[search] Switch to DFAs in search index retrieval.

1 files changed, 66 insertions, 0 deletions

diff --git a/base/dfa_helpers.hpp b/base/dfa_helpers.hpp
new file mode 100644
index 0000000000..5815f380f9
--- /dev/null
+++ b/base/dfa_helpers.hpp
@@ -0,0 +1,66 @@
+#pragma once
+
+#include "base/string_utils.hpp"
+
+#include "std/string.hpp"
+
+namespace strings
+{
+template <typename DFA>
+class PrefixDFAModifier
+{
+public:
+  class Iterator
+  {
+  public:
+    Iterator & Move(strings::UniChar c)
+    {
+      if (Accepts() || Rejects())
+        return *this;
+
+      m_it.Move(c);
+      if (m_it.Accepts())
+        m_accepts = true;
+
+      return *this;
+    }
+
+    bool Accepts() const { return m_accepts; }
+    bool Rejects() const { return !Accepts() && m_it.Rejects(); }
+
+  private:
+    friend class PrefixDFAModifier;
+
+    Iterator(typename DFA::Iterator it) : m_it(it), m_accepts(m_it.Accepts()) {}
+
+    typename DFA::Iterator m_it;
+    bool m_accepts;
+  };
+
+  explicit PrefixDFAModifier(DFA const & dfa) : m_dfa(dfa) {}
+
+  Iterator Begin() const { return Iterator(m_dfa.Begin()); }
+
+private:
+  DFA const m_dfa;
+};
+
+template <typename DFAIt, typename It>
+void DFAMove(DFAIt & it, It begin, It end)
+{
+  for (; begin != end; ++begin)
+    it.Move(*begin);
+}
+
+template <typename DFAIt>
+void DFAMove(DFAIt & it, UniString const & s)
+{
+  DFAMove(it, s.begin(), s.end());
+}
+
+template <typename DFAIt>
+void DFAMove(DFAIt & it, string const & s)
+{
+  DFAMove(it, MakeUniString(s));
+}
+}  // namespace strings