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// Copyright 2022 Datafuse Labs.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use std::sync::Arc;
use crate::Accessor;
/// Layer is used to intercept the operations on the underlying storage.
///
/// Struct that implement this trait must accept input `Arc<dyn Accessor>` as inner,
/// and returns a new `Arc<dyn Accessor>` as output.
///
/// All functions in `Accessor` requires `&self`, so it's implementor's responsibility
/// to maintain the internal mutability. Please also keep in mind that `Accessor`
/// requires `Send` and `Sync`.
///
/// # Examples
///
/// ```
/// use std::sync::Arc;
///
/// use opendal::Accessor;
/// use opendal::Layer;
///
/// #[derive(Debug)]
/// struct Trace {
/// inner: Arc<dyn Accessor>,
/// }
///
/// impl Accessor for Trace {}
///
/// impl Layer for Trace {
/// fn layer(&self, inner: Arc<dyn Accessor>) -> Arc<dyn Accessor> {
/// Arc::new(Trace { inner })
/// }
/// }
/// ```
pub trait Layer {
/// Intercept the operations on the underlying storage.
fn layer(&self, inner: Arc<dyn Accessor>) -> Arc<dyn Accessor>;
}
#[cfg(test)]
mod tests {
use std::io::Result;
use std::sync::Arc;
use futures::lock::Mutex;
use super::*;
use crate::ops::OpDelete;
use crate::services::fs;
use crate::Accessor;
use crate::Operator;
#[derive(Debug)]
struct Test {
#[allow(dead_code)]
inner: Option<Arc<dyn Accessor>>,
deleted: Arc<Mutex<bool>>,
}
impl Layer for &Test {
fn layer(&self, inner: Arc<dyn Accessor>) -> Arc<dyn Accessor> {
Arc::new(Test {
inner: Some(inner.clone()),
deleted: self.deleted.clone(),
})
}
}
#[async_trait::async_trait]
impl Accessor for Test {
async fn delete(&self, _args: &OpDelete) -> Result<()> {
let mut x = self.deleted.lock().await;
*x = true;
assert!(self.inner.is_some());
// We will not call anything here to test the layer.
Ok(())
}
}
#[tokio::test]
async fn test_layer() {
let test = Test {
inner: None,
deleted: Arc::new(Mutex::new(false)),
};
let op = Operator::new(fs::Backend::build().finish().await.unwrap()).layer(&test);
op.object("xxxxx").delete().await.unwrap();
assert!(*test.deleted.clone().lock().await);
}
}