the string encoding functions touch secret key material
in a bunch of places (devtls, devcap), so make sure we do
not leak information by cache timing side channels, making
the encoding and decoding routines constant time.
we also expose the alphabets through encXchr()/decXchr()
functions so caller can find the end of a encoded string
before calling decode function (for libmp).
the base32 encoding was broken in several ways. inputs
lengths of len%5 == [2,3,4] had output truncated and
it was using non-standard alphabet. documenting the alphabet
change in the manpage.
the QLp structure used to occupy 24 bytes on amd64.
with some rearranging the fields we can get it to 16 bytes,
saving 8K in the data section for the 1024 preallocated
structs in the ql arena.
the rest of the changes are of cosmetic nature:
- getqlp() zeros the next pointer, so there is no need to set
it when queueing the entry.
- always explicitely compare pointers to nil.
- delete unused code from ape's qlock.c
semaphore locks have much higher overhead than initially presented
in the "Semaphores in Plan9" paper. until the reason for it has been
found out i will revert the changes.
