Legion ECS | High Performance Rust ECS library

Legion

Legion aims to be a feature rich high performance Entity component system (ECS) library for Rust game projects with minimal boilerplate.

Getting Started

Worlds

Worlds are collections of entities, where each entity can have an arbitrary collection of components attached.

use legion::*;
let world = World::default();

Entities can be inserted via either push (for a single entity) or extend (for a collection of entities with the same component types). The world will create a unique ID for each entity upon insertion that you can use to refer to that entity later.

// a component is any type that is 'static, sized, send and sync
#[derive(Clone, Copy, Debug, PartialEq)]
struct Position {
    x: f32,
    y: f32,
}
#[derive(Clone, Copy, Debug, PartialEq)]
struct Velocity {
    dx: f32,
    dy: f32,
}

// push a component tuple into the world to create an entity
let entity: Entity = world.push((Position { x: 0.0, y: 0.0 }, Velocity { dx: 0.0, dy: 0.0 }));

// or extend via an IntoIterator of tuples to add many at once (this is faster)
let entities: &[Entity] = world.extend(vec![
    (Position { x: 0.0, y: 0.0 }, Velocity { dx: 0.0, dy: 0.0 }),
    (Position { x: 1.0, y: 1.0 }, Velocity { dx: 0.0, dy: 0.0 }),
    (Position { x: 2.0, y: 2.0 }, Velocity { dx: 0.0, dy: 0.0 }),
]);

You can access entities via entries. Entries allow you to query an entity to find out what types of components are attached to it, to get component references, or to add and remove components.

// entries return `None` if the entity does not exist
if let Some(mut entry) = world.entry(entity) {
    // access information about the entity's archetype
    println!("{:?} has {:?}", entity, entry.archetype().layout().component_types());

    // add an extra component
    entry.add_component(12f32);

    // access the entity's components, returns `None` if the entity does not have the component
    assert_eq!(entry.get_component::<f32>().unwrap(), &12f32);
}

Queries

Entries are not the most convenient or performant way to search or bulk-access a world. Queries allow for high performance and expressive iteration through the entities in a world.

// you define a query be declaring what components you want to find, and how you will access them
let mut query = <&Position>::query();

// you can then iterate through the components found in the world
for position in query.iter(&world) {
    println!("{:?}", position);
}

You can search for entities which have all of a set of components.

// construct a query from a "view tuple"
let mut query = <(&Velocity, &mut Position)>::query();

// this time we have &Velocity and &mut Position
for (velocity, position) in query.iter_mut(&mut world) {
    position.x += velocity.x;
    position.y += velocity.y;
}

You can augment a basic query with additional filters. For example, you can choose to exclude entities which also have a certain component, or only include entities for which a certain component has changed since the last time the query ran (this filtering is conservative and coarse-grained)

// you can use boolean expressions when adding filters
let mut query = <(&Velocity, &mut Position)>::query()
    .filter(!component::<Ignore>() & maybe_changed::<Position>());

for (velocity, position) in query.iter_mut(&mut world) {
    position.x += velocity.dx;
    position.y += velocity.dy;
}

There is much more than can be done with queries. See the module documentation for more information.

Systems

You may have noticed that when we wanted to write to a component, we needed to use iter_mut to iterate through our query. But perhaps your application wants to be able to process different components on different entities, perhaps even at the same time in parallel? While it is possible to do this manually (see World::split), this is very difficult to do when the different pieces of the application don't know what components each other need, or might or might not even have conflicting access requirements.

Systems and the Schedule automates this process, and can even schedule work at a more granular level than you can otherwise do manually. A system is a unit of work. Each system is defined as a function which is provided access to queries and shared resources. These systems can then be appended to a schedule, which is a linear sequence of systems, ordered by when side effects (such as writes to components) should be observed. The schedule will automatically parallelize the execution of all systems whilst maintaining the apparent order of execution from the perspective of each system.

