bitflags

KO | EN

gitlite — search

#python #react #machine-learning #deep-learning #linux #macos #nodejs #java #windows #cli #security #pytorch #ios #open-source

(★ 97)

Single-header header-only C++11 / C++14 / C++17 library for easily managing set of auto-generated type-safe flags.

파일 탐색기

최종 버전 다운로드 (.zip)

- - bitflags_benchmark.cpp
  - bitset_benchmark.cpp
  - CMakeLists.txt
  - raw_bitflags_benchmark.cpp
- CMakeLists.txt
- benchmark.png
- logo.png
- - bitflags.hpp
- - bitflags_test.cpp
  - CMakeLists.txt
- CMakeLists.txt
.gitignore
.gitmodules
.travis.yml
CMakeLists.txt
googlebench
googletest
LICENSE
plot.py
README.md

// repository documentation

Was this content helpful?

★ 0 (0 ratings)

Single-header header-only C++11 / C++14 / C++17 library for easily managing set of auto-generated type-safe flags.

[![License](https://img.shields.io/badge/license-MIT-brightgreen.svg?style=flat)](https://github.com/m-peko/bitflags/blob/master/LICENSE)
[![Build Status](https://travis-ci.org/m-peko/bitflags.svg?branch=master)](https://travis-ci.org/m-peko/bitflags)
[![Codecov](https://codecov.io/gh/m-peko/bitflags/branch/master/graph/badge.svg)](https://codecov.io/gh/m-peko/bitflags)
[![Standard](https://img.shields.io/badge/C%2B%2B-11-blue.svg)](https://en.wikipedia.org/wiki/C%2B%2B11)
[![Standard](https://img.shields.io/badge/C%2B%2B-14-blue.svg)](https://en.wikipedia.org/wiki/C%2B%2B14)
[![Standard](https://img.shields.io/badge/C%2B%2B-17-blue.svg)](https://en.wikipedia.org/wiki/C%2B%2B17)
[![Compiler explorer](https://img.shields.io/badge/compiler_explorer-online-blue.svg)](https://godbolt.org/z/cdG8dYjEj)

</div>

## Quick start

```cpp
#include <bitflags/bitflags.hpp>

BEGIN_BITFLAGS(Flags)
    FLAG(none)
    FLAG(flag_a)
    FLAG(flag_b)
    FLAG(flag_c)
END_BITFLAGS(Flags)

int main() {
    Flags flags = Flags::flag_a | Flags::flag_b;

if (flags & Flags::flag_a) {
        std::cout << "flag_a is set" << std::endl;
    } else {
        std::cout << "flag_a is not set" << std::endl;
    }

flags.toggle(Flags::flag_a);

// ...

return 0;
}
```

## Table of Contents

* [Motivation](#motivation)
* [Getting Started](#getting-started)
    * [Raw flags vs flags](#raw-flags-vs-flags)
    * [How to Declare Set of Flags?](#how-to-declare-set-of-flags)
    * [Important Notice For C++11](#important-notice-for-c11)
    * [Bits and Names](#bits-and-names)
    * [Bitwise Operators](#bitwise-operators)
    * [Is Specific Flag Set?](#is-specific-flag-set)
    * [All or Empty](#all-or-empty)
    * [Set and Remove Specific Flag](#set-and-remove-specific-flag)
    * [Toggle Flags](#toggle-flags)
    * [Clear Flags](#clear-flags)
* [Benchmark](#benchmark)
* [Building Tests](#building-tests)
* [Compiler Compatibility](#compiler-compatibility)
* [Contributing](#contributing)
* [License](#license)
* [Support](#support)

## Motivation

Inspiration for writing this `bitflags` library I got from the homonymous Rust's crate that you may find [here](https://docs.rs/bitflags/1.2.1/bitflags/).

Some people may ask: __Why not just use `enum class` and assign binary literals?__

Following example presents using `enum class` with `std::uint8_t` as underlying type (so that max number of flags is 9):

```c++
enum class Flags : std::uint8_t {
    none   = 0b0000,
    flag_a = 0b0001,
    flag_b = 0b0010,
    flag_c = 0b0010
};
```

_Nothing is wrong with above usage, right?_

Oh... you might not have noticed that both `Flags::flag_b` and `Flags::flag_c` have the same value assigned! That's the exact same mistake that developers make in everyday work... This mistake happened with `std::uint8_t` as underlying type but imagine how often would be mistakes if the underlying value is `std::uint32_t` or even `std::uint64_t`.

_You got the point?_

Assigning binary literals to flags is manual and error-prone process, especially if there is lots of flags and if developers change them over time.

_So, why should I use `bitflags` library?_

`bitflags` library provides you decently safe way of specifying your flags with 2 core features:

- __auto - generated flag values__
- __auto - detected underlying type__

## Getting Started

`bitflags` is a single-header header-only C++11 / C++14 / C++17 library for easily managing set of auto-generated type-safe flags.

