tree bb51b1761c10616d1fc41534eed1dd0df72e48de
parent 2e68a05c9943a8dec1758d4a393b2ae906fd3295
author David Benjamin <davidben@google.com> 1624417249 -0400
committer Adam Langley <agl@google.com> 1629138028 +0000

Add Span::first() and Span::last().

absl::Span, base::span, and std::span have first() and last() methods
which give prefixes and suffixes. first() just saves 5 characters, but
last() is nicer to write than subspan() for suffixes.

Unlike subspan(), they also do not have clipping behavior, so we're
guaranteed the length is correct. The clipping behavior comes from
absl::Span::subspan() and is not present in std::span or base::span.
I've left it in, in case we switch to absl::Span in the future, but I
imagine absl::Span will need to migrate this at some point.

Change-Id: I042dd6c566b6d753ec6de9d84e8c09ac7c270267
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/48905
Reviewed-by: Adam Langley <agl@google.com>