect. In particular, the
      * method has no effect for buffers mapped in read-only or private
      * mapping modes. This method may or may not have an effect for
      * implementation-specific mapping modes. </p>
      *
      * @throws UncheckedIOException
      *         If an I/O error occurs writing the buffer's content to the
      *         storage device containing the mapped file
      *
      * @return  This buffer
      */
     public final MappedByteBuffer force() {
         // Android-changed:: Android throws UOE for memory-backed direct byte buffer.
         // if (fd == null) {
         //     return this;
         // }
         checkMapped();
         int capacity = capacity();
         if (isSync || ((address != 0) && (capacity != 0))) {
             return force(0, capacity);
         }
         return this;
     }

     /**
      * Forces any changes made to a region of this buffer's content to
      * be written to the storage device containing the mapped
      * file. The region starts at the given {@code index} in this
      * buffer and is {@code length} bytes.
      *
      * <p> If the file mapped into this buffer resides on a local
      * storage device then when this method returns it is guaranteed
      * that all changes made to the selected region buffer since it
      * was created, or since this method was last invoked, will have
      * been written to that device. The force operation is free to
      * write bytes that lie outside the specified region, for example
      * to ensure that data blocks of some device-specific granularity
      * are transferred in their entirety.
      *
      * <p> If the file does not reside on a local device then no such
      * guarantee is made.
      *
      * <p> If this buffer was not mapped in read/write mode ({@link
      * java.nio.channels.FileChannel.MapMode#READ_WRITE}) then
      * invoking this method may have no effect. In particular, the
      * method has no effect for buffers mapped in read-only or private
      * mapping modes. This method may or may not have an effect for
      * implementation-specific mapping modes. </p>
      *
      * @param  index
      *         The index of the first byte in the buffer region that is
      *         to be written back to storage; must be non-negative
      *         and less than {@code capacity()}
      *
      * @param  length
      *         The length of the region in bytes; must be non-negative
      *         and no larger than {@code capacity() - index}
      *
      * @throws IndexOutOfBoundsException
      *         if the preconditions on the index and length do not
      *         hold.
      *
      * @throws UncheckedIOException
      *         If an I/O error occurs writing the buffer's content to the
      *         storage device containing the mapped file
      *
      * @return  This buffer
      *
      * @since 13
      */
     public final MappedByteBuffer force(int index, int length) {
         // Android-note: Android doesn't throw UOE, because new API doesn't need forward compat.
         if (fd == null) {
             return this;
         }
         int capacity = capacity();
         if ((address != 0) && (capacity != 0)) {
             // check inputs
             Objects.checkFromIndexSize(index, length, capacity);
             // Android-changed: Remove unsupported scoped memory access.
             // SCOPED_MEMORY_ACCESS.force(scope(), fd, address, isSync, index, length);
             long firstByteAddress = address + index;
             long offset = mappingOffset(firstByteAddress);
             force0(fd, mappingAddress(firstByteAddress, offset), mappingLength(length, offset));
         }
         return this;
     }

     // -- Covariant return type overrides

     /**
      * {@inheritDoc}
      */
     // Android-changed: covariant overloads of *Buffer methods that return this.
     @CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
     @CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
     @Override
     public final Buffer position(int newPosition) {
         super.position(newPosition);
         return this;
     }

     /**
      * {@inheritDoc}
      */
     // Android-changed: covariant overloads of *Buffer methods that return this.
     @CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
     @CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
     @Override
     public final Buffer limit(int newLimit) {
         super.limit(newLimit);
         return this;
     }

     /**
      * {@inheritDoc}
      */
     // Android-changed: covariant overloads of *Buffer methods that return this.
     @CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
     @CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
     @Override
     public final Buffer mark() {
         super.mark();
         return this;
     }

     /**
      * {@inheritDoc}
      */
     // Android-changed: covariant overloads of *Buffer methods that return this.
     @CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
     @CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
     @Override
     public final Buffer reset() {
         super.reset();
         return this;
     }

     /**
      * {@inheritDoc}
      */
     // Android-changed: covariant overloads of *Buffer methods that return this.
     @CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
     @CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
     @Override
     public final Buffer clear() {
         super.clear();
         return this;
     }

     /**
      * {@inheritDoc}
      */
     // Android-changed: covariant overloads of *Buffer methods that return this.
     @CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
     @CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
     @Override
     public final Buffer flip() {
         super.flip();
         return this;
     }

