https://openjdk.java.net/ 
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 *  DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package jdk.incubator.foreign;

import java.nio.ByteBuffer;

import jdk.internal.foreign.AbstractMemorySegmentImpl;
import jdk.internal.foreign.HeapMemorySegmentImpl;
import jdk.internal.foreign.MappedMemorySegmentImpl;
import jdk.internal.foreign.NativeMemorySegmentImpl;
import jdk.internal.foreign.Utils;

import java.io.IOException;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.util.Objects;
import java.util.Spliterator;
import java.util.function.Consumer;


A memory segment models a contiguous region of memory. A memory segment is associated with both spatial
and temporal bounds. Spatial bounds ensure that memory access operations on a memory segment cannot affect a memory location
which falls outside the boundaries of the memory segment being accessed. Temporal bounds ensure that memory access operations on a segment cannot occur after a memory segment has been closed (see close()). 

All implementations of this interface must be value-based; use of identity-sensitive operations (including reference equality (==), identity hash code, or synchronization) on instances of MemorySegment may have unpredictable results and should be avoided. The equals method should be used for comparisons. 
 Non-platform classes should not implement MemorySegment directly. 
Constructing memory segments from different sources
 There are multiple ways to obtain a memory segment. First, memory segments backed by off-heap memory can be allocated using one of the many factory methods provided (see allocateNative(MemoryLayout), allocateNative(long) and allocateNative(long, long)). Memory segments obtained in this way are called native memory segments.

 It is also possible to obtain a memory segment backed by an existing heap-allocated Java array, using one of the provided factory methods (e.g. ofArray(int[])). Memory segments obtained in this way are called array memory segments.

 It is possible to obtain a memory segment backed by an existing Java byte buffer (see ByteBuffer), using the factory method ofByteBuffer(ByteBuffer). Memory segments obtained in this way are called buffer memory segments. Note that buffer memory segments might be backed by native memory (as in the case of native memory segments) or heap memory (as in the case of array memory segments), depending on the characteristics of the byte buffer instance the segment is associated with. For instance, a buffer memory segment obtained from a byte buffer created with the ByteBuffer.allocateDirect(int) method will be backed by native memory. 
 Finally, it is also possible to obtain a memory segment backed by a memory-mapped file using the factory method mapFromPath(Path, long, long, MapMode). Such memory segments are called mapped memory segments (see MappedMemorySegment). 

Array and buffer segments are effectively views over existing memory regions which might outlive the lifecycle of the segments derived from them, and can even be manipulated directly (e.g. via array access, or direct use of the ByteBuffer API) by other clients. As a result, while sharing array or buffer segments is possible, it is strongly advised that clients wishing to do so take extra precautions to make sure that the underlying memory sources associated with such segments remain inaccessible, and that said memory sources are never aliased by more than one segment at a time - e.g. so as to prevent concurrent modifications of the contents of an array, or buffer segment. 
Closing a memory segment
 Memory segments are closed explicitly (see close()). When a segment is closed, it is no longer alive (see isAlive(), and subsequent operation on the segment (or on any MemoryAddress instance derived from it) will fail with IllegalStateException. 

Closing a segment might trigger the releasing of the underlying memory resources associated with said segment, depending on
the kind of memory segment being considered:

    
    
  • closing a native memory segment results in freeing the native memory associated with it
    • 
    
  • closing a mapped memory segment results in the backing memory-mapped file to be unmapped
    • 
    
  • closing a buffer, or a heap segment does not have any side-effect, other than marking the segment
    as not alive (see isAlive()). Also, since the buffer and heap segments might keep strong references to the original buffer or array instance, it is the responsibility of clients to ensure that these segments are discarded in a timely manner, so as not to prevent garbage collection to reclaim the underlying objects.
    • 



Access modes

Memory segments supports zero or more access modes. Supported access modes are READ, WRITE, CLOSE, ACQUIRE and HANDOFF. The set of access modes supported by a segment alters the set of operations that are supported by that segment. For instance, attempting to call close() on a segment which does not support the CLOSE access mode will result in an exception. 

The set of supported access modes can only be made stricter (by supporting fewer access modes). This means
that restricting the set of access modes supported by a segment before sharing it with other clients
is generally a good practice if the creator of the segment wants to retain some control over how the segment
is going to be accessed.

Memory segment views

Memory segments support views. For instance, it is possible to alter the set of supported access modes,
by creating an immutable view of a memory segment, as follows:


MemorySegment segment = ...
MemorySegment roSegment = segment.withAccessModes(segment.accessModes() & ~WRITE);

 It is also possible to create views whose spatial bounds are stricter than the ones of the original segment (see asSlice(long, long)). 
 Temporal bounds of the original segment are inherited by the view; that is, closing a segment view, such as a sliced view, will cause the original segment to be closed; as such special care must be taken when sharing views between multiple clients. If a client want to protect itself against early closure of a segment by another actor, it is the responsibility of that client to take protective measures, such as removing CLOSE from the set of supported access modes, before sharing the view with another client. 
 To allow for interoperability with existing code, a byte buffer view can be obtained from a memory segment (see asByteBuffer()). This can be useful, for instance, for those clients that want to keep using the ByteBuffer API, but need to operate on large memory segments. Byte buffers obtained in such a way support the same spatial and temporal access restrictions associated to the memory segment from which they originated. 
Thread confinement

Memory segments support strong thread-confinement guarantees. Upon creation, they are assigned an owner thread,
typically the thread which initiated the creation operation. After creation, only the owner thread will be allowed
to directly manipulate the memory segment (e.g. close the memory segment) or access the underlying memory associated with
the segment using a memory access var handle. Any attempt to perform such operations from a thread other than the
owner thread will result in a runtime failure.


Memory segments support serial thread confinement; that is, ownership of a memory segment can change (see withOwnerThread(Thread)). This allows, for instance, for two threads A and B to share a segment in a controlled, cooperative and race-free fashion. 
 In some cases, it might be useful for multiple threads to process the contents of the same memory segment concurrently (e.g. in the case of parallel processing); while memory segments provide strong confinement guarantees, it is possible to obtain a Spliterator from a segment, which can be used to slice the segment and allow multiple thread to work in parallel on disjoint segment slices (this assumes that the access mode ACQUIRE is set). For instance, the following code can be used to sum all int values in a memory segment in parallel: 

MemorySegment segment = ...
SequenceLayout SEQUENCE_LAYOUT = MemoryLayout.ofSequence(1024, MemoryLayouts.JAVA_INT);
VarHandle VH_int = SEQUENCE_LAYOUT.elementLayout().varHandle(int.class);
int sum = StreamSupport.stream(MemorySegment.spliterator(segment, SEQUENCE_LAYOUT), true)
.mapToInt(s -> (int)VH_int.get(s.baseAddress()))
.sum();



