tree 5534806d7ec75aafec9bd1ee2ff2e5b1e910226a
parent a4f7cc206f83223aca395c16cfd85dfbd546dbe4
author David Benjamin <davidben@google.com> 1495047751 -0400
committer Adam Langley <agl@google.com> 1495062707 +0000

Optimize constant-time base64 implementation slightly.

Rather than comparing against both endpoints, subtract the minimum and
rely on unsigned wraparound to do both comparisons at once. This seems
to be slightly faster.

In addition, constant_time_lt_8 becomes much simpler if it can assume
that |a| and |b| have the same MSB. But we can arrange that by casting
up to |crypto_word_t| (which is otherwise happening anyway).

Change-Id: I82bd676e487eb7bb079ba7286df724c1c380bbb4
Reviewed-on: https://boringssl-review.googlesource.com/16445
Reviewed-by: Adam Langley <agl@google.com>