ref: a7a315bff61bff58a9c918294f53c1e87d7ae7bb
dir: /sys/src/libsec/port/chachablock.c/
#include "os.h"
#define ROTATE(v,c) ((u32int)((v) << (c)) | ((v) >> (32 - (c))))
#define QUARTERROUND(ia,ib,ic,id) { \
u32int a, b, c, d, t; \
a = x[ia]; b = x[ib]; c = x[ic]; d = x[id]; \
a += b; t = d^a; d = ROTATE(t,16); \
c += d; t = b^c; b = ROTATE(t,12); \
a += b; t = d^a; d = ROTATE(t, 8); \
c += d; t = b^c; b = ROTATE(t, 7); \
x[ia] = a; x[ib] = b; x[ic] = c; x[id] = d; \
}
void
_chachablock(u32int x[16], int rounds)
{
for(; rounds > 0; rounds -= 2) {
QUARTERROUND(0, 4, 8,12)
QUARTERROUND(1, 5, 9,13)
QUARTERROUND(2, 6,10,14)
QUARTERROUND(3, 7,11,15)
QUARTERROUND(0, 5,10,15)
QUARTERROUND(1, 6,11,12)
QUARTERROUND(2, 7, 8,13)
QUARTERROUND(3, 4, 9,14)
}
}