Regex: make RegexIterator iterable and able to iter backwards

1 files changed, 26 insertions, 10 deletions

diff --git a/src/regex.hh b/src/regex.hh
index 11926d64..7fda8f0b 100644
--- a/src/regex.hh
+++ b/src/regex.hh
@@ -139,7 +139,7 @@ bool regex_search(It begin, It end, MatchResults<It>& res, const Regex& re,
 String option_to_string(const Regex& re);
 void option_from_string(StringView str, Regex& re);
 
-template<typename Iterator>
+template<typename Iterator, MatchDirection direction = MatchDirection::Forward>
 struct RegexIterator
 {
     using ValueType = MatchResults<Iterator>;
@@ -147,7 +147,8 @@ struct RegexIterator
     RegexIterator() = default;
     RegexIterator(Iterator begin, Iterator end, const Regex& re,
                   RegexExecFlags flags = RegexExecFlags::None)
-        : m_regex{&re}, m_next_begin{begin}, m_begin{begin}, m_end{end}, m_flags{flags}
+        : m_regex{&re}, m_next_pos{direction == MatchDirection::Forward ? begin : end},
+          m_begin{begin}, m_end{end}, m_flags{flags}
     {
         next();
     }
@@ -167,7 +168,7 @@ struct RegexIterator
             return true;
 
         return lhs.m_regex == rhs.m_regex and
-               lhs.m_next_begin == rhs.m_next_begin and
+               lhs.m_next_pos == rhs.m_next_pos and
                lhs.m_end == rhs.m_end and
                lhs.m_flags == rhs.m_flags and
                lhs.m_results == rhs.m_results;
@@ -178,6 +179,9 @@ struct RegexIterator
         return not (lhs == rhs);
     }
 
+    RegexIterator begin() { return *this; }
+    RegexIterator end() { return {}; }
+
 private:
     void next()
     {
@@ -186,19 +190,31 @@ private:
         RegexExecFlags additional_flags{};
         if (m_results.size() and m_results[0].first == m_results[0].second)
             additional_flags |= RegexExecFlags::NotInitialNull;
-        if (m_begin != m_next_begin)
-            additional_flags |= RegexExecFlags::NotBeginOfSubject | RegexExecFlags::PrevAvailable;
 
-        if (not regex_search(m_next_begin, m_end, m_results, *m_regex,
-                             m_flags | additional_flags))
-            m_regex = nullptr;
+        if (direction == MatchDirection::Forward)
+        {
+            if (m_begin != m_next_pos)
+                additional_flags |= RegexExecFlags::NotBeginOfSubject | RegexExecFlags::PrevAvailable;
+
+            if (not regex_search(m_next_pos, m_end, m_results, *m_regex,
+                                 m_flags | additional_flags))
+                m_regex = nullptr;
+            else
+                m_next_pos = m_results[0].second;
+        }
         else
-            m_next_begin = m_results[0].second;
+        {
+            if (not regex_search<Iterator, MatchDirection::Backward>(m_begin, m_next_pos, m_results, *m_regex,
+                                                                     m_flags | additional_flags))
+                m_regex = nullptr;
+            else
+                m_next_pos = m_results[0].first;
+        }
     }
 
     const Regex* m_regex = nullptr;
     MatchResults<Iterator> m_results;
-    Iterator m_next_begin{};
+    Iterator m_next_pos{};
     const Iterator m_begin{};
     const Iterator m_end{};
     const RegexExecFlags m_flags = RegexExecFlags::None;