private MethodHandle getMethodHandle(Method method) {
MethodHandle methodHandle;
try {
methodHandle = lookup().unreflect(method);
} catch (IllegalAccessException e) {
throw new PrestoException(FUNCTION_IMPLEMENTATION_ERROR, e);
}
if (!isStatic(method.getModifiers())) {
// Re-arrange the parameters, so that the "this" parameter is after the meta parameters
int[] permutedIndices = new int[methodHandle.type().parameterCount()];
permutedIndices[0] = dependencies.size();
MethodType newType =
methodHandle
.type()
.changeParameterType(dependencies.size(), methodHandle.type().parameterType(0));
for (int i = 0; i < dependencies.size(); i++) {
permutedIndices[i + 1] = i;
newType = newType.changeParameterType(i, methodHandle.type().parameterType(i + 1));
}
for (int i = dependencies.size() + 1; i < permutedIndices.length; i++) {
permutedIndices[i] = i;
}
methodHandle = permuteArguments(methodHandle, newType, permutedIndices);
}
return methodHandle;
}
public MethodType down(MethodType type) {
for (int i = 0; i < type.parameterCount(); i++) {
type = type.changeParameterType(i, type.parameterArray()[i]);
}
return type;
}
