gcra 0.3.3

A basic implementation of GCRA algorithm for rate limiting
Documentation 
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[![Build Status](https://travis-ci.com/lytefast/gcra.svg?branch=master)](https://travis-ci.com/lytefast/gcra)
[![License](https://img.shields.io/github/license/lytefast/gcra.svg)](LICENSE)
[![Documentation](https://docs.rs/gcra/badge.svg)](https://docs.rs/gcra/)
[![crates.io](https://img.shields.io/crates/v/gcra.svg)](https://crates.io/crates/gcra)

# GCRA: A basic implementation

Library which implements the core
[GCRA](https://en.wikipedia.org/wiki/Generic_cell_rate_algorithm) functionality in rust.

## Features

- `rate-limiter` a LRU + expiring rate limiter. Implements `Send + Sync` so can be used asynchronously.

## Usage

```rust
use gcra::{GcraState, RateLimit};

fn check_rate_limit() {
  const LIMIT: u32 = 1;
  // Create a rate limit that allows `1/1s`
  let rate_limit = RateLimit::per_sec(LIMIT);

  let mut user_state = GcraState::default();
  assert!(user_state.check_and_modify(&rate_limit, 1).is_ok());
  assert!(
      user_state.check_and_modify(&rate_limit, 1).is_err(),
      "We should be over the limit now"
  );
}
```

### With `rate-limiter`

```rust
use gcra::{GcraError, RateLimit, RateLimiter, RateLimiterError};

#[tokio::main]
async fn main() -> Result<(), RateLimiterError> {
    let rate_limit = RateLimit::per_sec(2);
    let mut rl = RateLimiter::new(4, 4);

    rl.check("key", rate_limit.clone(), 1).await?;
    rl.check("key", rate_limit.clone(), 1).await?;

    match rl.check("key", rate_limit.clone(), 1).await {
        Err(RateLimiterError::GcraError(GcraError::DeniedUntil { next_allowed_at })) => {
            print!("Denied: Request next at {:?}", next_allowed_at);
            Ok(())
        }
        unexpected => panic!("Opps something went wrong! {:?}", unexpected),
    }
}
```