/* mpz_addmul_ui, mpz_submul_ui - add or subtract small multiple.

   THE mpz_aorsmul_1 FUNCTION IN THIS FILE IS FOR INTERNAL USE ONLY AND IS

   ALMOST CERTAIN TO BE SUBJECT TO INCOMPATIBLE CHANGES OR DISAPPEAR

   COMPLETELY IN FUTURE GNU MP RELEASES.

Copyright 2001, 2002, 2004, 2005, 2012, 2021, 2022 Free Software

Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify

it under the terms of either:

  * the GNU Lesser General Public License as published by the Free

    Software Foundation; either version 3 of the License, or (at your

    option) any later version.

or

  * the GNU General Public License as published by the Free Software

    Foundation; either version 2 of the License, or (at your option) any

    later version.

or both in parallel, as here.

The GNU MP Library is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

for more details.

You should have received copies of the GNU General Public License and the

GNU Lesser General Public License along with the GNU MP Library.  If not,

see https://www.gnu.org/licenses/.  */

#include "gmp-impl.h"

#if HAVE_NATIVE_mpn_mul_1c

#define MPN_MUL_1C(cout, dst, src, size, n, cin)        \

  do {                                                  \

    (cout) = mpn_mul_1c (dst, src, size, n, cin);       \

  } while (0)

#else

#define MPN_MUL_1C(cout, dst, src, size, n, cin)        \

  do {                                                  \

    mp_limb_t __cy;                                     \

    __cy = mpn_mul_1 (dst, src, size, n);               \

    (cout) = __cy + mpn_add_1 (dst, dst, size, cin);    \

  } while (0)

#endif

/* sub>=0 means an addmul w += x*y, sub<0 means a submul w -= x*y.

   All that's needed to account for negative w or x is to flip "sub".

   The final w will retain its sign, unless an underflow occurs in a submul

   of absolute values, in which case it's flipped.

   If x has more limbs than w, then mpn_submul_1 followed by mpn_com is

   used.  The alternative would be mpn_mul_1 into temporary space followed

   by mpn_sub_n.  Avoiding temporary space seem good, and submul+com stands

   a chance of being faster since it involves only one set of carry

   propagations, not two.  Note that doing an addmul_1 with a

   twos-complement negative y doesn't work, because it effectively adds an

   extra x * 2^GMP_LIMB_BITS.  */

REGPARM_ATTR(1) void

mpz_aorsmul_1 (mpz_ptr w, mpz_srcptr x, mp_limb_t y, mp_size_t sub)

{

  mp_size_t  xsize, wsize, wsize_signed, new_wsize, min_size, dsize;

  mp_srcptr  xp;

  mp_ptr     wp;

  mp_limb_t  cy;

  /* w unaffected if x==0 or y==0 */

  xsize = SIZ (x);

  if (xsize == 0 || y == 0)

    return;

  sub ^= xsize;

  xsize = ABS (xsize);

  wsize_signed = SIZ (w);

  if (wsize_signed == 0)

    {

      /* nothing to add to, just set x*y, "sub" gives the sign */

      wp = MPZ_NEWALLOC (w, xsize+1);

      cy = mpn_mul_1 (wp, PTR(x), xsize, y);

      wp[xsize] = cy;

      xsize += (cy != 0);

      SIZ (w) = (sub >= 0 ? xsize : -xsize);

      return;

    }

  sub ^= wsize_signed;

  wsize = ABS (wsize_signed);

  new_wsize = MAX (wsize, xsize);

  wp = MPZ_REALLOC (w, new_wsize+1);

  xp = PTR (x);

  min_size = MIN (wsize, xsize);

  if (sub >= 0)

    {

      /* addmul of absolute values */

      cy = mpn_addmul_1 (wp, xp, min_size, y);

      wp += min_size;

      xp += min_size;

      dsize = xsize - wsize;

#if HAVE_NATIVE_mpn_mul_1c

      if (dsize > 0)

  cy = mpn_mul_1c (wp, xp, dsize, y, cy);

      else if (dsize < 0)

  {

    dsize = -dsize;

    cy = mpn_add_1 (wp, wp, dsize, cy);

  }

#else

      if (dsize != 0)

  {

    mp_limb_t  cy2;

    if (dsize > 0)

      cy2 = mpn_mul_1 (wp, xp, dsize, y);

    else

      {

        dsize = -dsize;

        cy2 = 0;

      }

    cy = cy2 + mpn_add_1 (wp, wp, dsize, cy);

  }

#endif

      wp[dsize] = cy;

      new_wsize += (cy != 0);

