pbn_mulus_add.c


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/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2007 H. Peter Anvin - All Rights Reserved
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as
 *   published by the Free Software Foundation, Inc.,
 *   59 Temple Place Ste 330, Boston MA 02111-1307, USA; version 2.1,
 *   incorporated herein by reference.
 *
 * ----------------------------------------------------------------------- */

/*
 * pbn_mulus_add.c
 *
 * Multiply a PBN with a single limb unsigned number, and add a single
 * limb unsigned number.
 */

#include "pbnint.h"

struct pbn *pbn_mulus_add(struct pbn *s1, pbn_limb_t s2, pbn_limb_t c)
{
    size_t i, len;
    struct pbn *d;
    pbn_limb_t *s1p, *dp;
    pbn_2limb_t t;

    if (unlikely(s1->bits == 0)) {
        pbn_free(s1);
	return pbn_uint(c);
    }

    len = (s1->bits+PBN_LIMB_BITS-1) >> PBN_LIMB_SHIFT;

    d = pbn_new(len+1);
    d->minus = s1->minus;

    s1p = s1->num;
    dp  = d->num;
    for (i = 0; i < len; i++) {
	t = (pbn_2limb_t)*s1p++ * s2 + c;
        *dp++ = (pbn_limb_t)t;
        c = t >> PBN_LIMB_BITS;
    }
    *dp = c;

    pbn_free(s1);

    return pbn_adjust_bits(d);
}