     /**
      * {@inheritDoc}
      */
     // Android-changed: covariant overloads of *Buffer methods that return this.
     @CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
     @CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
     @Override
     public final Buffer rewind() {
         super.rewind();
         return this;
     }

     /**
      * {@inheritDoc}
      *
      * <p> Reading bytes into physical memory by invoking {@code load()} on the
      * returned buffer, or writing bytes to the storage device by invoking
      * {@code force()} on the returned buffer, will only act on the sub-range
      * of this buffer that the returned buffer represents, namely
      * {@code [position(),limit())}.
      */
     // Android-changed: covariant overloads of *Buffer methods that return this.
     @CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
     @Override
     public abstract ByteBuffer slice();

     /**
      * {@inheritDoc}
      *
      * <p> Reading bytes into physical memory by invoking {@code load()} on the
      * returned buffer, or writing bytes to the storage device by invoking
      * {@code force()} on the returned buffer, will only act on the sub-range
      * of this buffer that the returned buffer represents, namely
      * {@code [index,index+length)}, where {@code index} and {@code length} are
      * assumed to satisfy the preconditions.
      */
     public abstract MappedByteBuffer slice(int index, int length);

     private native boolean isLoaded0(long address, long length, long pageCount);
     private native void load0(long address, long length);
     private native void force0(FileDescriptor fd, long address, long length);


     /**
      * {@inheritDoc}
      */
     // Android-changed: covariant overloads of *Buffer methods that return this.
     @CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
     @Override
     public abstract ByteBuffer duplicate();

     /**
      * {@inheritDoc}
      */
     // Android-changed: covariant overloads of *Buffer methods that return this.
     @CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
     @Override
     public abstract ByteBuffer compact();
 }
	/*
	* Copyright (C) 2014 The Android Open Source Project
	* Copyright (c) 2000, 2021, 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. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* 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.
	*/

	package java.nio;

	import dalvik.annotation.codegen.CovariantReturnType;

	import java.io.FileDescriptor;
	import java.io.UncheckedIOException;
	import java.lang.ref.Reference;
	import java.util.Objects;

	import jdk.internal.misc.Unsafe;


	/**
	* A direct byte buffer whose content is a memory-mapped region of a file.
	*
	* <p> Mapped byte buffers are created via the {@link
	* java.nio.channels.FileChannel#map FileChannel.map} method. This class
	* extends the {@link ByteBuffer} class with operations that are specific to
	* memory-mapped file regions.
	*
	* <p> A mapped byte buffer and the file mapping that it represents remain
	* valid until the buffer itself is garbage-collected.
	*
	* <p> The content of a mapped byte buffer can change at any time, for example
	* if the content of the corresponding region of the mapped file is changed by
	* this program or another. Whether or not such changes occur, and when they
	* occur, is operating-system dependent and therefore unspecified.
	*
	* <a id="inaccess"></a><p> All or part of a mapped byte buffer may become
	* inaccessible at any time, for example if the mapped file is truncated. An
	* attempt to access an inaccessible region of a mapped byte buffer will not
	* change the buffer's content and will cause an unspecified exception to be
	* thrown either at the time of the access or at some later time. It is
	* therefore strongly recommended that appropriate precautions be taken to
	* avoid the manipulation of a mapped file by this program, or by a
	* concurrently running program, except to read or write the file's content.
	*
	* <p> Mapped byte buffers otherwise behave no differently than ordinary direct
	* byte buffers. </p>
	*
	*
	* @author Mark Reinhold
	* @author JSR-51 Expert Group
	* @since 1.4
	*/

	public abstract class MappedByteBuffer
	extends ByteBuffer
	{

	// This is a little bit backwards: By rights MappedByteBuffer should be a
	// subclass of DirectByteBuffer, but to keep the spec clear and simple, and
	// for optimization purposes, it's easier to do it the other way around.
	// This works because DirectByteBuffer is a package-private class.

	// For mapped buffers, a FileDescriptor that may be used for mapping
	// operations if valid; null if the buffer is not mapped.
	private final FileDescriptor fd;

	// A flag true if this buffer is mapped against non-volatile
	// memory using one of the extended FileChannel.MapMode modes,
	// MapMode.READ_ONLY_SYNC or MapMode.READ_WRITE_SYNC and false if
	// it is mapped using any of the other modes. This flag only
	// determines the behavior of force operations.
	private final boolean isSync;

	// Android-removed: Remove unsupported scoped memory access.
	// static final ScopedMemoryAccess SCOPED_MEMORY_ACCESS = ScopedMemoryAccess.getScopedMemoryAccess();

