Module jdk.incubator.foreign
Package jdk.incubator.foreign

Class ValueLayout

java.lang.Object
jdk.incubator.foreign.ValueLayout
All Implemented Interfaces:
Constable, MemoryLayout
public final class ValueLayout
extends Object
implements MemoryLayout
A value layout. A value layout is used to model the memory layout associated with values of basic data types, such as integral types (either signed or unsigned) and floating-point types. Each value layout has a size and a byte order (see ByteOrder).

This is a value-based class; use of identity-sensitive operations (including reference equality (==), identity hash code, or synchronization) on instances of ValueLayout may have unpredictable results and should be avoided. The equals method should be used for comparisons.

Implementation Requirements:
This class is immutable and thread-safe.

  • Method Details

    • order

      public ByteOrder order()
      Returns the value's byte order.
      Returns:
      the value's byte order.

    • withOrder

      public ValueLayout withOrder​(ByteOrder order)
      Returns a new value layout with given byte order.
      Parameters:
      order - the desired byte order.
      Returns:
      a new value layout with given byte order.

    • describeConstable

      public Optional<DynamicConstantDesc<ValueLayout>> describeConstable()
      Description copied from interface: MemoryLayout
      Returns an Optional containing the nominal descriptor for this layout, if one can be constructed, or an empty Optional if one cannot be constructed.
      Specified by:
      describeConstable in interface Constable
      Specified by:
      describeConstable in interface MemoryLayout
      Returns:
      An Optional containing the resulting nominal descriptor, or an empty Optional if one cannot be constructed.

    • withName

      public ValueLayout withName​(String name)
      Creates a new layout which features the desired layout name.
      Specified by:
      withName in interface MemoryLayout
      Parameters:
      name - the layout name.
      Returns:
      a new layout which is the same as this layout, except for the name associated to it.
      See Also:
      MemoryLayout.name()

    • withBitAlignment

      public ValueLayout withBitAlignment​(long alignmentBits)
      Creates a new layout which features the desired alignment constraint.
      Specified by:
      withBitAlignment in interface MemoryLayout
      Parameters:
      alignmentBits - the layout alignment constraint, expressed in bits.
      Returns:
      a new layout which is the same as this layout, except for the alignment constraint associated to it.

    • name

      public final Optional<String> name()
      Description copied from interface: MemoryLayout
      Return the name (if any) associated with this layout.
      Specified by:
      name in interface MemoryLayout
      Returns:
      the layout name (if any).
      See Also:
      MemoryLayout.withName(String)

    • bitAlignment

      public final long bitAlignment()
      Description copied from interface: MemoryLayout
      Returns the alignment constraint associated with this layout, expressed in bits. Layout alignment defines a power of two A which is the bit-wise alignment of the layout. If A <= 8 then A/8 is the number of bytes that must be aligned for any pointer that correctly points to this layout. Thus:
      • A=8 means unaligned (in the usual sense), which is common in packets.
      • A=64 means word aligned (on LP64), A=32 int aligned, A=16 short aligned, etc.
      • A=512 is the most strict alignment required by the x86/SV ABI (for AVX-512 data).
      If no explicit alignment constraint was set on this layout (see MemoryLayout.withBitAlignment(long)), then this method returns the natural alignment constraint (in bits) associated with this layout.
      Specified by:
      bitAlignment in interface MemoryLayout
      Returns:
      the layout alignment constraint, in bits.

    • hasSize

      public boolean hasSize()
      Description copied from interface: MemoryLayout
      Does this layout have a specified size? A layout does not have a specified size if it is (or contains) a sequence layout whose size is unspecified (see SequenceLayout.elementCount()). Value layouts (see ValueLayout) and padding layouts (see MemoryLayout.ofPaddingBits(long)) always have a specified size, therefore this method always returns true in these cases.
      Specified by:
      hasSize in interface MemoryLayout
      Returns:
      true, if this layout has a specified size.

    • bitSize

      public long bitSize()
      Description copied from interface: MemoryLayout
      Computes the layout size, in bits.
      Specified by:
      bitSize in interface MemoryLayout
      Returns:
      the layout size, in bits.