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| 1 | //===-- include/flang/Parser/char-set.h -------------------------*- 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 | #ifndef FORTRAN_PARSER_CHAR_SET_H_ |
| 10 | #define FORTRAN_PARSER_CHAR_SET_H_ |
| 11 | |
| 12 | // Sets of distinct characters that are valid in Fortran programs outside |
| 13 | // character literals are encoded as 64-bit integers by mapping them to a 6-bit |
| 14 | // character set encoding in which the case of letters is lost (even if |
| 15 | // mixed case input reached the parser, which it does not). These sets |
| 16 | // need to be suitable for constexprs, so std::bitset<> was not eligible. |
| 17 | |
| 18 | #include <cinttypes> |
| 19 | #include <string> |
| 20 | |
| 21 | namespace Fortran::parser { |
| 22 | |
| 23 | struct SetOfChars { |
| 24 | constexpr SetOfChars() {} |
| 25 | |
| 26 | constexpr SetOfChars(char c) { |
| 27 | // This is basically the old DECSIX encoding, which maps the |
| 28 | // 7-bit ASCII codes [32..95] to [0..63]. Only '#', '&', '?', '\', and '^' |
| 29 | // in that range are unused in Fortran after preprocessing outside |
| 30 | // character literals. We repurpose '^' and '?' for newline and unknown |
| 31 | // characters (resp.), leaving the others alone in case this code might |
| 32 | // be useful in preprocssing. |
| 33 | if (c == '\n') { |
| 34 | // map newline to '^' |
| 35 | c = '^'; |
| 36 | } else if (c < 32 || c >= 127) { |
| 37 | // map other control characters, DEL, and 8-bit characters to '?' |
| 38 | c = '?'; |
| 39 | } else if (c >= 96) { |
| 40 | // map lower-case letters to upper-case |
| 41 | c -= 32; |
| 42 | } |
| 43 | // range is now [32..95]; reduce to [0..63] and use as a shift count |
| 44 | bits_ = static_cast<std::uint64_t>(1) << (c - 32); |
| 45 | } |
| 46 | |
| 47 | constexpr SetOfChars(const char str[], std::size_t n) { |
| 48 | for (std::size_t j{0}; j < n; ++j) { |
| 49 | bits_ |= SetOfChars{str[j]}.bits_; |
| 50 | } |
| 51 | } |
| 52 | |
| 53 | constexpr SetOfChars(const SetOfChars &) = default; |
| 54 | constexpr SetOfChars(SetOfChars &&) = default; |
| 55 | constexpr SetOfChars &operator=(const SetOfChars &) = default; |
| 56 | constexpr SetOfChars &operator=(SetOfChars &&) = default; |
| 57 | constexpr bool empty() const { return bits_ == 0; } |
| 58 | |
| 59 | constexpr bool Has(SetOfChars that) const { |
| 60 | return (that.bits_ & ~bits_) == 0; |
| 61 | } |
| 62 | constexpr SetOfChars Union(SetOfChars that) const { |
| 63 | return SetOfChars{bits_ | that.bits_}; |
| 64 | } |
| 65 | constexpr SetOfChars Intersection(SetOfChars that) const { |
| 66 | return SetOfChars{bits_ & that.bits_}; |
| 67 | } |
| 68 | constexpr SetOfChars Difference(SetOfChars that) const { |
| 69 | return SetOfChars{bits_ & ~that.bits_}; |
| 70 | } |
| 71 | |
| 72 | std::string ToString() const; |
| 73 | |
| 74 | private: |
| 75 | constexpr SetOfChars(std::uint64_t b) : bits_{b} {} |
| 76 | std::uint64_t bits_{0}; |
| 77 | }; |
| 78 | } // namespace Fortran::parser |
| 79 | #endif // FORTRAN_PARSER_CHAR_SET_H_ |
| 80 |
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