// a system fn which loops through Position and Velocity components, and reads the Time shared resource
// the #[system] macro generates a fn called update_positions_system() which will construct our system
#[system(for_each)]
fn update_positions(pos: &mut Position, vel: &Velocity, #[resource] time: &Time) {
    pos.x += vel.dx * time.elapsed_seconds;
    pos.y += vel.dy * time.elapsed_seconds;
}

// construct a schedule (you should do this on init)
let mut schedule = Schedule::builder()
    .add_system(update_positions_system())
    .build();

// run our schedule (you should do this each update)
schedule.execute(&mut world, &mut resources);

See the systems module and the system proc macro for more information.

Feature Flags

Legion provides a few feature flags:

• parallel - Enables parallel iterators and parallel schedule execution via the rayon library. Enabled by default.
• extended-tuple-impls - Extends the maximum size of view and component tuples from 8 to 24, at the cost of increased compile times. Off by default.
• serialize - Enables the serde serialization module and associated functionality. Enabled by default.
• crossbeam-events - Implements the EventSender trait for crossbeam Sender channels, allowing them to be used for event subscriptions. Enabled by default.

WASM

Legion runs with parallelism on by default, which is not currently supported by Web Assembly as it runs single-threaded. Therefore, to build for WASM, ensure you set default-features = false in Cargo.toml. Additionally, if you want to use the serialize feature, you must enable either the stdweb or wasm-bindgen features, which will be proxied through to the uuid crate. See the uuid crate for more information.

legion = { version = "*", default-features = false, features = ["wasm-bindgen"] }

Download Details:
Author: amethyst
Source Code: https://github.com/amethyst/legion
License: MIT license

#rust #gamedev

What is GEEK

Buddha Community

Serde Rust: Serialization Framework for Rust

Serde

*Serde is a framework for serializing and deserializing Rust data structures efficiently and generically.*

You may be looking for:

• An overview of Serde
• Data formats supported by Serde
• Setting up #[derive(Serialize, Deserialize)]
• Examples
• API documentation
• Release notes

Serde in action

Click to show Cargo.toml. Run this code in the playground.

[dependencies]

# The core APIs, including the Serialize and Deserialize traits. Always
# required when using Serde. The "derive" feature is only required when
# using #[derive(Serialize, Deserialize)] to make Serde work with structs
# and enums defined in your crate.
serde = { version = "1.0", features = ["derive"] }

# Each data format lives in its own crate; the sample code below uses JSON
# but you may be using a different one.
serde_json = "1.0"

 

use serde::{Serialize, Deserialize};

#[derive(Serialize, Deserialize, Debug)]
struct Point {
    x: i32,
    y: i32,
}

fn main() {
    let point = Point { x: 1, y: 2 };

    // Convert the Point to a JSON string.
    let serialized = serde_json::to_string(&point).unwrap();

    // Prints serialized = {"x":1,"y":2}
    println!("serialized = {}", serialized);

    // Convert the JSON string back to a Point.
    let deserialized: Point = serde_json::from_str(&serialized).unwrap();

    // Prints deserialized = Point { x: 1, y: 2 }
    println!("deserialized = {:?}", deserialized);
}

Getting help

Serde is one of the most widely used Rust libraries so any place that Rustaceans congregate will be able to help you out. For chat, consider trying the #rust-questions or #rust-beginners channels of the unofficial community Discord (invite: https://discord.gg/rust-lang-community), the #rust-usage or #beginners channels of the official Rust Project Discord (invite: https://discord.gg/rust-lang), or the #general stream in Zulip. For asynchronous, consider the [rust] tag on StackOverflow, the /r/rust subreddit which has a pinned weekly easy questions post, or the Rust Discourse forum. It's acceptable to file a support issue in this repo but they tend not to get as many eyes as any of the above and may get closed without a response after some time.

Download Details:
Author: serde-rs
Source Code: https://github.com/serde-rs/serde
License: View license

#rust  #rustlang 

Legion ECS | High Performance Rust ECS library

Legion

Legion aims to be a feature rich high performance Entity component system (ECS) library for Rust game projects with minimal boilerplate.

