Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/propensive/feudalism

Controlled borrowing of mutable values for safe concurrency
https://github.com/propensive/feudalism

mutexes scala

Last synced: 24 days ago
JSON representation

Controlled borrowing of mutable values for safe concurrency

Awesome Lists containing this project

README 

        
[GitHub Workflow](https://github.com/propensive/feudalism/actions)

[](https://discord.gg/7b6mpF6Qcf)




# Feudalism



__Controlled borrowing of mutable values for safe concurrency.__



A _mutex_ is a data structure designed for safe reading and writing to a

mutable variable in a concurrent environment. Specifically, a mutex variable

may be mutated (that is, its old value read and transformed into a new value)

so long as no other threads are reading or writing to the mutex at the same

time. However, any number of threads may read the mutex variable concurrently.



Feudalism implements a generic `Mutex` type which guarantees these constraints.



## Features



- implements a basic, generic mutex

- provides fast and safe concurrent access to a variable

- especially performant on Java 21 with virtual threads



## Availability Plan



Feudalism has not yet been published. The medium-term plan is to build Feudalism

with [Fury](https://github.com/propensive/fury) and to publish it as a source build on

[Vent](https://github.com/propensive/vent). This will enable ordinary users to write and build

software which depends on Feudalism.



Subsequently, Feudalism will also be made available as a binary in the Maven

Central repository. This will enable users of other build tools to use it.



For the overeager, curious and impatient, see [building](#building).



## Getting Started



### Creating a new Mutex



A new mutex, an instance of type `Mutex[ValueType]` for some choice of

`ValueTyp`, can be constructed by supplying its initial value to the `Mutex`

factory method, like so:

```scala

val count: Mutex[Int] = Mutex(32)

```



This represents a mutex variable, which is set to `32`. Any thread which has a

reference to `count` may read or modify this variable, but only in delimited

blocks.



We can read the value only through a lambda applied to the `read` method of

`Mutex`, which provides a reference for accessing the value.



## Status



Feudalism is classified as __fledgling__. For reference, Soundness projects are

categorized into one of the following five stability levels:



- _embryonic_: for experimental or demonstrative purposes only, without any guarantees of longevity

- _fledgling_: of proven utility, seeking contributions, but liable to significant redesigns

- _maturescent_: major design decisions broady settled, seeking probatory adoption and refinement

- _dependable_: production-ready, subject to controlled ongoing maintenance and enhancement; tagged as version `1.0.0` or later

- _adamantine_: proven, reliable and production-ready, with no further breaking changes ever anticipated



Projects at any stability level, even _embryonic_ projects, can still be used,

as long as caution is taken to avoid a mismatch between the project's stability

level and the required stability and maintainability of your own project.



Feudalism is designed to be _small_. Its entire source code currently consists

of 100 lines of code.



## Building



Feudalism will ultimately be built by Fury, when it is published. In the

meantime, two possibilities are offered, however they are acknowledged to be

fragile, inadequately tested, and unsuitable for anything more than

experimentation. They are provided only for the necessity of providing _some_

answer to the question, "how can I try Feudalism?".



1. *Copy the sources into your own project*

   

   Read the `fury` file in the repository root to understand Feudalism's build

   structure, dependencies and source location; the file format should be short

   and quite intuitive. Copy the sources into a source directory in your own

   project, then repeat (recursively) for each of the dependencies.



   The sources are compiled against the latest nightly release of Scala 3.

   There should be no problem to compile the project together with all of its

   dependencies in a single compilation.



2. *Build with [Wrath](https://github.com/propensive/wrath/)*



   Wrath is a bootstrapping script for building Feudalism and other projects in

   the absence of a fully-featured build tool. It is designed to read the `fury`

   file in the project directory, and produce a collection of JAR files which can

   be added to a classpath, by compiling the project and all of its dependencies,

   including the Scala compiler itself.

   

   Download the latest version of

   [`wrath`](https://github.com/propensive/wrath/releases/latest), make it

   executable, and add it to your path, for example by copying it to

   `/usr/local/bin/`.



   Clone this repository inside an empty directory, so that the build can

   safely make clones of repositories it depends on as _peers_ of `feudalism`.

   Run `wrath -F` in the repository root. This will download and compile the

   latest version of Scala, as well as all of Feudalism's dependencies.



   If the build was successful, the compiled JAR files can be found in the

   `.wrath/dist` directory.



## Contributing



Contributors to Feudalism are welcome and encouraged. New contributors may like

to look for issues marked

[beginner](https://github.com/propensive/feudalism/labels/beginner).



We suggest that all contributors read the [Contributing

Guide](/contributing.md) to make the process of contributing to Feudalism

easier.



Please __do not__ contact project maintainers privately with questions unless

there is a good reason to keep them private. While it can be tempting to

repsond to such questions, private answers cannot be shared with a wider

audience, and it can result in duplication of effort.



## Author



Feudalism was designed and developed by Jon Pretty, and commercial support and

training on all aspects of Scala 3 is available from [Propensive

OÜ](https://propensive.com/).



## Name



_Feudalism_ was the predominant social system in Medieval times, whereby

wealthy landowners would divide their land into strips, and lease it to tenants

to work. This is vaguely analogous, on some level, to the controlled access a

mutex provides to readers and writers of its variable.



In general, Soundness project names are always chosen with some rationale,

however it is usually frivolous. Each name is chosen for more for its

_uniqueness_ and _intrigue_ than its concision or catchiness, and there is no

bias towards names with positive or "nice" meanings—since many of the libraries

perform some quite unpleasant tasks.



Names should be English words, though many are obscure or archaic, and it

should be noted how willingly English adopts foreign words. Names are generally

of Greek or Latin origin, and have often arrived in English via a romance

language.



## Logo



The logo shows a ring, split into two halves representing read-access and

write-access; in the read-access half, the ring splits into multiple threads,

while in the write-access half, the ring is just a single thread.



## License



Feudalism is copyright © 2024 Jon Pretty & Propensive OÜ, and

is made available under the [Apache 2.0 License](/license.md).