Various TLV enhancements:

- New API function: tlv_append();
  - Added unit tests for tlv_append();
  - New internal functions: tlv_record_length(), tlv_next(), tlv_sequence_length();
  - Rework tlv_decode() to use new internal functions.

libfreefare/freefare.h

@@ -144,6 +144,7 @@ MifareSectorNumber *mifare_application_find (Mad mad, MadAid aid);
 
 uint8_t		*tlv_encode (const uint8_t type, const uint8_t *istream, uint16_t isize, size_t *osize);
 uint8_t		*tlv_decode (const uint8_t *istream, uint8_t *type, uint16_t *size);
+uint8_t		*tlv_append (uint8_t *a, uint8_t *b);
 
 #ifdef __cplusplus
     }

libfreefare/tlv.c

@@ -36,6 +36,10 @@
 
 #define TLV_TERMINATOR 0xFE
 
+size_t		 tlv_record_length (const uint8_t *stream, size_t *field_length_size, size_t *field_value_size);
+uint8_t		*tlv_next (uint8_t *stream);
+size_t		 tlv_sequence_length (uint8_t *stream);
+
 /*
  * TLV (Type Length Value) Manipulation Functions.
  */
@@ -85,28 +89,111 @@ tlv_encode (const uint8_t type, const uint8_t *istream, uint16_t isize, size_t *
 uint8_t *
 tlv_decode (const uint8_t *istream, uint8_t *type, uint16_t *size)
 {
-    size_t s;
-    off_t o = 1;
+    size_t fls = 0;
+    size_t fvs = 0;
     uint8_t *res = NULL;
 
     if (type)
 	*type = istream[0];
 
-    if (istream[1] == 0xff) {
-	uint16_t be_size;
-	memcpy (&be_size, istream + 2, sizeof (uint16_t));
-	s = be16toh(be_size);
-	o += 3;
-    } else {
-	s = istream[1];
-	o += 1;
-    }
+    tlv_record_length (istream, &fls, &fvs);
+
     if (size) {
-	*size = s;
+	*size = fvs;
     }
 
-    if ((res = malloc (s))) {
-	memcpy (res, istream + o, s);
+    if ((res = malloc (fvs))) {
+	memcpy (res, istream + 1 + fls, fvs);
     }
     return res;
 }
+
+/*
+ * Length of a TLV field
+ */
+size_t
+tlv_record_length (const uint8_t *stream, size_t *field_length_size, size_t *field_value_size)
+{
+    size_t fls = 0;
+    size_t fvs = 0;
+
+    switch (stream[0]) {
+	case 0x00:
+	case 0xfe:
+	    break;
+	case 0x01:
+	case 0x02:
+	case 0x03:
+	default: // FIXME Not supported.
+	    if (stream[1] == 0xff) {
+		uint16_t be_size;
+		memcpy (&be_size, stream + 2, sizeof (uint16_t));
+		fls = 3;
+		fvs = be16toh(be_size);
+	    } else {
+		fls = 1;
+		fvs = stream[1];
+	    }
+	    break;
+    }
+
+    if (field_length_size)
+	*field_length_size = fls;
+
+    if (field_value_size)
+	*field_value_size = fvs;
+
+    return 1 + fls + fvs;
+}
+
+/*
+ * Get a pointer to the next record in the provided TLV sequence.
+ *             | 0x03 | 0x02 | 0xbe | 0xef | 0x00 | 0x00 | 0xfe |
+ * First call  ---'                    |      |      |
+ * Second call ------------------------'      |      |
+ * Third call  -------------------------------'      |
+ * Fourth call --------------------------------------'
+ * Fifth call  NULL
+ */
+uint8_t *
+tlv_next (uint8_t *stream)
+{
+    uint8_t *res = NULL;
+    if (stream[0] != TLV_TERMINATOR)
+	res = stream + tlv_record_length (stream, NULL, NULL);
+
+    return res;
+}
+
+/*
+ * Full-length of all TLV fields.
+ */
+size_t
+tlv_sequence_length (uint8_t *stream)
+{
+    size_t res = 0;
+
+    do {
+	res += tlv_record_length (stream, NULL, NULL);
+    } while ((stream = tlv_next (stream)));
+
+    return res;
+}
+
+
+/*
+ * Append two TLV.  Acts like realloc(3).
+ */
+uint8_t *
+tlv_append (uint8_t *a, uint8_t *b)
+{
+    size_t a_size = tlv_sequence_length (a);
+    size_t b_size = tlv_sequence_length (b);
+    size_t new_size = a_size + b_size - 1;
+
+    if ((a = realloc (a, new_size))) {
+	memcpy (a + a_size - 1, b, b_size);
+    }
+
+    return a;
+}

test/test_tlv.c

@@ -130,3 +130,20 @@ test_tlv_rfu (void)
 
     free (data);
 }
+
+void
+test_tlv_append (void)
+{
+    const uint8_t a[] = { 0xde, 0xad, 0xbe, 0xef };
+    const uint8_t b[] = { 0x42 };
+
+    uint8_t ndef_ab_ref[] = { 0x03, 0x04, 0xde, 0xad, 0xbe, 0xef, 0x03, 0x01, 0x42, 0xfe };
+
+    uint8_t *ndef_a = tlv_encode (3, a, 4, NULL);
+    uint8_t *ndef_b = tlv_encode (3, b, 1, NULL);
+    ndef_a = tlv_append (ndef_a, ndef_b);
+    cut_assert_equal_memory (ndef_ab_ref, sizeof (ndef_ab_ref), ndef_a, sizeof (ndef_ab_ref), cut_message ("Wrong appended data"));
+
+    free (ndef_a);
+    free (ndef_b);
+}