- All Superinterfaces:
MemoryLayoutPREVIEW
- All Known Subinterfaces:
AddressLayoutPREVIEW
,ValueLayout.OfBooleanPREVIEW
,ValueLayout.OfBytePREVIEW
,ValueLayout.OfCharPREVIEW
,ValueLayout.OfDoublePREVIEW
,ValueLayout.OfFloatPREVIEW
,ValueLayout.OfIntPREVIEW
,ValueLayout.OfLongPREVIEW
,ValueLayout.OfShortPREVIEW
public sealed interface ValueLayout
extends MemoryLayoutPREVIEW
permits ValueLayout.OfBooleanPREVIEW, ValueLayout.OfBytePREVIEW, ValueLayout.OfCharPREVIEW, ValueLayout.OfShortPREVIEW, ValueLayout.OfIntPREVIEW, ValueLayout.OfFloatPREVIEW, ValueLayout.OfLongPREVIEW, ValueLayout.OfDoublePREVIEW, AddressLayoutPREVIEW
ValueLayout
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 layout that models values of basic data types. Examples of values modelled by a value layout are
integral values (either signed or unsigned), floating-point values and
address values.
Each value layout has a size, an alignment (both expressed in bytes), a byte order, and a carrier, that is, the Java type that should be used when accessingPREVIEW a region of memory using the value layout.
This class defines useful value layout constants for Java primitive types and addresses.
- API Note:
- Some characteristics of the Java layout constants are platform-dependent. For instance, the byte order of
these constants is set to the native byte order, thus making it easy to work
with other APIs, such as arrays and
ByteBuffer
. Moreover, the alignment constraint ofJAVA_LONG
andJAVA_DOUBLE
is set to 8 bytes on 64-bit platforms, but only to 4 bytes on 32-bit platforms. - Implementation Requirements:
- implementing classes and subclasses are immutable, thread-safe and value-based.
- Sealed Class Hierarchy Graph:
- Since:
- 19
-
Nested Class Summary
Modifier and TypeInterfaceDescriptionstatic interface
Preview.A value layout whose carrier isboolean.class
.static interface
Preview.A value layout whose carrier isbyte.class
.static interface
Preview.A value layout whose carrier ischar.class
.static interface
Preview.A value layout whose carrier isdouble.class
.static interface
Preview.A value layout whose carrier isfloat.class
.static interface
Preview.A value layout whose carrier isint.class
.static interface
Preview.A value layout whose carrier islong.class
.static interface
Preview.A value layout whose carrier isshort.class
.Nested classes/interfaces declared in interface java.lang.foreign.MemoryLayoutPREVIEW
MemoryLayout.PathElementPREVIEW
-
Field Summary
Modifier and TypeFieldDescriptionstatic final AddressLayoutPREVIEW
An address layout constant whose size is the same as that of a machine address (size_t
), byte alignment set tosizeof(size_t)
, byte order set toByteOrder.nativeOrder()
.static final AddressLayoutPREVIEW
An unaligned address layout constant whose size is the same as that of a machine address (size_t
), and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfBooleanPREVIEW
A value layout constant whose size is the same as that of a Javaboolean
, byte alignment set to 1, and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfBytePREVIEW
A value layout constant whose size is the same as that of a Javabyte
, byte alignment set to 1, and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfCharPREVIEW
A value layout constant whose size is the same as that of a Javachar
, byte alignment set to 2, and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfCharPREVIEW
An unaligned value layout constant whose size is the same as that of a Javachar
and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfDoublePREVIEW
A value layout constant whose size is the same as that of a Javadouble
, (platform-dependent) byte alignment set toADDRESS.byteSize()
, and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfDoublePREVIEW
An unaligned value layout constant whose size is the same as that of a Javadouble
and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfFloatPREVIEW
A value layout constant whose size is the same as that of a Javafloat
, byte alignment set to 4, and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfFloatPREVIEW
An unaligned value layout constant whose size is the same as that of a Javafloat
and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfIntPREVIEW
