container/experimental/segmented_copy_n_test.cpp

//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2025-2026. Distributed under the Boost
// Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/container for documentation.
//
//////////////////////////////////////////////////////////////////////////////

#include <boost/container/experimental/segmented_copy_n.hpp>
#include "../test/lightweight_test.hpp"
#include "segmented_test_helper.hpp"
#include <boost/container/vector.hpp>

using namespace boost::container;

void test_copy_n_full()
{
   test_detail::seg_vector<int> sv;
   int a1[] = {1, 2, 3};
   int a2[] = {4, 5};
   int a3[] = {6, 7, 8, 9};
   sv.add_segment_range(a1, a1 + 3);
   sv.add_segment_range(a2, a2 + 2);
   sv.add_segment_range(a3, a3 + 4);

   boost::container::vector<int> out(9, 0);
   boost::container::vector<int>::iterator result = segmented_copy_n(sv.begin(), 9, out.begin());

   BOOST_TEST(result == out.end());
   for(int i = 0; i < 9; ++i)
      BOOST_TEST_EQ(out[static_cast<std::size_t>(i)], i + 1);
}

void test_copy_n_partial()
{
   test_detail::seg_vector<int> sv;
   int a1[] = {1, 2, 3};
   int a2[] = {4, 5};
   int a3[] = {6, 7, 8, 9};
   sv.add_segment_range(a1, a1 + 3);
   sv.add_segment_range(a2, a2 + 2);
   sv.add_segment_range(a3, a3 + 4);

   boost::container::vector<int> out(5, 0);
   boost::container::vector<int>::iterator result = segmented_copy_n(sv.begin(), 5, out.begin());

   BOOST_TEST(result == out.end());
   BOOST_TEST_EQ(out[0], 1);
   BOOST_TEST_EQ(out[1], 2);
   BOOST_TEST_EQ(out[2], 3);
   BOOST_TEST_EQ(out[3], 4);
   BOOST_TEST_EQ(out[4], 5);
}

void test_copy_n_zero()
{
   test_detail::seg_vector<int> sv;
   int a[] = {1, 2, 3};
   sv.add_segment_range(a, a + 3);

   boost::container::vector<int> out(3, 99);
   boost::container::vector<int>::iterator result = segmented_copy_n(sv.begin(), 0, out.begin());

   BOOST_TEST(result == out.begin());
   BOOST_TEST_EQ(out[0], 99);
}

void test_copy_n_single_segment()
{
   test_detail::seg_vector<int> sv;
   int a[] = {10, 20, 30};
   sv.add_segment_range(a, a + 3);

   boost::container::vector<int> out(2, 0);
   boost::container::vector<int>::iterator result = segmented_copy_n(sv.begin(), 2, out.begin());

   BOOST_TEST(result == out.end());
   BOOST_TEST_EQ(out[0], 10);
   BOOST_TEST_EQ(out[1], 20);
}

void test_copy_n_non_segmented()
{
   boost::container::vector<int> in;
   in.push_back(1); in.push_back(2); in.push_back(3);

   boost::container::vector<int> out(2, 0);
   boost::container::vector<int>::iterator result = segmented_copy_n(in.begin(), 2, out.begin());

   BOOST_TEST(result == out.end());
   BOOST_TEST_EQ(out[0], 1);
   BOOST_TEST_EQ(out[1], 2);
}

void test_copy_n_seg2()
{
   test_detail::seg2_vector<int> sv2;
   int a1[] = {1, 2, 3};
   int a2[] = {4, 5};
   int a3[] = {6, 7, 8, 9};
   sv2.add_flat_segment_range(a1, a1 + 3);
   sv2.add_flat_segment_range(a2, a2 + 2);
   sv2.add_flat_segment_range(a3, a3 + 4);

   boost::container::vector<int> out(9, 0);
   boost::container::vector<int>::iterator result = segmented_copy_n(sv2.begin(), 9, out.begin());