API Note:In the future, if the Java language permits, MemorySegment may become a sealed interface, which would prohibit subclassing except by MappedMemorySegment and other explicitly permitted subtypes.
Implementation Requirements:
Implementations of this interface are immutable, thread-safe and value-based.
/**
 * A memory segment models a contiguous region of memory. A memory segment is associated with both spatial
 * and temporal bounds. Spatial bounds ensure that memory access operations on a memory segment cannot affect a memory location
 * which falls <em>outside</em> the boundaries of the memory segment being accessed. Temporal bounds ensure that memory access
 * operations on a segment cannot occur after a memory segment has been closed (see {@link MemorySegment#close()}).
 * <p>
 * All implementations of this interface must be <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>;
 * use of identity-sensitive operations (including reference equality ({@code ==}), identity hash code, or synchronization) on
 * instances of {@code MemorySegment} may have unpredictable results and should be avoided. The {@code equals} method should
 * be used for comparisons.
 * <p>
 * Non-platform classes should not implement {@linkplain MemorySegment} directly.
 *
 * <h2>Constructing memory segments from different sources</h2>
 *
 * There are multiple ways to obtain a memory segment. First, memory segments backed by off-heap memory can
 * be allocated using one of the many factory methods provided (see {@link MemorySegment#allocateNative(MemoryLayout)},
 * {@link MemorySegment#allocateNative(long)} and {@link MemorySegment#allocateNative(long, long)}). Memory segments obtained
 * in this way are called <em>native memory segments</em>.
 * <p>
 * It is also possible to obtain a memory segment backed by an existing heap-allocated Java array,
 * using one of the provided factory methods (e.g. {@link MemorySegment#ofArray(int[])}). Memory segments obtained
 * in this way are called <em>array memory segments</em>.
 * <p>
 * It is possible to obtain a memory segment backed by an existing Java byte buffer (see {@link ByteBuffer}),
 * using the factory method {@link MemorySegment#ofByteBuffer(ByteBuffer)}.
 * Memory segments obtained in this way are called <em>buffer memory segments</em>. Note that buffer memory segments might
 * be backed by native memory (as in the case of native memory segments) or heap memory (as in the case of array memory segments),
 * depending on the characteristics of the byte buffer instance the segment is associated with. For instance, a buffer memory
 * segment obtained from a byte buffer created with the {@link ByteBuffer#allocateDirect(int)} method will be backed
 * by native memory.
 * <p>
 * Finally, it is also possible to obtain a memory segment backed by a memory-mapped file using the factory method
 * {@link MemorySegment#mapFromPath(Path, long, long, FileChannel.MapMode)}. Such memory segments are called <em>mapped memory segments</em>
 * (see {@link MappedMemorySegment}).
 * <p>
 * Array and buffer segments are effectively <em>views</em> over existing memory regions which might outlive the
 * lifecycle of the segments derived from them, and can even be manipulated directly (e.g. via array access, or direct use
 * of the {@link ByteBuffer} API) by other clients. As a result, while sharing array or buffer segments is possible,
 * it is strongly advised that clients wishing to do so take extra precautions to make sure that the underlying memory sources
 * associated with such segments remain inaccessible, and that said memory sources are never aliased by more than one segment
 * at a time - e.g. so as to prevent concurrent modifications of the contents of an array, or buffer segment.
 *
 * <h2>Closing a memory segment</h2>
 *
 * Memory segments are closed explicitly (see {@link MemorySegment#close()}). When a segment is closed, it is no longer
 * <em>alive</em> (see {@link #isAlive()}, and subsequent operation on the segment (or on any {@link MemoryAddress} instance
 * derived from it) will fail with {@link IllegalStateException}.
 * <p>
 * Closing a segment might trigger the releasing of the underlying memory resources associated with said segment, depending on
 * the kind of memory segment being considered:
 * <ul>
 *     <li>closing a native memory segment results in <em>freeing</em> the native memory associated with it</li>
 *     <li>closing a mapped memory segment results in the backing memory-mapped file to be unmapped</li>
 *     <li>closing a buffer, or a heap segment does not have any side-effect, other than marking the segment
 *     as <em>not alive</em> (see {@link MemorySegment#isAlive()}). Also, since the buffer and heap segments might keep
 *     strong references to the original buffer or array instance, it is the responsibility of clients to ensure that
 *     these segments are discarded in a timely manner, so as not to prevent garbage collection to reclaim the underlying
 *     objects.</li>
 * </ul>
 *
 * <h2><a id = "access-modes">Access modes</a></h2>
 *
 * Memory segments supports zero or more <em>access modes</em>. Supported access modes are {@link #READ},
 * {@link #WRITE}, {@link #CLOSE}, {@link #ACQUIRE} and {@link #HANDOFF}. The set of access modes supported by a segment alters the
 * set of operations that are supported by that segment. For instance, attempting to call {@link #close()} on
 * a segment which does not support the {@link #CLOSE} access mode will result in an exception.
 * <p>
 * The set of supported access modes can only be made stricter (by supporting <em>fewer</em> access modes). This means
 * that restricting the set of access modes supported by a segment before sharing it with other clients
 * is generally a good practice if the creator of the segment wants to retain some control over how the segment
 * is going to be accessed.
 *
 * <h2>Memory segment views</h2>
 *
 * Memory segments support <em>views</em>. For instance, it is possible to alter the set of supported access modes,
 * by creating an <em>immutable</em> view of a memory segment, as follows:
 * <blockquote><pre>{@code
MemorySegment segment = ...
MemorySegment roSegment = segment.withAccessModes(segment.accessModes() & ~WRITE);
 * }</pre></blockquote>
 * It is also possible to create views whose spatial bounds are stricter than the ones of the original segment
 * (see {@link MemorySegment#asSlice(long, long)}).
 * <p>
 * Temporal bounds of the original segment are inherited by the view; that is, closing a segment view, such as a sliced
 * view, will cause the original segment to be closed; as such special care must be taken when sharing views
 * between multiple clients. If a client want to protect itself against early closure of a segment by
 * another actor, it is the responsibility of that client to take protective measures, such as removing {@link #CLOSE}
 * from the set of supported access modes, before sharing the view with another client.
 * <p>
 * To allow for interoperability with existing code, a byte buffer view can be obtained from a memory segment
 * (see {@link #asByteBuffer()}). This can be useful, for instance, for those clients that want to keep using the
 * {@link ByteBuffer} API, but need to operate on large memory segments. Byte buffers obtained in such a way support
 * the same spatial and temporal access restrictions associated to the memory segment from which they originated.
 *
 * <h2><a id = "thread-confinement">Thread confinement</a></h2>
 *
 * Memory segments support strong thread-confinement guarantees. Upon creation, they are assigned an <em>owner thread</em>,
 * typically the thread which initiated the creation operation. After creation, only the owner thread will be allowed
 * to directly manipulate the memory segment (e.g. close the memory segment) or access the underlying memory associated with
 * the segment using a memory access var handle. Any attempt to perform such operations from a thread other than the
 * owner thread will result in a runtime failure.
 * <p>
 * Memory segments support <em>serial thread confinement</em>; that is, ownership of a memory segment can change (see
 * {@link #withOwnerThread(Thread)}). This allows, for instance, for two threads {@code A} and {@code B} to share
 * a segment in a controlled, cooperative and race-free fashion.
 * <p>
 * In some cases, it might be useful for multiple threads to process the contents of the same memory segment concurrently
 * (e.g. in the case of parallel processing); while memory segments provide strong confinement guarantees, it is possible
 * to obtain a {@link Spliterator} from a segment, which can be used to slice the segment and allow multiple thread to
 * work in parallel on disjoint segment slices (this assumes that the access mode {@link #ACQUIRE} is set).
 * For instance, the following code can be used to sum all int values in a memory segment in parallel:
 * <blockquote><pre>{@code
MemorySegment segment = ...
SequenceLayout SEQUENCE_LAYOUT = MemoryLayout.ofSequence(1024, MemoryLayouts.JAVA_INT);
VarHandle VH_int = SEQUENCE_LAYOUT.elementLayout().varHandle(int.class);
int sum = StreamSupport.stream(MemorySegment.spliterator(segment, SEQUENCE_LAYOUT), true)
                       .mapToInt(s -> (int)VH_int.get(s.baseAddress()))
                       .sum();
 * }</pre></blockquote>
 *
 * @apiNote In the future, if the Java language permits, {@link MemorySegment}
 * may become a {@code sealed} interface, which would prohibit subclassing except by
 * {@link MappedMemorySegment} and other explicitly permitted subtypes.
 *
 * @implSpec
 * Implementations of this interface are immutable, thread-safe and <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>.
 */
public interface MemorySegment extends AutoCloseable {