A value layout constant whose size is the same as that of a Javaint
, byte alignment set to 4, and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfIntPREVIEW
An unaligned value layout constant whose size is the same as that of a Javaint
and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfLongPREVIEW
A value layout constant whose size is the same as that of a Javalong
, (platform-dependent) byte alignment set toADDRESS.byteSize()
, and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfLongPREVIEW
An unaligned value layout constant whose size is the same as that of a Javalong
and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfShortPREVIEW
A value layout constant whose size is the same as that of a Javashort
, byte alignment set to 2, and byte order set toByteOrder.nativeOrder()
.static final ValueLayout.OfShortPREVIEW
An unaligned value layout constant whose size is the same as that of a Javashort
and byte order set toByteOrder.nativeOrder()
. -
Method Summary
Modifier and TypeMethodDescriptionarrayElementVarHandle
(int... shape) Creates a strided var handle that can be used to access a memory segment as multi-dimensional array.Class
<?> carrier()
Returns the carrier associated with this value layout.order()
Returns the value's byte order.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.Methods declared in interface java.lang.foreign.MemoryLayoutPREVIEW
byteAlignment, byteOffset, byteOffsetHandle, byteSize, equals, hashCode, name, select, sliceHandle, toString, varHandle
-
Field Details
-
ADDRESS
An address layout constant whose size is the same as that of a machine address (size_t
), byte alignment set tosizeof(size_t)
, byte order set toByteOrder.nativeOrder()
. -
JAVA_BYTE
A value layout constant whose size is the same as that of a Javabyte
, byte alignment set to 1, and byte order set toByteOrder.nativeOrder()
. -
JAVA_BOOLEAN
A value layout constant whose size is the same as that of a Javaboolean
, byte alignment set to 1, and byte order set toByteOrder.nativeOrder()
. -
JAVA_CHAR
A value layout constant whose size is the same as that of a Javachar
, byte alignment set to 2, and byte order set toByteOrder.nativeOrder()
. -
JAVA_SHORT
A value layout constant whose size is the same as that of a Javashort
, byte alignment set to 2, and byte order set toByteOrder.nativeOrder()
. -
JAVA_INT
A value layout constant whose size is the same as that of a Javaint
, byte alignment set to 4, and byte order set toByteOrder.nativeOrder()
. -
JAVA_LONG
A value layout constant whose size is the same as that of a Javalong
, (platform-dependent) byte alignment set toADDRESS.byteSize()
, and byte order set toByteOrder.nativeOrder()
. -
JAVA_FLOAT
A value layout constant whose size is the same as that of a Javafloat
, byte alignment set to 4, and byte order set toByteOrder.nativeOrder()
. -
JAVA_DOUBLE
A value layout constant whose size is the same as that of a Javadouble
, (platform-dependent) byte alignment set toADDRESS.byteSize()
, and byte order set toByteOrder.nativeOrder()
. -
ADDRESS_UNALIGNED
An unaligned address layout constant whose size is the same as that of a machine address (size_t
), and byte order set toByteOrder.nativeOrder()
. Equivalent to the following code:ADDRESS.withByteAlignment(1);
- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
-
JAVA_CHAR_UNALIGNED
An unaligned value layout constant whose size is the same as that of a Javachar
and byte order set toByteOrder.nativeOrder()
. Equivalent to the following code:JAVA_CHAR.withByteAlignment(1);
- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
-
JAVA_SHORT_UNALIGNED
An unaligned value layout constant whose size is the same as that of a Javashort
and byte order set toByteOrder.nativeOrder()
. Equivalent to the following code:JAVA_SHORT.withByteAlignment(1);
- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
-
JAVA_INT_UNALIGNED
An unaligned value layout constant whose size is the same as that of a Javaint
and byte order set toByteOrder.nativeOrder()
. Equivalent to the following code:JAVA_INT.withByteAlignment(1);
- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
-
JAVA_LONG_UNALIGNED
An unaligned value layout constant whose size is the same as that of a Javalong
