Function rs_compare_block

crates/ffi/src/compile.rs:719–756

(
  rust_env: *const RustCompiledEnv,
  lowlink_name: LeanOwned,
  lean_bytes: LeanByteArray<LeanOwned>,
)

) -> *mut RustCompiledEnv {
  // Decode Lean environment
  let lean_env = crate::lean_env::decode_env(env_consts_ptr);
  let lean_env = Arc::new(lean_env);

  // Compile with Rust
  let rust_stt =
    match compile_env_with_options(&lean_env, CompileOptions::default()) {
      Ok(stt) => stt,
      Err(_e) => {
        return std::ptr::null_mut();
      },
    };

  // Build block map: lowlink name -> (serialized bytes, sharing len)
  let mut blocks: HashMap<Name, (Vec<u8>, usize)> = HashMap::new();

  // Iterate over all names and their addresses
  for entry in rust_stt.name_to_addr.iter() {
    let name = entry.key().clone();
    let addr = entry.value().clone();

    // Skip if we already have this block (multiple names map to same block)
    if blocks.contains_key(&name) {
      continue;
    }

    // Get the compiled constant
    if let Some(constant) = rust_stt.env.get_const(&addr) {
      let mut bytes = Vec::new();
      constant.put(&mut bytes);
      let sharing_len = constant.sharing.len();
      blocks.insert(name, (bytes, sharing_len));
    }
  }

  // Return boxed RustCompiledEnv with full compile state for pre-sharing access
  Box::into_raw(Box::new(RustCompiledEnv { blocks, compile_state: rust_stt }))
}

/// FFI: Compare a single block and return packed result.
/// Returns a packed u64: high 32 bits = matches (1) or error code (0 = mismatch, 2 = not found)
///                       low 32 bits = first diff offset (if mismatch)