Package org.codehaus.groovy.runtime

Interface GeneratedDispatcher

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface GeneratedDispatcher

A per-class table of compiler-generated dispatch targets, reached by a compact integer id instead of a MethodHandle.

The compiler emits per class: an array-shaped table ($packedDispatch$(int, Object[]), covering every target) plus array-free per-arity tables ($packedDispatch1$, $packedDispatch2$) for the hot shapes taking one or two values beyond the receiver — avoiding the packed argument array, which cannot be scalar-replaced when the dispatch call does not inline. Each table is a switch over the id whose case casts the arguments to the target's declared parameter types and invokes it directly, so the whole chain is ordinary, JIT-friendly bytecode. A single invokedynamic accessor per class links all three through bootstrap(java.lang.invoke.MethodHandles.Lookup, java.lang.String, java.lang.invoke.MethodType) into one constant GeneratedDispatcher.Bundle, created lazily on first use.

Adapters such as PackedClosure hold (dispatchers, id) and make a plain interface call per invocation. Unlike a MethodHandle held in an instance field — which the JIT cannot treat as a constant, so every call runs the (comparatively slow) method-handle invoker — this executes as a cheap indirect call, and inlines fully when the call site is monomorphic. The id space is not limited to packed closure bodies: any statically-known target the compiler wants to reach through a shared adapter (for example a statically-resolved method reference) can claim an id in the same tables.

Since:

6.0.0

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	GeneratedDispatcher.Arity1	Array-free companion for targets taking exactly one value beyond the receiver.
static interface	GeneratedDispatcher.Arity2	Array-free companion for targets taking exactly two values beyond the receiver.
static final class	GeneratedDispatcher.Bundle	The hosting class's three dispatch shapes, linked once by bootstrap(java.lang.invoke.MethodHandles.Lookup, java.lang.String, java.lang.invoke.MethodType) and shared by all of that class's adapters.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	TABLE_METHOD	Name of the generated array-shaped dispatch table method.
static final String	TABLE1_METHOD	Name of the generated one-value dispatch table method.
static final String	TABLE2_METHOD	Name of the generated two-value dispatch table method.

Method Summary

Modifier and Type	Method	Description
static CallSite	bootstrap(MethodHandles.Lookup caller, String name, MethodType type)	Invokedynamic bootstrap for the hosting class's dispatcher accessor: adapts the class's three private static dispatch tables to their functional interfaces (one hidden class each, via LambdaMetafactory with the caller's full-privilege lookup) and returns them as one constant GeneratedDispatcher.Bundle.
Object	dispatch(int id, Object[] args)	Invokes the dispatch target registered under id in the hosting class.
static Class<?>[]	paramTypes(MethodHandles.Lookup caller, String name, Class<?> type, String descriptor)	Constant-dynamic bootstrap for a closure literal's declared parameter types: decodes a method descriptor (which, unlike Class constants, can carry primitive types) with the hosting class's loader into a Class[] resolved once per literal site and shared by every adapter created there — closure creation then loads one constant instead of allocating and filling an array.

Field Details

TABLE_METHOD

static final String TABLE_METHOD

Name of the generated array-shaped dispatch table method.

See Also:

• Constant Field Values

TABLE1_METHOD

static final String TABLE1_METHOD

Name of the generated one-value dispatch table method.

See Also:

• Constant Field Values

TABLE2_METHOD

static final String TABLE2_METHOD

Name of the generated two-value dispatch table method.

See Also:

• Constant Field Values

Method Details

dispatch

Object dispatch(int id,
 Object[] args)

Invokes the dispatch target registered under id in the hosting class.

Parameters:

id - the compile-time-assigned index of the target in the hosting class's table

args - the packed argument array: args[0] is the receiver (the adapter's owner — ignored by static targets), followed by any captured values, then the call arguments, all in the target's declared parameter order

Returns:

the target's return value (null for a void target)

paramTypes

static Class<?>[] paramTypes(MethodHandles.Lookup caller,
 String name,
 Class<?> type,
 String descriptor)

Constant-dynamic bootstrap for a closure literal's declared parameter types: decodes a method descriptor (which, unlike Class constants, can carry primitive types) with the hosting class's loader into a Class[] resolved once per literal site and shared by every adapter created there — closure creation then loads one constant instead of allocating and filling an array. Sharing matches generated closure classes, whose parameter-type arrays are likewise cached per class. Emitted bytecode reaches this through org.codehaus.groovy.vmplugin.v8.IndyInterface#packedParamTypes, which delegates here.

Parameters:

caller - the hosting class's lookup (supplied by the JVM)

name - the constant's name (unused)

type - the constant's type: Class[]

descriptor - a method descriptor whose parameter types are the closure's declared parameter types (the return type is ignored)

Returns:

the declared parameter types

bootstrap

static CallSite bootstrap(MethodHandles.Lookup caller,
 String name,
 MethodType type)
                   throws Throwable

Invokedynamic bootstrap for the hosting class's dispatcher accessor: adapts the class's three private static dispatch tables to their functional interfaces (one hidden class each, via LambdaMetafactory with the caller's full-privilege lookup) and returns them as one constant GeneratedDispatcher.Bundle. Linked once per class, on first adapter creation. Emitted bytecode reaches this through org.codehaus.groovy.vmplugin.v8.IndyInterface#packedDispatchers — the central bytecode-facing bootstrap surface — which delegates here.

Parameters:

caller - the hosting class's lookup (supplied by the JVM)

name - the invoked name (unused)

type - the accessor's type: () -> Object as emitted (typed loosely so the Bundle type stays off the emitted-bytecode surface); the constant is typed off the requested return type, so () -> Bundle also links

Returns:

a constant call site producing the bundle

Throws:

Throwable - if the tables cannot be found or linked (a compiler bug)