Module java.base
Package java.lang.foreign

Class GroupLayout

java.lang.Object
java.lang.foreign.GroupLayout
All Implemented Interfaces:
MemoryLayoutPREVIEW
public final class GroupLayout extends Object implements MemoryLayoutPREVIEW
GroupLayout is a preview API of the Java platform.
Programs can only use GroupLayout when preview features are enabled.
Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.
A compound layout that aggregates multiple member layouts. There are two ways in which member layouts can be combined: if member layouts are laid out one after the other, the resulting group layout is said to be a struct (see MemoryLayout.structLayout(MemoryLayout...)PREVIEW); conversely, if all member layouts are laid out at the same starting offset, the resulting group layout is said to be a union (see MemoryLayout.unionLayout(MemoryLayout...)PREVIEW).
Implementation Requirements:
This class is immutable, thread-safe and value-based.
Since:
19

  • Method Details

    • memberLayouts

      public List<MemoryLayoutPREVIEW> memberLayouts()
      Returns the member layouts associated with this group.
      API Note:
      the order in which member layouts are returned is the same order in which member layouts have been passed to one of the group layout factory methods (see MemoryLayout.structLayout(MemoryLayout...)PREVIEW, MemoryLayout.unionLayout(MemoryLayout...)PREVIEW).
      Returns:
      the member layouts associated with this group.

    • toString

      public String toString()
      Returns the string representation of this layout.
      Specified by:
      toString in interface MemoryLayoutPREVIEW
      Returns:
      the string representation of this layout

    • isStruct

      public boolean isStruct()
      Returns true, if this group layout is a struct layout.
      Returns:
      true, if this group layout is a struct layout

    • isUnion

      public boolean isUnion()
      Returns true, if this group layout is a union layout.
      Returns:
      true, if this group layout is a union layout

    • equals

      public boolean equals(Object other)
      Compares the specified object with this layout for equality. Returns true if and only if the specified object is also a layout, and it is equal to this layout. Two layouts are considered equal if they are of the same kind, have the same size, name and alignment constraints. Furthermore, depending on the layout kind, additional conditions must be satisfied:
      Specified by:
      equals in interface MemoryLayoutPREVIEW
      Parameters:
      other - the object to be compared for equality with this layout.
      Returns:
      true if the specified object is equal to this layout.
      See Also:

    • hashCode

      public int hashCode()
      Returns the hash code value for this layout.
      Specified by:
      hashCode in interface MemoryLayoutPREVIEW
      Returns:
      the hash code value for this layout
      See Also:

    • withName

      public GroupLayoutPREVIEW withName(String name)
      Returns a memory layout with the same size and alignment constraints as this layout, but with the specified name.
      Specified by:
      withName in interface MemoryLayoutPREVIEW
      Parameters:
      name - the layout name.
      Returns:
      a memory layout with the given name.
      See Also:

    • withBitAlignment

      public GroupLayoutPREVIEW withBitAlignment(long alignmentBits)
      Returns a memory layout with the same size and name as this layout, but with the specified alignment constraints (in bits).
      Specified by:
      withBitAlignment in interface MemoryLayoutPREVIEW
      Parameters:
      alignmentBits - the layout alignment constraint, expressed in bits.
      Returns:
      a memory layout with the given alignment constraints.

    • name

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

    • 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)PREVIEW), then this method returns the natural alignment constraint (in bits) associated with this layout.
      Specified by:
      bitAlignment in interface MemoryLayoutPREVIEW
      Returns:
      the layout alignment constraint, in bits.

    • byteSize

      public long byteSize()
      Description copied from interface: MemoryLayout
      Returns the layout size, in bytes.
      Specified by:
      byteSize in interface MemoryLayoutPREVIEW
      Returns:
      the layout size, in bytes

    • bitSize

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

    • isPadding

      public boolean isPadding()
      Description copied from interface: MemoryLayout
      Returns true, if this layout is a padding layout.
      Specified by:
      isPadding in interface MemoryLayoutPREVIEW
      Returns:
      true, if this layout is a padding layout