Module java.base

Package java.lang.foreign

Interface AddressLayout

All Superinterfaces:

MemoryLayout, ValueLayout

public sealed interface AddressLayout
extends ValueLayout

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_INT 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:

• When accessing a memory segment that has been obtained by reading an address from another memory segment, e.g. using MemorySegment.getAtIndex(AddressLayout, long);
• When creating a downcall method handle, using Linker.downcallHandle(FunctionDescriptor, Option...)^RESTRICTED;
• When creating an upcall stub, using Linker.upcallStub(MethodHandle, FunctionDescriptor, Arena, Option...)^RESTRICTED.

Implementation Requirements:

Implementations of this interface are immutable, thread-safe and value-based.

Since:

22

See Also:

• ValueLayout.ADDRESS
• ValueLayout.ADDRESS_UNALIGNED

Nested Class Summary

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

MemoryLayout.PathElement

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

ValueLayout.OfBoolean, ValueLayout.OfByte, ValueLayout.OfChar, ValueLayout.OfDouble, ValueLayout.OfFloat, ValueLayout.OfInt, ValueLayout.OfLong, ValueLayout.OfShort

Field Summary

Fields declared in interface java.lang.foreign.ValueLayout

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

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

Methods declared in interface java.lang.foreign.ValueLayout

carrier, order, varHandle

Method Details

withName

AddressLayout withName(String name)

Returns a memory layout with the same characteristics as this layout, but with the given name.

Specified by:

withName in interface MemoryLayout

Specified by:

withName in interface ValueLayout

Parameters:

name - the layout name

Returns:

a memory layout with the same characteristics as this layout, but with the given name

See Also:

• MemoryLayout.name()

withoutName

AddressLayout withoutName()

Returns a memory layout with the same characteristics as this layout, but with no name.

Specified by:

withoutName in interface MemoryLayout

Specified by:

withoutName in interface ValueLayout

Returns:

a memory layout with the same characteristics as this layout, but with no name

See Also:

• MemoryLayout.name()

withByteAlignment

AddressLayout 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 MemoryLayout

Specified by:

withByteAlignment in interface ValueLayout

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

AddressLayout 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 ValueLayout

Parameters:

order - the desired byte order

Returns:

a value layout with the same characteristics as this layout, but with the given byte order

withTargetLayout

sealed AddressLayout withTargetLayout(MemoryLayout layout)

withTargetLayout is a restricted method of the Java platform.

Programs can only use withTargetLayout when access to restricted methods is enabled.

Restricted methods are unsafe, and, if used incorrectly, might crash the JVM or result in memory corruption.

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 segments 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(Long.MAX_VALUE, ValueLayout.JAVA_BYTE));

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:

• targetLayout()

withoutTargetLayout

AddressLayout 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()

targetLayout

Optional<MemoryLayout> targetLayout()

Returns the target layout associated with this address layout (if any).

Returns:

the target layout associated with this address layout (if any)