src/backup/read_chunk.rs: move read chunk trait into extra file

And implement LocalChunkReader.

src/backup/read_chunk.rs

@@ -0,0 +1,45 @@
+use failure::*;
+use std::sync::Arc;
+
+use super::datastore::*;
+use super::crypt_config::*;
+use super::data_chunk::*;
+
+/// The ReadChunk trait allows reading backup data chunks (local or remote)
+pub trait ReadChunk {
+    /// Returns the decoded chunk data
+    fn read_chunk(&self, digest:&[u8; 32]) -> Result<Vec<u8>, Error>;
+}
+
+pub struct LocalChunkReader {
+    store: DataStore,
+    crypt_config: Option<Arc<CryptConfig>>,
+}
+
+impl LocalChunkReader {
+
+    pub fn new(store: DataStore, crypt_config: Option<Arc<CryptConfig>>) -> Self {
+        Self { store, crypt_config }
+    }
+}
+
+impl ReadChunk for LocalChunkReader {
+
+    fn read_chunk(&self, digest:&[u8; 32]) -> Result<Vec<u8>, Error> {
+
+        let digest_str = proxmox::tools::digest_to_hex(digest);
+        println!("READ CHUNK {}", digest_str);
+
+        let (path, _) = self.store.chunk_path(digest);
+        let raw_data = crate::tools::file_get_contents(&path)?;
+        let chunk = DataChunk::from_raw(raw_data, *digest)?;
+        chunk.verify_crc()?;
+
+        let raw_data = match self.crypt_config {
+            Some(ref crypt_config) => chunk.decode(Some(crypt_config))?,
+            None => chunk.decode(None)?,
+        };
+
+        Ok(raw_data)
+    }
+}