[pbs-devel] [PATCH v4 pxar 07/58] decoder: set payload input range when decoding via accessor

[Christian Ebner]

When accessing the file contents via the sequential file restore
the range of the payload contents cannot be inferred a-priori but need
to be calculated based on the payload refereces encountered during
decoding.

Extending the `SeqRead` trait by the method `update_range` allows to
set the range in the payload reader instance by implementing the
method for `SeqReadAtAdapter`, thereby setting the correct content
range to be accessed.

Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
 src/accessor/mod.rs |  4 ++++
 src/decoder/mod.rs  | 10 ++++++++++
 2 files changed, 14 insertions(+)

diff --git a/src/accessor/mod.rs b/src/accessor/mod.rs
index 46afbe3..fadd3d2 100644
--- a/src/accessor/mod.rs
+++ b/src/accessor/mod.rs
@@ -1038,4 +1038,8 @@ impl<T: ReadAt> decoder::SeqRead for SeqReadAtAdapter<T> {
     fn poll_position(self: Pin<&mut Self>, _cx: &mut Context) -> Poll<Option<io::Result<u64>>> {
         Poll::Ready(Some(Ok(self.range.start)))
     }
+
+    fn update_range(&mut self, range: Range<u64>) {
+        self.range = range;
+    }
 }
diff --git a/src/decoder/mod.rs b/src/decoder/mod.rs
index 07b6c61..7c5cc12 100644
--- a/src/decoder/mod.rs
+++ b/src/decoder/mod.rs
@@ -8,6 +8,7 @@ use std::ffi::OsString;
 use std::future::poll_fn;
 use std::io;
 use std::mem::{self, size_of, size_of_val, MaybeUninit};
+use std::ops::Range;
 use std::os::unix::ffi::{OsStrExt, OsStringExt};
 use std::path::{Path, PathBuf};
 use std::pin::Pin;
@@ -55,6 +56,11 @@ pub trait SeqRead {
     fn poll_position(self: Pin<&mut Self>, _cx: &mut Context) -> Poll<Option<io::Result<u64>>> {
         Poll::Ready(None)
     }
+
+    /// Update range for Readers implementing `SeqReadAtAdapter`
+    fn update_range(&mut self, _range: Range<u64>) {
+        // nothing to be done, only implemented by `SeqReadAtAdapter`s
+    }
 }
 
 /// Allow using trait objects for generics taking a `SeqRead`:
@@ -576,6 +582,10 @@ impl<I: SeqRead> DecoderImpl<I> {
                         let to_skip = payload_ref.offset - self.payload_consumed;
                         Self::skip(payload_input, to_skip as usize).await?;
                         self.payload_consumed += to_skip;
+                    } else {
+                        let start = payload_ref.offset;
+                        let end = start + payload_ref.size + size_of::<Header>() as u64;
+                        payload_input.update_range(start..end);
                     }
 
                     let header: Header = seq_read_entry(payload_input).await?;
-- 
2.39.2