1 /*
2    Copyright (c) Marshall Clow 2012-2015.
3    Copyright (c) Glen Joseph Fernandes 2019 ([email protected])
4 
5    Distributed under the Boost Software License, Version 1.0. (See accompanying
6    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7 
8     For more information, see http://www.boost.org
9 
10     Based on the StringRef implementation in LLVM (http://llvm.org) and
11     N3422 by Jeffrey Yasskin
12         http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3442.html
13 
14 */
15 
16 #ifndef BOOST_STRING_REF_HPP
17 #define BOOST_STRING_REF_HPP
18 
19 #include <boost/config.hpp>
20 #include <boost/detail/workaround.hpp>
21 #include <boost/io/ostream_put.hpp>
22 #include <boost/utility/string_ref_fwd.hpp>
23 #include <boost/throw_exception.hpp>
24 
25 #include <cstddef>
26 #include <stdexcept>
27 #include <algorithm>
28 #include <iterator>
29 #include <string>
30 #include <iosfwd>
31 
32 #if defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS) || (defined(BOOST_GCC) && ((BOOST_GCC+0) / 100) <= 406)
33 // GCC 4.6 cannot handle a defaulted function with noexcept specifier
34 #define BOOST_STRING_REF_NO_CXX11_DEFAULTED_NOEXCEPT_FUNCTIONS
35 #endif
36 
37 namespace boost {
38 
39     namespace detail {
40     //  A helper functor because sometimes we don't have lambdas
41         template <typename charT, typename traits>
42         class string_ref_traits_eq {
43         public:
string_ref_traits_eq(charT ch)44             string_ref_traits_eq ( charT ch ) : ch_(ch) {}
operator ()(charT val) const45             bool operator () ( charT val ) const { return traits::eq ( ch_, val ); }
46             charT ch_;
47             };
48         }
49 
50     template<typename charT, typename traits>
51     class basic_string_ref {
52     public:
53         // types
54         typedef charT value_type;
55         typedef const charT* pointer;
56         typedef const charT& reference;
57         typedef const charT& const_reference;
58         typedef pointer const_iterator; // impl-defined
59         typedef const_iterator iterator;
60         typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
61         typedef const_reverse_iterator reverse_iterator;
62         typedef std::size_t size_type;
63         typedef std::ptrdiff_t difference_type;
64         static BOOST_CONSTEXPR_OR_CONST size_type npos = size_type(-1);
65 
66         // construct/copy
basic_string_ref()67         BOOST_CONSTEXPR basic_string_ref () BOOST_NOEXCEPT
68             : ptr_(NULL), len_(0) {}
69 
70         // by defaulting these functions, basic_string_ref becomes
71         //  trivially copy/move constructible.
72         BOOST_CONSTEXPR basic_string_ref (const basic_string_ref &rhs) BOOST_NOEXCEPT
73 #ifndef BOOST_STRING_REF_NO_CXX11_DEFAULTED_NOEXCEPT_FUNCTIONS
74             = default;
75 #else
76             : ptr_(rhs.ptr_), len_(rhs.len_) {}
77 #endif
78 
79         basic_string_ref& operator=(const basic_string_ref &rhs) BOOST_NOEXCEPT
80 #ifndef BOOST_STRING_REF_NO_CXX11_DEFAULTED_NOEXCEPT_FUNCTIONS
81             = default;
82 #else
83             {
84             ptr_ = rhs.ptr_;
85             len_ = rhs.len_;
86             return *this;
87             }
88 #endif
89 
basic_string_ref(const charT * str)90         basic_string_ref(const charT* str) BOOST_NOEXCEPT
91             : ptr_(str), len_(traits::length(str)) {}
92 
93         template<typename Allocator>
basic_string_ref(const std::basic_string<charT,traits,Allocator> & str)94         basic_string_ref(const std::basic_string<charT, traits, Allocator>& str)
95             : ptr_(str.data()), len_(str.length()) {}
96 
97 // #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES) && !defined(BOOST_NO_CXX11_DELETED_FUNCTIONS)
98 //         // Constructing a string_ref from a temporary string is a bad idea
99 //         template<typename Allocator>
100 //         basic_string_ref(      std::basic_string<charT, traits, Allocator>&&)
101 //             = delete;
102 // #endif
103 
basic_string_ref(const charT * str,size_type len)104         BOOST_CONSTEXPR basic_string_ref(const charT* str, size_type len) BOOST_NOEXCEPT
105             : ptr_(str), len_(len) {}
106 
107 #ifndef BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS
108         template<typename Allocator>
