https://github.com/adam-mcdaniel/regex-engine
A Regex📋 implementation in C++ using Thompson's NFA algorithm
https://github.com/adam-mcdaniel/regex-engine
cpp cpp98-compatible header-only regex regex-engine regex-match text-processing
Last synced: 8 months ago
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A Regex📋 implementation in C++ using Thompson's NFA algorithm
- Host: GitHub
- URL: https://github.com/adam-mcdaniel/regex-engine
- Owner: adam-mcdaniel
- License: mit
- Created: 2024-04-09T22:54:42.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2024-04-19T21:37:25.000Z (over 1 year ago)
- Last Synced: 2025-03-24T22:51:24.255Z (9 months ago)
- Topics: cpp, cpp98-compatible, header-only, regex, regex-engine, regex-match, text-processing
- Language: C++
- Homepage: https://adam-mcdaniel.net
- Size: 4.01 MB
- Stars: 4
- Watchers: 2
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# regex-engine
This repository implements a regex engine in C++ using Thompson's NFA algorithm. This algorithm prevents pathological backtracking, a common problem with most widely used regex implementations.
This implementation is also a header-only library.
## Usage
To use the library, first include it in your C++ file.
```c++
// Optionally, you can define `CACHING` to allow
// the regex engine to cache transition states.
// This can improve performance in many cases.
#define CACHING
// Include the regex header file
#include "regex.hpp"
```
To use the regex engine, first create a regex object with the desired regex pattern. You can use `std::cout` to print out the compiled regex NFA. Use the `match` method to use the regex on a given content string.
```c++
int main() {
// Compile a regex pattern
Regex r("((ab)*|c)+");
// Print out the compiled NFA
std::cout << r << std::endl;
// The content to match
std::string content = "abc";
// Check if the content matches the regex
if (r.match(content)) {
std::cout << "Matched!" << std::endl;
} else {
std::cout << "Not matched!" << std::endl;
}
return 0;
}
```
## Regex Syntax
The regex engine supports the following syntax:
| Syntax | Description |
|--------|-------------|
| `*` | Zero or more of the preceding expression |
| `+` | One or more of the preceding expression |
| `?` | Zero or one of the preceding expression |
| `\|` | Alternation |
| `()` | Grouping |
| `a`, `b`, `c`, ... | Any single character |
## Building
To build your program with the regex engine, simply add it to your include path and link against the C++ standard library.
```bash
g++ -I path/to/regex-engine main.cpp -o main
```
### CMake
To build with CMake, you can use a `CMakeLists.txt` file like the following:
```cmake
cmake_minimum_required(VERSION 3.0)
# Create a new project
project(HelloWorld)
# Add an executable
add_executable(HelloWorld main.cpp)
include_directories(path/to/regex-engine)
```
Alternatively, you can use `FetchContent` to download the regex engine repository and include it in your project.
```cmake
# Import the library from the git repo
include(FetchContent)
FetchContent_Declare(
regex-engine
GIT_REPOSITORY https://github.com/adam-mcdaniel/regex-engine
GIT_TAG main
)
FetchContent_MakeAvailable(regex-engine)
# Include the header only library
include_directories(${regex-engine_SOURCE_DIR})
```
## License
This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.