mirror of
https://github.com/bevyengine/bevy.git
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Carter Anderson
cd977df8eb
# Objective #22104 added `AsyncSeek` support, but it has some downsides: - It is very "loose": it relies on `AssetLoader` to "attest" that it needs the seek feature. However, AssetLoaders both have access to the `AsyncSeek` API no matter what (it is a supertrait of Reader), and AssetReaders provide `AsyncSeek` behavior even if it isn't requested. In practice this is likely to create situations where AssetLoaders don't request `AsyncSeek` and just rely on it being provided by default, causing unexpected incompatibilities when AssetLoader consumers try to use other AssetReaders that don't support AsyncSeek. - It encourages building "fallback" behavior into the AssetReader in cases where AsyncSeek cannot be supported directly (ex: read the while contents into a Vec). From the perspective of loaders, this _silently_ changes the performance characteristics, and _forces_ a specific kind of fallback behavior. It would be better if the fallback behavior was in the hands of the AssetLoader. ## Solution - Remove `ReaderRequiredFeatures` and associated functionality - Add a new `SeekableReader` trait, where `SeekableReader: Reader + AsyncSeek`. - Add a new `Reader::seekable(&mut self) -> Result<&mut dyn SeekableReader, ReaderNotSeekableError>`, which can either fail or cast to `SeekableReader`, if that is supported. ```rust let seekable_reader = reader.seekable()?; seekable_reader.seek(SeekFrom::Start(10)).await?; ``` This gives `AssetLoader` implementers more clarity when it comes to `Reader` feature support, gives them more autonomy over fallback behavior, makes our APIs more static, and cuts down on the complexity of the system as a whole. --------- Co-authored-by: andriyDev <andriydzikh@gmail.com> Co-authored-by: Jan Hohenheim <jan@hohenheim.ch>
66 lines
2.1 KiB
Rust
66 lines
2.1 KiB
Rust
//! Implements a custom asset io loader.
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//! An [`AssetReader`] is what the asset server uses to read the raw bytes of assets.
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//! It does not know anything about the asset formats, only how to talk to the underlying storage.
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use bevy::{
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asset::io::{
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AssetReader, AssetReaderError, AssetSource, AssetSourceBuilder, AssetSourceId,
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ErasedAssetReader, PathStream, Reader,
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},
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prelude::*,
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};
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use std::path::Path;
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/// A custom asset reader implementation that wraps a given asset reader implementation
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struct CustomAssetReader(Box<dyn ErasedAssetReader>);
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impl AssetReader for CustomAssetReader {
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async fn read<'a>(&'a self, path: &'a Path) -> Result<impl Reader + 'a, AssetReaderError> {
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info!("Reading {}", path.display());
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self.0.read(path).await
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}
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async fn read_meta<'a>(&'a self, path: &'a Path) -> Result<impl Reader + 'a, AssetReaderError> {
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self.0.read_meta(path).await
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}
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async fn read_directory<'a>(
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&'a self,
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path: &'a Path,
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) -> Result<Box<PathStream>, AssetReaderError> {
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self.0.read_directory(path).await
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}
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async fn is_directory<'a>(&'a self, path: &'a Path) -> Result<bool, AssetReaderError> {
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self.0.is_directory(path).await
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}
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}
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/// A plugins that registers our new asset reader
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struct CustomAssetReaderPlugin;
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impl Plugin for CustomAssetReaderPlugin {
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fn build(&self, app: &mut App) {
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app.register_asset_source(
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AssetSourceId::Default,
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AssetSourceBuilder::new(|| {
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Box::new(CustomAssetReader(
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// This is the default reader for the current platform
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AssetSource::get_default_reader("assets".to_string())(),
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))
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}),
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);
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}
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}
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fn main() {
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App::new()
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.add_plugins((CustomAssetReaderPlugin, DefaultPlugins))
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.add_systems(Startup, setup)
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.run();
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}
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fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
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commands.spawn(Camera2d);
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commands.spawn(Sprite::from_image(asset_server.load("branding/icon.png")));
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}
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