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asset_decompression.rs
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asset_decompression.rs
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//! Implements loader for a Gzip compressed asset.
use bevy::utils::thiserror;
use bevy::{
asset::{
io::{Reader, VecReader},
AssetLoader, AsyncReadExt, ErasedLoadedAsset, LoadContext, LoadDirectError,
},
prelude::*,
reflect::TypePath,
utils::BoxedFuture,
};
use flate2::read::GzDecoder;
use std::io::prelude::*;
use std::marker::PhantomData;
use thiserror::Error;
#[derive(Asset, TypePath)]
struct GzAsset {
uncompressed: ErasedLoadedAsset,
}
#[derive(Default)]
struct GzAssetLoader;
/// Possible errors that can be produced by [`GzAssetLoader`]
#[non_exhaustive]
#[derive(Debug, Error)]
pub enum GzAssetLoaderError {
/// An [IO](std::io) Error
#[error("Could not load asset: {0}")]
Io(#[from] std::io::Error),
/// An error caused when the asset path cannot be used to determine the uncompressed asset type.
#[error("Could not determine file path of uncompressed asset")]
IndeterminateFilePath,
/// An error caused by the internal asset loader.
#[error("Could not load contained asset: {0}")]
LoadDirectError(#[from] LoadDirectError),
}
impl AssetLoader for GzAssetLoader {
type Asset = GzAsset;
type Settings = ();
type Error = GzAssetLoaderError;
fn load<'a>(
&'a self,
reader: &'a mut Reader,
_settings: &'a (),
load_context: &'a mut LoadContext,
) -> BoxedFuture<'a, Result<Self::Asset, Self::Error>> {
Box::pin(async move {
let compressed_path = load_context.path();
let file_name = compressed_path
.file_name()
.ok_or(GzAssetLoaderError::IndeterminateFilePath)?
.to_string_lossy();
let uncompressed_file_name = file_name
.strip_suffix(".gz")
.ok_or(GzAssetLoaderError::IndeterminateFilePath)?;
let contained_path = compressed_path.join(uncompressed_file_name);
let mut bytes_compressed = Vec::new();
reader.read_to_end(&mut bytes_compressed).await?;
let mut decoder = GzDecoder::new(bytes_compressed.as_slice());
let mut bytes_uncompressed = Vec::new();
decoder.read_to_end(&mut bytes_uncompressed)?;
// Now that we have decompressed the asset, let's pass it back to the
// context to continue loading
let mut reader = VecReader::new(bytes_uncompressed);
let uncompressed = load_context
.load_direct_with_reader(&mut reader, contained_path)
.await?;
Ok(GzAsset { uncompressed })
})
}
fn extensions(&self) -> &[&str] {
&["gz"]
}
}
#[derive(Component, Default)]
struct Compressed<T> {
compressed: Handle<GzAsset>,
_phantom: PhantomData<T>,
}
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.init_asset::<GzAsset>()
.init_asset_loader::<GzAssetLoader>()
.add_systems(Startup, setup)
.add_systems(Update, decompress::<Image>)
.run();
}
fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
commands.spawn(Camera2dBundle::default());
commands.spawn((
Compressed::<Image> {
compressed: asset_server.load("data/compressed_image.png.gz"),
..default()
},
Sprite::default(),
TransformBundle::default(),
VisibilityBundle::default(),
));
}
fn decompress<A: Asset>(
mut commands: Commands,
asset_server: Res<AssetServer>,
mut compressed_assets: ResMut<Assets<GzAsset>>,
query: Query<(Entity, &Compressed<A>)>,
) {
for (entity, Compressed { compressed, .. }) in query.iter() {
let Some(GzAsset { uncompressed }) = compressed_assets.remove(compressed) else {
continue;
};
let uncompressed = uncompressed.take::<A>().unwrap();
commands
.entity(entity)
.remove::<Compressed<A>>()
.insert(asset_server.add(uncompressed));
}
}