/**
* Return a method handle that takes the indicated number of typed arguments and returns an array
* of them. The type argument is the array type.
*/
public static MethodHandle varargsArray(Class<?> arrayType, int nargs) {
Class<?> elemType = arrayType.getComponentType();
if (elemType == null) throw new IllegalArgumentException("not an array: " + arrayType);
// FIXME: Need more special casing and caching here.
if (nargs >= MAX_JVM_ARITY / 2 - 1) {
int slots = nargs;
final int MAX_ARRAY_SLOTS = MAX_JVM_ARITY - 1; // 1 for receiver MH
if (arrayType == double[].class || arrayType == long[].class) slots *= 2;
if (slots > MAX_ARRAY_SLOTS)
throw new IllegalArgumentException(
"too many arguments: " + arrayType.getSimpleName() + ", length " + nargs);
}
if (elemType == Object.class) return varargsArray(nargs);
// other cases: primitive arrays, subtypes of Object[]
MethodHandle cache[] = TYPED_COLLECTORS.get(elemType);
MethodHandle mh = nargs < cache.length ? cache[nargs] : null;
if (mh != null) return mh;
if (elemType.isPrimitive()) {
MethodHandle builder = FILL_NEW_ARRAY;
MethodHandle producer = buildArrayProducer(arrayType);
mh = buildVarargsArray(builder, producer, nargs);
} else {
@SuppressWarnings("unchecked")
Class<? extends Object[]> objArrayType = (Class<? extends Object[]>) arrayType;
Object[] example = Arrays.copyOf(NO_ARGS_ARRAY, 0, objArrayType);
MethodHandle builder = FILL_NEW_TYPED_ARRAY.bindTo(example);
MethodHandle producer = ARRAY_IDENTITY;
mh = buildVarargsArray(builder, producer, nargs);
}
mh =
mh.asType(MethodType.methodType(arrayType, Collections.<Class<?>>nCopies(nargs, elemType)));
assert (assertCorrectArity(mh, nargs));
if (nargs < cache.length) cache[nargs] = mh;
return mh;
}