    }

  else

    {

      /* submul of absolute values */

      cy = mpn_submul_1 (wp, xp, min_size, y);

      if (wsize >= xsize)

  {

    /* if w bigger than x, then propagate borrow through it */

    if (wsize != xsize)

      cy = mpn_sub_1 (wp+xsize, wp+xsize, wsize-xsize, cy);

    if (cy != 0)

      {

        /* Borrow out of w, take twos complement negative to get

     absolute value, flip sign of w.  */

        cy -= mpn_neg (wp, wp, new_wsize);

        wp[new_wsize] = cy;

        new_wsize += (cy != 0);

        wsize_signed = -wsize_signed;

      }

  }

      else /* wsize < xsize */

  {

    /* x bigger than w, so want x*y-w.  Submul has given w-x*y, so

       take twos complement and use an mpn_mul_1 for the rest.  */

    mp_limb_t  cy2;

    /* -(-cy*b^n + w-x*y) = (cy-1)*b^n + ~(w-x*y) + 1 */

    cy -= mpn_neg (wp, wp, wsize);

    /* If cy-1 == -1 then hold that -1 for latter.  mpn_submul_1 never

       returns cy==MP_LIMB_T_MAX so that value always indicates a -1. */

    cy2 = (cy == MP_LIMB_T_MAX);

    cy += cy2;

    MPN_MUL_1C (cy, wp+wsize, xp+wsize, xsize-wsize, y, cy);

    wp[new_wsize] = cy;

    new_wsize += (cy != 0);

    /* Apply any -1 from above.  The value at wp+wsize is non-zero

       because y!=0 and the high limb of x will be non-zero.  */

    if (cy2)

      MPN_DECR_U (wp+wsize, new_wsize-wsize, CNST_LIMB(1));

    wsize_signed = -wsize_signed;

  }

      /* submul can produce high zero limbs due to cancellation, both when w

   has more limbs or x has more  */

      MPN_NORMALIZE (wp, new_wsize);

    }

  SIZ (w) = (wsize_signed >= 0 ? new_wsize : -new_wsize);

  ASSERT (new_wsize == 0 || PTR(w)[new_wsize-1] != 0);

}

void

mpz_addmul_ui (mpz_ptr w, mpz_srcptr x, unsigned long y)

{

#if BITS_PER_ULONG > GMP_NUMB_BITS

  if (UNLIKELY (y > GMP_NUMB_MAX))

    {

      mpz_t t;

      mp_ptr tp;

      mp_size_t xn;

      TMP_DECL;

      TMP_MARK;

      xn = SIZ (x);

      if (xn == 0) return;

      MPZ_TMP_INIT (t, ABS (xn) + 1);

      tp = PTR (t);

      tp[0] = 0;

      MPN_COPY (tp + 1, PTR(x), ABS (xn));

      SIZ(t) = xn >= 0 ? xn + 1 : xn - 1;

      mpz_aorsmul_1 (w, t, (mp_limb_t) y >> GMP_NUMB_BITS, (mp_size_t) 0);

      PTR(t) = tp + 1;

      SIZ(t) = xn;

      mpz_aorsmul_1 (w, t, (mp_limb_t) y & GMP_NUMB_MASK, (mp_size_t) 0);

      TMP_FREE;

      return;

    }

#endif

  mpz_aorsmul_1 (w, x, (mp_limb_t) y, (mp_size_t) 0);

}

void

mpz_submul_ui (mpz_ptr w, mpz_srcptr x, unsigned long y)

{

#if BITS_PER_ULONG > GMP_NUMB_BITS

  if (y > GMP_NUMB_MAX)

    {

      mpz_t t;

      mp_ptr tp;

      mp_size_t xn;

      TMP_DECL;

      TMP_MARK;

      xn = SIZ (x);

      if (xn == 0) return;

      MPZ_TMP_INIT (t, ABS (xn) + 1);

      tp = PTR (t);

      tp[0] = 0;

      MPN_COPY (tp + 1, PTR(x), ABS (xn));

      SIZ(t) = xn >= 0 ? xn + 1 : xn - 1;

      mpz_aorsmul_1 (w, t, (mp_limb_t) y >> GMP_NUMB_BITS, (mp_size_t) -1);

      PTR(t) = tp + 1;

      SIZ(t) = xn;

      mpz_aorsmul_1 (w, t, (mp_limb_t) y & GMP_NUMB_MASK, (mp_size_t) -1);

      TMP_FREE;

      return;

    }

#endif

  mpz_aorsmul_1 (w, x, (mp_limb_t) y & GMP_NUMB_MASK, (mp_size_t) -1);

}