text: //------------------------------------------------------------------------------
  /*
      This file is part of Beast: https://github.com/vinniefalco/Beast
      Copyright 2014, Vinnie Falco <vinnie.falco@gmail.com>
  
      Permission to use, copy, modify, and/or distribute this software for any
      purpose  with  or without fee is hereby granted, provided that the above
      copyright notice and this permission notice appear in all copies.
  
      THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
      WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
      MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
      ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
      WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
      ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
      OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
  //==============================================================================
  
  #ifndef BEAST_RFC2616_HPP
  #define BEAST_RFC2616_HPP
  
  #include <boost/beast/http/message.hpp>
  #include <boost/beast/http/rfc7230.hpp>
  #include <boost/range/algorithm/equal.hpp>
  #include <boost/range/iterator_range.hpp>
  #include <boost/utility/string_ref.hpp>
  #include <algorithm>
  #include <cctype>
  #include <string>
  #include <iterator>
  #include <tuple> // for std::tie, remove ASAP
  #include <utility>
  #include <vector>
  
  namespace beast {
  namespace rfc2616 {
  
  namespace detail {
  
  /*  Routines for performing RFC2616 compliance.
      RFC2616:
          Hypertext Transfer Protocol -- HTTP/1.1
          http://www.w3.org/Protocols/rfc2616/rfc2616
  */
  
  struct ci_equal_pred
  {
      explicit ci_equal_pred() = default;
  
      bool operator()(char c1, char c2)
      {
          // VFALCO TODO Use a table lookup here
          return std::tolower(static_cast<unsigned char>(c1)) ==
                 std::tolower(static_cast<unsigned char>(c2));
      }
  };
  
  } // detail
  
  /** Returns `true` if `c` is linear white space.
  
      This excludes the CRLF sequence allowed for line continuations.
  */
  inline
  bool
  is_lws(char c)
  {
      return c == ' ' || c == '\t';
  }
  
  /** Returns `true` if `c` is any whitespace character. */
  inline
  bool
  is_white(char c)
  {
      switch (c)
      {
      case ' ':  case '\f': case '\n':
      case '\r': case '\t': case '\v':
          return true;
      };
      return false;
  }
  
  /** Returns `true` if `c` is a control character. */
  inline
  bool
  is_control(char c)
  {
      return c <= 31 || c >= 127;
  }
  
  /** Returns `true` if `c` is a separator. */
  inline
  bool
  is_separator(char c)
  {
      // VFALCO Could use a static table
      switch (c)
      {
      case '(': case ')': case '<': case '>':  case '@':
      case ',': case ';': case ':': case '\\': case '"':
      case '{': case '}': case ' ': case '\t':
          return true;
      };
      return false;
  }
  
  /** Returns `true` if `c` is a character. */
  inline
  bool
  is_char(char c)
  {
      return c >= 0 && c <= 127;
  }
  
  template <class FwdIter>
  FwdIter
  trim_left (FwdIter first, FwdIter last)
  {
      return std::find_if_not (first, last,
          is_white);
  }
  
  template <class FwdIter>
  FwdIter
  trim_right (FwdIter first, FwdIter last)
  {
      if (first == last)
          return last;
      do
      {
          --last;
          if (! is_white (*last))
              return ++last;
      }
      while (last != first);
      return first;
  }
  
  template <class CharT, class Traits, class Allocator>
  void
  trim_right_in_place (std::basic_string <
      CharT, Traits, Allocator>& s)
  {
      s.resize (std::distance (s.begin(),
          trim_right (s.begin(), s.end())));
  }
  
  template <class FwdIter>
  std::pair <FwdIter, FwdIter>
  trim (FwdIter first, FwdIter last)
  {
      first = trim_left (first, last);
      last = trim_right (first, last);
      return std::make_pair (first, last);
  }
  
  template <class String>
  String
  trim (String const& s)
  {
      using std::begin;
      using std::end;
      auto first = begin(s);
      auto last = end(s);
      std::tie (first, last) = trim (first, last);
      return { first, last };
  }
  
  template <class String>
  String
  trim_right (String const& s)
  {
      using std::begin;
      using std::end;
      auto first (begin(s));
      auto last (end(s));
      last = trim_right (first, last);
      return { first, last };
  }
  
  inline
  std::string
  trim (std::string const& s)
  {
      return trim <std::string> (s);
  }
  
  /** Parse a character sequence of values separated by commas.
      Double quotes and escape sequences will be converted.  Excess white
      space, commas, double quotes, and empty elements are not copied.
      Format:
         #(token|quoted-string)
      Reference:
          http://www.w3.org/Protocols/rfc2616/rfc2616-sec2.html#sec2
  */
  template <class FwdIt,
      class Result = std::vector<
          std::basic_string<typename
              std::iterator_traits<FwdIt>::value_type>>,
                  class Char>
  Result
  split(FwdIt first, FwdIt last, Char delim)
  {
      Result result;
      using string = typename Result::value_type;
      FwdIt iter = first;
      string e;
      while (iter != last)
      {
          if (*iter == '"')
          {
              // quoted-string
              ++iter;
              while (iter != last)
              {
                  if (*iter == '"')
                  {
                      ++iter;
                      break;
                  }
  