	// This should only be invoked by the DirectByteBuffer constructors
	//
	// Android-removed: Removed MemorySegmentProxy to be supported yet./
	MappedByteBuffer(int mark, int pos, int lim, int cap, // package-private
	FileDescriptor fd, boolean isSync) {
	super(mark, pos, lim, cap);
	this.fd = fd;
	this.isSync = isSync;
	}

	// Android-added: Additional constructor for use by Android's DirectByteBuffer.
	MappedByteBuffer(int mark, int pos, int lim, int cap, byte[] buf, int offset) {
	super(mark, pos, lim, cap, buf, offset);
	this.fd = null;
	isSync = false;
	}

	// Android-removed: Removed MemorySegmentProxy to be supported yet./
	MappedByteBuffer(int mark, int pos, int lim, int cap, // package-private
	boolean isSync) {
	super(mark, pos, lim, cap);
	this.fd = null;
	this.isSync = isSync;
	}

	// Android-removed: Removed MemorySegmentProxy to be supported yet.
	MappedByteBuffer(int mark, int pos, int lim, int cap) { // package-private
	super(mark, pos, lim, cap);
	this.fd = null;
	this.isSync = false;
	}

	// Android-removed: Remove unsupported UnmapperProxy.
	/*
	UnmapperProxy unmapper() {
	return fd != null ?
	new UnmapperProxy() {
	@Override
	public long address() {
	return address;
	}

	@Override
	public FileDescriptor fileDescriptor() {
	return fd;
	}

	@Override
	public boolean isSync() {
	return isSync;
	}

	@Override
	public void unmap() {
	Unsafe.getUnsafe().invokeCleaner(MappedByteBuffer.this);
	}
	} : null;
	}
	*/

	/**
	* Tells whether this buffer was mapped against a non-volatile
	* memory device by passing one of the sync map modes {@link
	* jdk.nio.mapmode.ExtendedMapMode#READ_ONLY_SYNC
	* ExtendedMapModeMapMode#READ_ONLY_SYNC} or {@link
	* jdk.nio.mapmode.ExtendedMapMode#READ_ONLY_SYNC
	* ExtendedMapMode#READ_WRITE_SYNC} in the call to {@link
	* java.nio.channels.FileChannel#map FileChannel.map} or was
	* mapped by passing one of the other map modes.
	*
	* @return true if the file was mapped using one of the sync map
	* modes, otherwise false.
	*/
	final boolean isSync() { // package-private
	return isSync;
	}

	/**
	* Returns the {@code FileDescriptor} associated with this
	* {@code MappedByteBuffer}.
	*
	* @return the buffer's file descriptor; may be {@code null}
	*/
	final FileDescriptor fileDescriptor() { // package-private
	return fd;
	}

	// Android-added: Added the unused field to avoid compiler optimization in load();
	private static byte unused;
	// Android-added: Added checkMapped as Android doesn't allow null fd in DirectByteBuffer.
	private void checkMapped() {
	if (fd == null)
	// Can only happen if a user explicitly casts a direct byte buffer
	throw new UnsupportedOperationException();
	}

	// BEGIN Android-added: Additional fields / methods for removing unsupported scoped memory.
	// Returns the distance (in bytes) of the buffer from the page aligned address
	// of the mapping. Computed each time to avoid storing in every direct buffer.
	private long mappingOffset() {
	return mappingOffset(address);
	}

	private static long mappingOffset(long addr) {
	int ps = Bits.pageSize();
	long offset = addr % ps;
	return (offset >= 0) ? offset : (ps + offset);
	}

	private long mappingAddress(long mappingOffset) {
	return address - mappingOffset;
	}

	private static long mappingAddress(long addr, long mappingOffset) {
	return addr - mappingOffset;
	}

	private long mappingLength(long mappingOffset) {
	return mappingLength(capacity(), mappingOffset);
	}

	private long mappingLength(long length, long mappingOffset) {
	return length + mappingOffset;
	}
	// END Android-added: Additional fields / methods for removing unsupported scoped memory.


