ceph/src/boost/boost/json/detail/buffer.hpp

   1 //
   2 // Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
   3 //
   4 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   5 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 //
   7 // Official repository: https://github.com/boostorg/json
   8 //
   9
  10 #ifndef BOOST_JSON_DETAIL_BUFFER_HPP
  11 #define BOOST_JSON_DETAIL_BUFFER_HPP
  12
  13 #include <boost/json/detail/config.hpp>
  14 #include <boost/json/string_view.hpp>
  15 #include <cstring>
  16
  17 BOOST_JSON_NS_BEGIN
  18 namespace detail {
  19
  20 // A simple string-like temporary static buffer
  21 template<std::size_t N>
  22 class buffer
  23 {
  24 public:
  25     using size_type = std::size_t;
  26
  27     buffer() = default;
  28
  29     bool
  30     empty() const noexcept
  31     {
  32         return size_ == 0;
  33     }
  34
  35     string_view
  36     get() const noexcept
  37     {
  38         return {buf_, size_};
  39     }
  40
  41     operator string_view() const noexcept
  42     {
  43         return get();
  44     }
  45
  46     char const*
  47     data() const noexcept
  48     {
  49         return buf_;
  50     }
  51
  52     size_type
  53     size() const noexcept
  54     {
  55         return size_;
  56     }
  57
  58     size_type
  59     capacity() const noexcept
  60     {
  61         return N - size_;
  62     }
  63
  64     size_type
  65     max_size() const noexcept
  66     {
  67         return N;
  68     }
  69
  70     void
  71     clear() noexcept
  72     {
  73         size_ = 0;
  74     }
  75
  76     void
  77     push_back(char ch) noexcept
  78     {
  79         BOOST_ASSERT(capacity() > 0);
  80         buf_[size_++] = ch;
  81     }
  82
  83     // append an unescaped string
  84     void
  85     append(
  86         char const* s,
  87         size_type n)
  88     {
  89         BOOST_ASSERT(n <= N - size_);
  90         std::memcpy(buf_ + size_, s, n);
  91         size_ += n;
  92     }
  93
  94     // append valid 32-bit code point as utf8
  95     void
  96     append_utf8(
  97         unsigned long cp) noexcept
  98     {
  99         auto dest = buf_ + size_;
 100         if(cp < 0x80)
 101         {
 102             BOOST_ASSERT(size_ <= N - 1);
 103             dest[0] = static_cast<char>(cp);
 104             size_ += 1;
 105             return;
 106         }
 107
 108         if(cp < 0x800)
 109         {
 110             BOOST_ASSERT(size_ <= N - 2);
 111             dest[0] = static_cast<char>( (cp >> 6)          | 0xc0);
 112             dest[1] = static_cast<char>( (cp & 0x3f)        | 0x80);
 113             size_ += 2;
 114             return;
 115         }
 116
 117         if(cp < 0x10000)
 118         {
 119             BOOST_ASSERT(size_ <= N - 3);
 120             dest[0] = static_cast<char>( (cp >> 12)         | 0xe0);
 121             dest[1] = static_cast<char>(((cp >> 6) & 0x3f)  | 0x80);
 122             dest[2] = static_cast<char>( (cp       & 0x3f)  | 0x80);
 123             size_ += 3;
 124             return;
 125         }
 126
 127         {
 128             BOOST_ASSERT(size_ <= N - 4);
 129             dest[0] = static_cast<char>( (cp >> 18)         | 0xf0);
 130             dest[1] = static_cast<char>(((cp >> 12) & 0x3f) | 0x80);
 131             dest[2] = static_cast<char>(((cp >> 6)  & 0x3f) | 0x80);
 132             dest[3] = static_cast<char>( (cp        & 0x3f) | 0x80);
 133             size_ += 4;
 134         }
 135     }
 136 private:
 137     char buf_[N];
 138     size_type size_ = 0;
 139 };
 140
 141 } // detail
 142 BOOST_JSON_NS_END
 143
 144 #endif