/*************************************************************************
* Copyright (C) 2010 Intel Corporation
*
* Licensed under the Apache License,  Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* 	http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law  or agreed  to  in  writing,  software
* distributed under  the License  is  distributed  on  an  "AS IS"  BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the  specific  language  governing  permissions  and
* limitations under the License.
*************************************************************************/

/*
//
//  Purpose:
//     Intel(R) Cryptography Primitives Library
//     Internal EC over GF(p^m) basic Definitions & Function Prototypes
//
//     Context:
//        gfec_MulPoint()
//
*/

#include "owndefs.h"
#include "owncp.h"
#include "gfpec/pcpgfpecstuff.h"
#include "gsscramble.h"
#include "pcpmask_ct.h"


/* clang-format off */
IPP_OWN_DEFN(void, gfec_point_mul, (BNU_CHUNK_T* pRdata,
                                    const BNU_CHUNK_T* pPdata,
                                    const Ipp8u* pScalar8,
                                    int scalarBitSize,
                                    IppsGFpECState* pEC,
                                    Ipp8u* pScratchBuffer))
/* clang-format on */
{
    int pointLen = ECP_POINTLEN(pEC);

    /* optimal size of window */
    const int window_size = 5;

    /* aligned pre-computed table */
    BNU_CHUNK_T* pTable = (BNU_CHUNK_T*)IPP_ALIGNED_PTR(pScratchBuffer, CACHE_LINE_SIZE);
    setupTable(pTable, pPdata, pEC);

    {
        IppsGFpState* pGF = ECP_GFP(pEC);
        gsModEngine* pGFE = GFP_PMA(pGF);
        int elemLen       = GFP_FELEN(pGFE);

        mod_neg negF = GFP_METHOD(pGFE)->neg;

        BNU_CHUNK_T* pHy = cpGFpGetPool(1, pGFE);

        BNU_CHUNK_T* pTdata = cpEcGFpGetPool(1, pEC); /* points from the pool */
        BNU_CHUNK_T* pHdata = cpEcGFpGetPool(1, pEC);

        int wvalue;
        Ipp8u digit, sign;
        int mask = (1 << (window_size + 1)) - 1;
        int bit  = scalarBitSize - (scalarBitSize % window_size);

        /* first window */
        if (bit) {
            wvalue = *((Ipp16u*)&pScalar8[(bit - 1) / 8]);
            wvalue = (wvalue >> ((bit - 1) % 8)) & mask;
        } else
            wvalue = 0;
        booth_recode(&sign, &digit, (Ipp8u)wvalue, window_size);
        gsScrambleGet_sscm(pTdata, pointLen, pTable, digit - 1, 5 - 1);

        for (bit -= window_size; bit >= window_size; bit -= window_size) {
            gfec_point_double(pTdata,
                              pTdata,
                              pEC); /* probably it's better to have separate calls */
            gfec_point_double(pTdata, pTdata, pEC); /* instead of gfec_point_double_k() */
            gfec_point_double(pTdata, pTdata, pEC);
            gfec_point_double(pTdata, pTdata, pEC);
            gfec_point_double(pTdata, pTdata, pEC);

            wvalue = *((Ipp16u*)&pScalar8[(bit - 1) / 8]);
            wvalue = (wvalue >> ((bit - 1) % 8)) & mask;
            booth_recode(&sign, &digit, (Ipp8u)wvalue, window_size);
            gsScrambleGet_sscm(pHdata, pointLen, pTable, digit - 1, 5 - 1);

            negF(pHy, pHdata + elemLen, pGFE);
            cpMaskedReplace_ct(pHdata + elemLen, pHy, elemLen, ~cpIsZero_ct(sign));
            gfec_point_add(pTdata, pTdata, pHdata, pEC);
        }

        /* last window */
        gfec_point_double(pTdata, pTdata, pEC);
        gfec_point_double(pTdata, pTdata, pEC);
        gfec_point_double(pTdata, pTdata, pEC);
        gfec_point_double(pTdata, pTdata, pEC);
        gfec_point_double(pTdata, pTdata, pEC);

        wvalue = *((Ipp16u*)&pScalar8[0]);
        wvalue = (wvalue << 1) & mask;
        booth_recode(&sign, &digit, (Ipp8u)wvalue, window_size);
        gsScrambleGet_sscm(pHdata, pointLen, pTable, digit - 1, 5 - 1);

        negF(pHy, pHdata + elemLen, pGFE);
        cpMaskedReplace_ct(pHdata + elemLen, pHy, elemLen, ~cpIsZero_ct(sign));
        gfec_point_add(pTdata, pTdata, pHdata, pEC);

        cpGFpElementCopy(pRdata, pTdata, pointLen);

        cpEcGFpReleasePool(2, pEC);
        cpGFpReleasePool(1, pGFE);
    }
}
