simple-utf8-cpp

Tiny simple library to convert between utf8 bytes and char32_t codepoints in C++.

Reference

The default decoder function Decode is based on statemachine approach: https://bjoern.hoehrmann.de/utf-8/decoder/dfa.
I also implemented a naive approach decoder function: DecodeNaive, which seems to be a little faster. benchmark.
rfc3629 - UTF-8

Requirements

No external dependencies except a compiler that supports at least C++17.

Example

#include <iostream>
#include <string>
#include "simple_utf8.h"

int main() {
  // Decoding via DFA
  std::string s("你好世界, hello world! 😊");
  std::u32string p(simple_utf8::CountCodes(s), 0);
  auto n = simple_utf8::Decode(s, p);  // returns number of codepoints.
  for (auto codepoint : p) std::cout << codepoint << std::endl;

  // Decoding via naive approach.
  std::u32string p1(simple_utf8::CountCodes(s), 0);
  auto n1 = simple_utf8::DecodeNaive(s, p1);
  for (auto codepoint : p1) std::cout << codepoint << std::endl;

  // Encoding
  std::string s2(simple_utf8::CountBytes(p), 0);
  auto k = simple_utf8::Encode(p, s2);
  std::cout << s2 << std::endl;
  return 0;
}

Run tests

Install Catch2 via conan (optional, or cmake will download it automatically if missing):

conan install . --output-folder=build --build=missing

Run tests:

cmake -B build -S . -DSIMPLE_UTF8_TEST=1
cmake --build build --target runtests

OR using ctest:

cmake -B build -S . -DSIMPLE_UTF8_TEST=1
cmake --build build --target tests
ctest --test-dir ./build/tests

Benchmark

How to run benchmark:

cmake -B build -S . -DSIMPLE_UTF8_TEST=1
cmake --build build --target runbenchmark

Benchmark results on my computer for a 24KB random utf8 string UTF-8-random-1.txt:

benchmark name                       samples       iterations    estimated
                                     mean          low mean      high mean
                                     std dev       low std dev   high std dev
-------------------------------------------------------------------------------
Decode benchmark (random)                      100             1    29.1183 ms
                                        290.334 us    288.784 us    293.289 us
                                        10.5697 us    6.32333 us    16.5749 us

DecodeNaive benchmark (random)                 100             1    29.1823 ms
                                        288.386 us    285.644 us    293.052 us
                                        17.8809 us    11.8848 us    25.5662 us

Links

中文博客: https://writings.sh/post/utf8

License

Copyright (c) 2023 Chao Wang <hit9@icloud.com> for this library.
Copyright (c) 2008-2009 Bjoern Hoehrmann <bjoern@hoehrmann.de> for the utf8 dfa decoder.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

hit9/simple-utf8-cpp