tree 6ce6bb698ef40beb8b99c3bfb21cef4d9805c7e4
parent fdd86bf1ae343ad46bbe7be9fc8b7e6bb3bc8958
author bnc <bnc@google.com> 1651601504 -0700
committer Copybara-Service <copybara-worker@google.com> 1651601552 -0700

Do not recalculate BalsaHeaders::iterator_base::value_ unless necessary.

Frequently there are back-to-back it->first and it->second calls.  By making
`value_` an absl::optional<> type, it is possible to avoid recalculating it on
every Lookup() call.

`value_` is initialized to absl::nullopt upon construction.  It is copied by the
implicit copy assignment operator and copy constructor, and will contain the
correct views into `*header_`.  It is now reset upon iterator increment.  There
should be no other ways to mutate the iterator.

PiperOrigin-RevId: 446239817