flang/runtime/utf.cpp

   1 //===-- runtime/utf.cpp ---------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "utf.h"
  10
  11 namespace Fortran::runtime {
  12
  13 // clang-format off
  14 const std::uint8_t UTF8FirstByteTable[256]{
  15   /* 00 - 7F:  7 bit payload in single byte */
  16     1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  17     1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  18     1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  19     1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  20     1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  21     1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  22     1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  23     1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  24   /* 80 - BF: invalid first byte, valid later byte */
  25     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  26     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  27     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  28     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  29   /* C0 - DF: 11 bit payload */
  30     2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
  31     2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
  32   /* E0 - EF: 16 bit payload */
  33     3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
  34   /* F0 - F7: 21 bit payload */ 4, 4, 4, 4, 4, 4, 4, 4,
  35   /* F8 - FB: 26 bit payload */ 5, 5, 5, 5,
  36   /* FC - FD: 31 bit payload */ 6, 6,
  37   /* FE:      32 bit payload */ 7,
  38   /* FF:      invalid */ 0
  39 };
  40 // clang-format on
  41
  42 // Non-minimal encodings are accepted.
  43 std::optional<char32_t> DecodeUTF8(const char *p0) {
  44   const std::uint8_t *p{reinterpret_cast<const std::uint8_t *>(p0)};
  45   std::size_t bytes{MeasureUTF8Bytes(*p0)};
  46   if (bytes == 1) {
  47     return char32_t{*p};
  48   } else if (bytes > 1) {
  49     std::uint64_t result{char32_t{*p} & (0x7f >> bytes)};
  50     for (std::size_t j{1}; j < bytes; ++j) {
  51       std::uint8_t next{p[j]};
  52       if (next < 0x80 || next > 0xbf) {
  53         return std::nullopt;
  54       }
  55       result = (result << 6) | (next & 0x3f);
  56     }
  57     if (result <= 0xffffffff) {
  58       return static_cast<char32_t>(result);
  59     }
  60   }
  61   return std::nullopt;
  62 }
  63
  64 std::size_t EncodeUTF8(char *p0, char32_t ucs) {
  65   std::uint8_t *p{reinterpret_cast<std::uint8_t *>(p0)};
  66   if (ucs <= 0x7f) {
  67     p[0] = ucs;
  68     return 1;
  69   } else if (ucs <= 0x7ff) {
  70     p[0] = 0xc0 | (ucs >> 6);
  71     p[1] = 0x80 | (ucs & 0x3f);
  72     return 2;
  73   } else if (ucs <= 0xffff) {
  74     p[0] = 0xe0 | (ucs >> 12);
  75     p[1] = 0x80 | ((ucs >> 6) & 0x3f);
  76     p[2] = 0x80 | (ucs & 0x3f);
  77     return 3;
  78   } else if (ucs <= 0x1fffff) {
  79     p[0] = 0xf0 | (ucs >> 18);
  80     p[1] = 0x80 | ((ucs >> 12) & 0x3f);
  81     p[2] = 0x80 | ((ucs >> 6) & 0x3f);
  82     p[3] = 0x80 | (ucs & 0x3f);
  83     return 4;
  84   } else if (ucs <= 0x3ffffff) {
  85     p[0] = 0xf8 | (ucs >> 24);
  86     p[1] = 0x80 | ((ucs >> 18) & 0x3f);
  87     p[2] = 0x80 | ((ucs >> 12) & 0x3f);
  88     p[3] = 0x80 | ((ucs >> 6) & 0x3f);
  89     p[4] = 0x80 | (ucs & 0x3f);
  90     return 5;
  91   } else if (ucs <= 0x7ffffff) {
  92     p[0] = 0xf8 | (ucs >> 30);
  93     p[1] = 0x80 | ((ucs >> 24) & 0x3f);
  94     p[2] = 0x80 | ((ucs >> 18) & 0x3f);
  95     p[3] = 0x80 | ((ucs >> 12) & 0x3f);
  96     p[4] = 0x80 | ((ucs >> 6) & 0x3f);
  97     p[5] = 0x80 | (ucs & 0x3f);
  98     return 6;
  99   } else {
 100     p[0] = 0xfe;
 101     p[1] = 0x80 | ((ucs >> 30) & 0x3f);
 102     p[2] = 0x80 | ((ucs >> 24) & 0x3f);
 103     p[3] = 0x80 | ((ucs >> 18) & 0x3f);
 104     p[4] = 0x80 | ((ucs >> 12) & 0x3f);
 105     p[5] = 0x80 | ((ucs >> 6) & 0x3f);
 106     p[6] = 0x80 | (ucs & 0x3f);
 107     return 7;
 108   }
 109 }
 110
 111 } // namespace Fortran::runtime