feat(applet): StructuralCbor.elementSpan (M2B.2)

applet/src/test/java/com/dangerousthings/aliro/StructuralCborTest.java

@@ -251,6 +251,115 @@ class StructuralCborTest {
         assertEquals(ISO7816.SW_DATA_INVALID, ex.getReason() & 0xFFFF);
     }
 
+    // ---------------------------------------------------------------------
+    // elementSpan tests (M2B.2) — span of a complete CBOR element including
+    // nested children, used by M2B.3 / M2D.1 to walk IssuerSigned / docRequests.
+    // ---------------------------------------------------------------------
+
+    /** Shared 4B scratch for elementSpan's decodeHeader calls. */
+    private final byte[] scratch = new byte[4];
+
+    @Test
+    void elementSpan_uintImmediate() {
+        // 0x17 = uint 23, immediate argument. One header byte, no payload.
+        byte[] buf = hex("17");
+        short span = StructuralCbor.elementSpan(
+            buf, (short) 0, (short) buf.length, scratch, (short) 0);
+        assertEquals(1, span);
+    }
+
+    @Test
+    void elementSpan_uintOneByteArgument() {
+        // 0x18 0x64 = uint 100. Header byte + 1B argument, no payload.
+        byte[] buf = hex("1864");
+        short span = StructuralCbor.elementSpan(
+            buf, (short) 0, (short) buf.length, scratch, (short) 0);
+        assertEquals(2, span);
+    }
+
+    @Test
+    void elementSpan_bstrEmpty() {
+        // 0x40 = bstr len 0. One header byte, zero payload.
+        byte[] buf = hex("40");
+        short span = StructuralCbor.elementSpan(
+            buf, (short) 0, (short) buf.length, scratch, (short) 0);
+        assertEquals(1, span);
+    }
+
+    @Test
+    void elementSpan_bstrLen3() {
+        // 0x43 0x01 0x02 0x03 = bstr h'010203'. Header + 3 payload bytes.
+        byte[] buf = hex("43010203");
+        short span = StructuralCbor.elementSpan(
+            buf, (short) 0, (short) buf.length, scratch, (short) 0);
+        assertEquals(4, span);
+    }
+
+    @Test
+    void elementSpan_tstrHello() {
+        // 0x65 + "hello" = tstr "hello". Header + 5 payload bytes.
+        byte[] buf = hex("6568656c6c6f");
+        short span = StructuralCbor.elementSpan(
+            buf, (short) 0, (short) buf.length, scratch, (short) 0);
+        assertEquals(6, span);
+    }
+
+    @Test
+    void elementSpan_arrayOfThreeUints() {
+        // 0x83 0x01 0x02 0x03 = [1, 2, 3]. Header + 3 single-byte children.
+        byte[] buf = hex("83010203");
+        short span = StructuralCbor.elementSpan(
+            buf, (short) 0, (short) buf.length, scratch, (short) 0);
+        assertEquals(4, span);
+    }
+
+    @Test
+    void elementSpan_nestedArray() {
+        // 0x82 0x82 0x01 0x02 0x03 = [[1, 2], 3]. Exercises recursion.
+        byte[] buf = hex("8282010203");
+        short span = StructuralCbor.elementSpan(
+            buf, (short) 0, (short) buf.length, scratch, (short) 0);
+        assertEquals(5, span);
+    }
+
+    @Test
+    void elementSpan_mapTwoUintPairs() {
+        // 0xa2 0x01 0x02 0x03 0x04 = {1: 2, 3: 4}. Header + 4 single-byte items.
+        byte[] buf = hex("a201020304");
+        short span = StructuralCbor.elementSpan(
+            buf, (short) 0, (short) buf.length, scratch, (short) 0);
+        assertEquals(5, span);
+    }
+
+    @Test
+    void elementSpan_mapWithBstrUintPairs() {
+        // 0xa2 0x43 010203 0x1864 0x41 ff 0x17
+        //   = { h'010203': 100, h'ff': 23 }
+        // Header(1) + bstr(4) + uint(2) + bstr(2) + uint(1) = 10.
+        byte[] buf = hex("a2 43 010203 1864 41 ff 17");
+        short span = StructuralCbor.elementSpan(
+            buf, (short) 0, (short) buf.length, scratch, (short) 0);
+        assertEquals(10, span);
+    }
+
+    @Test
+    void elementSpan_tagUint() {
+        // 0xc1 0x01 = tag(1, 1). Tag header + tagged element span.
+        byte[] buf = hex("c101");
+        short span = StructuralCbor.elementSpan(
+            buf, (short) 0, (short) buf.length, scratch, (short) 0);
+        assertEquals(2, span);
+    }
+
+    @Test
+    void elementSpan_honoursBufOff() {
+        // Pad with 4 junk bytes, then a 4-byte array [1,2,3]; span starts at offset 4.
+        byte[] buf = hex("deadbeef" + "83010203");
+        short span = StructuralCbor.elementSpan(
+            buf, (short) 4, (short) (buf.length - 4), scratch, (short) 0);
+        assertEquals(4, span);
+    }
+
     private static byte[] hex(String s) {
         s = s.replaceAll("\\s+", "");
         byte[] out = new byte[s.length() / 2];