add an AsyncReadChunk trait

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

src/client/remote_chunk_reader.rs

@@ -1,10 +1,12 @@
+use std::future::Future;
 use std::collections::HashMap;
+use std::pin::Pin;
 use std::sync::Arc;
 
 use anyhow::Error;
 
 use super::BackupReader;
-use crate::backup::{CryptConfig, DataBlob, ReadChunk};
+use crate::backup::{AsyncReadChunk, CryptConfig, DataBlob, ReadChunk};
 use crate::tools::runtime::block_on;
 
 /// Read chunks from remote host using ``BackupReader``
@@ -31,6 +33,19 @@ impl RemoteChunkReader {
             cache: HashMap::new(),
         }
     }
+
+    pub async fn read_raw_chunk(&mut self, digest: &[u8; 32]) -> Result<DataBlob, Error> {
+        let mut chunk_data = Vec::with_capacity(4 * 1024 * 1024);
+
+        self.client
+            .download_chunk(&digest, &mut chunk_data)
+            .await?;
+
+        let chunk = DataBlob::from_raw(chunk_data)?;
+        chunk.verify_crc()?;
+
+        Ok(chunk)
+    }
 }
 
 impl ReadChunk for RemoteChunkReader {
@@ -57,7 +72,7 @@ impl ReadChunk for RemoteChunkReader {
             return Ok(raw_data.to_vec());
         }
 
-        let chunk = self.read_raw_chunk(digest)?;
+        let chunk = ReadChunk::read_raw_chunk(self, digest)?;
 
         let raw_data = chunk.decode(self.crypt_config.as_ref().map(Arc::as_ref))?;
 
@@ -71,3 +86,36 @@ impl ReadChunk for RemoteChunkReader {
         Ok(raw_data)
     }
 }
+
+impl AsyncReadChunk for RemoteChunkReader {
+    fn read_raw_chunk<'a>(
+        &'a mut self,
+        digest: &'a [u8; 32],
+    ) -> Pin<Box<dyn Future<Output = Result<DataBlob, Error>> + Send + 'a>> {
+        Box::pin(Self::read_raw_chunk(self, digest))
+    }
+
+    fn read_chunk<'a>(
+        &'a mut self,
+        digest: &'a [u8; 32],
+    ) -> Pin<Box<dyn Future<Output = Result<Vec<u8>, Error>> + Send + 'a>> {
+        Box::pin(async move {
+            if let Some(raw_data) = self.cache.get(digest) {
+                return Ok(raw_data.to_vec());
+            }
+
+            let chunk = Self::read_raw_chunk(self, digest).await?;
+
+            let raw_data = chunk.decode(self.crypt_config.as_ref().map(Arc::as_ref))?;
+
+            // fixme: verify digest?
+
+            let use_cache = self.cache_hint.contains_key(digest);
+            if use_cache {
+                self.cache.insert(*digest, raw_data.to_vec());
+            }
+
+            Ok(raw_data)
+        })
+    }
+}