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Interface FunctionDescriptor

public sealed interface FunctionDescriptor

A function descriptor models the signature of a foreign function. A function descriptor is made up of zero or more argument layouts, and zero or one return layout. A function descriptor is used to create downcall method handles^RESTRICTED and upcall stubs^RESTRICTED.

Implementation Requirements:

Implementing classes are immutable, thread-safe and value-based.

Since:

See Also:

Method Summary

Modifier and Type	Method	Description
`FunctionDescriptor`	`appendArgumentLayouts(MemoryLayout... addedLayouts)`	Returns a function descriptor with the given argument layouts appended to the argument layouts of this function descriptor.
`List<MemoryLayout>`	`argumentLayouts()`	Returns the argument layouts of this function descriptor (as an unmodifiable list).
`FunctionDescriptor`	`changeReturnLayout(MemoryLayout newReturn)`	Returns a function descriptor with the provided return layout.
`FunctionDescriptor`	`dropReturnLayout()`	Returns a new function descriptor, with no return layout.
`FunctionDescriptor`	`insertArgumentLayouts(int index, MemoryLayout... addedLayouts)`	Returns a function descriptor with the given argument layouts inserted at the given index, into the argument layout array of this function descriptor.
`static FunctionDescriptor`	`of(MemoryLayout resLayout, MemoryLayout... argLayouts)`	Creates a function descriptor with the given return and argument layouts.
`static FunctionDescriptor`	`ofVoid(MemoryLayout... argLayouts)`	Creates a function descriptor with the given argument layouts and no return layout.
`Optional<MemoryLayout>`	`returnLayout()`	Returns the return layout (if any) of this function descriptor.
`MethodType`	`toMethodType()`	Returns the method type consisting of the carrier types of the layouts in this function descriptor.

Method Details

returnLayout

Optional<MemoryLayout> returnLayout()

Returns the return layout (if any) of this function descriptor.

Returns:: the return layout (if any) of this function descriptor

argumentLayouts

List<MemoryLayout> argumentLayouts()

Returns the argument layouts of this function descriptor (as an unmodifiable list).

Returns:: the argument layouts of this function descriptor (as an unmodifiable list)

appendArgumentLayouts

FunctionDescriptor appendArgumentLayouts(MemoryLayout... addedLayouts)

Returns a function descriptor with the given argument layouts appended to the argument layouts of this function descriptor.

Parameters:: addedLayouts - the argument layouts to append
Returns:: a new function descriptor, with the provided additional argument layouts
Throws:: IllegalArgumentException - if one of the layouts in addedLayouts is a padding layout

insertArgumentLayouts

FunctionDescriptor insertArgumentLayouts(int index, MemoryLayout... addedLayouts)

Returns a function descriptor with the given argument layouts inserted at the given index, into the argument layout array of this function descriptor.

Parameters:: index - the index at which to insert the arguments; addedLayouts - the argument layouts to insert at given index
Returns:: a new function descriptor, with the provided additional argument layouts
Throws:: IllegalArgumentException - if one of the layouts in addedLayouts is a padding layout; IllegalArgumentException - if index < 0 || index > argumentLayouts().size()

changeReturnLayout

FunctionDescriptor changeReturnLayout(MemoryLayout newReturn)

Returns a function descriptor with the provided return layout.

Parameters:: newReturn - the new return layout
Returns:: a new function descriptor, with the provided return layout
Throws:: IllegalArgumentException - if newReturn is a padding layout

dropReturnLayout

FunctionDescriptor dropReturnLayout()

Returns a new function descriptor, with no return layout.

Returns:: a new function descriptor, with no return layout

toMethodType

MethodType toMethodType()

Returns the method type consisting of the carrier types of the layouts in this function descriptor.

The carrier type of a layout L is determined as follows:

If L is a ValueLayout the carrier type is determined through ValueLayout.carrier().
If L is a GroupLayout or a SequenceLayout, the carrier type is MemorySegment.

API Note:: A function descriptor cannot, by construction, contain any padding layouts. As such, it is not necessary to specify how padding layout should be mapped to carrier types.
Returns:: the method type consisting of the carrier types of the layouts in this function descriptor

of

static FunctionDescriptor of(MemoryLayout resLayout, MemoryLayout... argLayouts)

Creates a function descriptor with the given return and argument layouts.

Parameters:: resLayout - the return layout; argLayouts - the argument layouts
Returns:: a new function descriptor with the provided return and argument layouts
Throws:: IllegalArgumentException - if resLayout is a padding layout; IllegalArgumentException - if one of the layouts in argLayouts is a padding layout

ofVoid

static FunctionDescriptor ofVoid(MemoryLayout... argLayouts)

Creates a function descriptor with the given argument layouts and no return layout. This is useful to model functions that return no values.

Parameters:: argLayouts - the argument layouts
Returns:: a new function descriptor with the provided argument layouts
Throws:: IllegalArgumentException - if one of the layouts in argLayouts is a padding layout

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https://docs.oracle.com/en/java/javase/25/docs/api/java.base/java/lang/foreign/FunctionDescriptor.html