	/**
	* Tells whether or not this buffer's content is resident in physical
	* memory.
	*
	* <p> A return value of {@code true} implies that it is highly likely
	* that all of the data in this buffer is resident in physical memory and
	* may therefore be accessed without incurring any virtual-memory page
	* faults or I/O operations. A return value of {@code false} does not
	* necessarily imply that the buffer's content is not resident in physical
	* memory.
	*
	* <p> The returned value is a hint, rather than a guarantee, because the
	* underlying operating system may have paged out some of the buffer's data
	* by the time that an invocation of this method returns. </p>
	*
	* @return {@code true} if it is likely that this buffer's content
	* is resident in physical memory
	*/
	public final boolean isLoaded() {
	// Android-added: Android throws UOE for memory-backed direct byte buffer.
	// if (fd == null) {
	// return true;
	// }
	checkMapped();
	// Android-changed: Remove unsupported scoped memory access.
	// return SCOPED_MEMORY_ACCESS.isLoaded(scope(), address, isSync, capacity());
	if ((address == 0) \|\| (capacity() == 0))
	return true;
	long offset = mappingOffset();
	long length = mappingLength(offset);
	return isLoaded0(mappingAddress(offset), length, Bits.pageCount(length));
	}

	/**
	* Loads this buffer's content into physical memory.
	*
	* <p> This method makes a best effort to ensure that, when it returns,
	* this buffer's content is resident in physical memory. Invoking this
	* method may cause some number of page faults and I/O operations to
	* occur. </p>
	*
	* @return This buffer
	*/
	public final MappedByteBuffer load() {
	// Android-added: Android throws UOE for memory-backed direct byte buffer.
	// if (fd == null) {
	// return this;
	// }
	checkMapped();
	// Android-changed: Remove unsupported scoped memory access.
	/*
	try {
	SCOPED_MEMORY_ACCESS.load(scope(), address, isSync, capacity());
	} finally {
	Reference.reachabilityFence(this);
	}
	*/
	if ((address == 0) \|\| (capacity() == 0))
	return this;
	long offset = mappingOffset();
	long length = mappingLength(offset);
	load0(mappingAddress(offset), length);

	// Read a byte from each page to bring it into memory. A checksum
	// is computed as we go along to prevent the compiler from otherwise
	// considering the loop as dead code.
	Unsafe unsafe = Unsafe.getUnsafe();
	int ps = Bits.pageSize();
	long count = Bits.pageCount(length);
	long a = mappingAddress(offset);
	byte x = 0;
	for (int i=0; i<count; i++) {
	x ^= unsafe.getByte(a);
	a += ps;
	}
	if (unused != 0)
	unused = x;

	return this;
	}

	/**
	* Forces any changes made to this buffer's content to be written to the
	* storage device containing the mapped file. The region starts at index
	* zero in this buffer and is {@code capacity()} bytes.
	*
	* <p> If the file mapped into this buffer resides on a local storage
	* device then when this method returns it is guaranteed that all changes
	* made to the buffer since it was created, or since this method was last
	* invoked, will have been written to that device.
	*
	* <p> If the file does not reside on a local device then no such guarantee
	* is made.
	*
	* <p> If this buffer was not mapped in read/write mode ({@link
	* java.nio.channels.FileChannel.MapMode#READ_WRITE}) then
	* invoking this method may have no effect. In particular, the
	* method has no effect for buffers mapped in read-only or private
	* mapping modes. This method may or may not have an effect for
	* implementation-specific mapping modes. </p>
	*
	* @throws UncheckedIOException
	* If an I/O error occurs writing the buffer's content to the
	* storage device containing the mapped file
	*
	* @return This buffer
	*/
	public final MappedByteBuffer force() {
	// Android-changed:: Android throws UOE for memory-backed direct byte buffer.
	// if (fd == null) {
	// return this;
	// }
	checkMapped();
	int capacity = capacity();
	if (isSync \|\| ((address != 0) && (capacity != 0))) {
	return force(0, capacity);
	}
	return this;
	}