                  if (*iter == '\\')
                  {
                      // quoted-pair
                      ++iter;
                      if (iter != last)
                          e.append (1, *iter++);
                  }
                  else
                  {
                      // qdtext
                      e.append (1, *iter++);
                  }
              }
              if (! e.empty())
              {
                  result.emplace_back(std::move(e));
                  e.clear();
              }
          }
          else if (*iter == delim)
          {
              e = trim_right (e);
              if (! e.empty())
              {
                  result.emplace_back(std::move(e));
                  e.clear();
              }
              ++iter;
          }
          else if (is_lws (*iter))
          {
              ++iter;
          }
          else
          {
              e.append (1, *iter++);
          }
      }
  
      if (! e.empty())
      {
          e = trim_right (e);
          if (! e.empty())
              result.emplace_back(std::move(e));
      }
      return result;
  }
  
  template <class FwdIt,
      class Result = std::vector<
          std::basic_string<typename std::iterator_traits<
              FwdIt>::value_type>>>
  Result
  split_commas(FwdIt first, FwdIt last)
  {
      return split(first, last, ',');
  }
  
  template <class Result = std::vector<std::string>>
  Result
  split_commas(boost::beast::string_view const& s)
  {
      return split_commas(s.begin(), s.end());
  }
  
  //------------------------------------------------------------------------------
  
  /** Iterates through a comma separated list.
  
      Meets the requirements of ForwardIterator.
  
      List defined in rfc2616 2.1.
  
      @note Values returned may contain backslash escapes.
  */
  class list_iterator
  {
      using iter_type = boost::string_ref::const_iterator;
  
      iter_type it_;
      iter_type end_;
      boost::string_ref value_;
  
  public:
      using value_type = boost::string_ref;
      using pointer = value_type const*;
      using reference = value_type const&;
      using difference_type = std::ptrdiff_t;
      using iterator_category =
          std::forward_iterator_tag;
  
      list_iterator(iter_type begin, iter_type end)
          : it_(begin)
          , end_(end)
      {
          if(it_ != end_)
              increment();
      }
  
      bool
      operator==(list_iterator const& other) const
      {
          return other.it_ == it_ && other.end_ == end_
              && other.value_.size() == value_.size();
      }
  
      bool
      operator!=(list_iterator const& other) const
      {
          return !(*this == other);
      }
  
      reference
      operator*() const
      {
          return value_;
      }
  
      pointer
      operator->() const
      {
          return &*(*this);
      }
  
      list_iterator&
      operator++()
      {
          increment();
          return *this;
      }
  
      list_iterator
      operator++(int)
      {
          auto temp = *this;
          ++(*this);
          return temp;
      }
  
  private:
      template<class = void>
      void
      increment();
  };
  
  template<class>
  void
  list_iterator::increment()
  {
      value_.clear();
      while(it_ != end_)
      {
          if(*it_ == '"')
          {
              // quoted-string
              ++it_;
              if(it_ == end_)
                  return;
              if(*it_ != '"')
              {
                  auto start = it_;
                  for(;;)
                  {
                      ++it_;
                      if(it_ == end_)
                      {
                          value_ = boost::string_ref(
                              &*start, std::distance(start, it_));
                          return;
                      }
                      if(*it_ == '"')
                      {
                          value_ = boost::string_ref(
                              &*start, std::distance(start, it_));
                          ++it_;
                          return;
                      }
                  }
              }
              ++it_;
          }
          else if(*it_ == ',')
          {
              it_++;
              continue;
          }
          else if(is_lws(*it_))
          {
              ++it_;
              continue;
          }
          else
          {
              auto start = it_;
              for(;;)
              {
                  ++it_;
                  if(it_ == end_ ||
                      *it_ == ',' ||
                          is_lws(*it_))
                  {
                      value_ = boost::string_ref(
                          &*start, std::distance(start, it_));
                      return;
                  }
              }
          }
      }
  }
  
  /** Returns true if two strings are equal.
  
      A case-insensitive comparison is used.
  */
  inline
  bool
  ci_equal(boost::string_ref s1, boost::string_ref s2)
  {
      return boost::range::equal(s1, s2,
          detail::ci_equal_pred{});
  }
  
  /** Returns a range representing the list. */
  inline
  boost::iterator_range<list_iterator>
  make_list(boost::string_ref const& field)
  {
      return boost::iterator_range<list_iterator>{
          list_iterator{field.begin(), field.end()},
              list_iterator{field.end(), field.end()}};
  }
  
  /** Returns true if the specified token exists in the list.
  
      A case-insensitive comparison is used.
  */
  template<class = void>
  bool
  token_in_list(boost::string_ref const& value,
      boost::string_ref const& token)
  {
      for(auto const& item : make_list(value))
          if(ci_equal(item, token))
              return true;
      return false;
  }
  
  template<bool isRequest, class Body, class Fields>
  bool
  is_keep_alive(boost::beast::http::message<isRequest, Body, Fields> const& m)
  {
      if(m.version() <= 10)
          return boost::beast::http::token_list{
              m[boost::beast::http::field::connection]}.exists("keep-alive");
      return ! boost::beast::http::token_list{
          m[boost::beast::http::field::connection]}.exists("close");
  }
  
  } // rfc2616
  } // beast
  
  #endif
  