- All Superinterfaces:
MemoryLayoutPREVIEW
- All Known Subinterfaces:
ValueLayout.OfAddressPREVIEW,ValueLayout.OfBooleanPREVIEW,ValueLayout.OfBytePREVIEW,ValueLayout.OfCharPREVIEW,ValueLayout.OfDoublePREVIEW,ValueLayout.OfFloatPREVIEW,ValueLayout.OfIntPREVIEW,ValueLayout.OfLongPREVIEW,ValueLayout.OfShortPREVIEW
ValueLayout is a preview API of the Java platform.
Each value layout has a size, an alignment (in bits), 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.
The layout constants in this class make implicit alignment and byte-ordering assumption: all layout
constants in this class are byte-aligned, and their byte order is set to the platform default,
thus making it easy to work with other APIs, such as arrays and ByteBuffer.
- Implementation Requirements:
- implementing classes and subclasses are immutable, thread-safe and value-based.
- Since:
- 19
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Nested Class Summary
Nested ClassesModifier and TypeInterfaceDescriptionstatic interfacePreview.A value layout whose carrier isMemorySegment.class.static interfacePreview.A value layout whose carrier isboolean.class.static interfacePreview.A value layout whose carrier isbyte.class.static interfacePreview.A value layout whose carrier ischar.class.static interfacePreview.A value layout whose carrier isdouble.class.static interfacePreview.A value layout whose carrier isfloat.class.static interfacePreview.A value layout whose carrier isint.class.static interfacePreview.A value layout whose carrier islong.class.static interfacePreview.A value layout whose carrier isshort.class.Nested classes/interfaces declared in interface java.lang.foreign.MemoryLayoutPREVIEW
MemoryLayout.PathElementPREVIEW -
Field Summary
FieldsModifier and TypeFieldDescriptionstatic final ValueLayout.OfAddressPREVIEWA value layout constant whose size is the same as that of a machine address (size_t), bit alignment set tosizeof(size_t) * 8, byte order set toByteOrder.nativeOrder().static final ValueLayout.OfAddressPREVIEWAn unaligned value layout constant whose size is the same as that of a machine address (size_t), and byte order set toByteOrder.nativeOrder().static final ValueLayout.OfBooleanPREVIEWA value layout constant whose size is the same as that of a Javaboolean, bit alignment set to 8, and byte order set toByteOrder.nativeOrder().static final ValueLayout.OfBytePREVIEWA value layout constant whose size is the same as that of a Javabyte, bit alignment set to 8, and byte order set toByteOrder.nativeOrder().static final ValueLayout.OfCharPREVIEWA value layout constant whose size is the same as that of a Javachar, bit alignment set to 16, and byte order set toByteOrder.nativeOrder().static final ValueLayout.OfCharPREVIEWAn unaligned value layout constant whose size is the same as that of a Javacharand byte order set toByteOrder.nativeOrder().static final ValueLayout.OfDoublePREVIEWA value layout constant whose size is the same as that of a Javadouble, bit alignment set to 64, and byte order set toByteOrder.nativeOrder().static final ValueLayout.OfDoublePREVIEWAn unaligned value layout constant whose size is the same as that of a Javadoubleand byte order set toByteOrder.nativeOrder().static final ValueLayout.OfFloatPREVIEWA value layout constant whose size is the same as that of a Javafloat, bit alignment set to 32, and byte order set toByteOrder.nativeOrder().static final ValueLayout.OfFloatPREVIEWAn unaligned value layout constant whose size is the same as that of a Javafloatand byte order set toByteOrder.nativeOrder().static final ValueLayout.OfIntPREVIEWA value layout constant whose size is the same as that of a Javaint, bit alignment set to 32, and byte order set toByteOrder.nativeOrder().static final ValueLayout.OfIntPREVIEWAn unaligned value layout constant whose size is the same as that of a Javaintand byte order set toByteOrder.nativeOrder().static final ValueLayout.OfLongPREVIEWA value layout constant whose size is the same as that of a Javalong, bit alignment set to 64, and byte order set toByteOrder.nativeOrder().static final ValueLayout.OfLongPREVIEWAn unaligned value layout constant whose size is the same as that of a Javalongand byte order set toByteOrder.nativeOrder().static final ValueLayout.OfShortPREVIEWA value layout constant whose size is the same as that of a Javashort, bit alignment set to 16, and byte