   BOOST_TEST(result == out.end());
   for(int i = 0; i < 9; ++i)
      BOOST_TEST_EQ(out[static_cast<std::size_t>(i)], i + 1);
}

void test_copy_n_segmented_output()
{
   test_detail::seg_vector<int> sv;
   int a1[] = {1, 2, 3};
   int a2[] = {4, 5};
   int a3[] = {6, 7, 8, 9};
   sv.add_segment_range(a1, a1 + 3);
   sv.add_segment_range(a2, a2 + 2);
   sv.add_segment_range(a3, a3 + 4);

   test_detail::seg_vector<int> out;
   out.add_segment(4, 0);
   out.add_segment(3, 0);
   out.add_segment(2, 0);

   typedef test_detail::seg_vector<int>::iterator iter_t;
   iter_t result = segmented_copy_n(sv.begin(), 9, out.begin());

   BOOST_TEST(result == out.end());
   iter_t it = out.begin();
   for(int i = 0; i < 9; ++i, ++it)
      BOOST_TEST_EQ(*it, i + 1);
}

void test_copy_n_seg2_to_seg2()
{
   test_detail::seg2_vector<int> sv2;
   int a1[] = {1, 2, 3};
   int a2[] = {4, 5};
   int a3[] = {6, 7, 8, 9};
   sv2.add_flat_segment_range(a1, a1 + 3);
   sv2.add_flat_segment_range(a2, a2 + 2);
   sv2.add_flat_segment_range(a3, a3 + 4);

   test_detail::seg2_vector<int> out;
   {
      test_detail::seg_vector<int> s1; s1.add_segment(5, 0);
      test_detail::seg_vector<int> s2; s2.add_segment(4, 0);
      out.add_segment(s1);
      out.add_segment(s2);
   }

   typedef test_detail::seg2_vector<int>::iterator iter_t;
   iter_t result = segmented_copy_n(sv2.begin(), 9, out.begin());

   BOOST_TEST(result == out.end());
   iter_t it = out.begin();
   for(int i = 0; i < 9; ++i, ++it)
      BOOST_TEST_EQ(*it, i + 1);
}

void test_copy_n_seg_to_seg_misaligned()
{
   test_detail::seg_vector<int> sv;
   int a1[] = {1, 2, 3, 4, 5};
   int a2[] = {6, 7, 8};
   sv.add_segment_range(a1, a1 + 5);
   sv.add_segment_range(a2, a2 + 3);

   test_detail::seg_vector<int> out;
   out.add_segment(2, 0);
   out.add_segment(3, 0);
   out.add_segment(3, 0);

   typedef test_detail::seg_vector<int>::iterator iter_t;
   iter_t result = segmented_copy_n(sv.begin(), 8, out.begin());

   BOOST_TEST(result == out.end());
   iter_t it = out.begin();
   for(int i = 0; i < 8; ++i, ++it)
      BOOST_TEST_EQ(*it, i + 1);
}

void test_copy_n_partial_segmented_output()
{
   test_detail::seg_vector<int> sv;
   int a1[] = {1, 2, 3};
   int a2[] = {4, 5};
   int a3[] = {6, 7, 8, 9};
   sv.add_segment_range(a1, a1 + 3);
   sv.add_segment_range(a2, a2 + 2);
   sv.add_segment_range(a3, a3 + 4);

   test_detail::seg_vector<int> out;
   out.add_segment(3, 0);
   out.add_segment(3, 0);

   typedef test_detail::seg_vector<int>::iterator iter_t;
   iter_t result = segmented_copy_n(sv.begin(), 5, out.begin());

   std::size_t count = 0;
   iter_t it = out.begin();
   for(; it != result; ++it)
      ++count;
   BOOST_TEST_EQ(count, 5u);

   it = out.begin();
   for(int i = 0; i < 5; ++i, ++it)
      BOOST_TEST_EQ(*it, i + 1);
}

void test_copy_n_single_segment_interior()
{
   test_detail::seg_vector<int> sv;
   int a[] = {1, 2, 3, 4, 5, 6};
   sv.add_segment_range(a, a + 6);

   boost::container::vector<int> out(6, 0);
   boost::container::vector<int>::iterator result =
      segmented_copy_n(test_detail::iter_at(sv, 1), 4, out.begin());