### Raw flags vs flags?

`bitflags` library provides you with 2 flag types:

- __raw_flag__ without its string representation (sort of lightweight version)
- __flag__ with its string representation

### How to Declare Set of Flags?

In order to declare a set of auto-generated flags, there are few helper macros that hide kind of "ugly" declaration syntax and provide auto-generated value for each flag.

Macros for creating set of raw flags, i.e. flags __without__ string representation:

* `BEGIN_RAW_BITFLAGS(NAME)`
    - `NAME` - name of set of raw flags

* `RAW_FLAG(NAME)`
    - `NAME` - name of specific raw flag

* `END_RAW_BITFLAGS(NAME)`
    - `NAME` - name of set of raw flags

Macros for creating set of ordinary flags, i.e. flags __with__ string representation:

* `BEGIN_BITFLAGS(NAME)`
    - `NAME` - name of set of flags

* `FLAG(NAME)`
    - `NAME` - name of specific flag

* `END_BITFLAGS(NAME)`
    - `NAME` - name of set of flags

Following snippet shows the use case of the above macros:

```cpp
BEGIN_BITFLAGS(Flags)
    FLAG(none)
    FLAG(flag_a)
    FLAG(flag_b)
    FLAG(flag_c)
END_BITFLAGS()
```

and is translated into:

```cpp
template <typename T>
struct FlagsImpl {
    using flag = bf::internal::flag<FlagsImpl, T>
    static constexpr flag none{ 0b0000, "none" };
    static constexpr flag flag_a{ 0b0001, "flag_a" };
    static constexpr flag flag_b{ 0b0010, "flag_b" };
    static constexpr flag flag_c{ 0b0100, "flag_c" };
};

using Flags = bf::bitflags<
    FlagsImpl<
        bf::bitflags<
            FlagsImpl<std::uint8_t>
        >::underlying_type
    >
>;
```

Usage is basically the same for `raw_flag`s.

### Important Notice For C++11

In case you are using C++11, you need to define your flags separately like:

```cpp
DEFINE_FLAG(Flags, none)
DEFINE_FLAG(Flags, flag_a)
DEFINE_FLAG(Flags, flag_b)
DEFINE_FLAG(Flags, flag_c)
```

This is because C++11 requires static class members to have an out-of-class definition.

### Bits and Names

While bits are part of both `raw_flag` and `flag`, names are part of `flag` type only.

Once the flags are specified, it is possible to get bits representing each flag as well as string representation of each flag:

```cpp
BEGIN_RAW_BITFLAGS(RawFlags)
    RAW_FLAG(none)
    RAW_FLAG(flag_a)
    RAW_FLAG(flag_b)
END_RAW_BITFLAGS(RawFlags)

std::cout << RawFlags::flag_a.bits << std::endl;
```

and

```cpp
BEGIN_BITFLAGS(Flags)
    FLAG(none)
    FLAG(flag_a)
    FLAG(flag_b)
END_BITFLAGS(Flags)

std::cout << Flags::flag_a.bits << " - " << Flags::flag_a.name << std::endl;
```

### Bitwise Operators

The following binary operators are implemented for the generated flags:

* NOT (`~`) operator
* AND (`&`) operator
* OR (`|`) operator
* XOR (`^`) operator

### Is Specific Flag Set?

In case we want to check whether specific flag is set or not, we have 2 options:

1. use AND operator

```cpp
BEGIN_BITFLAGS(Flags)
    FLAG(none)
    FLAG(flag_a)
    FLAG(flag_b)
END_BITFLAGS(Flags)

Flags flags = Flags::flag_a;

std::cout << static_cast<bool>(flags & Flags::flag_a) << std::endl; // true
std::cout << static_cast<bool>(flags & Flags::flag_b) << std::endl; // false
```

2. use `contains` member function

```cpp
BEGIN_BITFLAGS(Flags)
    FLAG(none)
    FLAG(flag_a)
    FLAG(flag_b)
    FLAG(flag_c)
END_BITFLAGS(Flags)

Flags flags_1 = Flags::flag_a;

std::cout << flags_1.contains(Flags::flag_a) << std::endl; // true
std::cout << flags_1.contains(Flags::flag_b) << std::endl; // false

Flags flags_2 = Flags::flag_a | Flags::flag_b;

std::cout << flags_2.contains(Flags::flag_a, Flags::flag_b) << std::endl; // true
std::cout << flags_2.contains(Flags::flag_a, Flags::flag_c) << std::endl; // false
```

### All or Empty

Following member functions are available for setting all the flags or setting no flag:

