tree 2cd94b2ecec4f144ae2659aec0f4bac5f5971861
parent 6b541a026b98060a253be2f697146b8d1432ffa9
author Gilles Peskine <Gilles.Peskine@arm.com> 1627473242 +0200
committer Gilles Peskine <Gilles.Peskine@arm.com> 1635189428 +0200

Base64 decoding: use ranges instead of tables

Instead of doing constant-flow table lookup, which requires 128 memory loads
for each lookup into a 128-entry table, do a range-based calculation, which
requires more CPU instructions per range but there are only 5 ranges.

Experimentally, this is ~12x faster on my PC (based on
programs/x509/load_roots). The code is slightly smaller, too.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>