    
The base memory address associated with this memory segment. The returned address is
a checked memory address and can therefore be used in derefrence operations (see MemoryAddress). 
Returns:The base memory address.
/**
     * The base memory address associated with this memory segment. The returned address is
     * a <em>checked</em> memory address and can therefore be used in derefrence operations
     * (see {@link MemoryAddress}).
     * @return The base memory address.
     */
    MemoryAddress baseAddress();

    
Returns a spliterator for the given memory segment. The returned spliterator reports Spliterator.SIZED, Spliterator.SUBSIZED, Spliterator.IMMUTABLE, Spliterator.NONNULL and Spliterator.ORDERED characteristics. 
 The returned spliterator splits the segment according to the specified sequence layout; that is, if the supplied layout is a sequence layout whose element count is N, then calling Spliterator.trySplit() will result in a spliterator serving approximatively N/2 elements (depending on whether N is even or not). As such, splitting is possible as long as N >= 2. The spliterator returns segments that feature the same access modes as the given segment less the CLOSE access mode. 
 The returned spliterator effectively allows to slice a segment into disjoint sub-segments, which can then be processed in parallel by multiple threads (if the access mode ACQUIRE is set). While closing the segment (see close()) during pending concurrent execution will generally fail with an exception, it is possible to close a segment when a spliterator has been obtained but no thread is actively working on it using Spliterator.tryAdvance(Consumer); in such cases, any subsequent call to Spliterator.tryAdvance(Consumer) will fail with an exception. 
Params:
  • segment – the segment to be used for splitting.
  • layout – the layout to be used for splitting.
Type parameters:
  • <S> – the memory segment type
Throws:
  • IllegalStateException – if the segment is not alive, or if access occurs from a thread other than the
thread owning this segment
Returns:the element spliterator for this segment
/**
     * Returns a spliterator for the given memory segment. The returned spliterator reports {@link Spliterator#SIZED},
     * {@link Spliterator#SUBSIZED}, {@link Spliterator#IMMUTABLE}, {@link Spliterator#NONNULL} and {@link Spliterator#ORDERED}
     * characteristics.
     * <p>
     * The returned spliterator splits the segment according to the specified sequence layout; that is,
     * if the supplied layout is a sequence layout whose element count is {@code N}, then calling {@link Spliterator#trySplit()}
     * will result in a spliterator serving approximatively {@code N/2} elements (depending on whether N is even or not).
     * As such, splitting is possible as long as {@code N >= 2}. The spliterator returns segments that feature the same
     * <a href="#access-modes">access modes</a> as the given segment less the {@link #CLOSE} access mode.
     * <p>
     * The returned spliterator effectively allows to slice a segment into disjoint sub-segments, which can then
     * be processed in parallel by multiple threads (if the access mode {@link #ACQUIRE} is set).
     * While closing the segment (see {@link #close()}) during pending concurrent execution will generally
     * fail with an exception, it is possible to close a segment when a spliterator has been obtained but no thread
     * is actively working on it using {@link Spliterator#tryAdvance(Consumer)}; in such cases, any subsequent call
     * to {@link Spliterator#tryAdvance(Consumer)} will fail with an exception.
     * @param segment the segment to be used for splitting.
     * @param layout the layout to be used for splitting.
     * @param <S> the memory segment type
     * @return the element spliterator for this segment
     * @throws IllegalStateException if the segment is not <em>alive</em>, or if access occurs from a thread other than the
     * thread owning this segment
     */
    static <S extends MemorySegment> Spliterator<S> spliterator(S segment, SequenceLayout layout) {
        return AbstractMemorySegmentImpl.spliterator(segment, layout);
    }

    
The thread owning this segment.

Returns:the thread owning this segment.
/**
     * The thread owning this segment.
     * @return the thread owning this segment.
     */
    Thread ownerThread();

    
Obtains a new memory segment backed by the same underlying memory region as this segment,
but with different owner thread. As a side-effect, this segment will be marked as not alive,
and subsequent operations on this segment will result in runtime errors.


Write accesses to the segment's content happens-before
hand-over from the current owner thread to the new owner thread, which in turn happens before read accesses to the segment's contents on
the new owner thread.

Params:
  • newOwner – the new owner thread.
Throws:
Returns:a new memory segment backed by the same underlying memory region as this segment, owned by newOwner.
/**
     * Obtains a new memory segment backed by the same underlying memory region as this segment,
     * but with different owner thread. As a side-effect, this segment will be marked as <em>not alive</em>,
     * and subsequent operations on this segment will result in runtime errors.
     * <p>
     * Write accesses to the segment's content <a href="../../../java/util/concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a>
     * hand-over from the current owner thread to the new owner thread, which in turn <i>happens before</i> read accesses to the segment's contents on
     * the new owner thread.
     *
     * @param newOwner the new owner thread.
     * @return a new memory segment backed by the same underlying memory region as this segment,
     *      owned by {@code newOwner}.
     * @throws IllegalStateException if this segment is not <em>alive</em>, or if access occurs from a thread other than the
     * thread owning this segment, or if the segment cannot be closed because it is being operated upon by a different
     * thread (see {@link #spliterator(MemorySegment, SequenceLayout)}).
     * @throws NullPointerException if {@code newOwner == null}
     * @throws IllegalArgumentException if the segment is already a confined segment owner by {@code newOnwer}.
     * @throws UnsupportedOperationException if this segment does not support the {@link #HANDOFF} access mode.
     */
    MemorySegment withOwnerThread(Thread newOwner);

    
The size (in bytes) of this memory segment.

