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Diffstat (limited to 'absl/strings/charset.h')
| -rw-r--r-- | absl/strings/charset.h | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/absl/strings/charset.h b/absl/strings/charset.h new file mode 100644 index 00000000..ff4e81a4 --- /dev/null +++ b/absl/strings/charset.h @@ -0,0 +1,164 @@ +// Copyright 2022 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +// ----------------------------------------------------------------------------- +// File: charset.h +// ----------------------------------------------------------------------------- +// +// This file contains absl::CharSet, a fast, bit-vector set of 8-bit unsigned +// characters. +// +// Instances can be initialized as constexpr constants. For example: +// +// constexpr absl::CharSet kJustX = absl::CharSet::Char('x'); +// constexpr absl::CharSet kMySymbols = absl::CharSet("$@!"); +// constexpr absl::CharSet kLetters = absl::CharSet::Range('a', 'z'); +// +// Multiple instances can be combined that still forms a constexpr expression. +// For example: +// +// constexpr absl::CharSet kLettersAndNumbers = +// absl::CharSet::Range('a', 'z') | absl::CharSet::Range('0', '9'); +// +// Several pre-defined character classes are available that mirror the methods +// from <cctype>. For example: +// +// constexpr absl::CharSet kLettersAndWhitespace = +// absl::CharSet::AsciiAlphabet() | absl::CharSet::AsciiWhitespace(); +// +// To check membership, use the .contains method, e.g. +// +// absl::CharSet hex_letters("abcdef"); +// hex_letters.contains('a'); // true +// hex_letters.contains('g'); // false + +#ifndef ABSL_STRINGS_CHARSET_H_ +#define ABSL_STRINGS_CHARSET_H_ + +#include <cstddef> +#include <cstdint> +#include <cstring> + +#include "absl/base/macros.h" +#include "absl/base/port.h" +#include "absl/strings/string_view.h" + +namespace absl { + +class CharSet { + public: + constexpr CharSet() : m_() {} + + // Initializes with a given string_view. + constexpr explicit CharSet(absl::string_view str) : m_() { + for (char c : str) { + SetChar(static_cast<unsigned char>(c)); + } + } + + constexpr bool contains(char c) const { + return ((m_[static_cast<unsigned char>(c) / 64] >> + (static_cast<unsigned char>(c) % 64)) & + 0x1) == 0x1; + } + + constexpr bool empty() const { + for (uint64_t c : m_) { + if (c != 0) return false; + } + return true; + } + + // Containing only a single specified char. + static constexpr CharSet Char(char x) { + return CharSet(CharMaskForWord(x, 0), CharMaskForWord(x, 1), + CharMaskForWord(x, 2), CharMaskForWord(x, 3)); + } + + // Containing all the chars in the closed interval [lo,hi]. + static constexpr CharSet Range(char lo, char hi) { + return CharSet(RangeForWord(lo, hi, 0), RangeForWord(lo, hi, 1), + RangeForWord(lo, hi, 2), RangeForWord(lo, hi, 3)); + } + + friend constexpr CharSet operator&(const CharSet& a, const CharSet& b) { + return CharSet(a.m_[0] & b.m_[0], a.m_[1] & b.m_[1], a.m_[2] & b.m_[2], + a.m_[3] & b.m_[3]); + } + + friend constexpr CharSet operator|(const CharSet& a, const CharSet& b) { + return CharSet(a.m_[0] | b.m_[0], a.m_[1] | b.m_[1], a.m_[2] | b.m_[2], + a.m_[3] | b.m_[3]); + } + + friend constexpr CharSet operator~(const CharSet& a) { + return CharSet(~a.m_[0], ~a.m_[1], ~a.m_[2], ~a.m_[3]); + } + + // Mirrors the char-classifying predicates in <cctype>. + static constexpr CharSet AsciiUppercase() { return CharSet::Range('A', 'Z'); } + static constexpr CharSet AsciiLowercase() { return CharSet::Range('a', 'z'); } + static constexpr CharSet AsciiDigits() { return CharSet::Range('0', '9'); } + static constexpr CharSet AsciiAlphabet() { + return AsciiLowercase() | AsciiUppercase(); + } + static constexpr CharSet AsciiAlphanumerics() { + return AsciiDigits() | AsciiAlphabet(); + } + static constexpr CharSet AsciiHexDigits() { + return AsciiDigits() | CharSet::Range('A', 'F') | CharSet::Range('a', 'f'); + } + static constexpr CharSet AsciiPrintable() { + return CharSet::Range(0x20, 0x7e); + } + static constexpr CharSet AsciiWhitespace() { return CharSet("\t\n\v\f\r "); } + static constexpr CharSet AsciiPunctuation() { + return AsciiPrintable() & ~AsciiWhitespace() & ~AsciiAlphanumerics(); + } + + private: + constexpr CharSet(uint64_t b0, uint64_t b1, uint64_t b2, uint64_t b3) + : m_{b0, b1, b2, b3} {} + + static constexpr uint64_t RangeForWord(char lo, char hi, uint64_t word) { + return OpenRangeFromZeroForWord(static_cast<unsigned char>(hi) + 1, word) & + ~OpenRangeFromZeroForWord(static_cast<unsigned char>(lo), word); + } + + // All the chars in the specified word of the range [0, upper). + static constexpr uint64_t OpenRangeFromZeroForWord(uint64_t upper, + uint64_t word) { + return (upper <= 64 * word) ? 0 + : (upper >= 64 * (word + 1)) + ? ~static_cast<uint64_t>(0) + : (~static_cast<uint64_t>(0) >> (64 - upper % 64)); + } + + static constexpr uint64_t CharMaskForWord(char x, uint64_t word) { + return (static_cast<unsigned char>(x) / 64 == word) + ? (static_cast<uint64_t>(1) + << (static_cast<unsigned char>(x) % 64)) + : 0; + } + + constexpr void SetChar(unsigned char c) { + m_[c / 64] |= static_cast<uint64_t>(1) << (c % 64); + } + + uint64_t m_[4]; +}; + +} // namespace absl + +#endif // ABSL_STRINGS_CHARSET_H_ |