Module java.base
Package java.lang.foreign

Interface SequenceLayout

All Superinterfaces:
MemoryLayoutPREVIEW
public sealed interface SequenceLayout extends MemoryLayoutPREVIEW
SequenceLayout is a preview API of the Java platform.
Programs can only use SequenceLayout 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 denotes a homogeneous repetition of a given element layout. The repetition count is said to be the sequence layout's element count. A sequence layout can be thought of as a struct layout where the sequence layout's element layout is repeated a number of times that is equal to the sequence layout's element count. In other words this layout: 
MemoryLayout.sequenceLayout(3, ValueLayout.JAVA_INT.withOrder(ByteOrder.BIG_ENDIAN));
is equivalent to the following layout: 
MemoryLayout.structLayout(
    ValueLayout.JAVA_INT.withOrder(ByteOrder.BIG_ENDIAN),
    ValueLayout.JAVA_INT.withOrder(ByteOrder.BIG_ENDIAN),
    ValueLayout.JAVA_INT.withOrder(ByteOrder.BIG_ENDIAN));
Implementation Requirements:
This class is immutable, thread-safe and value-based.
Since:
19

  • Method Details

    • elementLayout

      MemoryLayoutPREVIEW elementLayout()
      Returns the element layout of this sequence layout.
      Returns:
      the element layout of this sequence layout

    • elementCount

      long elementCount()
      Returns the element count of this sequence layout.
      Returns:
      the element count of this sequence layout

    • withElementCount

      SequenceLayoutPREVIEW withElementCount(long elementCount)
      Returns a sequence layout with the same characteristics of this layout, but with the given element count.
      Parameters:
      elementCount - the new element count.
      Returns:
      a sequence layout with the same characteristics of this layout, but with the given element count
      Throws:
      IllegalArgumentException - if elementCount is negative.
      IllegalArgumentException - if elementLayout.bitSize() * elementCount overflows.

    • reshape

      SequenceLayoutPREVIEW reshape(long... elementCounts)
      Rearranges the elements in this sequence layout into a multi-dimensional sequence layout. The resulting layout is a sequence layout where element layouts in the flattened projection of this sequence layout are rearranged into one or more nested sequence layouts according to the provided element counts. This transformation preserves the layout size; that is, multiplying the provided element counts must yield the same element count as the flattened projection of this sequence layout.

      For instance, given a sequence layout of the kind: 

      var seq = MemoryLayout.sequenceLayout(4, MemoryLayout.sequenceLayout(3, ValueLayout.JAVA_INT));
      calling seq.reshape(2, 6) will yield the following sequence layout: 
      var reshapeSeq = MemoryLayout.sequenceLayout(2, MemoryLayout.sequenceLayout(6, ValueLayout.JAVA_INT));

      If one of the provided element count is the special value -1, then the element count in that position will be inferred from the remaining element counts and the element count of the flattened projection of this layout. For instance, a layout equivalent to the above reshapeSeq can also be computed in the following ways: 

      var reshapeSeqImplicit1 = seq.reshape(-1, 6);
var reshapeSeqImplicit2 = seq.reshape(2, -1);

      Parameters:
      elementCounts - an array of element counts, of which at most one can be -1.
      Returns:
      a sequence layout where element layouts in the flattened projection of this sequence layout (see flatten()) are re-arranged into one or more nested sequence layouts.
      Throws:
      IllegalArgumentException - if two or more element counts are set to -1, or if one or more element count is <= 0 (but other than -1) or, if, after any required inference, multiplying the element counts does not yield the same element count as the flattened projection of this sequence layout.

    • flatten

      SequenceLayoutPREVIEW flatten()
      Returns a flattened sequence layout. The element layout of the returned sequence layout is the first non-sequence layout found by inspecting (recursively, if needed) the element layout of this sequence layout: 
      MemoryLayout flatElementLayout(SequenceLayout sequenceLayout) {
   return switch (sequenceLayout.elementLayout()) {
       case SequenceLayout nestedSequenceLayout -> flatElementLayout(nestedSequenceLayout);
       case MemoryLayout layout -> layout;
   };
}

      This transformation preserves the layout size; nested sequence layout in this sequence layout will be dropped and their element counts will be incorporated into that of the returned sequence layout. For instance, given a sequence layout of the kind: 

      var seq = MemoryLayout.sequenceLayout(4, MemoryLayout.sequenceLayout(3, ValueLayout.JAVA_INT));
      calling seq.flatten() will yield the following sequence layout: 
      var flattenedSeq = MemoryLayout.sequenceLayout(12, ValueLayout.JAVA_INT);

      Returns:
      a sequence layout with the same size as this layout (but, possibly, with different element count), whose element layout is not a sequence layout.

    • withName

      SequenceLayoutPREVIEW withName(String name)
      Returns a memory layout with the same characteristics as this layout, but with the given name.
      Specified by:
      withName in interface MemoryLayoutPREVIEW
      Parameters:
      name - the layout name.
      Returns:
      a memory layout with the same characteristics as this layout, but with the given name
      See Also:

    • withByteAlignment

      SequenceLayoutPREVIEW withByteAlignment(long byteAlignment)
      Returns a memory layout with the same characteristics as this layout, but with the given alignment constraint (in bytes).
      Specified by:
      withByteAlignment in interface MemoryLayoutPREVIEW
      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 - if byteAlignment is not a power of two.
      IllegalArgumentException - if byteAlignment < elementLayout().byteAlignment().