operator std::basic_string<charT,traits,Allocator>() const109         explicit operator std::basic_string<charT, traits, Allocator>() const {
110             return std::basic_string<charT, traits, Allocator> ( begin(), end());
111             }
112 #endif
113 
to_string() const114         std::basic_string<charT, traits> to_string () const {
115             return std::basic_string<charT, traits> ( begin(), end());
116             }
117 
118         // iterators
begin() const119         BOOST_CONSTEXPR const_iterator   begin() const { return ptr_; }
cbegin() const120         BOOST_CONSTEXPR const_iterator  cbegin() const { return ptr_; }
end() const121         BOOST_CONSTEXPR const_iterator     end() const { return ptr_ + len_; }
cend() const122         BOOST_CONSTEXPR const_iterator    cend() const { return ptr_ + len_; }
rbegin() const123                 const_reverse_iterator  rbegin() const { return const_reverse_iterator (end()); }
crbegin() const124                 const_reverse_iterator crbegin() const { return const_reverse_iterator (end()); }
rend() const125                 const_reverse_iterator    rend() const { return const_reverse_iterator (begin()); }
crend() const126                 const_reverse_iterator   crend() const { return const_reverse_iterator (begin()); }
127 
128         // capacity
size() const129         BOOST_CONSTEXPR size_type size()     const { return len_; }
length() const130         BOOST_CONSTEXPR size_type length()   const { return len_; }
max_size() const131         BOOST_CONSTEXPR size_type max_size() const { return len_; }
empty() const132         BOOST_CONSTEXPR bool empty()         const { return len_ == 0; }
133 
134         // element access
operator [](size_type pos) const135         BOOST_CONSTEXPR const charT& operator[](size_type pos) const { return ptr_[pos]; }
136 
at(size_t pos) const137         const charT& at(size_t pos) const {
138             if ( pos >= len_ )
139                 BOOST_THROW_EXCEPTION( std::out_of_range ( "boost::string_ref::at" ) );
140             return ptr_[pos];
141             }
142 
front() const143         BOOST_CONSTEXPR const charT& front() const { return ptr_[0]; }
back() const144         BOOST_CONSTEXPR const charT& back()  const { return ptr_[len_-1]; }
data() const145         BOOST_CONSTEXPR const charT* data()  const { return ptr_; }
146 
147         // modifiers
clear()148         void clear() { len_ = 0; }
remove_prefix(size_type n)149         void remove_prefix(size_type n) {
150             if ( n > len_ )
151                 n = len_;
152             ptr_ += n;
153             len_ -= n;
154             }
155 
remove_suffix(size_type n)156         void remove_suffix(size_type n) {
157             if ( n > len_ )
158                 n = len_;
159             len_ -= n;
160             }
161 
162 
163         // basic_string_ref string operations
substr(size_type pos,size_type n=npos) const164         basic_string_ref substr(size_type pos, size_type n=npos) const {
165             if ( pos > size())
166                 BOOST_THROW_EXCEPTION( std::out_of_range ( "string_ref::substr" ) );
167             return basic_string_ref(data() + pos, (std::min)(size() - pos, n));
168             }
169 
compare(basic_string_ref x) const170         int compare(basic_string_ref x) const {
171             const int cmp = traits::compare ( ptr_, x.ptr_, (std::min)(len_, x.len_));
172             return cmp != 0 ? cmp : ( len_ == x.len_ ? 0 : len_ < x.len_ ? -1 : 1 );
173             }
174 
starts_with(charT c) const175         bool starts_with(charT c) const { return !empty() && traits::eq ( c, front()); }
starts_with(basic_string_ref x) const176         bool starts_with(basic_string_ref x) const {
177             return len_ >= x.len_ && traits::compare ( ptr_, x.ptr_, x.len_ ) == 0;
178             }
179 
ends_with(charT c) const180         bool ends_with(charT c) const { return !empty() && traits::eq ( c, back()); }
ends_with(basic_string_ref x) const181         bool ends_with(basic_string_ref x) const {
182             return len_ >= x.len_ && traits::compare ( ptr_ + len_ - x.len_, x.ptr_, x.len_ ) == 0;
183             }
184 
find(basic_string_ref s) const185         size_type find(basic_string_ref s) const {
186             if (s.empty()) return 0;
187             const_iterator iter = std::search ( this->cbegin (), this->cend (),
