From a2b10e7042ec97a186a3cd76638ca43b2986440b Mon Sep 17 00:00:00 2001
From: Sergey Magidovich <mgsergio@mapswithme.com>
Date: Tue, 15 Dec 2015 21:04:34 +0300
Subject: [PATCH] Add range_iterator.

---
 base/base.pro                           |  1 +
 base/base_tests/base_tests.pro          |  1 +
 base/base_tests/range_iterator_test.cpp | 43 ++++++++++++
 base/range_iterator.hpp                 | 93 +++++++++++++++++++++++++
 4 files changed, 138 insertions(+)
 create mode 100644 base/base_tests/range_iterator_test.cpp
 create mode 100644 base/range_iterator.hpp

diff --git a/base/base.pro b/base/base.pro
index 3d85e27022..df72d751d2 100644
--- a/base/base.pro
+++ b/base/base.pro
@@ -51,6 +51,7 @@ HEADERS += \
     mutex.hpp \
     object_tracker.hpp \
     observer_list.hpp \
+    range_iterator.hpp \
     regexp.hpp \
     rolling_hash.hpp \
     scope_guard.hpp \
diff --git a/base/base_tests/base_tests.pro b/base/base_tests/base_tests.pro
index 6f4a12b939..07b397a618 100644
--- a/base/base_tests/base_tests.pro
+++ b/base/base_tests/base_tests.pro
@@ -24,6 +24,7 @@ SOURCES += \
   matrix_test.cpp \
   mem_trie_test.cpp \
   observer_list_test.cpp \
+  range_iterator_test.cpp \
   regexp_test.cpp \
   rolling_hash_test.cpp \
   scope_guard_test.cpp \
diff --git a/base/base_tests/range_iterator_test.cpp b/base/base_tests/range_iterator_test.cpp
new file mode 100644
index 0000000000..29b857283d
--- /dev/null
+++ b/base/base_tests/range_iterator_test.cpp
@@ -0,0 +1,43 @@
+#include "testing/testing.hpp"
+
+#include "base/range_iterator.hpp"
+
+#include "std/vector.hpp"
+
+UNIT_TEST(RangeIterator)
+{
+  using namespace base;
+
+  {
+    vector<int> result;
+    for (auto const i : range(5))
+      result.push_back(i);
+    TEST_EQUAL(result, (vector<int>{0, 1, 2, 3, 4}), ());
+  }
+
+  {
+    vector<int> result;
+    for (auto const i : range(2, 5))
+      result.push_back(i);
+    TEST_EQUAL(result, (vector<int>{2, 3, 4}), ());
+  }
+
+  {
+    vector<int> result;
+    for (auto const i : reverse_range(5))
+      result.push_back(i);
+    TEST_EQUAL(result, (vector<int>{4, 3, 2, 1, 0}), ());
+  }
+
+  {
+    vector<int> result;
+    for (auto const i : reverse_range(2, 5))
+      result.push_back(i);
+    TEST_EQUAL(result, (vector<int>{4, 3, 2}), ());
+  }
+
+  {
+    TEST_EQUAL(std::vector<int>(MakeRangeIterator(0), MakeRangeIterator(5)),
+               (std::vector<int>{0, 1, 2, 3, 4}), ());
+  }
+}
diff --git a/base/range_iterator.hpp b/base/range_iterator.hpp
new file mode 100644
index 0000000000..bb799aa76e
--- /dev/null
+++ b/base/range_iterator.hpp
@@ -0,0 +1,93 @@
+#include "std/iterator.hpp"
+#include "std/type_traits.hpp"
+
+namespace base
+{
+template <typename TCounter>
+struct RangeIterator
+{
+  explicit RangeIterator(TCounter const current):
+      m_current(current)
+  {
+  }
+
+  RangeIterator & operator++() { ++m_current; return *this; }
+  RangeIterator & operator--() { --m_current; return *this; }
+
+  bool operator==(RangeIterator const & it) const { return m_current == it.m_current; }
+  bool operator!=(RangeIterator const & it) const { return !(*this == it); }
+
+  TCounter operator*() const { return m_current; }
+
+  TCounter m_current;
+};
+} // namespace base
+
+namespace std
+{
+template <typename T>
+struct iterator_traits<base::RangeIterator<T>>
+{
+  using difference_type = T;
+  using value_type = T;
+  using pointer = void;
+  using reference = T;
+  using iterator_category = std::bidirectional_iterator_tag;
+};
+} // namespace std
+
+namespace base
+{
+template <typename TCounter, bool forward>
+struct RangeWrapper
+{
+
+  using value_type = typename std::remove_cv<TCounter>::type;
+  using iterator_base = RangeIterator<value_type>;
+  using iterator = typename std::conditional<forward,
+                                             iterator_base,
+                                             std::reverse_iterator<iterator_base>>::type;
+
+  RangeWrapper(TCounter const from, TCounter const to):
+      m_begin(from),
+      m_end(to)
+  {
+  }
+
+  iterator begin() const { return iterator(iterator_base(m_begin)); }
+  iterator end() const { return iterator(iterator_base(m_end)); }
+
+  value_type const m_begin;
+  value_type const m_end;
+};
+
+template <typename TCounter>
+RangeWrapper<TCounter, true> range(TCounter const to)
+{
+  return {{}, to};
+}
+
+template <typename TCounter>
+RangeWrapper<TCounter, true> range(TCounter const from, TCounter const to)
+{
+  return {from, to};
+}
+
+template <typename TCounter>
+RangeWrapper<TCounter, false> reverse_range(TCounter const to)
+{
+  return {to, {}};
+}
+
+template <typename TCounter>
+RangeWrapper<TCounter, false> reverse_range(TCounter const from, TCounter const to)
+{
+  return {to, from};
+}
+
+template <typename TCounter>
+RangeIterator<TCounter> MakeRangeIterator(TCounter const counter)
+{
+  return RangeIterator<TCounter>(counter);
+}
+} // namespace base