and byte order set toByteOrder.nativeOrder()
. Equivalent to the following code:JAVA_LONG.withByteAlignment(1);
- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
-
JAVA_FLOAT_UNALIGNED
An unaligned value layout constant whose size is the same as that of a Javafloat
and byte order set toByteOrder.nativeOrder()
. Equivalent to the following code:JAVA_FLOAT.withByteAlignment(1);
- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
-
JAVA_DOUBLE_UNALIGNED
An unaligned value layout constant whose size is the same as that of a Javadouble
and byte order set toByteOrder.nativeOrder()
. Equivalent to the following code:JAVA_DOUBLE.withByteAlignment(1);
- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
-
-
Method Details
-
order
ByteOrder order()Returns the value's byte order.- Returns:
- the value's byte order
-
withOrder
Returns a value layout with the same characteristics as this layout, but with the given byte order.- Parameters:
order
- the desired byte order.- Returns:
- a value layout with the same characteristics as this layout, but with the given byte order
-
withoutName
ValueLayoutPREVIEW withoutName()Returns a memory layout with the same characteristics as this layout, but with no name.- Specified by:
withoutName
in interfaceMemoryLayoutPREVIEW
- Returns:
- a memory layout with the same characteristics as this layout, but with no name
- See Also:
-
arrayElementVarHandle
Creates a strided var handle that can be used to access a memory segment as multi-dimensional array. This array has a notional sequence layout featuringshape.length
nested sequence layouts. The element layout of the innermost sequence layout in the notional sequence layout is this value layout. The resulting var handle is obtained as if calling theMemoryLayout.varHandle(PathElement...)
PREVIEW method on the notional layout, with a layout path containing exactlyshape.length + 1
open sequence layout path elementsPREVIEW.For instance, the following method call:
VarHandle arrayHandle = ValueLayout.JAVA_INT.arrayElementVarHandle(10, 20);
SequenceLayout notionalLayout = MemoryLayout.sequenceLayout( MemoryLayout.sequenceLayout(10, MemoryLayout.sequenceLayout(20, ValueLayout.JAVA_INT))); VarHandle arrayHandle = notionalLayout.varHandle(PathElement.sequenceElement(), PathElement.sequenceElement(), PathElement.sequenceElement());
arrayHandle
will feature 3 coordinates of typelong
; each coordinate is interpreted as an index into the corresponding sequence layout. If we refer to the var handle coordinates, from left to right, asx
,y
andz
respectively, the final offset accessed by the var handle can be computed with the following formula:
Additionally, the values ofoffset = (10 * 20 * 4 * x) + (20 * 4 * y) + (4 * z)
x
,y
andz
are constrained as follows:0 <= x < notionalLayout.elementCount()
0 <= y < 10
0 <= z < 20
Consider the following access expressions:
int value1 = (int) arrayHandle.get(10, 2, 4); // ok, accessed offset = 8176 int value2 = (int) arrayHandle.get(0, 0, 30); // out of bounds value for z
x
,y
andz
conform to the bounds specified above. In the second case, access fails withIndexOutOfBoundsException
, as the value forz
is outside its specified bounds.- Parameters:
shape
- the size of each nested array dimension.- Returns:
- a var handle which can be used to access a memory segment as a multi-dimensional array,
featuring
shape.length + 1
long
coordinates. - Throws:
IllegalArgumentException
- ifshape[i] < 0
, for at least one indexi
.UnsupportedOperationException
- ifbyteAlignment() > byteSize()
.- See Also:
-
carrier
Class<?> carrier()Returns the carrier associated with this value layout.- Returns:
- the carrier associated with this value layout
-
withName
Returns a memory layout with the same characteristics as this layout, but with the given name.- Specified by:
withName
in interfaceMemoryLayoutPREVIEW
- Parameters:
name
- the layout name.- Returns:
- a memory layout with the same characteristics as this layout, but with the given 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
- 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)
- Throws:
IllegalArgumentException
- ifbyteAlignment
is not a power of two.
-
ValueLayout
when preview features are enabled.