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bytecount 0.4.0

count occurrences of a given byte, or the number of UTF-8 code points, in a byte slice, fast
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# bytecount

Counting bytes really fast

[![Build Status](https://travis-ci.org/llogiq/bytecount.svg?branch=master)](https://travis-ci.org/llogiq/bytecount)
[![Windows build status](https://ci.appveyor.com/api/projects/status/github/llogiq/bytecount?svg=true)](https://ci.appveyor.com/project/llogiq/bytecount)
[![Current Version](http://meritbadge.herokuapp.com/bytecount)](https://crates.io/crates/bytecount)
[![License: Apache 2.0/MIT](https://img.shields.io/crates/l/bytecount.svg)](#license)

This uses the "hyperscreamingcount" algorithm by Joshua Landau to count bytes faster than anything else.
The [newlinebench](https://github.com/llogiq/newlinebench) repository has further benchmarks for old versions of this repository.

To use bytecount in your crate, if you have [cargo-edit](https://github.com/killercup/cargo-edit), just type
`cargo add bytecount` in a terminal with the crate root as the current path. Otherwise you can manually edit your
`Cargo.toml` to add `bytecount = 0.4.0` to your `[dependencies]` section.

In your crate root (`lib.rs` or `main.rs`, depending on if you are writing a
library or application), add `extern crate bytecount;`. Now you can simply use
`bytecount::count` as follows:

```Rust
extern crate bytecount;

fn main() {
    let mytext = "some potentially large text, perhaps read from disk?";
    let spaces = bytecount::count(mytext.as_bytes(), b' ');
    ..
}
```

bytecount supports two features to make use of modern CPU's features to speed up counting considerably. To allow your
users to use them, add the following to your `Cargo.toml`:

```
[features]
runtime-dispatch-simd = ["bytecount/runtime-dispatch-simd"]
generic-simd = ["bytecount/generic-simd"]
```

The first, `runtime-dispatch-simd`, enables detection of SIMD capabilities at runtime, which allows using the SSE2 and
AVX2 codepaths, but cannot be used with `no_std`.

Your users can then compile with runtime dispacth using:

```
cargo build --release --features runtime-dispatch-simd
```

The second, `generic-simd`, uses `packed_simd` to provide a fast
architecture-agnostic SIMD codepath, but requires running on nightly.

Your users can compile with this codepath using:

```
cargo build --release --features generic-simd
```

Building for a more specific architecture will also improve performance.
You can do this with

```
RUSTFLAGS="-C target-cpu=native" cargo build --release
```

The scalar algorithm is explained in depth [here](https://llogiq.github.io/2016/09/27/count.html).

## License

Licensed under either of at your discretion:

- [Apache 2.0](LICENSE.Apache2)
- [MIT](LICENSE.MIT)