188                                                 s.cbegin (), s.cend (), traits::eq );
189             return iter == this->cend () ? npos : std::distance ( this->cbegin (), iter );
190             }
191 
find(charT c) const192         size_type find(charT c) const {
193             const_iterator iter = std::find_if ( this->cbegin (), this->cend (),
194                                     detail::string_ref_traits_eq<charT, traits> ( c ));
195             return iter == this->cend () ? npos : std::distance ( this->cbegin (), iter );
196             }
197 
rfind(basic_string_ref s) const198         size_type rfind(basic_string_ref s) const {
199             if (s.empty()) return 0;
200             const_reverse_iterator iter = std::search ( this->crbegin (), this->crend (),
201                                                 s.crbegin (), s.crend (), traits::eq );
202             return iter == this->crend () ? npos : (std::distance(iter, this->crend()) - s.size());
203             }
204 
rfind(charT c) const205         size_type rfind(charT c) const {
206             const_reverse_iterator iter = std::find_if ( this->crbegin (), this->crend (),
207                                     detail::string_ref_traits_eq<charT, traits> ( c ));
208             return iter == this->crend () ? npos : (this->size() - 1 - std::distance(this->crbegin(), iter));
209             }
210 
find_first_of(charT c) const211         size_type find_first_of(charT c) const { return  find (c); }
find_last_of(charT c) const212         size_type find_last_of (charT c) const { return rfind (c); }
213 
find_first_of(basic_string_ref s) const214         size_type find_first_of(basic_string_ref s) const {
215             const_iterator iter = std::find_first_of
216                 ( this->cbegin (), this->cend (), s.cbegin (), s.cend (), traits::eq );
217             return iter == this->cend () ? npos : std::distance ( this->cbegin (), iter );
218             }
219 
find_last_of(basic_string_ref s) const220         size_type find_last_of(basic_string_ref s) const {
221             const_reverse_iterator iter = std::find_first_of
222                 ( this->crbegin (), this->crend (), s.cbegin (), s.cend (), traits::eq );
223             return iter == this->crend () ? npos : (this->size() - 1 - std::distance(this->crbegin(), iter));
224             }
225 
find_first_not_of(basic_string_ref s) const226         size_type find_first_not_of(basic_string_ref s) const {
227             const_iterator iter = find_not_of ( this->cbegin (), this->cend (), s );
228             return iter == this->cend () ? npos : std::distance ( this->cbegin (), iter );
229             }
230 
find_first_not_of(charT c) const231         size_type find_first_not_of(charT c) const {
232             for ( const_iterator iter = this->cbegin (); iter != this->cend (); ++iter )
233                 if ( !traits::eq ( c, *iter ))
234                     return std::distance ( this->cbegin (), iter );
235             return npos;
236             }
237 
find_last_not_of(basic_string_ref s) const238         size_type find_last_not_of(basic_string_ref s) const {
239             const_reverse_iterator iter = find_not_of ( this->crbegin (), this->crend (), s );
240             return iter == this->crend () ? npos : (this->size() - 1 - std::distance(this->crbegin(), iter));
241             }
242 
find_last_not_of(charT c) const243         size_type find_last_not_of(charT c) const {
244             for ( const_reverse_iterator iter = this->crbegin (); iter != this->crend (); ++iter )
245                 if ( !traits::eq ( c, *iter ))
246                     return this->size() - 1 - std::distance(this->crbegin(), iter);
247             return npos;
248             }
249 
250     private:
251 
252         template <typename Iterator>
find_not_of(Iterator first,Iterator last,basic_string_ref s) const253         Iterator find_not_of ( Iterator first, Iterator last, basic_string_ref s ) const {
254             for ( ; first != last ; ++first )
255                 if ( 0 == traits::find ( s.ptr_, s.len_, *first ))
256                     return first;
257             return last;
258             }
259 
260 
261 
262         const charT *ptr_;
263         std::size_t len_;
264         };
265 
266 
267 //  Comparison operators
