/*
 * Copyright 2017-2018 The OpenSSL Project Authors. All Rights Reserved.
 * Copyright 2014 Cryptography Research, Inc.
 *
 * Licensed under the OpenSSL license (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 *
 * Originally written by Mike Hamburg
 */

#include "field.h"

#if (defined(__OPTIMIZE__) && !defined(__OPTIMIZE_SIZE__) && !I_HATE_UNROLLED_LOOPS) \
     || defined(C448_FORCE_UNROLL)
# define REPEAT8(_x) _x _x _x _x _x _x _x _x
# define FOR_LIMB(_i,_start,_end,_x) do { _i=_start; REPEAT8( if (_i<_end) { _x; } _i++;) } while (0)
#else
# define FOR_LIMB(_i,_start,_end,_x) do { for (_i=_start; _i<_end; _i++) _x; } while (0)
#endif

void gf_mul(gf_s * RESTRICT cs, const gf as, const gf bs)
{
    const uint32_t *a = as->limb, *b = bs->limb;
    uint32_t *c = cs->limb;
    uint64_t accum0 = 0, accum1 = 0, accum2 = 0;
    uint32_t mask = (1 << 28) - 1;
    uint32_t aa[8], bb[8];
    int i, j;

    for (i = 0; i < 8; i++) {
        aa[i] = a[i] + a[i + 8];
        bb[i] = b[i] + b[i + 8];
    }

    FOR_LIMB(j, 0, 8, {
             accum2 = 0;
             FOR_LIMB(i, 0, j + 1, {
                      accum2 += widemul(a[j - i], b[i]);
                      accum1 += widemul(aa[j - i], bb[i]);
                      accum0 += widemul(a[8 + j - i], b[8 + i]);
                      }
             ); accum1 -= accum2; accum0 += accum2;
             accum2 = 0;
             FOR_LIMB(i, j + 1, 8, {
                      accum0 -=
                      widemul(a[8 + j - i], b[i]);
                      accum2 +=
                      widemul(aa[8 + j - i],
                              bb[i]);
                      accum1 += widemul(a[16 + j - i], b[8 + i]);
                      }
             );
             accum1 += accum2;
             accum0 += accum2;
             c[j] = ((uint32_t)(accum0)) & mask;
             c[j + 8] = ((uint32_t)(accum1)) & mask;
             accum0 >>= 28; accum1 >>= 28;
             });

    accum0 += accum1;
    accum0 += c[8];
    accum1 += c[0];
    c[8] = ((uint32_t)(accum0)) & mask;
    c[0] = ((uint32_t)(accum1)) & mask;

    accum0 >>= 28;
    accum1 >>= 28;
    c[9] += ((uint32_t)(accum0));
    c[1] += ((uint32_t)(accum1));
}

void gf_mulw_unsigned(gf_s * RESTRICT cs, const gf as, uint32_t b)
{
    const uint32_t *a = as->limb;
    uint32_t *c = cs->limb;
    uint64_t accum0 = 0, accum8 = 0;
    uint32_t mask = (1 << 28) - 1;
    int i;

    assert(b < 1 << 28);

    FOR_LIMB(i, 0, 8, {
             accum0 += widemul(b, a[i]); accum8 += widemul(b, a[i + 8]);
             c[i] = accum0 & mask; accum0 >>= 28;
             c[i + 8] = accum8 & mask; accum8 >>= 28;
             });

    accum0 += accum8 + c[8];
    c[8] = ((uint32_t)accum0) & mask;
    c[9] += (uint32_t)(accum0 >> 28);

    accum8 += c[0];
    c[0] = ((uint32_t)accum8) & mask;
    c[1] += (uint32_t)(accum8 >> 28);
}

void gf_sqr(gf_s * RESTRICT cs, const gf as)
{
    gf_mul(cs, as, as);         /* Performs better with a dedicated square */
}