order set toByteOrder.nativeOrder().static final ValueLayout.OfShortPREVIEWAn unaligned value layout constant whose size is the same as that of a Javashortand 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.withBitAlignment(long bitAlignment) Returns a memory layout of the same type with the same size and name as this layout, but with the specified alignment constraint (in bits).Returns a memory layout of the same type with the same size and alignment constraint as this layout, but with the specified name.Returns a value layout with the same carrier, alignment constraint and name as this value layout, but with the specified byte order.Methods declared in interface java.lang.foreign.MemoryLayoutPREVIEW
bitAlignment, bitOffset, bitOffsetHandle, bitSize, byteAlignment, byteOffset, byteOffsetHandle, byteSize, equals, hashCode, name, select, sliceHandle, toString, varHandle
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Field Details
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ADDRESS
A value layout constant whose size is the same as that of a machine address (size_t), bit alignment set tosizeof(size_t) * 8, byte order set toByteOrder.nativeOrder(). Equivalent to the following code:MemoryLayout.valueLayout(MemorySegment.class, ByteOrder.nativeOrder()); -
JAVA_BYTE
A value layout constant whose size is the same as that of a Javabyte, bit alignment set to 8, and byte order set toByteOrder.nativeOrder(). Equivalent to the following code:MemoryLayout.valueLayout(byte.class, ByteOrder.nativeOrder()); -
JAVA_BOOLEAN
A value layout constant whose size is the same as that of a Javaboolean, bit alignment set to 8, and byte order set toByteOrder.nativeOrder(). Equivalent to the following code:MemoryLayout.valueLayout(boolean.class, ByteOrder.nativeOrder()); -
JAVA_CHAR
A value layout constant whose size is the same as that of a Javachar, bit alignment set to 16, and byte order set toByteOrder.nativeOrder(). Equivalent to the following code:MemoryLayout.valueLayout(char.class, ByteOrder.nativeOrder()); -
JAVA_SHORT
A value layout constant whose size is the same as that of a Javashort, bit alignment set to 16, and byte order set toByteOrder.nativeOrder(). Equivalent to the following code:MemoryLayout.valueLayout(short.class, ByteOrder.nativeOrder()); -
JAVA_INT
A value layout constant whose size is the same as that of a Javaint, bit alignment set to 32, and byte order set toByteOrder.nativeOrder(). Equivalent to the following code:MemoryLayout.valueLayout(int.class, ByteOrder.nativeOrder()); -
JAVA_LONG
A value layout constant whose size is the same as that of a Javalong, bit alignment set to 64, and byte order set toByteOrder.nativeOrder(). Equivalent to the following code:MemoryLayout.valueLayout(long.class, ByteOrder.nativeOrder()); -
JAVA_FLOAT
A value layout constant whose size is the same as that of a Javafloat, bit alignment set to 32, and byte order set toByteOrder.nativeOrder(). Equivalent to the following code:MemoryLayout.valueLayout(float.class, ByteOrder.nativeOrder()).withBitAlignment(32); -
JAVA_DOUBLE
A value layout constant whose size is the same as that of a Javadouble, bit alignment set to 64, and byte order set toByteOrder.nativeOrder(). Equivalent to the following code:MemoryLayout.valueLayout(double.class, ByteOrder.nativeOrder()); -
ADDRESS_UNALIGNED
An unaligned value 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.withBitAlignment(8);- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
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JAVA_CHAR_UNALIGNED
An unaligned value layout constant whose size is the same as that of a Javacharand byte order set toByteOrder.nativeOrder(). Equivalent to the following code:JAVA_CHAR.withBitAlignment(8);- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
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JAVA_SHORT_UNALIGNED
An unaligned value layout constant whose size is the same as that of a Javashortand byte order set toByteOrder.nativeOrder(). Equivalent to the following code:JAVA_SHORT.withBitAlignment(8);- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
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JAVA_INT_UNALIGNED
An unaligned value layout constant whose size is the same as that of a Javaintand byte order set toByteOrder.nativeOrder(). Equivalent to the following code:JAVA_INT.withBitAlignment(8);- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
