LUMIERA.clone/tests/library/lazy-init-test.cpp

/*
  LazyInit(Test)  -  verify a mechanism to install a self-initialising functor

  Copyright (C)         Lumiera.org
    2023,               Hermann Vosseler <Ichthyostega@web.de>

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; either version 2 of
  the License, or (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

* *****************************************************/

/** @file lazy-init-test.cpp
 ** unit test \ref LazyInit_test
 */



#include "lib/test/run.hpp"
#include "lib/lazy-init.hpp"
//#include "lib/format-string.hpp"
//#include "lib/test/test-helper.hpp"
#include "lib/test/testdummy.hpp"
#include "lib/test/diagnostic-output.hpp" /////////////////////TODO TODOH
#include "lib/util.hpp"

//#include <array>



namespace lib {
namespace test{
  
//  using util::_Fmt;
  using util::isSameObject;
  using lib::meta::isFunMember;
//  using lib::meta::_FunRet;
//  using err::LUMIERA_ERROR_LIFECYCLE;
  
  
  
  namespace { // policy and configuration for test...

    //
  }//(End) Test config


  
  
  
  /***********************************************************************************//**
   * @test Verify a mix-in to allow for lazy initialisation of complex infrastructure
   *       tied to a std::function; the intention is to have a »trap« hidden in the
   *       function itself to trigger on first use and perform the one-time
   *       initialisation, then finally lock the object in place.
   * @see lazy-init.hpp
   * @see lib::RandomDraw
   */
  class LazyInit_test
    : public Test
    {
      
      void
      run (Arg)
        {
          simpleUse();
          
          verify_trojanLambda();
          verify_inlineStorage();
//          verify_numerics();
//          verify_adaptMapping();
//          verify_dynamicChange();
        }
      
      
      
      /** @test demonstrate a basic usage scenario
       */
      void
      simpleUse()
        {
        }
      
      
      
      /** @test verify construction of the »trap« front-end eventually to trigger initialisation
       *      - this test does not involve any std::function, rather a heap-allocated copy of a λ
       *      # the _target function_ finally to be invoked performs a verifiable computation
       *      # the _delegate_ receives an memory location and returns a reference to the target
       *      # the generated _»trojan λ«_ captures its own address, invokes the delegate,
       *        retrieves a reference to a target functor, and invokes these with actual arguments.
       * @remark the purpose of this convoluted scheme is for the _delegate to perform initialisation,_
       *         taking into account the current memory location „sniffed“ by the trojan.
       */
      void
      verify_trojanLambda()
        {
          size_t beacon;
          auto fun = [&](uint challenge){ return beacon+challenge; };
          
          using Sig = size_t(uint);
          CHECK (isFunMember<Sig> (&fun));
          
          beacon = rand();
          uint c = beacon % 42;
          // verify we can invoke the target function
          CHECK (beacon+c == fun(c));

          // verify we can also invoke the target function through a reference
          using FunType = decltype(fun);
          FunType& funRef = fun;
          CHECK (beacon+c == funRef(c));
          
          // construct delegate function exposing the expected behaviour;
          // additionally this function captures the passed-in address.
          RawAddr location{nullptr};
          auto delegate = [&](RawAddr adr) -> FunType&
                            {
                              location = adr;
                              return fun;
                            };
          using Delegate = decltype(delegate);
          Delegate *delP = new Delegate(delegate);
          
          // verify the heap-allocated copy of the delegate behaves as expected
          location = nullptr;
          CHECK (beacon+c == (*delP)(this)(c));
          CHECK (location == this);
          
          // now (finally) build the »trap function«,
          // taking ownership of the heap-allocated delegate copy
          auto trojanLambda = TrojanFun<Sig>::generateTrap (delP);
          CHECK (sizeof(trojanLambda) == 2*sizeof(size_t));
          
          // on invocation...
          // - it captures its current location
          // - passes this to the delegate
          // - invokes the target function returned from the delegate
          CHECK (beacon+c == trojanLambda(c));
          CHECK (location == &trojanLambda);
          
          // repeat that with a copy, and changed beacon value
          auto trojanClone = trojanLambda;
          beacon = rand();
          c = beacon % 55;
          CHECK (beacon+c == trojanClone(c));
          CHECK (location == &trojanClone);
          CHECK (beacon+c == trojanLambda(c));
          CHECK (location == &trojanLambda);
        }
      
      
      
      /** @test verify that std::function indeed stores a simple functor inline
       */
      void
      verify_inlineStorage()
        {
          Dummy::checksum() = 0;
          using DummyManager = std::shared_ptr<Dummy>;
          
          DummyManager dummy{new Dummy};
          long currSum = Dummy::checksum();
          CHECK (currSum > 0);
          CHECK (currSum == dummy->getVal());
          CHECK (1 == dummy.use_count());
          {
            // --- nested Scope ---
            auto lambda = [dummy]{ return &dummy; };
            CHECK (2 == dummy.use_count());
            CHECK (currSum == Dummy::checksum());
            
            RawAddr location = lambda();
            CHECK (location == &lambda);
            
            std::function funWrap{lambda};
            CHECK (funWrap);
            CHECK (not isSameObject (funWrap, lambda));
            CHECK (3 == dummy.use_count());
            CHECK (currSum == Dummy::checksum());
            
SHOW_EXPR(location)
            location = funWrap();
SHOW_EXPR(location)
SHOW_EXPR(RawAddr(&funWrap))
SHOW_EXPR(RawAddr(dummy.get()))

            std::function fuckWrap{[location]{ return &location; }};
            CHECK (fuckWrap);
SHOW_EXPR(RawAddr(&location))
SHOW_EXPR(RawAddr(fuckWrap()))
SHOW_EXPR(RawAddr(&fuckWrap))
          }
          CHECK (1 == dummy.use_count());
          CHECK (currSum == Dummy::checksum());
          dummy.reset();
          CHECK (0 == dummy.use_count());
          CHECK (0 == Dummy::checksum());
        }
      
      
      
    };
  
  
  /** Register this test class... */
  LAUNCHER (LazyInit_test, "unit common");
  
  
}} // namespace lib::test