Returns:The size (in bytes) of this memory segment.
/**
     * The size (in bytes) of this memory segment.
     * @return The size (in bytes) of this memory segment.
     */
    long byteSize();

    
Obtains a segment view with specific access modes. Supported access modes are READ, WRITE, CLOSE, ACQUIRE and HANDOFF. It is generally not possible to go from a segment with stricter access modes to one with less strict access modes. For instance, attempting to add WRITE access mode to a read-only segment will be met with an exception. 
Params:
  • accessModes – an ORed mask of zero or more access modes.
Throws:
  • IllegalArgumentException – when mask is an access mask which is less strict than the one supported by this segment, or when mask contains bits not associated with any of the supported access modes.
Returns:a segment view with specific access modes.
/**
     * Obtains a segment view with specific <a href="#access-modes">access modes</a>. Supported access modes are {@link #READ}, {@link #WRITE},
     * {@link #CLOSE}, {@link #ACQUIRE} and {@link #HANDOFF}. It is generally not possible to go from a segment with stricter access modes
     * to one with less strict access modes. For instance, attempting to add {@link #WRITE} access mode to a read-only segment
     * will be met with an exception.
     * @param accessModes an ORed mask of zero or more access modes.
     * @return a segment view with specific access modes.
     * @throws IllegalArgumentException when {@code mask} is an access mask which is less strict than the one supported by this
     * segment, or when {@code mask} contains bits not associated with any of the supported access modes.
     */
    MemorySegment withAccessModes(int accessModes);

    
Does this segment support a given set of access modes?

Params:
  • accessModes – an ORed mask of zero or more access modes.
Throws:
Returns:true, if the access modes in accessModes are stricter than the ones supported by this segment.
/**
     * Does this segment support a given set of access modes?
     * @param accessModes an ORed mask of zero or more access modes.
     * @return true, if the access modes in {@code accessModes} are stricter than the ones supported by this segment.
     * @throws IllegalArgumentException when {@code mask} contains bits not associated with any of the supported access modes.
     */
    boolean hasAccessModes(int accessModes);

    
Returns the access modes associated with this segment; the result is represented as ORed values from READ, WRITE, CLOSE, ACQUIRE and HANDOFF. 
Returns:the access modes associated with this segment.
/**
     * Returns the <a href="#access-modes">access modes</a> associated with this segment; the result is represented as ORed values from
     * {@link #READ}, {@link #WRITE}, {@link #CLOSE}, {@link #ACQUIRE} and {@link #HANDOFF}.
     * @return the access modes associated with this segment.
     */
    int accessModes();

    
Obtains a new memory segment view whose base address is the same as the base address of this segment plus a given offset,
and whose new size is specified by the given argument.

Params:
  • offset – The new segment base offset (relative to the current segment base address), specified in bytes.
  • newSize – The new segment size, specified in bytes.
Throws:
Returns:a new memory segment view with updated base/limit addresses.
/**
     * Obtains a new memory segment view whose base address is the same as the base address of this segment plus a given offset,
     * and whose new size is specified by the given argument.
     * @param offset The new segment base offset (relative to the current segment base address), specified in bytes.
     * @param newSize The new segment size, specified in bytes.
     * @return a new memory segment view with updated base/limit addresses.
     * @throws IndexOutOfBoundsException if {@code offset < 0}, {@code offset > byteSize()}, {@code newSize < 0}, or {@code newSize > byteSize() - offset}
     */
    MemorySegment asSlice(long offset, long newSize);

    
Is this segment alive?

See Also:
Returns:true, if the segment is alive.
/**
     * Is this segment alive?
     * @return true, if the segment is alive.
     * @see MemorySegment#close()
     */
    boolean isAlive();

    
Closes this memory segment. Once a memory segment has been closed, any attempt to use the memory segment, or to access any MemoryAddress instance associated with it will fail with IllegalStateException. Depending on the kind of memory segment being closed, calling this method further triggers deallocation of all the resources associated with the memory segment. 
Throws:
/**
     * Closes this memory segment. Once a memory segment has been closed, any attempt to use the memory segment,
     * or to access any {@link MemoryAddress} instance associated with it will fail with {@link IllegalStateException}.
     * Depending on the kind of memory segment being closed, calling this method further triggers deallocation of all the resources
     * associated with the memory segment.
     * @throws IllegalStateException if this segment is not <em>alive</em>, or if access occurs from a thread other than the
     * thread owning this segment, or if the segment cannot be closed because it is being operated upon by a different
     * thread (see {@link #spliterator(MemorySegment, SequenceLayout)}).
     * @throws UnsupportedOperationException if this segment does not support the {@link #CLOSE} access mode.
     */
    void close();

    
Fills a value into this memory segment.


More specifically, the given value is filled into each address of this
segment. Equivalent to (but likely more efficient than) the following code:


byteHandle = MemoryLayout.ofSequence(MemoryLayouts.JAVA_BYTE)
.varHandle(byte.class, MemoryLayout.PathElement.sequenceElement());
for (long l = 0; l < segment.byteSize(); l++) {
byteHandle.set(segment.baseAddress(), l, value);


without any regard or guarantees on the ordering of particular memory
elements being set.


Fill can be useful to initialize or reset the memory of a segment.

Params:
  • value – the value to fill into this segment
Throws:
Returns:this memory segment
/**
     * Fills a value into this memory segment.
     * <p>
     * More specifically, the given value is filled into each address of this
     * segment. Equivalent to (but likely more efficient than) the following code:
     *
     * <pre>{@code
byteHandle = MemoryLayout.ofSequence(MemoryLayouts.JAVA_BYTE)
         .varHandle(byte.class, MemoryLayout.PathElement.sequenceElement());
for (long l = 0; l < segment.byteSize(); l++) {
     byteHandle.set(segment.baseAddress(), l, value);
}
     * }</pre>
     *
     * without any regard or guarantees on the ordering of particular memory
     * elements being set.
     * <p>
     * Fill can be useful to initialize or reset the memory of a segment.
     *
     * @param value the value to fill into this segment
     * @return this memory segment
     * @throws IllegalStateException if this segment is not <em>alive</em>, or if access occurs from a thread other than the
     * thread owning this segment
     * @throws UnsupportedOperationException if this segment does not support the {@link #WRITE} access mode
     */
    MemorySegment fill(byte value);