   BOOST_TEST_EQ(static_cast<std::size_t>(result - out.begin()), 4u);
   BOOST_TEST_EQ(out[0], 2);
   BOOST_TEST_EQ(out[1], 3);
   BOOST_TEST_EQ(out[2], 4);
   BOOST_TEST_EQ(out[3], 5);
   BOOST_TEST_EQ(out[4], 0);
   BOOST_TEST_EQ(out[5], 0);
}

void test_copy_n_single_segment_exact()
{
   test_detail::seg_vector<int> sv;
   int a[] = {1, 2, 3, 4, 5, 6};
   sv.add_segment_range(a, a + 6);

   boost::container::vector<int> out(6, 0);
   boost::container::vector<int>::iterator result =
      segmented_copy_n(test_detail::iter_at(sv, 1), 5, out.begin());

   BOOST_TEST_EQ(static_cast<std::size_t>(result - out.begin()), 5u);
   for(int i = 0; i < 5; ++i)
      BOOST_TEST_EQ(out[static_cast<std::size_t>(i)], i + 2);
   BOOST_TEST_EQ(out[5], 0);
}

void test_copy_n_single_segment_zero_mid()
{
   test_detail::seg_vector<int> sv;
   int a[] = {1, 2, 3, 4, 5, 6};
   sv.add_segment_range(a, a + 6);

   boost::container::vector<int> out(3, 99);
   boost::container::vector<int>::iterator result =
      segmented_copy_n(test_detail::iter_at(sv, 3), 0, out.begin());

   BOOST_TEST(result == out.begin());
   BOOST_TEST_EQ(out[0], 99);
   BOOST_TEST_EQ(out[1], 99);
   BOOST_TEST_EQ(out[2], 99);
}

void test_copy_n_single_segment_count_beyond_segment()
{
   test_detail::seg_vector<int> sv;
   int a1[] = {1, 2, 3};
   int a2[] = {4, 5, 6};
   sv.add_segment_range(a1, a1 + 3);
   sv.add_segment_range(a2, a2 + 3);

   boost::container::vector<int> out(6, 0);
   boost::container::vector<int>::iterator result =
      segmented_copy_n(test_detail::iter_at(sv, 1), 4, out.begin());

   BOOST_TEST_EQ(static_cast<std::size_t>(result - out.begin()), 4u);
   BOOST_TEST_EQ(out[0], 2);
   BOOST_TEST_EQ(out[1], 3);
   BOOST_TEST_EQ(out[2], 4);
   BOOST_TEST_EQ(out[3], 5);
   BOOST_TEST_EQ(out[4], 0);
}

void test_copy_n_single_segment_seg2_outer()
{
   test_detail::seg2_vector<int> sv2;
   test_detail::seg_vector<int> inner;
   int a1[] = {1, 2, 3};
   int a2[] = {4, 5};
   int a3[] = {6, 7};
   inner.add_segment_range(a1, a1 + 3);
   inner.add_segment_range(a2, a2 + 2);
   inner.add_segment_range(a3, a3 + 2);
   sv2.add_segment(inner);

   boost::container::vector<int> out(8, 0);
   boost::container::vector<int>::iterator result =
      segmented_copy_n(test_detail::iter_at(sv2, 1), 5, out.begin());