Getting Started

Worlds

Worlds are collections of entities, where each entity can have an arbitrary collection of components attached.

use legion::*;
let world = World::default();

Entities can be inserted via either push (for a single entity) or extend (for a collection of entities with the same component types). The world will create a unique ID for each entity upon insertion that you can use to refer to that entity later.

// a component is any type that is 'static, sized, send and sync
#[derive(Clone, Copy, Debug, PartialEq)]
struct Position {
    x: f32,
    y: f32,
}
#[derive(Clone, Copy, Debug, PartialEq)]
struct Velocity {
    dx: f32,
    dy: f32,
}

// push a component tuple into the world to create an entity
let entity: Entity = world.push((Position { x: 0.0, y: 0.0 }, Velocity { dx: 0.0, dy: 0.0 }));

// or extend via an IntoIterator of tuples to add many at once (this is faster)
let entities: &[Entity] = world.extend(vec![
    (Position { x: 0.0, y: 0.0 }, Velocity { dx: 0.0, dy: 0.0 }),
    (Position { x: 1.0, y: 1.0 }, Velocity { dx: 0.0, dy: 0.0 }),
    (Position { x: 2.0, y: 2.0 }, Velocity { dx: 0.0, dy: 0.0 }),
]);

You can access entities via entries. Entries allow you to query an entity to find out what types of components are attached to it, to get component references, or to add and remove components.

// entries return `None` if the entity does not exist
if let Some(mut entry) = world.entry(entity) {
    // access information about the entity's archetype
    println!("{:?} has {:?}", entity, entry.archetype().layout().component_types());

    // add an extra component
    entry.add_component(12f32);

    // access the entity's components, returns `None` if the entity does not have the component
    assert_eq!(entry.get_component::<f32>().unwrap(), &12f32);
}

Queries

Entries are not the most convenient or performant way to search or bulk-access a world. Queries allow for high performance and expressive iteration through the entities in a world.

// you define a query be declaring what components you want to find, and how you will access them
let mut query = <&Position>::query();

// you can then iterate through the components found in the world
for position in query.iter(&world) {
    println!("{:?}", position);
}

You can search for entities which have all of a set of components.

// construct a query from a "view tuple"
let mut query = <(&Velocity, &mut Position)>::query();

// this time we have &Velocity and &mut Position
for (velocity, position) in query.iter_mut(&mut world) {
    position.x += velocity.x;
    position.y += velocity.y;
}

You can augment a basic query with additional filters. For example, you can choose to exclude entities which also have a certain component, or only include entities for which a certain component has changed since the last time the query ran (this filtering is conservative and coarse-grained)

// you can use boolean expressions when adding filters
let mut query = <(&Velocity, &mut Position)>::query()
    .filter(!component::<Ignore>() & maybe_changed::<Position>());

for (velocity, position) in query.iter_mut(&mut world) {
    position.x += velocity.dx;
    position.y += velocity.dy;
}

There is much more than can be done with queries. See the module documentation for more information.

Systems

You may have noticed that when we wanted to write to a component, we needed to use iter_mut to iterate through our query. But perhaps your application wants to be able to process different components on different entities, perhaps even at the same time in parallel? While it is possible to do this manually (see World::split), this is very difficult to do when the different pieces of the application don't know what components each other need, or might or might not even have conflicting access requirements.

Systems and the Schedule automates this process, and can even schedule work at a more granular level than you can otherwise do manually. A system is a unit of work. Each system is defined as a function which is provided access to queries and shared resources. These systems can then be appended to a schedule, which is a linear sequence of systems, ordered by when side effects (such as writes to components) should be observed. The schedule will automatically parallelize the execution of all systems whilst maintaining the apparent order of execution from the perspective of each system.

// a system fn which loops through Position and Velocity components, and reads the Time shared resource
// the #[system] macro generates a fn called update_positions_system() which will construct our system
#[system(for_each)]
fn update_positions(pos: &mut Position, vel: &Velocity, #[resource] time: &Time) {
    pos.x += vel.dx * time.elapsed_seconds;
    pos.y += vel.dy * time.elapsed_seconds;
}

// construct a schedule (you should do this on init)
let mut schedule = Schedule::builder()
    .add_system(update_positions_system())
    .build();

// run our schedule (you should do this each update)
schedule.execute(&mut world, &mut resources);

See the systems module and the system proc macro for more information.

