-rw-r--r-- 1100 lib25519-20220726/crypto_sign/ed25519/amd64-maa4/sc25519_slide.c raw
#include "sc25519.h" void sc25519_slide(signed char r[256], const sc25519 *s, int swindowsize) { int i,j,k,b,m=(1<<(swindowsize-1))-1, soplen=256; unsigned long long sv0 = s->v[0]; unsigned long long sv1 = s->v[1]; unsigned long long sv2 = s->v[2]; unsigned long long sv3 = s->v[3]; /* first put the binary expansion into r */ for(i=0;i<64;i++) { r[i] = sv0 & 1; r[i+64] = sv1 & 1; r[i+128] = sv2 & 1; r[i+192] = sv3 & 1; sv0 >>= 1; sv1 >>= 1; sv2 >>= 1; sv3 >>= 1; } /* Making it sliding window */ for (j = 0;j < soplen;++j) { if (r[j]) { for (b = 1;b < soplen - j && b <= 6;++b) { if (r[j] + (r[j + b] << b) <= m) { r[j] += r[j + b] << b; r[j + b] = 0; } else if (r[j] - (r[j + b] << b) >= -m) { r[j] -= r[j + b] << b; for (k = j + b;k < soplen;++k) { if (!r[k]) { r[k] = 1; break; } r[k] = 0; } } else if (r[j + b]) break; } } } }