ZeroTierOne/ext/ed25519-amd64-asm/sc25519_window4.c

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#include "sc25519.h"
void sc25519_window4(signed char r[64], const sc25519 *s)
{
char carry;
int i;
for(i=0;i<16;i++)
r[i] = (s->v[0] >> (4*i)) & 15;
for(i=0;i<16;i++)
r[i+16] = (s->v[1] >> (4*i)) & 15;
for(i=0;i<16;i++)
r[i+32] = (s->v[2] >> (4*i)) & 15;
for(i=0;i<16;i++)
r[i+48] = (s->v[3] >> (4*i)) & 15;
/* Making it signed */
carry = 0;
for(i=0;i<63;i++)
{
r[i] += carry;
r[i+1] += r[i] >> 4;
r[i] &= 15;
carry = r[i] >> 3;
r[i] -= carry << 4;
}
r[63] += carry;
}