   BOOST_TEST_EQ(static_cast<std::size_t>(result - out.begin()), 5u);
   for(int i = 0; i < 5; ++i)
      BOOST_TEST_EQ(out[static_cast<std::size_t>(i)], i + 2);
   BOOST_TEST_EQ(out[5], 0);
}

void test_copy_n_single_segment_seg2_both()
{
   test_detail::seg2_vector<int> sv2;
   test_detail::seg_vector<int> inner;
   int a[] = {1, 2, 3, 4, 5, 6};
   inner.add_segment_range(a, a + 6);
   sv2.add_segment(inner);

   boost::container::vector<int> out(6, 0);
   boost::container::vector<int>::iterator result =
      segmented_copy_n(test_detail::iter_at(sv2, 1), 4, out.begin());

   BOOST_TEST_EQ(static_cast<std::size_t>(result - out.begin()), 4u);
   BOOST_TEST_EQ(out[0], 2);
   BOOST_TEST_EQ(out[1], 3);
   BOOST_TEST_EQ(out[2], 4);
   BOOST_TEST_EQ(out[3], 5);
   BOOST_TEST_EQ(out[4], 0);
}

void test_copy_n_single_segment_src_multi_dst()
{
   test_detail::seg_vector<int> sv;
   int a[] = {1, 2, 3, 4, 5, 6, 7};
   sv.add_segment_range(a, a + 7);

   test_detail::seg_vector<int> out;
   out.add_segment(2, 0);
   out.add_segment(3, 0);
   out.add_segment(3, 0);

   typedef test_detail::seg_vector<int>::iterator iter_t;
   iter_t result = segmented_copy_n(test_detail::iter_at(sv, 1), 5, out.begin());

   BOOST_TEST(result == test_detail::iter_at(out, 5));
   iter_t it = out.begin();
   for(int i = 0; i < 5; ++i, ++it)
      BOOST_TEST_EQ(*it, i + 2);
   for(int i = 0; i < 3; ++i, ++it)
      BOOST_TEST_EQ(*it, 0);
}

void test_copy_n_single_segment_src_and_dst()
{
   test_detail::seg_vector<int> sv;
   int a[] = {1, 2, 3, 4, 5, 6};
   sv.add_segment_range(a, a + 6);

   test_detail::seg_vector<int> out;
   out.add_segment(6, 0);

   typedef test_detail::seg_vector<int>::iterator iter_t;
   iter_t result = segmented_copy_n(test_detail::iter_at(sv, 1), 4, out.begin());

   BOOST_TEST(result == test_detail::iter_at(out, 4));
   iter_t it = out.begin();
   for(int i = 0; i < 4; ++i, ++it)
      BOOST_TEST_EQ(*it, i + 2);
   BOOST_TEST_EQ(*it, 0); ++it;
   BOOST_TEST_EQ(*it, 0);
}

void test_copy_n_single_segment_dst_from_flat()
{
   boost::container::vector<int> in;
   in.push_back(1); in.push_back(2); in.push_back(3); in.push_back(4);

   test_detail::seg_vector<int> out;
   out.add_segment(6, 0);

   typedef test_detail::seg_vector<int>::iterator iter_t;
   iter_t result = segmented_copy_n(in.begin(), 4, out.begin());

   BOOST_TEST(result == test_detail::iter_at(out, 4));
   iter_t it = out.begin();
   for(int i = 0; i < 4; ++i, ++it)
      BOOST_TEST_EQ(*it, i + 1);
   BOOST_TEST_EQ(*it, 0); ++it;
   BOOST_TEST_EQ(*it, 0);
}

