tree afc104f525fbb276ec18631e0b5f4dd777daa18f
parent ea96b3aed9c9d6d9ba51b360142d814ed3fe709e
author Gilles Peskine <Gilles.Peskine@arm.com> 1627475499 +0200
committer Gilles Peskine <Gilles.Peskine@arm.com> 1627475666 +0200

Base64 encoding: use ranges instead of tables

Instead of doing constant-flow table lookup, which requires 64 memory loads
for each lookup into a 64-entry table, do a range-based calculation, which
requires more CPU instructions per range but there are only 5 ranges.

I expect a significant performance gain (although smaller than for decoding
since the encoding table is half the size), but I haven't measured. Code
size is slightly smaller.

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