    
Performs a bulk copy from given source segment to this segment. More specifically, the bytes at offset 0 through src.byteSize() - 1 in the source segment are copied into this segment at offset 0 through src.byteSize() - 1. If the source segment overlaps with this segment, then the copying is performed as if the bytes at offset 0 through src.byteSize() - 1 in the source segment were first copied into a temporary segment with size bytes, and then the contents of the temporary segment were copied into this segment at offset 0 through src.byteSize() - 1. 
 The result of a bulk copy is unspecified if, in the uncommon case, the source segment and this segment do not overlap, but refer to overlapping regions of the same backing storage using different addresses. For example, this may occur if the same file is mapped to two segments. 
Params:
  • src – the source segment.
Throws:
  • IndexOutOfBoundsException – if src.byteSize() > this.byteSize().
  • IllegalStateException – if either the source segment or this segment have been already closed,
or if access occurs from a thread other than the thread owning either segment.
  • UnsupportedOperationException – if either the source segment or this segment do not feature required access modes; more specifically, src should feature at least the READ access mode, while this segment should feature at least the WRITE access mode.
/**
     * Performs a bulk copy from given source segment to this segment. More specifically, the bytes at
     * offset {@code 0} through {@code src.byteSize() - 1} in the source segment are copied into this segment
     * at offset {@code 0} through {@code src.byteSize() - 1}.
     * If the source segment overlaps with this segment, then the copying is performed as if the bytes at
     * offset {@code 0} through {@code src.byteSize() - 1} in the source segment were first copied into a
     * temporary segment with size {@code bytes}, and then the contents of the temporary segment were copied into
     * this segment at offset {@code 0} through {@code src.byteSize() - 1}.
     * <p>
     * The result of a bulk copy is unspecified if, in the uncommon case, the source segment and this segment
     * do not overlap, but refer to overlapping regions of the same backing storage using different addresses.
     * For example, this may occur if the same file is {@link MemorySegment#mapFromPath mapped} to two segments.
     *
     * @param src the source segment.
     * @throws IndexOutOfBoundsException if {@code src.byteSize() > this.byteSize()}.
     * @throws IllegalStateException if either the source segment or this segment have been already closed,
     * or if access occurs from a thread other than the thread owning either segment.
     * @throws UnsupportedOperationException if either the source segment or this segment do not feature required access modes;
     * more specifically, {@code src} should feature at least the {@link MemorySegment#READ} access mode,
     * while this segment should feature at least the {@link MemorySegment#WRITE} access mode.
     */
    void copyFrom(MemorySegment src);

    
Finds and returns the offset, in bytes, of the first mismatch between this segment and a given other segment. The offset is relative to the base address of each segment and will be in the range of 0 (inclusive) up to the size (in bytes) of the smaller memory segment (exclusive). 
 If the two segments share a common prefix then the returned offset is the length of the common prefix and it follows that there is a mismatch between the two segments at that offset within the respective segments. If one segment is a proper prefix of the other then the returned offset is the smaller of the segment sizes, and it follows that the offset is only valid for the larger segment. Otherwise, there is no mismatch and 
-1 is returned. 
Params:
  • other – the segment to be tested for a mismatch with this segment
Throws:
  • IllegalStateException – if either this segment of the other segment
have been already closed, or if access occurs from a thread other than the
thread owning either segment
  • UnsupportedOperationException – if either this segment or the other segment does not feature at least the READ access mode
Returns:the relative offset, in bytes, of the first mismatch between this
and the given other segment, otherwise -1 if no mismatch
/**
     * Finds and returns the offset, in bytes, of the first mismatch between
     * this segment and a given other segment. The offset is relative to the
     * {@link #baseAddress() base address} of each segment and will be in the
     * range of 0 (inclusive) up to the {@link #byteSize() size} (in bytes) of
     * the smaller memory segment (exclusive).
     * <p>
     * If the two segments share a common prefix then the returned offset is
     * the length of the common prefix and it follows that there is a mismatch
     * between the two segments at that offset within the respective segments.
     * If one segment is a proper prefix of the other then the returned offset is
     * the smaller of the segment sizes, and it follows that the offset is only
     * valid for the larger segment. Otherwise, there is no mismatch and {@code
     * -1} is returned.
     *
     * @param other the segment to be tested for a mismatch with this segment
     * @return the relative offset, in bytes, of the first mismatch between this
     * and the given other segment, otherwise -1 if no mismatch
     * @throws IllegalStateException if either this segment of the other segment
     * have been already closed, or if access occurs from a thread other than the
     * thread owning either segment
     * @throws UnsupportedOperationException if either this segment or the other
     * segment does not feature at least the {@link MemorySegment#READ} access mode
     */
    long mismatch(MemorySegment other);

    
Wraps this segment in a ByteBuffer. Some of the properties of the returned buffer are linked to the properties of this segment. For instance, if this segment is immutable (e.g. the segment has access mode READ but not WRITE), then the resulting buffer is read-only (see Buffer.isReadOnly(). Additionally, if this is a native memory segment, the resulting buffer is direct (see ByteBuffer.isDirect()). 
 The life-cycle of the returned buffer will be tied to that of this segment. That means that if the this segment is closed (see close(), accessing the returned buffer will throw an IllegalStateException. 
 The resulting buffer's byte order is ByteOrder.BIG_ENDIAN; this can be changed using ByteBuffer.order(ByteOrder). 
Throws:
Returns:a ByteBuffer view of this memory segment.
/**
     * Wraps this segment in a {@link ByteBuffer}. Some of the properties of the returned buffer are linked to
     * the properties of this segment. For instance, if this segment is <em>immutable</em>
     * (e.g. the segment has access mode {@link #READ} but not {@link #WRITE}), then the resulting buffer is <em>read-only</em>
     * (see {@link ByteBuffer#isReadOnly()}. Additionally, if this is a native memory segment, the resulting buffer is
     * <em>direct</em> (see {@link ByteBuffer#isDirect()}).
     * <p>
     * The life-cycle of the returned buffer will be tied to that of this segment. That means that if the this segment
     * is closed (see {@link MemorySegment#close()}, accessing the returned
     * buffer will throw an {@link IllegalStateException}.
     * <p>
     * The resulting buffer's byte order is {@link java.nio.ByteOrder#BIG_ENDIAN}; this can be changed using
     * {@link ByteBuffer#order(java.nio.ByteOrder)}.
     *
     * @return a {@link ByteBuffer} view of this memory segment.
     * @throws UnsupportedOperationException if this segment cannot be mapped onto a {@link ByteBuffer} instance,
     * e.g. because it models an heap-based segment that is not based on a {@code byte[]}), or if its size is greater
     * than {@link Integer#MAX_VALUE}, or if the segment does not support the {@link #READ} access mode.
     */
    ByteBuffer asByteBuffer();

    
Copy the contents of this memory segment into a fresh byte array.

Throws:
Returns:a fresh byte array copy of this memory segment.
/**
     * Copy the contents of this memory segment into a fresh byte array.
     * @return a fresh byte array copy of this memory segment.
     * @throws UnsupportedOperationException if this segment does not feature the {@link #READ} access mode, or if this
     * segment's contents cannot be copied into a {@link byte[]} instance, e.g. its size is greater than {@link Integer#MAX_VALUE},
     * @throws IllegalStateException if this segment has been closed, or if access occurs from a thread other than the
     * thread owning this segment.
     */
    byte[] toByteArray();

    
Creates a new buffer memory segment that models the memory associated with the given byte
buffer. The segment starts relative to the buffer's position (inclusive)
and ends relative to the buffer's limit (exclusive).