	/**
	* Forces any changes made to a region of this buffer's content to
	* be written to the storage device containing the mapped
	* file. The region starts at the given {@code index} in this
	* buffer and is {@code length} bytes.
	*
	* <p> If the file mapped into this buffer resides on a local
	* storage device then when this method returns it is guaranteed
	* that all changes made to the selected region buffer since it
	* was created, or since this method was last invoked, will have
	* been written to that device. The force operation is free to
	* write bytes that lie outside the specified region, for example
	* to ensure that data blocks of some device-specific granularity
	* are transferred in their entirety.
	*
	* <p> If the file does not reside on a local device then no such
	* guarantee is made.
	*
	* <p> If this buffer was not mapped in read/write mode ({@link
	* java.nio.channels.FileChannel.MapMode#READ_WRITE}) then
	* invoking this method may have no effect. In particular, the
	* method has no effect for buffers mapped in read-only or private
	* mapping modes. This method may or may not have an effect for
	* implementation-specific mapping modes. </p>
	*
	* @param index
	* The index of the first byte in the buffer region that is
	* to be written back to storage; must be non-negative
	* and less than {@code capacity()}
	*
	* @param length
	* The length of the region in bytes; must be non-negative
	* and no larger than {@code capacity() - index}
	*
	* @throws IndexOutOfBoundsException
	* if the preconditions on the index and length do not
	* hold.
	*
	* @throws UncheckedIOException
	* If an I/O error occurs writing the buffer's content to the
	* storage device containing the mapped file
	*
	* @return This buffer
	*
	* @since 13
	*/
	public final MappedByteBuffer force(int index, int length) {
	// Android-note: Android doesn't throw UOE, because new API doesn't need forward compat.
	if (fd == null) {
	return this;
	}
	int capacity = capacity();
	if ((address != 0) && (capacity != 0)) {
	// check inputs
	Objects.checkFromIndexSize(index, length, capacity);
	// Android-changed: Remove unsupported scoped memory access.
	// SCOPED_MEMORY_ACCESS.force(scope(), fd, address, isSync, index, length);
	long firstByteAddress = address + index;
	long offset = mappingOffset(firstByteAddress);
	force0(fd, mappingAddress(firstByteAddress, offset), mappingLength(length, offset));
	}
	return this;
	}

	// -- Covariant return type overrides

	/**
	* {@inheritDoc}
	*/
	// Android-changed: covariant overloads of *Buffer methods that return this.
	@CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
	@CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
	@Override
	public final Buffer position(int newPosition) {
	super.position(newPosition);
	return this;
	}

	/**
	* {@inheritDoc}
	*/
	// Android-changed: covariant overloads of *Buffer methods that return this.
	@CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
	@CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
	@Override
	public final Buffer limit(int newLimit) {
	super.limit(newLimit);
	return this;
	}

	/**
	* {@inheritDoc}
	*/
	// Android-changed: covariant overloads of *Buffer methods that return this.
	@CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
	@CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
	@Override
	public final Buffer mark() {
	super.mark();
	return this;
	}

	/**
	* {@inheritDoc}
	*/
	// Android-changed: covariant overloads of *Buffer methods that return this.
	@CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
	@CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
	@Override
	public final Buffer reset() {
	super.reset();
	return this;
	}

	/**
	* {@inheritDoc}
	*/
	// Android-changed: covariant overloads of *Buffer methods that return this.
	@CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
	@CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
	@Override
	public final Buffer clear() {
	super.clear();
	return this;
	}

	/**
	* {@inheritDoc}
	*/
	// Android-changed: covariant overloads of *Buffer methods that return this.
	@CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
	@CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
	@Override
	public final Buffer flip() {
	super.flip();
	return this;
	}

	/**
	* {@inheritDoc}
	*/
	// Android-changed: covariant overloads of *Buffer methods that return this.
	@CovariantReturnType(returnType = ByteBuffer.class, presentAfter = 34)
	@CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
	@Override
	public final Buffer rewind() {
	super.rewind();
	return this;
	}

	/**
	* {@inheritDoc}
	*
	* <p> Reading bytes into physical memory by invoking {@code load()} on the
	* returned buffer, or writing bytes to the storage device by invoking
	* {@code force()} on the returned buffer, will only act on the sub-range
	* of this buffer that the returned buffer represents, namely
	* {@code [position(),limit())}.
	*/
	// Android-changed: covariant overloads of *Buffer methods that return this.
	@CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
	@Override
	public abstract ByteBuffer slice();

	/**
	* {@inheritDoc}
	*
	* <p> Reading bytes into physical memory by invoking {@code load()} on the
	* returned buffer, or writing bytes to the storage device by invoking
	* {@code force()} on the returned buffer, will only act on the sub-range
	* of this buffer that the returned buffer represents, namely
	* {@code [index,index+length)}, where {@code index} and {@code length} are
	* assumed to satisfy the preconditions.
	*/
	public abstract MappedByteBuffer slice(int index, int length);

	private native boolean isLoaded0(long address, long length, long pageCount);
	private native void load0(long address, long length);
	private native void force0(FileDescriptor fd, long address, long length);


	/**
	* {@inheritDoc}
	*/
	// Android-changed: covariant overloads of *Buffer methods that return this.
	@CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
	@Override
	public abstract ByteBuffer duplicate();

	/**
	* {@inheritDoc}
	*/
	// Android-changed: covariant overloads of *Buffer methods that return this.
	@CovariantReturnType(returnType = MappedByteBuffer.class, presentAfter = 34)
	@Override
	public abstract ByteBuffer compact();
	}