Feature Flags

Legion provides a few feature flags:

• parallel - Enables parallel iterators and parallel schedule execution via the rayon library. Enabled by default.
• extended-tuple-impls - Extends the maximum size of view and component tuples from 8 to 24, at the cost of increased compile times. Off by default.
• serialize - Enables the serde serialization module and associated functionality. Enabled by default.
• crossbeam-events - Implements the EventSender trait for crossbeam Sender channels, allowing them to be used for event subscriptions. Enabled by default.

WASM

Legion runs with parallelism on by default, which is not currently supported by Web Assembly as it runs single-threaded. Therefore, to build for WASM, ensure you set default-features = false in Cargo.toml. Additionally, if you want to use the serialize feature, you must enable either the stdweb or wasm-bindgen features, which will be proxied through to the uuid crate. See the uuid crate for more information.

legion = { version = "*", default-features = false, features = ["wasm-bindgen"] }

Download Details:
Author: amethyst
Source Code: https://github.com/amethyst/legion
License: MIT license

#rust #gamedev

Serde JSON: JSON Support for Serde Framework

Serde JSON

Serde is a framework for serializing and deserializing Rust data structures efficiently and generically.

[dependencies]
serde_json = "1.0"

You may be looking for:

• JSON API documentation
• Serde API documentation
• Detailed documentation about Serde
• Setting up #[derive(Serialize, Deserialize)]
• Release notes

JSON is a ubiquitous open-standard format that uses human-readable text to transmit data objects consisting of key-value pairs.

{
    "name": "John Doe",
    "age": 43,
    "address": {
        "street": "10 Downing Street",
        "city": "London"
    },
    "phones": [
        "+44 1234567",
        "+44 2345678"
    ]
}

There are three common ways that you might find yourself needing to work with JSON data in Rust.

• As text data. An unprocessed string of JSON data that you receive on an HTTP endpoint, read from a file, or prepare to send to a remote server.
• As an untyped or loosely typed representation. Maybe you want to check that some JSON data is valid before passing it on, but without knowing the structure of what it contains. Or you want to do very basic manipulations like insert a key in a particular spot.
• As a strongly typed Rust data structure. When you expect all or most of your data to conform to a particular structure and want to get real work done without JSON's loosey-goosey nature tripping you up.

Serde JSON provides efficient, flexible, safe ways of converting data between each of these representations.

Operating on untyped JSON values

Any valid JSON data can be manipulated in the following recursive enum representation. This data structure is serde_json::Value.

enum Value {
    Null,
    Bool(bool),
    Number(Number),
    String(String),
    Array(Vec<Value>),
    Object(Map<String, Value>),
}

A string of JSON data can be parsed into a serde_json::Value by the serde_json::from_str function. There is also from_slice for parsing from a byte slice &[u8] and from_reader for parsing from any io::Read like a File or a TCP stream.

use serde_json::{Result, Value};

fn untyped_example() -> Result<()> {
    // Some JSON input data as a &str. Maybe this comes from the user.
    let data = r#"
        {
            "name": "John Doe",
            "age": 43,
            "phones": [
                "+44 1234567",
                "+44 2345678"
            ]
        }"#;

    // Parse the string of data into serde_json::Value.
    let v: Value = serde_json::from_str(data)?;

    // Access parts of the data by indexing with square brackets.
    println!("Please call {} at the number {}", v["name"], v["phones"][0]);

    Ok(())
}

The result of square bracket indexing like v["name"] is a borrow of the data at that index, so the type is &Value. A JSON map can be indexed with string keys, while a JSON array can be indexed with integer keys. If the type of the data is not right for the type with which it is being indexed, or if a map does not contain the key being indexed, or if the index into a vector is out of bounds, the returned element is Value::Null.

