Add README

Author: alixinne

README.md

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+# [hyperion.rs](https://github.com/vtavernier/hyperion.rs)
+
+[![Build](https://github.com/vtavernier/hyperion.rs/workflows/build/badge.svg)](https://github.com/vtavernier/hyperion.rs/actions)
+[![Docs](https://img.shields.io/badge/docs-master-blue)](https://vtavernier.github.io/hyperion.rs/hyperion/)
+[![GitHub](https://img.shields.io/github/license/vtavernier/hyperion.rs)](LICENSE)
+
+hyperion.rs is a rewrite of
+[hyperion.ng](https://github.com/hyperion-project/hyperion.ng) in the Rust
+Programming Language. This version features:
+
+* Very low resource requirements (can be run on a single thread, useful for the
+  Raspberry Pi Zero for example)
+* No memory leaks (most allocations are static anyways)
+* Easy to compile *and* cross-compile
+
+***Disclaimer: this is an early work-in-progress***:
+* A lot of internals may still change, in case you would like to contribute
+  please contact me beforehand.
+* Only a small subset of the original project's features are currently
+  supported. This means that unless you're using it in the exact same context as
+  I am (Android TV Grabber + Raspberry Pi Zero W + WS2815 LED strip), this might
+  not be for you.
+
+## Compatibility
+
+Currently implemented features:
+
+* Loading settings from the hyperion.ng database
+* Basic WS2812SPI device (no invert, no latch time)
+* JSON, Protobuf and Flatbuffers server
+
+## Migrating your settings
+
+Due to the ORM being used in this project, we need the settings database to have
+primary keys setup. This doesn't change the schema, but to ensure compatibility,
+it is best to use a separate database for hyperion.ng and hyperion.rs.
+
+This process will be more streamlined in the future, but for testing purposes
+you can follow these instructions: assuming you have the sqlite3 client
+installed, and you are in your home directory, with hyperion.rs being a clone of
+this repository:
+
+```bash
+# Create config directory for hyperion.rs
+$ mkdir -p .config/hyperion.rs/
+
+# (if not done already) Install the ORM client diesel
+$ cargo install --force diesel_cli
+
+# Setup the database
+$ (cd hyperion.rs && DATABASE_URL=$HOME/.config/hyperion.rs/hyperion.db diesel setup)
+
+# Open sqlite3
+$ sqlite3
+> ATTACH ".hyperion/db/hyperion.db" AS db1;        -- Attach the original hyperion.ng database
+> ATTACH ".config/hyperion.rs/hyperion.db" AS db2; -- Attach the new hyperion.rs database
+> -- Copy the tables
+> BEGIN TRANSACTION;
+> 	INSERT INTO db2.instances SELECT * FROM db1.instances;
+> 	INSERT INTO db2.auth SELECT * FROM db1.auth;
+> 	INSERT INTO db2.meta SELECT * FROM db1.meta;
+> 	INSERT INTO db2.settings SELECT * FROM db1.settings;
+> COMMIT;
+```
+
+## Running hyperion.rs
+
+Once your settings database has been migrated, you can run hyperion.rs using
+`cargo`:
+
+```bash
+$ cargo run
+```
+
+If running from a release archive, invoke the `hyperiond-rs` binary directly.
+
+## Cross-compiling
+
+Cross-compiling is done using [cross](https://github.com/rustembedded/cross). As
+hyperion.rs has native dependencies, we first need to prepare a Docker image
+with the required dependencies, and then build using the resulting image.
+
+*Note: these images will be published on dockerhub as the project stabilizes.*
+
+Let's say we are building for the Raspberry Pi Zero, which corresponds to the
+Rust target arm-unknown-linux-gnueabihf.
+
+```bash
+$ export TARGET=arm-unknown-linux-gnueabihf
+
+# Build the Docker image
+$ (cd docker && docker build . -f Dockerfile.$TARGET -t vtavernier/cross-hyperion:$TARGET)
+
+# (if not done already) Install cross
+$ cargo install --force cross
+
+# Build the project
+$ cross build --release --target $TARGET
+
+# The resulting binaries will be in target/$TARGET/release
+```
+
+## License
+
+This work is licensed under the [MIT License](LICENSE).
+
+## Author
+
+Vincent Tavernier <[email protected]>. Original project and protocol
+source files by [hyperion-project](https://github.com/hyperion-project).