268 //  Equality
269     template<typename charT, typename traits>
operator ==(basic_string_ref<charT,traits> x,basic_string_ref<charT,traits> y)270     inline bool operator==(basic_string_ref<charT, traits> x, basic_string_ref<charT, traits> y) {
271         if ( x.size () != y.size ()) return false;
272         return x.compare(y) == 0;
273         }
274 
275     template<typename charT, typename traits, typename Allocator>
operator ==(basic_string_ref<charT,traits> x,const std::basic_string<charT,traits,Allocator> & y)276     inline bool operator==(basic_string_ref<charT, traits> x, const std::basic_string<charT, traits, Allocator> & y) {
277         return x == basic_string_ref<charT, traits>(y);
278         }
279 
280     template<typename charT, typename traits, typename Allocator>
operator ==(const std::basic_string<charT,traits,Allocator> & x,basic_string_ref<charT,traits> y)281     inline bool operator==(const std::basic_string<charT, traits, Allocator> & x, basic_string_ref<charT, traits> y) {
282         return basic_string_ref<charT, traits>(x) == y;
283         }
284 
285     template<typename charT, typename traits>
operator ==(basic_string_ref<charT,traits> x,const charT * y)286     inline bool operator==(basic_string_ref<charT, traits> x, const charT * y) {
287         return x == basic_string_ref<charT, traits>(y);
288         }
289 
290     template<typename charT, typename traits>
operator ==(const charT * x,basic_string_ref<charT,traits> y)291     inline bool operator==(const charT * x, basic_string_ref<charT, traits> y) {
292         return basic_string_ref<charT, traits>(x) == y;
293         }
294 
295 //  Inequality
296     template<typename charT, typename traits>
operator !=(basic_string_ref<charT,traits> x,basic_string_ref<charT,traits> y)297     inline bool operator!=(basic_string_ref<charT, traits> x, basic_string_ref<charT, traits> y) {
298         if ( x.size () != y.size ()) return true;
299         return x.compare(y) != 0;
300         }
301 
302     template<typename charT, typename traits, typename Allocator>
operator !=(basic_string_ref<charT,traits> x,const std::basic_string<charT,traits,Allocator> & y)303     inline bool operator!=(basic_string_ref<charT, traits> x, const std::basic_string<charT, traits, Allocator> & y) {
304         return x != basic_string_ref<charT, traits>(y);
305         }
306 
307     template<typename charT, typename traits, typename Allocator>
operator !=(const std::basic_string<charT,traits,Allocator> & x,basic_string_ref<charT,traits> y)308     inline bool operator!=(const std::basic_string<charT, traits, Allocator> & x, basic_string_ref<charT, traits> y) {
309         return basic_string_ref<charT, traits>(x) != y;
310         }
311 
312     template<typename charT, typename traits>
operator !=(basic_string_ref<charT,traits> x,const charT * y)313     inline bool operator!=(basic_string_ref<charT, traits> x, const charT * y) {
314         return x != basic_string_ref<charT, traits>(y);
315         }
316 
317     template<typename charT, typename traits>
operator !=(const charT * x,basic_string_ref<charT,traits> y)318     inline bool operator!=(const charT * x, basic_string_ref<charT, traits> y) {
319         return basic_string_ref<charT, traits>(x) != y;
320         }
321 
322 //  Less than
323     template<typename charT, typename traits>
operator <(basic_string_ref<charT,traits> x,basic_string_ref<charT,traits> y)324     inline bool operator<(basic_string_ref<charT, traits> x, basic_string_ref<charT, traits> y) {
325         return x.compare(y) < 0;
326         }
327 
328     template<typename charT, typename traits, typename Allocator>
operator <(basic_string_ref<charT,traits> x,const std::basic_string<charT,traits,Allocator> & y)329     inline bool operator<(basic_string_ref<charT, traits> x, const std::basic_string<charT, traits, Allocator> & y) {
330         return x < basic_string_ref<charT, traits>(y);
331         }
332 
333     template<typename charT, typename traits, typename Allocator>
operator <(const std::basic_string<charT,traits,Allocator> & x,basic_string_ref<charT,traits> y)334     inline bool operator<(const std::basic_string<charT, traits, Allocator> & x, basic_string_ref<charT, traits> y) {
335         return basic_string_ref<charT, traits>(x) < y;
336         }
337 