//////////////////////////////////////////////////////////////////////////////
// Shape matrix.
//
// for_each_shape2_all walks the twelve branch specs of the source range
// against the twelve of the destination range, so the two segmentations vary
// independently: 144 pairs per size pair, over both segmentation depths.  The
// 'e' specs carry empty segments, which is the only way to reach the
// sfirst == slast branch of the destination bounded helpers.
//
// segmented_copy_n takes no end bound, so the count is a third axis: the
// matrix is run for a count equal to the source length, a count that stops
// short of it and a zero count.  A count larger than the source range is
// undefined and is therefore never tested.  The reference answer is
// flatten_n_ints over the logical source range; flatten_all_ints is not used,
// as it deliberately includes the guard.
//////////////////////////////////////////////////////////////////////////////

const int shape_filler = -999;   // guard just past the end of every range
const int shape_fill   = -1;     // every destination slot before the call

const int shape_src_vals[] = {5, 3, 9, 1, 7, 2, 8, 4, 6, 11};
const int shape_dst_vals[] = {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1};

struct copy_n_shape_check
{
   std::size_t cnt;

   explicit copy_n_shape_check(std::size_t c) : cnt(c) {}

   template<class CSrc, class CDst>
   void operator()(CSrc& src, std::size_t n_src, const char* src_spec,
                   CDst& dst, std::size_t n_dst, const char* dst_spec) const
   {
      typedef typename CDst::iterator dst_iter_t;

      const boost::container::vector<int> ref = test_detail::flatten_n_ints(src, n_src);

      const dst_iter_t r = segmented_copy_n
         (src.begin(), static_cast<std::ptrdiff_t>(cnt), dst.begin());

      BOOST_TEST(r == test_detail::iter_at(dst, cnt));
      BOOST_TEST(test_detail::filler_intact(src, n_src, shape_filler));
      BOOST_TEST(test_detail::filler_intact(dst, n_dst, shape_filler));

      const boost::container::vector<int> got = test_detail::flatten_n_ints(dst, n_dst);
      BOOST_TEST_EQ(got.size(), n_dst);
      for(std::size_t i = 0; i != n_dst; ++i)
         BOOST_TEST_EQ(got[i], i < cnt ? ref[i] : shape_fill);

      // The source is read-only, so it has to come back unchanged.
      const boost::container::vector<int> src_after = test_detail::flatten_n_ints(src, n_src);
      for(std::size_t i = 0; i != n_src; ++i)
         BOOST_TEST_EQ(src_after[i], ref[i]);

      BOOST_TEST(src_spec != 0 && dst_spec != 0);
   }
};

void test_copy_n_shape_matrix()
{
   static const std::size_t sizes[][2] =
      { {0, 0}, {1, 1}, {1, 3}, {2, 2}, {3, 3}, {3, 6}, {5, 5}, {6, 10} };

   for(std::size_t i = 0; i != sizeof(sizes)/sizeof(sizes[0]); ++i) {
      const std::size_t n_src = sizes[i][0];
      const std::size_t n_dst = sizes[i][1];
      // Whole range, a proper prefix of it and nothing at all.
      std::size_t counts[3];
      counts[0] = n_src;
      counts[1] = n_src/2u;
      counts[2] = 0u;
      for(std::size_t c = 0; c != 3u; ++c)
         test_detail::for_each_shape2_all<int, int>
            (shape_src_vals, n_src, shape_dst_vals, n_dst,
             shape_filler, copy_n_shape_check(counts[c]));
   }
}

int main()
{
   test_copy_n_full();
   test_copy_n_partial();
   test_copy_n_zero();
   test_copy_n_single_segment();
   test_copy_n_single_segment_interior();
   test_copy_n_single_segment_exact();
   test_copy_n_single_segment_zero_mid();
   test_copy_n_single_segment_count_beyond_segment();
   test_copy_n_single_segment_seg2_outer();
   test_copy_n_single_segment_seg2_both();
   test_copy_n_non_segmented();
   test_copy_n_seg2();
   test_copy_n_segmented_output();
   test_copy_n_seg2_to_seg2();
   test_copy_n_seg_to_seg_misaligned();
   test_copy_n_partial_segmented_output();
   test_copy_n_single_segment_src_multi_dst();
   test_copy_n_single_segment_src_and_dst();
   test_copy_n_single_segment_dst_from_flat();

   test_copy_n_shape_matrix();
   return boost::report_errors();
}