[pbs-devel] [PATCH v3 pxar 12/58] format: add payload stream start marker

[Christian Ebner]

Mark the beginning of the payload stream with a magic number. Allows for
version and file type detection.

Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
changes since version 2:
- not present in previous version

 examples/mk-format-hashes.rs |  5 +++++
 src/decoder/mod.rs           | 17 +++++++++++++++--
 src/encoder/mod.rs           | 18 +++++++++++-------
 src/format/mod.rs            |  2 ++
 4 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/examples/mk-format-hashes.rs b/examples/mk-format-hashes.rs
index de73df0..35cff99 100644
--- a/examples/mk-format-hashes.rs
+++ b/examples/mk-format-hashes.rs
@@ -56,6 +56,11 @@ const CONSTANTS: &[(&str, &str, &str)] = &[
         "PXAR_GOODBYE_TAIL_MARKER",
         "__PROXMOX_FORMAT_PXAR_GOODBYE_TAIL_MARKER__",
     ),
+    (
+        "The start marker used in the separate payload stream",
+        "PXAR_PAYLOAD_START_MARKER",
+        "__PROXMOX_FORMAT_PXAR_PAYLOAD_START_MARKER__",
+    ),
     (
         "The end marker used in the separate payload stream",
         "PXAR_PAYLOAD_TAIL_MARKER",
diff --git a/src/decoder/mod.rs b/src/decoder/mod.rs
index 8cc4877..00d9abf 100644
--- a/src/decoder/mod.rs
+++ b/src/decoder/mod.rs
@@ -213,8 +213,21 @@ impl<I: SeqRead> DecoderImpl<I> {
         input: I,
         path: PathBuf,
         eof_after_entry: bool,
-        payload_input: Option<I>,
+        mut payload_input: Option<I>,
     ) -> io::Result<Self> {
+        let payload_consumed = if let Some(payload_input) = payload_input.as_mut() {
+            let header: Header = seq_read_entry(payload_input).await?;
+            if header.htype != format::PXAR_PAYLOAD_START_MARKER {
+                io_bail!(
+                    "unexpected header in payload input: expected {:#x?} , got {header:#x?}",
+                    format::PXAR_PAYLOAD_START_MARKER,
+                );
+            }
+            header.full_size()
+        } else {
+            0
+        };
+
         let this = DecoderImpl {
             input,
             current_header: unsafe { mem::zeroed() },
@@ -227,7 +240,7 @@ impl<I: SeqRead> DecoderImpl<I> {
             state: State::Begin,
             with_goodbye_tables: false,
             payload_input,
-            payload_consumed: 0,
+            payload_consumed,
             eof_after_entry,
         };
 
diff --git a/src/encoder/mod.rs b/src/encoder/mod.rs
index 24dcbc9..88c0ed5 100644
--- a/src/encoder/mod.rs
+++ b/src/encoder/mod.rs
@@ -313,15 +313,23 @@ impl<'a, T: SeqWrite + 'a> EncoderImpl<'a, T> {
     pub async fn new(
         output: EncoderOutput<'a, T>,
         metadata: &Metadata,
-        payload_output: Option<T>,
+        mut payload_output: Option<T>,
     ) -> io::Result<EncoderImpl<'a, T>> {
         if !metadata.is_dir() {
             io_bail!("directory metadata must contain the directory mode flag");
         }
+
+        let mut state = EncoderState::default();
+        if let Some(payload_output) = payload_output.as_mut() {
+            let header = format::Header::with_content_size(format::PXAR_PAYLOAD_START_MARKER, 0);
+            header.check_header_size()?;
+            seq_write_struct(payload_output, header, &mut state.payload_write_position).await?;
+        }
+
         let mut this = Self {
             output,
-            payload_output: EncoderOutput::Owned(None),
-            state: vec![EncoderState::default()],
+            payload_output: EncoderOutput::Owned(payload_output),
+            state: vec![state],
             finished: false,
             file_copy_buffer: Arc::new(Mutex::new(unsafe {
                 crate::util::vec_new_uninitialized(1024 * 1024)
@@ -332,10 +340,6 @@ impl<'a, T: SeqWrite + 'a> EncoderImpl<'a, T> {
         let state = this.state_mut()?;
         state.files_offset = state.position();
 
-        if let Some(payload_output) = payload_output {
-            this.payload_output = EncoderOutput::Owned(Some(payload_output));
-        }
-
         Ok(this)
     }
 
diff --git a/src/format/mod.rs b/src/format/mod.rs
index 10192e7..a672d19 100644
--- a/src/format/mod.rs
+++ b/src/format/mod.rs
@@ -106,6 +106,8 @@ pub const PXAR_PAYLOAD_REF: u64 = 0x419d3d6bc4ba977e;
 pub const PXAR_GOODBYE: u64 = 0x2fec4fa642d5731d;
 /// The end marker used in the GOODBYE object
 pub const PXAR_GOODBYE_TAIL_MARKER: u64 = 0xef5eed5b753e1555;
+/// The start marker used in the separate payload stream
+pub const PXAR_PAYLOAD_START_MARKER: u64 = 0x834c68c2194a4ed2;
 /// The end marker used in the separate payload stream
 pub const PXAR_PAYLOAD_TAIL_MARKER: u64 = 0x6c72b78b984c81b5;
 
-- 
2.39.2