338     template<typename charT, typename traits>
operator <(basic_string_ref<charT,traits> x,const charT * y)339     inline bool operator<(basic_string_ref<charT, traits> x, const charT * y) {
340         return x < basic_string_ref<charT, traits>(y);
341         }
342 
343     template<typename charT, typename traits>
operator <(const charT * x,basic_string_ref<charT,traits> y)344     inline bool operator<(const charT * x, basic_string_ref<charT, traits> y) {
345         return basic_string_ref<charT, traits>(x) < y;
346         }
347 
348 //  Greater than
349     template<typename charT, typename traits>
operator >(basic_string_ref<charT,traits> x,basic_string_ref<charT,traits> y)350     inline bool operator>(basic_string_ref<charT, traits> x, basic_string_ref<charT, traits> y) {
351         return x.compare(y) > 0;
352         }
353 
354     template<typename charT, typename traits, typename Allocator>
operator >(basic_string_ref<charT,traits> x,const std::basic_string<charT,traits,Allocator> & y)355     inline bool operator>(basic_string_ref<charT, traits> x, const std::basic_string<charT, traits, Allocator> & y) {
356         return x > basic_string_ref<charT, traits>(y);
357         }
358 
359     template<typename charT, typename traits, typename Allocator>
operator >(const std::basic_string<charT,traits,Allocator> & x,basic_string_ref<charT,traits> y)360     inline bool operator>(const std::basic_string<charT, traits, Allocator> & x, basic_string_ref<charT, traits> y) {
361         return basic_string_ref<charT, traits>(x) > y;
362         }
363 
364     template<typename charT, typename traits>
operator >(basic_string_ref<charT,traits> x,const charT * y)365     inline bool operator>(basic_string_ref<charT, traits> x, const charT * y) {
366         return x > basic_string_ref<charT, traits>(y);
367         }
368 
369     template<typename charT, typename traits>
operator >(const charT * x,basic_string_ref<charT,traits> y)370     inline bool operator>(const charT * x, basic_string_ref<charT, traits> y) {
371         return basic_string_ref<charT, traits>(x) > y;
372         }
373 
374 //  Less than or equal to
375     template<typename charT, typename traits>
operator <=(basic_string_ref<charT,traits> x,basic_string_ref<charT,traits> y)376     inline bool operator<=(basic_string_ref<charT, traits> x, basic_string_ref<charT, traits> y) {
377         return x.compare(y) <= 0;
378         }
379 
380     template<typename charT, typename traits, typename Allocator>
operator <=(basic_string_ref<charT,traits> x,const std::basic_string<charT,traits,Allocator> & y)381     inline bool operator<=(basic_string_ref<charT, traits> x, const std::basic_string<charT, traits, Allocator> & y) {
382         return x <= basic_string_ref<charT, traits>(y);
383         }
384 
385     template<typename charT, typename traits, typename Allocator>
operator <=(const std::basic_string<charT,traits,Allocator> & x,basic_string_ref<charT,traits> y)386     inline bool operator<=(const std::basic_string<charT, traits, Allocator> & x, basic_string_ref<charT, traits> y) {
387         return basic_string_ref<charT, traits>(x) <= y;
388         }
389 
390     template<typename charT, typename traits>
operator <=(basic_string_ref<charT,traits> x,const charT * y)391     inline bool operator<=(basic_string_ref<charT, traits> x, const charT * y) {
392         return x <= basic_string_ref<charT, traits>(y);
393         }
394 
395     template<typename charT, typename traits>
operator <=(const charT * x,basic_string_ref<charT,traits> y)396     inline bool operator<=(const charT * x, basic_string_ref<charT, traits> y) {
397         return basic_string_ref<charT, traits>(x) <= y;
398         }
399 
400 //  Greater than or equal to
401     template<typename charT, typename traits>
operator >=(basic_string_ref<charT,traits> x,basic_string_ref<charT,traits> y)402     inline bool operator>=(basic_string_ref<charT, traits> x, basic_string_ref<charT, traits> y) {
403         return x.compare(y) >= 0;
404         }
405 
406     template<typename charT, typename traits, typename Allocator>
operator >=(basic_string_ref<charT,traits> x,const std::basic_string<charT,traits,Allocator> & y)407     inline bool operator>=(basic_string_ref<charT, traits> x, const std::basic_string<charT, traits, Allocator> & y) {
