refs #16 Корректный алгоритм продвижения итератора склейки на несколь…

…ко элементов назад.
izvolov · Feb 6, 2015 · 9fd5fa4 · 9fd5fa4
1 parent 81c9e91
commit 9fd5fa4
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Showing 2 changed files with 27 additions and 6 deletions.
diff --git a/burst/iterator/detail/join_iterator.hpp b/burst/iterator/detail/join_iterator.hpp
@@ -294,15 +294,18 @@ namespace burst
             {
                 while (n > 0)
                 {
-                    auto items_remaining_in_current_range = m_inner_range_index;
-                    auto items_to_scroll_in_current_range = std::min(n, items_remaining_in_current_range);
-                    n -= items_to_scroll_in_current_range;
-
-                    m_inner_range_index -= items_to_scroll_in_current_range;
                     if (m_inner_range_index == 0)
                     {
                         --m_outer_range_index;
-                        m_inner_range_index = (*m_ranges)[m_outer_range_index].size();
+                        m_inner_range_index = (*m_ranges)[m_outer_range_index].size() - 1;
+                        --n;
+                    }
+                    else
+                    {
+                        auto items_remaining_in_current_range = m_inner_range_index;
+                        auto items_to_scroll_in_current_range = std::min(n, items_remaining_in_current_range);
+                        n -= items_to_scroll_in_current_range;
+                        m_inner_range_index -= items_to_scroll_in_current_range;
                     }
                 }
             }

diff --git a/test/iterator/join_iterator.cpp b/test/iterator/join_iterator.cpp
@@ -188,4 +188,22 @@ BOOST_AUTO_TEST_SUITE(join_iterator)
             expected.rbegin(), expected.rend()
         );
     }
+
+    BOOST_AUTO_TEST_CASE(random_accessing_near_range_bounds_is_correct)
+    {
+        auto  first = {3, 2};
+        auto second = {1, 0};
+        auto ranges = {boost::make_iterator_range(first), boost::make_iterator_range(second)};
+
+        auto joined_begin = burst::make_join_iterator(ranges);
+        auto joined_end   = burst::make_join_iterator(ranges, burst::iterator::end_tag);
+
+        joined_begin += 2;
+        BOOST_CHECK_EQUAL(*joined_begin, 1);
+        BOOST_CHECK_EQUAL(joined_end - joined_begin, 2);
+
+        joined_begin -= 2;
+        BOOST_CHECK_EQUAL(*joined_begin, 3);
+        BOOST_CHECK_EQUAL(joined_end - joined_begin, 4);
+    }
 BOOST_AUTO_TEST_SUITE_END()