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 ft=cpp
   3
   4 #pragma once
   5
   6 #include <boost/archive/iterators/base64_from_binary.hpp>
   7 #include <boost/archive/iterators/binary_from_base64.hpp>
   8 #include <boost/archive/iterators/insert_linebreaks.hpp>
   9 #include <boost/archive/iterators/transform_width.hpp>
  10 #include <boost/archive/iterators/remove_whitespace.hpp>
  11 #include <limits>
  12 #include <string>
  13 #include <string_view>
  14
  15 namespace rgw {
  16
  17   /*
  18    * A header-only Base64 encoder built on boost::archive.  The
  19    * formula is based on a class poposed for inclusion in boost in
  20    * 2011 by Denis Shevchenko (abandoned), updated slightly
  21    * (e.g., uses std::string_view).
  22    *
  23    * Also, wrap_width added as template argument, based on
  24    * feedback from Marcus.
  25    */
  26
  27   template<int wrap_width = std::numeric_limits<int>::max()>
  28   inline std::string to_base64(std::string_view sview)
  29   {
  30     using namespace boost::archive::iterators;
  31
  32     // output must be =padded modulo 3
  33     auto psize = sview.size();
  34     while ((psize % 3) != 0) {
  35       ++psize;
  36     }
  37
  38     /* RFC 2045 requires linebreaks to be present in the output
  39      * sequence every at-most 76 characters (MIME-compliance),
  40      * but we could likely omit it. */
  41     typedef
  42       insert_linebreaks<
  43         base64_from_binary<
  44           transform_width<
  45             std::string_view::const_iterator
  46             ,6,8>
  47           >
  48           ,wrap_width
  49         > b64_iter;
  50
  51     std::string outstr(b64_iter(sview.data()),
  52                        b64_iter(sview.data() + sview.size()));
  53
  54     // pad outstr with '=' to a length that is a multiple of 3
  55     for (size_t ix = 0; ix < (psize-sview.size()); ++ix)
  56       outstr.push_back('=');
  57
  58     return outstr;
  59   }
  60
  61   inline std::string from_base64(std::string_view sview)
  62   {
  63     using namespace boost::archive::iterators;
  64     if (sview.empty())
  65       return std::string();
  66     /* MIME-compliant input will have line-breaks, so we have to
  67      * filter WS */
  68     typedef
  69       transform_width<
  70       binary_from_base64<
  71         remove_whitespace<
  72           std::string_view::const_iterator>>
  73       ,8,6
  74       > b64_iter;
  75
  76     while (sview.back() == '=')
  77       sview.remove_suffix(1);
  78
  79     std::string outstr(b64_iter(sview.data()),
  80                       b64_iter(sview.data() + sview.size()));
  81
  82     return outstr;
  83   }
  84 } /* namespace */