[patch 4/4] std::regex refactoring

[Jonathan Wakely]

As I suggested yesterday on the libstdc++ list, this adds an overload
for string and vector iterators to extract a raw pointer and re-use
the _Compiler<const C*,...> specialization, so that std::regex(".")
and std::regex(std::string(".")) and std::regex(std::vector<char>(1,
'.')) only instantiate _Compiler<It,Tr> once.

2013-11-08  Jonathan Wakely  <jwakely....@gmail.com>

        * include/bits/regex_compiler.h (__detail::__compile_nfa): Overload
        so that std::basic_string<C> and std::vector<C> iterators dispatch to
        the const C* compiler.

Tested x86_64-linux, committed to trunk.

commit 76e9d5349657d9eed04d3429dbf7b6527bf03deb
Author: Jonathan Wakely <jwakely....@gmail.com>
Date:   Fri Nov 8 13:33:06 2013 +0000

        * include/bits/regex_compiler.h (__detail::__compile_nfa): Overload
        so that std::basic_string<C> and std::vector<C> iterators dispatch to
        the const C* compiler.

diff --git a/libstdc++-v3/include/bits/regex_compiler.h 
b/libstdc++-v3/include/bits/regex_compiler.h
index 406d9a9..741098f 100644
--- a/libstdc++-v3/include/bits/regex_compiler.h
+++ b/libstdc++-v3/include/bits/regex_compiler.h
@@ -129,8 +129,40 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       _StackT         _M_stack;
     };
 
+  template<typename _Tp>
+    struct __has_contiguous_iter : std::false_type { };
+
+  template<typename _Ch, typename _Tr, typename _Alloc>
+    struct __has_contiguous_iter<std::basic_string<_Ch, _Tr, _Alloc>>
+    : std::true_type
+    { };
+
+  template<typename _Tp, typename _Alloc>
+    struct __has_contiguous_iter<std::vector<_Tp, _Alloc>>
+    : std::true_type
+    { };
+
+  template<typename _Tp>
+    struct __is_contiguous_normal_iter : std::false_type { };
+
+  template<typename _Tp, typename _Cont>
+    struct
+    __is_contiguous_normal_iter<__gnu_cxx::__normal_iterator<_Tp, _Cont>>
+    : __has_contiguous_iter<_Cont>::type
+    { };
+
+  template<typename _Iter, typename _TraitsT>
+    using __enable_if_contiguous_normal_iter
+      = typename enable_if< __is_contiguous_normal_iter<_Iter>::value,
+                           std::shared_ptr<_NFA<_TraitsT>> >::type;
+
+  template<typename _Iter, typename _TraitsT>
+    using __disable_if_contiguous_normal_iter
+      = typename enable_if< !__is_contiguous_normal_iter<_Iter>::value,
+                           std::shared_ptr<_NFA<_TraitsT>> >::type;
+
   template<typename _FwdIter, typename _TraitsT>
-    inline std::shared_ptr<_NFA<_TraitsT>>
+    inline __disable_if_contiguous_normal_iter<_FwdIter, _TraitsT>
     __compile_nfa(_FwdIter __first, _FwdIter __last, const _TraitsT& __traits,
                  regex_constants::syntax_option_type __flags)
     {
@@ -138,6 +170,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       return _Cmplr(__first, __last, __traits, __flags)._M_get_nfa();
     }
 
+  template<typename _Iter, typename _TraitsT>
+    inline __enable_if_contiguous_normal_iter<_Iter, _TraitsT>
+    __compile_nfa(_Iter __first, _Iter __last, const _TraitsT& __traits,
+                 regex_constants::syntax_option_type __flags)
+    {
+      size_t __len = __last - __first;
+      const auto* __cfirst = __len ? std::__addressof(*__first) : nullptr;
+      return __compile_nfa(__cfirst, __cfirst + __len, __traits, __flags);
+    }
+
   template<typename _TraitsT>
     struct _AnyMatcher
     {