When a Value is printed, it is printed as a JSON string. So in the code above, the output looks like Please call "John Doe" at the number "+44 1234567". The quotation marks appear because v["name"] is a &Value containing a JSON string and its JSON representation is "John Doe". Printing as a plain string without quotation marks involves converting from a JSON string to a Rust string with as_str() or avoiding the use of Value as described in the following section.

The Value representation is sufficient for very basic tasks but can be tedious to work with for anything more significant. Error handling is verbose to implement correctly, for example imagine trying to detect the presence of unrecognized fields in the input data. The compiler is powerless to help you when you make a mistake, for example imagine typoing v["name"] as v["nmae"] in one of the dozens of places it is used in your code.

Parsing JSON as strongly typed data structures

Serde provides a powerful way of mapping JSON data into Rust data structures largely automatically.

use serde::{Deserialize, Serialize};
use serde_json::Result;

#[derive(Serialize, Deserialize)]
struct Person {
    name: String,
    age: u8,
    phones: Vec<String>,
}

fn typed_example() -> Result<()> {
    // Some JSON input data as a &str. Maybe this comes from the user.
    let data = r#"
        {
            "name": "John Doe",
            "age": 43,
            "phones": [
                "+44 1234567",
                "+44 2345678"
            ]
        }"#;

    // Parse the string of data into a Person object. This is exactly the
    // same function as the one that produced serde_json::Value above, but
    // now we are asking it for a Person as output.
    let p: Person = serde_json::from_str(data)?;

    // Do things just like with any other Rust data structure.
    println!("Please call {} at the number {}", p.name, p.phones[0]);

    Ok(())
}

This is the same serde_json::from_str function as before, but this time we assign the return value to a variable of type Person so Serde will automatically interpret the input data as a Person and produce informative error messages if the layout does not conform to what a Person is expected to look like.

Any type that implements Serde's Deserialize trait can be deserialized this way. This includes built-in Rust standard library types like Vec<T> and HashMap<K, V>, as well as any structs or enums annotated with #[derive(Deserialize)].

Once we have p of type Person, our IDE and the Rust compiler can help us use it correctly like they do for any other Rust code. The IDE can autocomplete field names to prevent typos, which was impossible in the serde_json::Value representation. And the Rust compiler can check that when we write p.phones[0], then p.phones is guaranteed to be a Vec<String> so indexing into it makes sense and produces a String.

The necessary setup for using Serde's derive macros is explained on the Using derive page of the Serde site.

Constructing JSON values

Serde JSON provides a json! macro to build serde_json::Value objects with very natural JSON syntax.

use serde_json::json;

fn main() {
    // The type of `john` is `serde_json::Value`
    let john = json!({
        "name": "John Doe",
        "age": 43,
        "phones": [
            "+44 1234567",
            "+44 2345678"
        ]
    });

    println!("first phone number: {}", john["phones"][0]);

    // Convert to a string of JSON and print it out
    println!("{}", john.to_string());
}

The Value::to_string() function converts a serde_json::Value into a String of JSON text.

One neat thing about the json! macro is that variables and expressions can be interpolated directly into the JSON value as you are building it. Serde will check at compile time that the value you are interpolating is able to be represented as JSON.

let full_name = "John Doe";
let age_last_year = 42;

// The type of `john` is `serde_json::Value`
let john = json!({
    "name": full_name,
    "age": age_last_year + 1,
    "phones": [
        format!("+44 {}", random_phone())
    ]
});

This is amazingly convenient, but we have the problem we had before with Value: the IDE and Rust compiler cannot help us if we get it wrong. Serde JSON provides a better way of serializing strongly-typed data structures into JSON text.

