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# is_utf8
Most strings online are in unicode using the UTF-8 encoding. Validating strings
quickly before accepting them is important.
## How to use is_utf8
This is a simple one-source file library to validate UTF-8 strings at high
speeds using SIMD instructions. It works on all platforms (ARM, x64).
Build and link `is_utf8.cpp` with your project. Code usage:
```C++
#include "is_utf8.h"
char * mystring = ...
bool is_it_valid = is_utf8(mystring, thestringlength);
```
It should be able to validate strings using less than 1 cycle per input byte.
## Requirements
- C++11 compatible compiler. We support LLVM clang, GCC, Visual Studio. (Our
optional benchmark tool requires C++17.)
- For high speed, you should have a recent 64-bit system (e.g., ARM or x64).
- If you rely on CMake, you should use a recent CMake (at least 3.15).
- AVX-512 support require a processor with AVX512-VBMI2 (Ice Lake or better) and
a recent compiler (GCC 8 or better, Visual Studio 2019 or better, LLVM clang 6
or better). You need a correspondingly recent assembler such as gas (2.30+) or
nasm (2.14+): recent compilers usually come with recent assemblers. If you mix
a recent compiler with an incompatible/old assembler (e.g., when using a
recent compiler with an old Linux distribution), you may get errors at build
time because the compiler produces instructions that the assembler does not
recognize: you should update your assembler to match your compiler (e.g.,
upgrade binutils to version 2.30 or better under Linux) or use an older
compiler matching the capabilities of your assembler.
## Build with CMake
```
cmake -B build
cmake --build build
cd build
ctest .
```
Visual Studio users must specify whether they want to build the Release or Debug
version.
To run benchmarks, build and execute the `bench` command.
```
cmake -B build
cmake --build build
./build/benchmarks/bench
```
Instructions are similar for Visual Studio users.
## Real-word usage
This C++ library is part of the JavaScript package
[utf-8-validate](https://github.com/websockets/utf-8-validate). The
utf-8-validate package is routinely downloaded more than
[a million times per week](https://www.npmjs.com/package/utf-8-validate).
If you are using Node JS (19.4.0 or better), you already have access to this
function as
[`buffer.isUtf8(input)`](https://nodejs.org/api/buffer.html#bufferisutf8input).
## Reference
- John Keiser, Daniel Lemire,
[Validating UTF-8 In Less Than One Instruction Per Byte](https://arxiv.org/abs/2010.03090),
Software: Practice & Experience 51 (5), 2021
## Want more?
If you want a wide range of fast Unicode function for production use, you can
rely on the simdutf library. It is as simple as the following:
```C++
#include "simdutf.cpp"
#include "simdutf.h"
int main(int argc, char *argv[]) {
const char *source = "1234";
// 4 == strlen(source)
bool validutf8 = simdutf::validate_utf8(source, 4);
if (validutf8) {
std::cout << "valid UTF-8" << std::endl;
} else {
std::cerr << "invalid UTF-8" << std::endl;
return EXIT_FAILURE;
}
}
```
See https://github.com/simdutf/
## License
This library is distributed under the terms of any of the following licenses, at
your option:
- Apache License (Version 2.0) [LICENSE-APACHE](LICENSE-APACHE),
- Boost Software License [LICENSE-BOOST](LICENSE-BOOST), or
- MIT License [LICENSE-MIT](LICENSE-MIT).
|
