[PATCH proxmox-backup v3 04/30] datastore: blob: implement async reader for data blobs

[Christian Ebner <c.ebner@proxmox.com>]

So it can be used to load the blob file when server side encryption
is required during push sync jobs, which runs in async context.

Factor out the DataBlob and CRC check, which is identical for sync
and async reader implementation.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
---
changes since version 2:
- fix typos in commit message for async DataBlob reader patch.

 pbs-datastore/src/data_blob.rs | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/pbs-datastore/src/data_blob.rs b/pbs-datastore/src/data_blob.rs
index 0c05c5a40..b434243c0 100644
--- a/pbs-datastore/src/data_blob.rs
+++ b/pbs-datastore/src/data_blob.rs
@@ -2,6 +2,7 @@ use std::io::Write;
 
 use anyhow::{bail, Error};
 use openssl::symm::{decrypt_aead, Mode};
+use tokio::io::{AsyncRead, AsyncReadExt};
 
 use proxmox_io::{ReadExt, WriteExt};
 
@@ -238,15 +239,26 @@ impl DataBlob {
         }
     }
 
-    /// Load blob from ``reader``, verify CRC
+    /// Load data blob via given sync ``reader`` and verify its CRC
     pub fn load_from_reader(reader: &mut dyn std::io::Read) -> Result<Self, Error> {
         let mut data = Vec::with_capacity(1024 * 1024);
         reader.read_to_end(&mut data)?;
+        Self::from_raw_with_crc_check(data)
+    }
 
-        let blob = Self::from_raw(data)?;
+    /// Load data blob via given async ``reader`` and verify its CRC
+    pub async fn load_from_async_reader(
+        reader: &mut (dyn AsyncRead + Unpin + Send),
+    ) -> Result<Self, Error> {
+        let mut data = Vec::with_capacity(1024 * 1024);
+        reader.read_to_end(&mut data).await?;
+        Self::from_raw_with_crc_check(data)
+    }
 
+    /// Generates a data blob from raw input data and checks for matching CRC in header
+    fn from_raw_with_crc_check(raw_data: Vec<u8>) -> Result<Self, Error> {
+        let blob = Self::from_raw(raw_data)?;
         blob.verify_crc()?;
-
         Ok(blob)
     }
 
-- 
2.47.3