<p dir="auto">For production code, return offsets with each error so a 400-byte trace does not force operators to count bytes manually.</p>

<p dir="auto">Keep the structure description beside the payload in test evidence. Without it, a compact array cannot be decoded unambiguously.</p>

<p dir="auto">The parser below is intentionally small and defensive. It rejects trailing bytes instead of guessing a schema.</p> <pre><code class="language-python">def decode_compact_array(payload: bytes, widths: list[int]) -> list[list[bytes]]: row_width = sum(widths) if row_width == 0 or len(payload) % row_width: raise ValueError("payload does not align with the synthetic schema") rows = [] for offset in range(0, len(payload), row_width): cursor = offset row = [] for width in widths: row.append(payload[cursor:cursor + width]) cursor += width rows.append(row) return rows </code></pre> <table class="table table-bordered table-striped"> <thead> <tr> <th>Column</th> <th style="text-align:right">Width</th> <th>Synthetic meaning</th> </tr> </thead> <tbody> <tr> <td>timestamp</td> <td style="text-align:right">12</td> <td>octet string</td> </tr> <tr> <td>active energy</td> <td style="text-align:right">4</td> <td>unsigned</td> </tr> <tr> <td>status</td> <td style="text-align:right">1</td> <td>bit flags</td> </tr> </tbody> </table>

<p dir="auto">Only retry transport-class failures. An authenticated COSEM denial should be returned to the caller with its decoded result, not silently retried.</p>

<p dir="auto">A retry must create a new evidence boundary. Reusing a half-open connection can hide whether the counter, challenge, or transport failed.</p> <pre><code class="language-java">public final class AssociationRetry { public Result execute(ClientFactory factory, int maxAttempts) throws Exception { Exception last = null; for (int attempt = 1; attempt <= maxAttempts; attempt++) { try (DlmsClient client = factory.open()) { client.associate(); return client.read("0.0.40.0.0.255", 2); } catch (TemporaryTransportException ex) { last = ex; } } throw last; } } </code></pre> <p dir="auto">Synthetic stack excerpt:</p> <pre><code class="language-text">com.example.dlms.TemporaryTransportException: UA not received before 3000 ms at com.example.dlms.HdlcLink.awaitUa(HdlcLink.java:184) at com.example.dlms.DlmsClient.associate(DlmsClient.java:91) at com.example.dlms.AssociationRetry.execute(AssociationRetry.java:7) Caused by: java.net.SocketTimeoutException: synthetic timeout </code></pre>