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 #ifndef FLANG_RUNTIME_NO_GLOBAL_VAR_DEFS
  14 // clang-format off
  15 RT_OFFLOAD_VAR_GROUP_BEGIN
  16 const RT_CONST_VAR_ATTRS std::uint8_t UTF8FirstByteTable[256]{
  17   /* 00 - 7F:  7 bit payload in single byte */
  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     1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  25     1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  26   /* 80 - BF: invalid first byte, valid later byte */
  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     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  30     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  31   /* C0 - DF: 11 bit payload */
  32     2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
  33     2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
  34   /* E0 - EF: 16 bit payload */
  35     3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
  36   /* F0 - F7: 21 bit payload */ 4, 4, 4, 4, 4, 4, 4, 4,
  37   /* F8 - FB: 26 bit payload */ 5, 5, 5, 5,
  38   /* FC - FD: 31 bit payload */ 6, 6,
  39   /* FE:      32 bit payload */ 7,
  40   /* FF:      invalid */ 0
  41 };
  42 RT_OFFLOAD_VAR_GROUP_END
  43 // clang-format on
  44 #endif // FLANG_RUNTIME_NO_GLOBAL_VAR_DEFS
  45
  46 RT_OFFLOAD_API_GROUP_BEGIN
  47
  48 std::size_t MeasurePreviousUTF8Bytes(const char *end, std::size_t limit) {
  49   // Scan back over UTF-8 continuation bytes, if any
  50   for (std::size_t n{1}; n <= limit; ++n) {
  51     if ((end[-n] & 0xc0) != 0x80) {
  52       return n;
  53     }
  54   }
  55   return limit;
  56 }
  57
  58 // Non-minimal encodings are accepted.
  59 Fortran::common::optional<char32_t> DecodeUTF8(const char *p0) {
  60   const std::uint8_t *p{reinterpret_cast<const std::uint8_t *>(p0)};
  61   std::size_t bytes{MeasureUTF8Bytes(*p0)};
  62   if (bytes == 1) {
  63     return char32_t{*p};
  64   } else if (bytes > 1) {
  65     std::uint64_t result{char32_t{*p} & (0x7f >> bytes)};
  66     for (std::size_t j{1}; j < bytes; ++j) {
  67       std::uint8_t next{p[j]};
  68       if (next < 0x80 || next > 0xbf) {
  69         return Fortran::common::nullopt;
  70       }
  71       result = (result << 6) | (next & 0x3f);
  72     }
  73     if (result <= 0xffffffff) {
  74       return static_cast<char32_t>(result);
  75     }
  76   }
  77   return Fortran::common::nullopt;
  78 }
  79
  80 std::size_t EncodeUTF8(char *p0, char32_t ucs) {
  81   std::uint8_t *p{reinterpret_cast<std::uint8_t *>(p0)};
  82   if (ucs <= 0x7f) {
  83     p[0] = ucs;
  84     return 1;
  85   } else if (ucs <= 0x7ff) {
  86     p[0] = 0xc0 | (ucs >> 6);
  87     p[1] = 0x80 | (ucs & 0x3f);
  88     return 2;
  89   } else if (ucs <= 0xffff) {
  90     p[0] = 0xe0 | (ucs >> 12);
  91     p[1] = 0x80 | ((ucs >> 6) & 0x3f);
  92     p[2] = 0x80 | (ucs & 0x3f);
  93     return 3;
  94   } else if (ucs <= 0x1fffff) {
  95     p[0] = 0xf0 | (ucs >> 18);
  96     p[1] = 0x80 | ((ucs >> 12) & 0x3f);
  97     p[2] = 0x80 | ((ucs >> 6) & 0x3f);
  98     p[3] = 0x80 | (ucs & 0x3f);
  99     return 4;
 100   } else if (ucs <= 0x3ffffff) {
 101     p[0] = 0xf8 | (ucs >> 24);
 102     p[1] = 0x80 | ((ucs >> 18) & 0x3f);
 103     p[2] = 0x80 | ((ucs >> 12) & 0x3f);
 104     p[3] = 0x80 | ((ucs >> 6) & 0x3f);
 105     p[4] = 0x80 | (ucs & 0x3f);
 106     return 5;
 107   } else if (ucs <= 0x7ffffff) {
 108     p[0] = 0xf8 | (ucs >> 30);
 109     p[1] = 0x80 | ((ucs >> 24) & 0x3f);
 110     p[2] = 0x80 | ((ucs >> 18) & 0x3f);
 111     p[3] = 0x80 | ((ucs >> 12) & 0x3f);
 112     p[4] = 0x80 | ((ucs >> 6) & 0x3f);
 113     p[5] = 0x80 | (ucs & 0x3f);
 114     return 6;
 115   } else {
 116     p[0] = 0xfe;
 117     p[1] = 0x80 | ((ucs >> 30) & 0x3f);
 118     p[2] = 0x80 | ((ucs >> 24) & 0x3f);
 119     p[3] = 0x80 | ((ucs >> 18) & 0x3f);
 120     p[4] = 0x80 | ((ucs >> 12) & 0x3f);
 121     p[5] = 0x80 | ((ucs >> 6) & 0x3f);
 122     p[6] = 0x80 | (ucs & 0x3f);
 123     return 7;
 124   }
 125 }
 126 RT_OFFLOAD_API_GROUP_END
 127
 128 } // namespace Fortran::runtime