Don't bother passing through the mac_length, the caller already knows it since they supplied it

include/axolotl/list.hh

@@ -18,12 +18,12 @@ public:
     /**
      * Is the list empty?
      */
-    bool empty() { return _end == _data; }
+    bool empty() const { return _end == _data; }
 
     /**
      * The number of items in the list.
      */
-    std::size_t size() { return _end - _data; }
+    std::size_t size() const { return _end - _data; }
 
     T & operator[](std::size_t index) { return _data[index]; }
 

include/axolotl/message.hh

@@ -29,7 +29,6 @@ struct MessageReader {
     std::uint32_t counter;
     std::size_t ratchet_key_length;
     std::size_t ciphertext_length;
-    std::size_t mac_length;
     std::uint8_t const * ratchet_key;
     std::uint8_t const * ciphertext;
     std::uint8_t const * mac;

src/message.cpp

@@ -120,7 +120,6 @@ axolotl::MessageReader axolotl::decode_message(
     std::uint8_t const * end = input + input_length - mac_length;
     std::uint8_t flags = 0;
     result.mac = end;
-    result.mac_length = mac_length;
     if (pos == end) return result;
     result.version = *(pos++);
     while (pos != end) {

tests/test_message.cpp

@@ -20,7 +20,6 @@ assert_equals(std::uint8_t(3), reader.version);
 assert_equals(std::uint32_t(1), reader.counter);
 assert_equals(std::size_t(10), reader.ratchet_key_length);
 assert_equals(std::size_t(10), reader.ciphertext_length);
-assert_equals(std::size_t(8), reader.mac_length);
 
 assert_equals(ratchetkey, reader.ratchet_key, 10);
 assert_equals(ciphertext, reader.ciphertext, 10);
@@ -47,7 +46,6 @@ std::memcpy(writer.mac, hmacsha2, 8);
 
 assert_equals(message2, output, 35);
 
-
 } /* Message encode test */
 
 }