408         return x >= basic_string_ref<charT, traits>(y);
409         }
410 
411     template<typename charT, typename traits, typename Allocator>
operator >=(const std::basic_string<charT,traits,Allocator> & x,basic_string_ref<charT,traits> y)412     inline bool operator>=(const std::basic_string<charT, traits, Allocator> & x, basic_string_ref<charT, traits> y) {
413         return basic_string_ref<charT, traits>(x) >= y;
414         }
415 
416     template<typename charT, typename traits>
operator >=(basic_string_ref<charT,traits> x,const charT * y)417     inline bool operator>=(basic_string_ref<charT, traits> x, const charT * y) {
418         return x >= basic_string_ref<charT, traits>(y);
419         }
420 
421     template<typename charT, typename traits>
operator >=(const charT * x,basic_string_ref<charT,traits> y)422     inline bool operator>=(const charT * x, basic_string_ref<charT, traits> y) {
423         return basic_string_ref<charT, traits>(x) >= y;
424         }
425 
426     // Inserter
427     template<class charT, class traits>
428     inline std::basic_ostream<charT, traits>&
operator <<(std::basic_ostream<charT,traits> & os,const basic_string_ref<charT,traits> & str)429     operator<<(std::basic_ostream<charT, traits>& os, const basic_string_ref<charT,traits>& str) {
430         return boost::io::ostream_put(os, str.data(), str.size());
431         }
432 
433 #if 0
434     // numeric conversions
435     //
436     //  These are short-term implementations.
437     //  In a production environment, I would rather avoid the copying.
438     //
439     inline int stoi (string_ref str, size_t* idx=0, int base=10) {
440         return std::stoi ( std::string(str), idx, base );
441         }
442 
443     inline long stol (string_ref str, size_t* idx=0, int base=10) {
444         return std::stol ( std::string(str), idx, base );
445         }
446 
447     inline unsigned long stoul (string_ref str, size_t* idx=0, int base=10) {
448         return std::stoul ( std::string(str), idx, base );
449         }
450 
451     inline long long stoll (string_ref str, size_t* idx=0, int base=10) {
452         return std::stoll ( std::string(str), idx, base );
453         }
454 
455     inline unsigned long long stoull (string_ref str, size_t* idx=0, int base=10) {
456         return std::stoull ( std::string(str), idx, base );
457         }
458 
459     inline float stof (string_ref str, size_t* idx=0) {
460         return std::stof ( std::string(str), idx );
461         }
462 
463     inline double stod (string_ref str, size_t* idx=0) {
464         return std::stod ( std::string(str), idx );
465         }
466 
467     inline long double stold (string_ref str, size_t* idx=0)  {
468         return std::stold ( std::string(str), idx );
469         }
470 
471     inline int  stoi (wstring_ref str, size_t* idx=0, int base=10) {
472         return std::stoi ( std::wstring(str), idx, base );
473         }
474 
475     inline long stol (wstring_ref str, size_t* idx=0, int base=10) {
476         return std::stol ( std::wstring(str), idx, base );
477         }
478 
479     inline unsigned long stoul (wstring_ref str, size_t* idx=0, int base=10) {
480         return std::stoul ( std::wstring(str), idx, base );
481         }
482 
483     inline long long stoll (wstring_ref str, size_t* idx=0, int base=10) {
484         return std::stoll ( std::wstring(str), idx, base );
485         }
486 
487     inline unsigned long long stoull (wstring_ref str, size_t* idx=0, int base=10) {
488         return std::stoull ( std::wstring(str), idx, base );
489         }
490 
491     inline float  stof (wstring_ref str, size_t* idx=0) {
492         return std::stof ( std::wstring(str), idx );
493         }
494 
495     inline double stod (wstring_ref str, size_t* idx=0) {
496         return std::stod ( std::wstring(str), idx );
497         }
498 
499     inline long double stold (wstring_ref str, size_t* idx=0) {
500         return std::stold ( std::wstring(str), idx );
501         }
502 #endif
503 
504 }
505 
506 #if 0
507 namespace std {
508     // Hashing
509     template<> struct hash<boost::string_ref>;
510     template<> struct hash<boost::u16string_ref>;
511     template<> struct hash<boost::u32string_ref>;
512     template<> struct hash<boost::wstring_ref>;
513 }
514 #endif
515 
516 #endif
517