Implement MeshFoundry pipeline (#77)

crates/libremetaverse-structured-data/src/binary.rs

@@ -21,10 +21,14 @@ const fn is_binary_whitespace(byte: u8) -> bool {
 }
 
 pub(crate) fn deserialize_bytes(data: Vec<u8>) -> Result<OSD, Error> {
+    deserialize_prefix(&data).map(|(value, _)| value)
+}
+
+pub(crate) fn deserialize_prefix(data: &[u8]) -> Result<(OSD, usize), Error> {
     if data.len() > MAX_INPUT_BYTES {
         return Err(parse_error(0, "binary LLSD input exceeds allocation limit"));
     }
-    let mut parser = Parser::new(&data);
+    let mut parser = Parser::new(data);
     parser.skip_whitespace();
     if parser.consume_prefix_ignore_ascii_case(ALT_HEADER)
         || parser.consume_prefix_ignore_ascii_case(HEADER)
@@ -37,7 +41,7 @@ pub(crate) fn deserialize_bytes(data: Vec<u8>) -> Result<OSD, Error> {
         OSD::DEFAULT_MAX_NODES,
         OSD::DEFAULT_MAX_BINARY_BYTES,
     )?;
-    Ok(value)
+    Ok((value, parser.position))
 }
 
 pub(crate) fn deserialize_stream(mut stream: Box<dyn ReadWrite + Send>) -> Result<OSD, Error> {
@@ -596,6 +600,18 @@ mod tests {
         );
     }
 
+    #[test]
+    fn prefix_decode_reports_exact_payload_boundary() {
+        let value = OSD::Map(HashMap::from([("offset".into(), OSD::Integer(7))]));
+        let encoded = serialize_with_header(value.clone(), false).unwrap();
+        let mut container = encoded.clone();
+        container.extend_from_slice(b"\x78\x9c appended payload");
+        let (decoded, consumed) = deserialize_prefix(&container).unwrap();
+        assert_eq!(decoded, value);
+        assert_eq!(consumed, encoded.len());
+        assert_eq!(&container[consumed..], b"\x78\x9c appended payload");
+    }
+
     #[test]
     fn malformed_seed_corpus_is_rejected_with_positions() {
         let expected: &[(&str, &str)] = &[

crates/libremetaverse-structured-data/src/lib.rs

@@ -54,3 +54,15 @@ pub mod xml {
 pub use generated::*;
 pub use libremetaverse_types as types;
 pub use libremetaverse_types::Error;
+
+/// Decodes one bounded binary LLSD value and returns the number of consumed
+/// bytes, allowing native container formats to locate payloads appended after
+/// an LLSD header without duplicating the codec.
+///
+/// # Errors
+///
+/// Returns a positioned parse error when the prefix is malformed, truncated,
+/// or exceeds the shared LLSD depth, node, input, or allocation bounds.
+pub fn deserialize_llsd_binary_prefix(data: &[u8]) -> Result<(OSD, usize), Error> {
+    binary::deserialize_prefix(data)
+}