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# libfringe

libfringe is a library implementing lightweight context switches,
without relying on kernel services. It can be used in hosted environments
(using `std`) as well as on bare metal (using `core`).

It provides high-level, safe abstractions:
  * an implementation of internal iterators, also known as generators,
    [Generator](https://edef1c.github.io/libfringe/fringe/generator/struct.Generator.html).

It also provides low-level, unsafe building blocks:
  * a trait that can be implemented by stack allocators,
    [Stack](https://edef1c.github.io/libfringe/fringe/struct.Stack.html);
  * a stack allocator based on anonymous memory mappings with guard pages,
    [OsStack](https://edef1c.github.io/libfringe/fringe/struct.OsStack.html).

## Performance

  libfringe does context switches in 2.5ns flat on x86_64!
```
test swap ... bench:         5 ns/iter (+/- 1)
```

  …and on x86:

```
test swap ... bench:         5 ns/iter (+/- 1)
```

## Limitations

  libfringe currently doesn't work on anything but x86 and x86_64,
  and is untested on anything but Linux.

## Installation

  libfringe is a [Cargo](https://crates.io) package.
  It's not stable software yet, so you'll have to use it as a git dependency.
  Add this to your `Cargo.toml`:
```toml
[dependencies.fringe]
git = "https://github.com/edef1c/libfringe.git"
```

### Feature flags

  [Cargo's feature flags]: http://doc.crates.io/manifest.html#the-[features]-section
  libfringe provides some optional features through [Cargo's feature flags].
  Currently, all of them are enabled by default.

#### `valgrind`

  [Valgrind]: http://valgrind.org
  [Valgrind] integration. libfringe will register context stacks with Valgrind.