The segment will feature all access modes (see ALL_ACCESS), unless the given buffer is read-only in which case the segment will not feature the WRITE access mode. 

The resulting memory segment keeps a reference to the backing buffer, to ensure it remains reachable
for the life-time of the segment.

Params:
  • bb – the byte buffer backing the buffer memory segment.
Returns:a new buffer memory segment.
/**
     * Creates a new buffer memory segment that models the memory associated with the given byte
     * buffer. The segment starts relative to the buffer's position (inclusive)
     * and ends relative to the buffer's limit (exclusive).
     * <p>
     * The segment will feature all <a href="#access-modes">access modes</a> (see {@link #ALL_ACCESS}),
     * unless the given buffer is {@linkplain ByteBuffer#isReadOnly() read-only} in which case the segment will
     * not feature the {@link #WRITE} access mode.
     * <p>
     * The resulting memory segment keeps a reference to the backing buffer, to ensure it remains <em>reachable</em>
     * for the life-time of the segment.
     *
     * @param bb the byte buffer backing the buffer memory segment.
     * @return a new buffer memory segment.
     */
    static MemorySegment ofByteBuffer(ByteBuffer bb) {
        return AbstractMemorySegmentImpl.ofBuffer(bb);
    }

    
Creates a new array memory segment that models the memory associated with a given heap-allocated byte array.


The resulting memory segment keeps a reference to the backing array, to ensure it remains reachable
for the life-time of the segment. The segment will feature all access modes (see ALL_ACCESS). 
Params:
  • arr – the primitive array backing the array memory segment.
Returns:a new array memory segment.
/**
     * Creates a new array memory segment that models the memory associated with a given heap-allocated byte array.
     * <p>
     * The resulting memory segment keeps a reference to the backing array, to ensure it remains <em>reachable</em>
     * for the life-time of the segment. The segment will feature all <a href="#access-modes">access modes</a>
     * (see {@link #ALL_ACCESS}).
     *
     * @param arr the primitive array backing the array memory segment.
     * @return a new array memory segment.
     */
    static MemorySegment ofArray(byte[] arr) {
        return HeapMemorySegmentImpl.makeArraySegment(arr);
    }

    
Creates a new array memory segment that models the memory associated with a given heap-allocated char array.


The resulting memory segment keeps a reference to the backing array, to ensure it remains reachable
for the life-time of the segment. The segment will feature all access modes (see ALL_ACCESS). 
Params:
  • arr – the primitive array backing the array memory segment.
Returns:a new array memory segment.
/**
     * Creates a new array memory segment that models the memory associated with a given heap-allocated char array.
     * <p>
     * The resulting memory segment keeps a reference to the backing array, to ensure it remains <em>reachable</em>
     * for the life-time of the segment. The segment will feature all <a href="#access-modes">access modes</a>
     * (see {@link #ALL_ACCESS}).
     *
     * @param arr the primitive array backing the array memory segment.
     * @return a new array memory segment.
     */
    static MemorySegment ofArray(char[] arr) {
        return HeapMemorySegmentImpl.makeArraySegment(arr);
    }

    
Creates a new array memory segment that models the memory associated with a given heap-allocated short array.


The resulting memory segment keeps a reference to the backing array, to ensure it remains reachable
for the life-time of the segment. The segment will feature all access modes (see ALL_ACCESS). 
Params:
  • arr – the primitive array backing the array memory segment.
Returns:a new array memory segment.
/**
     * Creates a new array memory segment that models the memory associated with a given heap-allocated short array.
     * <p>
     * The resulting memory segment keeps a reference to the backing array, to ensure it remains <em>reachable</em>
     * for the life-time of the segment. The segment will feature all <a href="#access-modes">access modes</a>
     * (see {@link #ALL_ACCESS}).
     *
     * @param arr the primitive array backing the array memory segment.
     * @return a new array memory segment.
     */
    static MemorySegment ofArray(short[] arr) {
        return HeapMemorySegmentImpl.makeArraySegment(arr);
    }

    
Creates a new array memory segment that models the memory associated with a given heap-allocated int array.


The resulting memory segment keeps a reference to the backing array, to ensure it remains reachable
for the life-time of the segment. The segment will feature all access modes.

Params:
  • arr – the primitive array backing the array memory segment.
Returns:a new array memory segment.
/**
     * Creates a new array memory segment that models the memory associated with a given heap-allocated int array.
     * <p>
     * The resulting memory segment keeps a reference to the backing array, to ensure it remains <em>reachable</em>
     * for the life-time of the segment. The segment will feature all <a href="#access-modes">access modes</a>.
     *
     * @param arr the primitive array backing the array memory segment.
     * @return a new array memory segment.
     */
    static MemorySegment ofArray(int[] arr) {
        return HeapMemorySegmentImpl.makeArraySegment(arr);
    }

    
Creates a new array memory segment that models the memory associated with a given heap-allocated float array.


The resulting memory segment keeps a reference to the backing array, to ensure it remains reachable
for the life-time of the segment. The segment will feature all access modes (see ALL_ACCESS). 
Params:
  • arr – the primitive array backing the array memory segment.
Returns:a new array memory segment.
/**
     * Creates a new array memory segment that models the memory associated with a given heap-allocated float array.
     * <p>
     * The resulting memory segment keeps a reference to the backing array, to ensure it remains <em>reachable</em>
     * for the life-time of the segment. The segment will feature all <a href="#access-modes">access modes</a>
     * (see {@link #ALL_ACCESS}).
     *
     * @param arr the primitive array backing the array memory segment.
     * @return a new array memory segment.
     */
    static MemorySegment ofArray(float[] arr) {
        return HeapMemorySegmentImpl.makeArraySegment(arr);
    }

    
Creates a new array memory segment that models the memory associated with a given heap-allocated long array.


The resulting memory segment keeps a reference to the backing array, to ensure it remains reachable
for the life-time of the segment. The segment will feature all access modes (see ALL_ACCESS). 
Params:
  • arr – the primitive array backing the array memory segment.
Returns:a new array memory segment.
/**
     * Creates a new array memory segment that models the memory associated with a given heap-allocated long array.
     * <p>
     * The resulting memory segment keeps a reference to the backing array, to ensure it remains <em>reachable</em>
     * for the life-time of the segment. The segment will feature all <a href="#access-modes">access modes</a>
     * (see {@link #ALL_ACCESS}).
     *
     * @param arr the primitive array backing the array memory segment.
     * @return a new array memory segment.
     */
    static MemorySegment ofArray(long[] arr) {
        return HeapMemorySegmentImpl.makeArraySegment(arr);
    }

    
Creates a new array memory segment that models the memory associated with a given heap-allocated double array.


