1//===-- lib/runtime/utf.cpp -------------------------------------*- C++ -*-===//
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 "flang-rt/runtime/utf.h"
10
11namespace Fortran::runtime {
12
13#ifndef FLANG_RUNTIME_NO_GLOBAL_VAR_DEFS
14// clang-format off
15RT_OFFLOAD_VAR_GROUP_BEGIN
16const 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};
42RT_OFFLOAD_VAR_GROUP_END
43// clang-format on
44#endif // FLANG_RUNTIME_NO_GLOBAL_VAR_DEFS
45
46RT_OFFLOAD_API_GROUP_BEGIN
47
48std::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.
59Fortran::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
80std::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}
126RT_OFFLOAD_API_GROUP_END
127
128} // namespace Fortran::runtime
129

source code of flang-rt/lib/runtime/utf.cpp