ceph/src/rgw/rgw_b64.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3
   4 #ifndef RGW_B64_H
   5 #define RGW_B64_H
   6
   7 #include <boost/utility/string_ref.hpp>
   8 #include <boost/utility/string_view.hpp>
   9 #include <boost/archive/iterators/base64_from_binary.hpp>
  10 #include <boost/archive/iterators/binary_from_base64.hpp>
  11 #include <boost/archive/iterators/insert_linebreaks.hpp>
  12 #include <boost/archive/iterators/transform_width.hpp>
  13 #include <boost/archive/iterators/remove_whitespace.hpp>
  14 #include <limits>
  15
  16 namespace rgw {
  17
  18   /*
  19    * A header-only Base64 encoder built on boost::archive.  The
  20    * formula is based on a class poposed for inclusion in boost in
  21    * 2011 by Denis Shevchenko (abandoned), updated slightly
  22    * (e.g., uses boost::string_view).
  23    *
  24    * Also, wrap_width added as template argument, based on
  25    * feedback from Marcus.
  26    */
  27
  28   template<int wrap_width = std::numeric_limits<int>::max()>
  29   inline std::string to_base64(boost::string_view sview)
  30   {
  31     using namespace boost::archive::iterators;
  32
  33     // output must be =padded modulo 3
  34     auto psize = sview.size();
  35     while ((psize % 3) != 0) {
  36       ++psize;
  37     }
  38
  39     /* RFC 2045 requires linebreaks to be present in the output
  40      * sequence every at-most 76 characters (MIME-compliance),
  41      * but we could likely omit it. */
  42     typedef
  43       insert_linebreaks<
  44         base64_from_binary<
  45           transform_width<
  46             boost::string_view::const_iterator
  47             ,6,8>
  48           >
  49           ,wrap_width
  50         > b64_iter;
  51
  52     std::string outstr(b64_iter(sview.data()),
  53                        b64_iter(sview.data() + sview.size()));
  54
  55     // pad outstr with '=' to a length that is a multiple of 3
  56     for (size_t ix = 0; ix < (psize-sview.size()); ++ix)
  57       outstr.push_back('=');
  58
  59     return outstr;
  60   }
  61
  62   inline std::string from_base64(boost::string_view sview)
  63   {
  64     using namespace boost::archive::iterators;
  65     if (sview.empty())
  66       return std::string();
  67     /* MIME-compliant input will have line-breaks, so we have to
  68      * filter WS */
  69     typedef
  70       transform_width<
  71       binary_from_base64<
  72         remove_whitespace<
  73           boost::string_view::const_iterator>>
  74       ,8,6
  75       > b64_iter;
  76
  77     while (sview.back() == '=')
  78       sview.remove_suffix(1);
  79
  80     std::string outstr(b64_iter(sview.data()),
  81                       b64_iter(sview.data() + sview.size()));
  82
  83     return outstr;
  84   }
  85 } /* namespace */
  86
  87 #endif /* RGW_B64_H */