ed448goldilocks/src/p448/arch_ref64/f_impl.h

/* Copyright (c) 2014-2016 Cryptography Research, Inc.
 * Released under the MIT License.  See LICENSE.txt for license information.
 */

#define FIELD_LITERAL(a,b,c,d,e,f,g,h) {{a,b,c,d,e,f,g,h}}

void gf_add_RAW (gf out, const gf a, const gf b) {
    for (unsigned int i=0; i<8; i++) {
        out->limb[i] = a->limb[i] + b->limb[i];
    }
    gf_weak_reduce(out);
}

void gf_sub_RAW (gf out, const gf a, const gf b) {
    uint64_t co1 = ((1ull<<56)-1)*2, co2 = co1-2;
    for (unsigned int i=0; i<8; i++) {
        out->limb[i] = a->limb[i] - b->limb[i] + ((i==4) ? co2 : co1);
    }
    gf_weak_reduce(out);
}

void gf_bias (gf a, int amt) {
    (void) a;
    (void) amt;
}

void gf_weak_reduce (gf a) {
    uint64_t mask = (1ull<<56) - 1;
    uint64_t tmp = a->limb[7] >> 56;
    a->limb[4] += tmp;
    for (unsigned int i=7; i>0; i--) {
        a->limb[i] = (a->limb[i] & mask) + (a->limb[i-1]>>56);
    }
    a->limb[0] = (a->limb[0] & mask) + tmp;
}