The resulting memory segment keeps a reference to the backing array, to ensure it remains reachable
for the life-time of the segment. The segment will feature all access modes (see ALL_ACCESS). 
Params:
  • arr – the primitive array backing the array memory segment.
Returns:a new array memory segment.
/**
     * Creates a new array memory segment that models the memory associated with a given heap-allocated double array.
     * <p>
     * The resulting memory segment keeps a reference to the backing array, to ensure it remains <em>reachable</em>
     * for the life-time of the segment. The segment will feature all <a href="#access-modes">access modes</a>
     * (see {@link #ALL_ACCESS}).
     *
     * @param arr the primitive array backing the array memory segment.
     * @return a new array memory segment.
     */
    static MemorySegment ofArray(double[] arr) {
        return HeapMemorySegmentImpl.makeArraySegment(arr);
    }

    
Creates a new native memory segment that models a newly allocated block of off-heap memory with given layout.


This is equivalent to the following code:


allocateNative(layout.bytesSize(), layout.bytesAlignment());



Params:
  • layout – the layout of the off-heap memory block backing the native memory segment.
Throws:
Implementation Note:The block of off-heap memory associated with the returned native memory segment is initialized to zero. Moreover, a client is responsible to call the close() on a native memory segment, to make sure the backing off-heap memory block is deallocated accordingly. Failure to do so will result in off-heap memory leaks.
Returns:a new native memory segment.
/**
     * Creates a new native memory segment that models a newly allocated block of off-heap memory with given layout.
     * <p>
     * This is equivalent to the following code:
     * <blockquote><pre>{@code
    allocateNative(layout.bytesSize(), layout.bytesAlignment());
     * }</pre></blockquote>
     *
     * @implNote The block of off-heap memory associated with the returned native memory segment is initialized to zero.
     * Moreover, a client is responsible to call the {@link MemorySegment#close()} on a native memory segment,
     * to make sure the backing off-heap memory block is deallocated accordingly. Failure to do so will result in off-heap memory leaks.
     *
     * @param layout the layout of the off-heap memory block backing the native memory segment.
     * @return a new native memory segment.
     * @throws IllegalArgumentException if the specified layout has illegal size or alignment constraint.
     */
    static MemorySegment allocateNative(MemoryLayout layout) {
        return allocateNative(layout.byteSize(), layout.byteAlignment());
    }

    
Creates a new native memory segment that models a newly allocated block of off-heap memory with given size (in bytes).


This is equivalent to the following code:


allocateNative(bytesSize, 1);



Params:
  • bytesSize – the size (in bytes) of the off-heap memory block backing the native memory segment.
Throws:
Implementation Note:The block of off-heap memory associated with the returned native memory segment is initialized to zero. Moreover, a client is responsible to call the close() on a native memory segment, to make sure the backing off-heap memory block is deallocated accordingly. Failure to do so will result in off-heap memory leaks.
Returns:a new native memory segment.
/**
     * Creates a new native memory segment that models a newly allocated block of off-heap memory with given size (in bytes).
     * <p>
     * This is equivalent to the following code:
     * <blockquote><pre>{@code
allocateNative(bytesSize, 1);
     * }</pre></blockquote>
     *
     * @implNote The block of off-heap memory associated with the returned native memory segment is initialized to zero.
     * Moreover, a client is responsible to call the {@link MemorySegment#close()} on a native memory segment,
     * to make sure the backing off-heap memory block is deallocated accordingly. Failure to do so will result in off-heap memory leaks.
     *
     * @param bytesSize the size (in bytes) of the off-heap memory block backing the native memory segment.
     * @return a new native memory segment.
     * @throws IllegalArgumentException if {@code bytesSize < 0}.
     */
    static MemorySegment allocateNative(long bytesSize) {
        return allocateNative(bytesSize, 1);
    }

    
Creates a new mapped memory segment that models a memory-mapped region of a file from a given path.


The segment will feature all access modes (see ALL_ACCESS), unless the given mapping mode is READ_ONLY, in which case the segment will not feature the WRITE access mode. 
Params:
  • path – the path to the file to memory map.
  • bytesOffset – the offset (expressed in bytes) within the file at which the mapped segment is to start.
  • bytesSize – the size (in bytes) of the mapped memory backing the memory segment.
  • mapMode – a file mapping mode, see FileChannel.map(MapMode, long, long); the chosen mapping mode might affect the behavior of the returned memory mapped segment (see MappedMemorySegment.force()).
Throws:
Implementation Note:When obtaining a mapped segment from a newly created file, the initialization state of the contents of the block
of mapped memory associated with the returned mapped memory segment is unspecified and should not be relied upon.
Returns:a new mapped memory segment.
/**
     * Creates a new mapped memory segment that models a memory-mapped region of a file from a given path.
     * <p>
     * The segment will feature all <a href="#access-modes">access modes</a> (see {@link #ALL_ACCESS}),
     * unless the given mapping mode is {@linkplain FileChannel.MapMode#READ_ONLY READ_ONLY}, in which case
     * the segment will not feature the {@link #WRITE} access mode.
     *
     * @implNote When obtaining a mapped segment from a newly created file, the initialization state of the contents of the block
     * of mapped memory associated with the returned mapped memory segment is unspecified and should not be relied upon.
     *
     * @param path the path to the file to memory map.
     * @param bytesOffset the offset (expressed in bytes) within the file at which the mapped segment is to start.
     * @param bytesSize the size (in bytes) of the mapped memory backing the memory segment.
     * @param mapMode a file mapping mode, see {@link FileChannel#map(FileChannel.MapMode, long, long)}; the chosen mapping mode
     *                might affect the behavior of the returned memory mapped segment (see {@link MappedMemorySegment#force()}).
     * @return a new mapped memory segment.
     * @throws IllegalArgumentException if {@code bytesOffset < 0}.
     * @throws IllegalArgumentException if {@code bytesSize < 0}.
     * @throws UnsupportedOperationException if an unsupported map mode is specified.
     * @throws IOException if the specified path does not point to an existing file, or if some other I/O error occurs.
     */
    static MappedMemorySegment mapFromPath(Path path, long bytesOffset, long bytesSize, FileChannel.MapMode mapMode) throws IOException {
        return MappedMemorySegmentImpl.makeMappedSegment(path, bytesOffset, bytesSize, mapMode);
    }