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JAVA_LONG_UNALIGNED
An unaligned value layout constant whose size is the same as that of a Javalongand byte order set toByteOrder.nativeOrder(). Equivalent to the following code:JAVA_LONG.withBitAlignment(8);- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
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JAVA_FLOAT_UNALIGNED
An unaligned value layout constant whose size is the same as that of a Javafloatand byte order set toByteOrder.nativeOrder(). Equivalent to the following code:JAVA_FLOAT.withBitAlignment(8);- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
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JAVA_DOUBLE_UNALIGNED
An unaligned value layout constant whose size is the same as that of a Javadoubleand byte order set toByteOrder.nativeOrder(). Equivalent to the following code:JAVA_DOUBLE.withBitAlignment(8);- API Note:
- Care should be taken when using unaligned value layouts as they may induce performance and portability issues.
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Method Details
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order
ByteOrder order()Returns the value's byte order.- Returns:
- the value's byte order
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withOrder
Returns a value layout with the same carrier, alignment constraint and name as this value layout, but with the specified byte order.- Parameters:
order- the desired byte order.- Returns:
- a value layout with the given byte order.
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arrayElementVarHandle
Creates a strided var handle that can be used to access a memory segment as multi-dimensional array. The layout of this array is a sequence layout withshape.lengthnested sequence layouts. The element layout of the sequence layout at depthshape.lengthis this value layout. As a result, ifshape.length == 0, the array layout will feature only one dimension.The resulting var handle will feature
sizes.length + 1coordinates of typelong, which are used as indices into a multi-dimensional array.For instance, the following method call:
Can be used to access a multi-dimensional array whose layout is as follows:VarHandle arrayHandle = ValueLayout.JAVA_INT.arrayElementVarHandle(10, 20);The resulting var handleSequenceLayout arrayLayout = MemoryLayout.sequenceLayout( MemoryLayout.sequenceLayout(10, MemoryLayout.sequenceLayout(20, ValueLayout.JAVA_INT)));arrayHandlewill 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,yandzrespectively, 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,yandzare constrained as follows:0 <= x < arrayLayout.elementCount()0 <= y < 100 <= z < 20
Consider the following access expressions:
In the first case, access is well-formed, as the values forint value1 = arrayHandle.get(10, 2, 4); // ok, accessed offset = 8176 int value2 = arrayHandle.get(0, 0, 30); // out of bounds value for zx,yandzconform to the bounds specified above. In the second case, access fails withIndexOutOfBoundsException, as the value forzis 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 + 1longcoordinates. - Throws:
IllegalArgumentException- ifshape[i] < 0, for at least one indexi.UnsupportedOperationException- ifbitAlignment() > bitSize().- See Also:
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carrier
Class<?> carrier()Returns the carrier associated with this value layout.- Returns:
- the carrier associated with this value layout
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withName
Returns a memory layout of the same type with the same size and alignment constraint as this layout, but with the specified name.- Specified by:
withNamein interfaceMemoryLayoutPREVIEW- Parameters:
name- the layout name.- Returns:
- a memory layout with the given name.
- See Also:
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withBitAlignment
Returns a memory layout of the same type with the same size and name as this layout, but with the specified alignment constraint (in bits).- Specified by:
withBitAlignmentin interfaceMemoryLayoutPREVIEW- Parameters:
bitAlignment- the layout alignment constraint, expressed in bits.- Returns:
- a memory layout with the given alignment constraint.
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ValueLayoutwhen preview features are enabled.