- All Superinterfaces:
MemoryLayoutPREVIEW
,ValueLayoutPREVIEW
AddressLayout
is a preview API of the Java platform.
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_INT
PREVIEW 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)
PREVIEW; - When creating a downcall method handle, using
Linker.downcallHandle(FunctionDescriptor, Option...)
PREVIEW; - When creating an upcall stub, using
Linker.upcallStub(MethodHandle, FunctionDescriptor, Arena, Option...)
PREVIEW.
- 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 TypeMethodDescriptionReturns the target layout associated with this address layout (if any).withByteAlignment
(long byteAlignment) Returns a memory layout with the same characteristics as this layout, but with the given alignment constraint (in bytes).Returns a memory layout with the same characteristics as this layout, but with the given name.Returns a value layout with the same characteristics as this layout, but with the given byte order.Returns a memory layout with the same characteristics as this layout, but with no name.Returns an address layout with the same carrier, alignment constraint, name and order as this address layout, but with no target layout.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
Returns a memory layout with the same characteristics as this layout, but with the given name.- Specified by:
withName
in interfaceMemoryLayoutPREVIEW
- Specified by:
withName
in interfaceValueLayoutPREVIEW
- 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 interfaceMemoryLayoutPREVIEW
- Specified by:
withoutName
in interfaceValueLayoutPREVIEW
- Returns:
- a memory layout with the same characteristics as this layout, but with no name
- See Also:
-
withByteAlignment
Returns a memory layout with the same characteristics as this layout, but with the given alignment constraint (in bytes).- Specified by:
withByteAlignment
in interfaceMemoryLayoutPREVIEW
- Specified by:
withByteAlignment
in interfaceValueLayoutPREVIEW
- 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
Returns a value layout with the same characteristics as this layout, but with the given byte order.- Specified by:
withOrder
in interfaceValueLayoutPREVIEW
- Parameters:
order
- the desired byte order.- Returns:
- a value layout with the same characteristics as this layout, but with the given byte order
-
withTargetLayout
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)
-
AddressLayout
when preview features are enabled.