Creating JSON by serializing data structures

A data structure can be converted to a JSON string by serde_json::to_string. There is also serde_json::to_vec which serializes to a Vec<u8> and serde_json::to_writer which serializes to any io::Write such as a File or a TCP stream.

use serde::{Deserialize, Serialize};
use serde_json::Result;

#[derive(Serialize, Deserialize)]
struct Address {
    street: String,
    city: String,
}

fn print_an_address() -> Result<()> {
    // Some data structure.
    let address = Address {
        street: "10 Downing Street".to_owned(),
        city: "London".to_owned(),
    };

    // Serialize it to a JSON string.
    let j = serde_json::to_string(&address)?;

    // Print, write to a file, or send to an HTTP server.
    println!("{}", j);

    Ok(())
}

Any type that implements Serde's Serialize trait can be serialized this way. This includes built-in Rust standard library types like Vec<T> and HashMap<K, V>, as well as any structs or enums annotated with #[derive(Serialize)].

Performance

It is fast. You should expect in the ballpark of 500 to 1000 megabytes per second deserialization and 600 to 900 megabytes per second serialization, depending on the characteristics of your data. This is competitive with the fastest C and C++ JSON libraries or even 30% faster for many use cases. Benchmarks live in the serde-rs/json-benchmark repo.

Getting help

Serde is one of the most widely used Rust libraries, so any place that Rustaceans congregate will be able to help you out. For chat, consider trying the #rust-questions or #rust-beginners channels of the unofficial community Discord (invite: https://discord.gg/rust-lang-community), the #rust-usage or #beginners channels of the official Rust Project Discord (invite: https://discord.gg/rust-lang), or the #general stream in Zulip. For asynchronous, consider the [rust] tag on StackOverflow, the /r/rust subreddit which has a pinned weekly easy questions post, or the Rust Discourse forum. It's acceptable to file a support issue in this repo, but they tend not to get as many eyes as any of the above and may get closed without a response after some time.

No-std support

As long as there is a memory allocator, it is possible to use serde_json without the rest of the Rust standard library. This is supported on Rust 1.36+. Disable the default "std" feature and enable the "alloc" feature:

[dependencies]
serde_json = { version = "1.0", default-features = false, features = ["alloc"] }

For JSON support in Serde without a memory allocator, please see the serde-json-core crate.

Link: https://crates.io/crates/serde_json

#rust  #rustlang  #encode   #json 

Legion: High Performance Entity Component System (ECS) Library

Legion aims to be a feature rich high performance Entity component system (ECS) library for Rust game projects with minimal boilerplate.

Getting Started

Worlds

Worlds are collections of entities, where each entity can have an arbitrary collection of components attached.

use legion::*;
let world = World::default();

Entities can be inserted via either push (for a single entity) or extend (for a collection of entities with the same component types). The world will create a unique ID for each entity upon insertion that you can use to refer to that entity later.

// a component is any type that is 'static, sized, send and sync
#[derive(Clone, Copy, Debug, PartialEq)]
struct Position {
    x: f32,
    y: f32,
}
#[derive(Clone, Copy, Debug, PartialEq)]
struct Velocity {
    dx: f32,
    dy: f32,
}

// push a component tuple into the world to create an entity
let entity: Entity = world.push((Position { x: 0.0, y: 0.0 }, Velocity { dx: 0.0, dy: 0.0 }));

// or extend via an IntoIterator of tuples to add many at once (this is faster)
let entities: &[Entity] = world.extend(vec![
    (Position { x: 0.0, y: 0.0 }, Velocity { dx: 0.0, dy: 0.0 }),
    (Position { x: 1.0, y: 1.0 }, Velocity { dx: 0.0, dy: 0.0 }),
    (Position { x: 2.0, y: 2.0 }, Velocity { dx: 0.0, dy: 0.0 }),
]);

You can access entities via entries. Entries allow you to query an entity to find out what types of components are attached to it, to get component references, or to add and remove components.

// entries return `None` if the entity does not exist
if let Some(mut entry) = world.entry(entity) {
    // access information about the entity's archetype
    println!("{:?} has {:?}", entity, entry.archetype().layout().component_types());

    // add an extra component
    entry.add_component(12f32);

    // access the entity's components, returns `None` if the entity does not have the component
    assert_eq!(entry.get_component::<f32>().unwrap(), &12f32);
}

Queries

Entries are not the most convenient or performant way to search or bulk-access a world. Queries allow for high performance and expressive iteration through the entities in a world.