    
Creates a new native memory segment that models a newly allocated block of off-heap memory with given size and
alignment constraint (in bytes). The segment will feature all access modes (see ALL_ACCESS). 
Params:
  • bytesSize – the size (in bytes) of the off-heap memory block backing the native memory segment.
  • alignmentBytes – the alignment constraint (in bytes) of the off-heap memory block backing the native memory segment.
Throws:
Implementation Note:The block of off-heap memory associated with the returned native memory segment is initialized to zero. Moreover, a client is responsible to call the close() on a native memory segment, to make sure the backing off-heap memory block is deallocated accordingly. Failure to do so will result in off-heap memory leaks.
Returns:a new native memory segment.
/**
     * Creates a new native memory segment that models a newly allocated block of off-heap memory with given size and
     * alignment constraint (in bytes). The segment will feature all <a href="#access-modes">access modes</a>
     * (see {@link #ALL_ACCESS}).
     *
     * @implNote The block of off-heap memory associated with the returned native memory segment is initialized to zero.
     * Moreover, a client is responsible to call the {@link MemorySegment#close()} on a native memory segment,
     * to make sure the backing off-heap memory block is deallocated accordingly. Failure to do so will result in off-heap memory leaks.
     *
     * @param bytesSize the size (in bytes) of the off-heap memory block backing the native memory segment.
     * @param alignmentBytes the alignment constraint (in bytes) of the off-heap memory block backing the native memory segment.
     * @return a new native memory segment.
     * @throws IllegalArgumentException if {@code bytesSize < 0}, {@code alignmentBytes < 0}, or if {@code alignmentBytes}
     * is not a power of 2.
     */
    static MemorySegment allocateNative(long bytesSize, long alignmentBytes) {
        if (bytesSize <= 0) {
            throw new IllegalArgumentException("Invalid allocation size : " + bytesSize);
        }

        if (alignmentBytes < 0 ||
                ((alignmentBytes & (alignmentBytes - 1)) != 0L)) {
            throw new IllegalArgumentException("Invalid alignment constraint : " + alignmentBytes);
        }

        return NativeMemorySegmentImpl.makeNativeSegment(bytesSize, alignmentBytes);
    }

    
Returns a new native memory segment with given base address and size; the returned segment has its own temporal bounds, and can therefore be closed; closing such a segment can optionally result in calling an user-provided cleanup action. This method can be very useful when interacting with custom native memory sources (e.g. custom allocators, GPU memory, etc.), where an address to some underlying memory region is typically obtained from native code (often as a plain long value). The segment will feature all access modes (see ALL_ACCESS). 

This method is restricted. Restricted methods are unsafe, and, if used incorrectly, their use might crash
the JVM or, worse, silently result in memory corruption. Thus, clients should refrain from depending on
restricted methods, and use safe and supported functionalities, where possible.

Params:
  • addr – the desired base address
  • bytesSize – the desired size.
  • owner – the desired owner thread. If owner == null, the returned segment is not confined.
  • cleanup – a cleanup action to be executed when the close() method is called on the returned segment. If cleanup == null, no cleanup action is executed.
  • attachment – an object that must be kept alive by the returned segment; this can be useful when the returned segment depends on memory which could be released if a certain object is determined to be unreacheable. In most cases this will be set to null.
Throws:
Returns:a new native memory segment with given base address, size, owner, cleanup action and object attachment.
/**
     * Returns a new native memory segment with given base address and size; the returned segment has its own temporal
     * bounds, and can therefore be closed; closing such a segment can optionally result in calling an user-provided cleanup
     * action. This method can be very useful when interacting with custom native memory sources (e.g. custom allocators,
     * GPU memory, etc.), where an address to some underlying memory region is typically obtained from native code
     * (often as a plain {@code long} value). The segment will feature all <a href="#access-modes">access modes</a>
     * (see {@link #ALL_ACCESS}).
     * <p>
     * This method is <em>restricted</em>. Restricted methods are unsafe, and, if used incorrectly, their use might crash
     * the JVM or, worse, silently result in memory corruption. Thus, clients should refrain from depending on
     * restricted methods, and use safe and supported functionalities, where possible.
     *
     * @param addr the desired base address
     * @param bytesSize the desired size.
     * @param owner the desired owner thread. If {@code owner == null}, the returned segment is <em>not</em> confined.
     * @param cleanup a cleanup action to be executed when the {@link MemorySegment#close()} method is called on the
     *                returned segment. If {@code cleanup == null}, no cleanup action is executed.
     * @param attachment an object that must be kept alive by the returned segment; this can be useful when
     *                   the returned segment depends on memory which could be released if a certain object
     *                   is determined to be unreacheable. In most cases this will be set to {@code null}.
     * @return a new native memory segment with given base address, size, owner, cleanup action and object attachment.
     * @throws IllegalArgumentException if {@code bytesSize <= 0}.
     * @throws UnsupportedOperationException if {@code addr} is associated with an heap segment.
     * @throws IllegalAccessError if the runtime property {@code foreign.restricted} is not set to either
     * {@code permit}, {@code warn} or {@code debug} (the default value is set to {@code deny}).
     * @throws NullPointerException if {@code addr == null}.
     */
    static MemorySegment ofNativeRestricted(MemoryAddress addr, long bytesSize, Thread owner, Runnable cleanup, Object attachment) {
        Objects.requireNonNull(addr);
        if (bytesSize <= 0) {
            throw new IllegalArgumentException("Invalid size : " + bytesSize);
        }
        Utils.checkRestrictedAccess("MemorySegment.ofNativeRestricted");
        return NativeMemorySegmentImpl.makeNativeSegmentUnchecked(addr, bytesSize, owner, cleanup, attachment);
    }

    // access mode masks

    
Read access mode; read operations are supported by a segment which supports this access mode.

See Also:
/**
     * Read access mode; read operations are supported by a segment which supports this access mode.
     * @see MemorySegment#accessModes()
     * @see MemorySegment#withAccessModes(int)
     */
    int READ = 1;

    
Write access mode; write operations are supported by a segment which supports this access mode.

See Also:
/**
     * Write access mode; write operations are supported by a segment which supports this access mode.
     * @see MemorySegment#accessModes()
     * @see MemorySegment#withAccessModes(int)
     */
    int WRITE = READ << 1;

    
Close access mode; calling close() is supported by a segment which supports this access mode. 
See Also:
/**
     * Close access mode; calling {@link #close()} is supported by a segment which supports this access mode.
     * @see MemorySegment#accessModes()
     * @see MemorySegment#withAccessModes(int)
     */
    int CLOSE = WRITE << 1;

    
Acquire access mode; this segment support sharing with threads other than the owner thread, via spliterator (see spliterator(MemorySegment, SequenceLayout)). 
See Also:
/**
     * Acquire access mode; this segment support sharing with threads other than the owner thread, via spliterator
     * (see {@link #spliterator(MemorySegment, SequenceLayout)}).
     * @see MemorySegment#accessModes()
     * @see MemorySegment#withAccessModes(int)
     */
    int ACQUIRE = CLOSE << 1;

    
Handoff access mode; this segment support serial thread-confinement via thread ownership changes (see withOwnerThread(Thread)). 
See Also:
/**
     * Handoff access mode; this segment support serial thread-confinement via thread ownership changes
     * (see {@link #withOwnerThread(Thread)}).
     * @see MemorySegment#accessModes()
     * @see MemorySegment#withAccessModes(int)
     */
    int HANDOFF = ACQUIRE << 1;

    
Default access mode; this is a union of all the access modes supported by memory segments.

See Also:
/**
     * Default access mode; this is a union of all the access modes supported by memory segments.
     * @see MemorySegment#accessModes()
     * @see MemorySegment#withAccessModes(int)
     */
    int ALL_ACCESS = READ | WRITE | CLOSE | ACQUIRE | HANDOFF;
}