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/OpenJDK 21

Interface AddressLayout

All Superinterfaces:
MemoryLayoutPREVIEW, ValueLayoutPREVIEW 
public sealed interface AddressLayout extends ValueLayoutPREVIEW
AddressLayout is a preview API of the Java platform.
Programs can only use AddressLayout when preview features are enabled.
Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.
A value layout used to model the address of some region of memory. The carrier associated with an address layout is MemorySegment.class. The size and alignment of an address layout are platform-dependent (e.g. on a 64-bit platform, the size and alignment of an address layout are set to 8 bytes).

An address layout may optionally feature a target layout. An address layout with target layout T can be used to model the address of a region of memory whose layout is T. For instance, an address layout with target layout ValueLayout.JAVA_INTPREVIEW can be used to model the address of a region of memory that is 4 bytes long. Specifying a target layout can be useful in the following situations:

Since:
19
See Also:

Nested Class Summary

Nested classes/interfaces declared in interface java.lang.foreign.MemoryLayoutPREVIEW

MemoryLayout.PathElementPREVIEW

Nested classes/interfaces declared in interface java.lang.foreign.ValueLayoutPREVIEW

ValueLayout.OfBooleanPREVIEW, ValueLayout.OfBytePREVIEW, ValueLayout.OfCharPREVIEW, ValueLayout.OfDoublePREVIEW, ValueLayout.OfFloatPREVIEW, ValueLayout.OfIntPREVIEW, ValueLayout.OfLongPREVIEW, ValueLayout.OfShortPREVIEW

Field Summary

Fields declared in interface java.lang.foreign.ValueLayoutPREVIEW

ADDRESS, ADDRESS_UNALIGNED, JAVA_BOOLEAN, JAVA_BYTE, JAVA_CHAR, JAVA_CHAR_UNALIGNED, JAVA_DOUBLE, JAVA_DOUBLE_UNALIGNED, JAVA_FLOAT, JAVA_FLOAT_UNALIGNED, JAVA_INT, JAVA_INT_UNALIGNED, JAVA_LONG, JAVA_LONG_UNALIGNED, JAVA_SHORT, JAVA_SHORT_UNALIGNED

Method Summary

Modifier and Type Method Description
Optional<MemoryLayoutPREVIEW> targetLayout()
Returns the target layout associated with this address layout (if any).
AddressLayoutPREVIEW withByteAlignment(long byteAlignment)
Returns a memory layout with the same characteristics as this layout, but with the given alignment constraint (in bytes).
AddressLayoutPREVIEW withName(String name)
Returns a memory layout with the same characteristics as this layout, but with the given name.
AddressLayoutPREVIEW withOrder(ByteOrder order)
Returns a value layout with the same characteristics as this layout, but with the given byte order.
AddressLayoutPREVIEW withoutName()
Returns a memory layout with the same characteristics as this layout, but with no name.
AddressLayoutPREVIEW withoutTargetLayout()
Returns an address layout with the same carrier, alignment constraint, name and order as this address layout, but with no target layout.
AddressLayoutPREVIEW withTargetLayout(MemoryLayoutPREVIEW layout)
Returns an address layout with the same carrier, alignment constraint, name and order as this address layout, but associated with the specified target layout.

Methods declared in interface java.lang.foreign.MemoryLayoutPREVIEW

byteAlignment, byteOffset, byteOffsetHandle, byteSize, equals, hashCode, name, select, sliceHandle, toString, varHandle

Methods declared in interface java.lang.foreign.ValueLayoutPREVIEW

arrayElementVarHandle, carrier, order

Method Details

withName

AddressLayoutPREVIEW withName(String name)
Returns a memory layout with the same characteristics as this layout, but with the given name.
Specified by:
withName in interface MemoryLayoutPREVIEW
Specified by:
withName in interface ValueLayoutPREVIEW
Parameters:
name - the layout name.
Returns:
a memory layout with the same characteristics as this layout, but with the given name
See Also:

withoutName

AddressLayoutPREVIEW withoutName()
Returns a memory layout with the same characteristics as this layout, but with no name.
Specified by:
withoutName in interface MemoryLayoutPREVIEW
Specified by:
withoutName in interface ValueLayoutPREVIEW
Returns:
a memory layout with the same characteristics as this layout, but with no name
See Also:

withByteAlignment

AddressLayoutPREVIEW withByteAlignment(long byteAlignment)
Returns a memory layout with the same characteristics as this layout, but with the given alignment constraint (in bytes).
Specified by:
withByteAlignment in interface MemoryLayoutPREVIEW
Specified by:
withByteAlignment in interface ValueLayoutPREVIEW
Parameters:
byteAlignment - the layout alignment constraint, expressed in bytes.
Returns:
a memory layout with the same characteristics as this layout, but with the given alignment constraint (in bytes)

withOrder

AddressLayoutPREVIEW withOrder(ByteOrder order)
Returns a value layout with the same characteristics as this layout, but with the given byte order.
Specified by:
withOrder in interface ValueLayoutPREVIEW
Parameters:
order - the desired byte order.
Returns:
a value layout with the same characteristics as this layout, but with the given byte order

withTargetLayout

AddressLayoutPREVIEW withTargetLayout(MemoryLayoutPREVIEW layout)
Returns an address layout with the same carrier, alignment constraint, name and order as this address layout, but associated with the specified target layout. The returned address layout allows raw addresses to be accessed as memory segmentsPREVIEW whose size is set to the size of the specified layout. Moreover, if the accessed raw address is not compatible with the alignment constraint in the provided layout, IllegalArgumentException will be thrown.
API Note:
This method can also be used to create an address layout which, when used, creates native memory segments with maximal size (e.g. Long.MAX_VALUE). This can be done by using a target sequence layout with unspecified size, as follows: 
 AddressLayout addressLayout   = ...
 AddressLayout unboundedLayout = addressLayout.withTargetLayout(
         MemoryLayout.sequenceLayout(ValueLayout.JAVA_BYTE));

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.

Parameters:
layout - the target layout.
Returns:
an address layout with same characteristics as this layout, but with the provided target layout.
Throws:
IllegalCallerException - If the caller is in a module that does not have native access enabled.
See Also:

withoutTargetLayout

AddressLayoutPREVIEW withoutTargetLayout()
Returns an address layout with the same carrier, alignment constraint, name and order as this address layout, but with no target layout.
API Note:
This can be useful to compare two address layouts that have different target layouts, but are otherwise equal.
Returns:
an address layout with same characteristics as this layout, but with no target layout.
See Also:

targetLayout

Optional<MemoryLayoutPREVIEW> targetLayout()
Returns the target layout associated with this address layout (if any)..
Returns:
the target layout associated with this address layout (if any)

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/foreign/AddressLayout.html