1. `all` / `is_all`

```cpp
BEGIN_BITFLAGS(Flags)
    FLAG(none)
    FLAG(flag_a)
    FLAG(flag_b)
END_BITFLAGS(Flags)

Flags flags = Flags::all();

std::cout << flags.is_all() << std::endl;                // true
std::cout << flags.contains(Flags::flag_a) << std::endl; // true
std::cout << flags.contains(Flags::flag_b) << std::endl; // true
std::cout << flags.is_empty() << std::endl;              // false
```

2. `empty` / `is_empty`

```cpp
BEGIN_BITFLAGS(Flags)
    FLAG(none)
    FLAG(flag_a)
    FLAG(flag_b)
END_BITFLAGS(Flags)

Flags flags = Flags::empty();

std::cout << flags.is_all() << std::endl;                // false
std::cout << flags.contains(Flags::flag_a) << std::endl; // false
std::cout << flags.contains(Flags::flag_b) << std::endl; // false
std::cout << flags.is_empty() << std::endl;              // true
```

### Set and Remove Specific Flag

Not only that one can set and remove specific flag by using bitwise operators, but there are also special member functions `set` and `remove` that have the same purpose.

```cpp
BEGIN_BITFLAGS(Flags)
    FLAG(none)
    FLAG(flag_a)
    FLAG(flag_b)
END_BITFLAGS(Flags)

Flags flags = Flags::empty();

std::cout << flags.contains(Flags::flag_a) << std::endl; // false
std::cout << flags.contains(Flags::flag_b) << std::endl; // false

flags.set(Flags::flag_a);
flags.set(Flags::flag_b);

std::cout << flags.contains(Flags::flag_a) << std::endl; // true
std::cout << flags.contains(Flags::flag_b) << std::endl; // true

flags.remove(Flags::flag_a);

std::cout << flags.contains(Flags::flag_a) << std::endl; // false
std::cout << flags.contains(Flags::flag_b) << std::endl; // true
```

### Toggle Flags

It is possible to toggle specific flag, i.e. if the flag is not already set, it will be set. On the other hand, if the flag is already set, it will be unset.

```cpp
BEGIN_BITFLAGS(Flags)
    FLAG(none)
    FLAG(flag_a)
    FLAG(flag_b)
END_BITFLAGS(Flags)

Flags flags = Flags::flag_a;

std::cout << flags.contains(Flags::flag_a) << std::endl; // true
flags.toggle(Flags::flag_a);
std::cout << flags.contains(Flags::flag_a) << std::endl; // false

std::cout << flags.contains(Flags::flag_b) << std::endl; // false
flags.toggle(Flags::flag_b);
std::cout << flags.contains(Flags::flag_b) << std::endl; // true
```

### Clear Flags

In order to clear all the flags currently set, one can use `clear` member function.

```cpp
BEGIN_BITFLAGS(Flags)
    FLAG(none)
    FLAG(flag_a)
    FLAG(flag_b)
    FLAG(flag_c)
END_BITFLAGS(Flags)

Flags flags = Flags::flag_a | Flags::flag_b;

std::cout << flags.contains(Flags::flag_a) << std::endl; // true
std::cout << flags.contains(Flags::flag_b) << std::endl; // true
std::cout << flags.contains(Flags::flag_c) << std::endl; // false

flags.clear();

std::cout << flags.contains(Flags::flag_a) << std::endl; // false
std::cout << flags.contains(Flags::flag_b) << std::endl; // false
std::cout << flags.contains(Flags::flag_c) << std::endl; // false
```

## Benchmark

As you can see from the following chart, using `raw_flag`s is as fast as using `std::bitset`. However, using ordinary `flag`s (i.e. flags with string representation) is a bit slower (as it is expected because of additional feature of having string representation).

If you want to run the benchmark yourself, you can use `plot.py` script like:

```bash
$ python3 plot.py --benchmarks-dir <benchmark-json-dir>
```

## Building Tests

```bash
$ git clone https://github.com/m-peko/bitflags
$ cd bitflags

$ # create the build directory
$ mkdir build
$ cd build

$ # configure the project
$ cmake -DBITFLAGS_BUILD_TESTS=ON ..

$ # compile
$ make

$ # compile tests
$ make tests

$ # run tests
$ make test
```

## Compiler Compatibility

* Clang/LLVM >= 5
* MSVC++ >= 14.11 / Visual Studio >= 2017
* GCC >= 7.3

There are no 3<sup>rd</sup> party dependencies.

## Contributing

Feel free to contribute.

If you find that any of the tests **fail**, please create a ticket in the issue tracker indicating the following information:

* platform
* architecture
* library version
* minimal reproducible example

## License

The project is available under the [MIT](https://opensource.org/licenses/MIT) license.

## Support

If you like the work `bitflags` library is doing, please consider supporting it:

bitflags

파일 탐색기

오늘의 추천 프로젝트

Was this content helpful?

Recent Feedback

bitflags

파일 탐색기

오늘의 추천 프로젝트

Was this content helpful?

Recent Feedback

Download README