// you define a query be declaring what components you want to find, and how you will access them
let mut query = <&Position>::query();

// you can then iterate through the components found in the world
for position in query.iter(&world) {
    println!("{:?}", position);
}

You can search for entities which have all of a set of components.

// construct a query from a "view tuple"
let mut query = <(&Velocity, &mut Position)>::query();

// this time we have &Velocity and &mut Position
for (velocity, position) in query.iter_mut(&mut world) {
    position.x += velocity.x;
    position.y += velocity.y;
}

You can augment a basic query with additional filters. For example, you can choose to exclude entities which also have a certain component, or only include entities for which a certain component has changed since the last time the query ran (this filtering is conservative and coarse-grained)

// you can use boolean expressions when adding filters
let mut query = <(&Velocity, &mut Position)>::query()
    .filter(!component::<Ignore>() & maybe_changed::<Position>());

for (velocity, position) in query.iter_mut(&mut world) {
    position.x += velocity.dx;
    position.y += velocity.dy;
}

There is much more than can be done with queries. See the module documentation for more information.

Systems

You may have noticed that when we wanted to write to a component, we needed to use iter_mut to iterate through our query. But perhaps your application wants to be able to process different components on different entities, perhaps even at the same time in parallel? While it is possible to do this manually (see World::split), this is very difficult to do when the different pieces of the application don't know what components each other need, or might or might not even have conflicting access requirements.

Systems and the Schedule automates this process, and can even schedule work at a more granular level than you can otherwise do manually. A system is a unit of work. Each system is defined as a function which is provided access to queries and shared resources. These systems can then be appended to a schedule, which is a linear sequence of systems, ordered by when side effects (such as writes to components) should be observed. The schedule will automatically parallelize the execution of all systems whilst maintaining the apparent order of execution from the perspective of each system.

// a system fn which loops through Position and Velocity components, and reads the Time shared resource
// the #[system] macro generates a fn called update_positions_system() which will construct our system
#[system(for_each)]
fn update_positions(pos: &mut Position, vel: &Velocity, #[resource] time: &Time) {
    pos.x += vel.dx * time.elapsed_seconds;
    pos.y += vel.dy * time.elapsed_seconds;
}

// construct a schedule (you should do this on init)
let mut schedule = Schedule::builder()
    .add_system(update_positions_system())
    .build();

// run our schedule (you should do this each update)
schedule.execute(&mut world, &mut resources);

See the systems module and the system proc macro for more information.

Feature Flags

Legion provides a few feature flags:

• parallel - Enables parallel iterators and parallel schedule execution via the rayon library. Enabled by default.
• extended-tuple-impls - Extends the maximum size of view and component tuples from 8 to 24, at the cost of increased compile times. Off by default.
• serialize - Enables the serde serialization module and associated functionality. Enabled by default.
• crossbeam-events - Implements the EventSender trait for crossbeam Sender channels, allowing them to be used for event subscriptions. Enabled by default.

WASM

Legion runs with parallelism on by default, which is not currently supported by Web Assembly as it runs single-threaded. Therefore, to build for WASM, ensure you set default-features = false in Cargo.toml. Additionally, if you want to use the serialize feature, you must enable either the stdweb or wasm-bindgen features, which will be proxied through to the uuid crate. See the uuid crate for more information.

legion = { version = "*", default-features = false, features = ["wasm-bindgen"] }

Link: https://crates.io/crates/legion

#rust #rustlang #game #wgpu

Rust Dublin Lightning Talks April 2021 - Rust crypto libraries

Evervault founder Shane Curran discusses his company’s mission to encrypt the web, with a brief survey of the landscape of Rust crypto libraries.

00:00:00 Intro
00:00:08 Background
00:02:08 evervault encryption engine
00:03:39 AWS Nitro Enclaves
00:05:55 E3 Architecture
00:06:47 Why Rust?
00:10:50 Rust Crypto Libraries
00:17:14 What crypto work is needed in Rust?

#rust #rust crypto libraries