/* mpn_set_str (mp_ptr res_ptr, const char *str, size_t str_len, int base) --

   Convert a STR_LEN long base BASE byte string pointed to by STR to a limb

   vector pointed to by RES_PTR.  Return the number of limbs in RES_PTR.

   Contributed to the GNU project by Torbjorn Granlund.

   THE FUNCTIONS IN THIS FILE, EXCEPT mpn_set_str, ARE INTERNAL WITH MUTABLE

   INTERFACES.  IT IS ONLY SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES.

   IN FACT, IT IS ALMOST GUARANTEED THAT THEY WILL CHANGE OR DISAPPEAR IN A

   FUTURE GNU MP RELEASE.

Copyright 1991-2017 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/.  */

/* TODO:

      Perhaps do not compute the highest power?

      Instead, multiply twice by the 2nd highest power:

         _______

        |_______|  hp

        |_______|  pow

       _______________

      |_______________|  final result

         _______

        |_______|  hp

      |___|  pow[-1]

     ___________

    |___________|  intermediate result

      |___|  pow[-1]

       _______________

      |_______________|  final result

      Generalizing that idea, perhaps we should make powtab contain successive

      cubes, not squares.

*/

#include "gmp-impl.h"

mp_size_t

mpn_set_str (mp_ptr rp, const unsigned char *str, size_t str_len, int base)

{

  if (POW2_P (base))

    {

      /* The base is a power of 2.  Read the input string from least to most

   significant character/digit.  */

      const unsigned char *s;

      int next_bitpos;

      mp_limb_t res_digit;

      mp_size_t size;

      int bits_per_indigit = mp_bases[base].big_base;

      size = 0;

      res_digit = 0;

      next_bitpos = 0;

      for (s = str + str_len - 1; s >= str; s--)

  {

    int inp_digit = *s;

    res_digit |= ((mp_limb_t) inp_digit << next_bitpos) & GMP_NUMB_MASK;

    next_bitpos += bits_per_indigit;

    if (next_bitpos >= GMP_NUMB_BITS)

      {

        rp[size++] = res_digit;

        next_bitpos -= GMP_NUMB_BITS;

        res_digit = inp_digit >> (bits_per_indigit - next_bitpos);

      }

  }

      if (res_digit != 0)

  rp[size++] = res_digit;

      return size;

    }

  if (BELOW_THRESHOLD (str_len, SET_STR_PRECOMPUTE_THRESHOLD))

    return mpn_bc_set_str (rp, str, str_len, base);

  else

    {

      mp_ptr powtab_mem, tp;

      powers_t powtab[GMP_LIMB_BITS];

      int chars_per_limb;

      mp_size_t size;

      mp_size_t un;

      TMP_DECL;

      TMP_MARK;

      chars_per_limb = mp_bases[base].chars_per_limb;

      un = str_len / chars_per_limb + 1; /* FIXME: scalar integer division */

      /* Allocate one large block for the powers of big_base.  */

      powtab_mem = TMP_BALLOC_LIMBS (mpn_str_powtab_alloc (un));

      size_t n_pows = mpn_compute_powtab (powtab, powtab_mem, un, base);

      powers_t *pt = powtab + n_pows;

      tp = TMP_BALLOC_LIMBS (mpn_dc_set_str_itch (un));

      size = mpn_dc_set_str (rp, str, str_len, pt, tp);

      TMP_FREE;

      return size;

    }

}

mp_size_t

mpn_dc_set_str (mp_ptr rp, const unsigned char *str, size_t str_len,

    const powers_t *powtab, mp_ptr tp)

{

  size_t len_lo, len_hi;

  mp_limb_t cy;

  mp_size_t ln, hn, n, sn;

  len_lo = powtab->digits_in_base;

  if (str_len <= len_lo)

    {

      if (BELOW_THRESHOLD (str_len, SET_STR_DC_THRESHOLD))

  return mpn_bc_set_str (rp, str, str_len, powtab->base);

      else

  return mpn_dc_set_str (rp, str, str_len, powtab - 1, tp);

    }

  len_hi = str_len - len_lo;

  ASSERT (len_lo >= len_hi);

  if (BELOW_THRESHOLD (len_hi, SET_STR_DC_THRESHOLD))

    hn = mpn_bc_set_str (tp, str, len_hi, powtab->base);

  else

    hn = mpn_dc_set_str (tp, str, len_hi, powtab - 1, rp);

  sn = powtab->shift;

  if (hn == 0)

    {

      /* Zero +1 limb here, to avoid reading an allocated but uninitialised

   limb in mpn_incr_u below.  */

      MPN_ZERO (rp, powtab->n + sn + 1);

    }

  else

    {

      if (powtab->n > hn)

  mpn_mul (rp + sn, powtab->p, powtab->n, tp, hn);

      else

  mpn_mul (rp + sn, tp, hn, powtab->p, powtab->n);

      MPN_ZERO (rp, sn);

    }

  str = str + str_len - len_lo;

  if (BELOW_THRESHOLD (len_lo, SET_STR_DC_THRESHOLD))

    ln = mpn_bc_set_str (tp, str, len_lo, powtab->base);

  else

    ln = mpn_dc_set_str (tp, str, len_lo, powtab - 1, tp + powtab->n + sn + 1);

  if (ln != 0)

    {

      cy = mpn_add_n (rp, rp, tp, ln);

      mpn_incr_u (rp + ln, cy);

    }

  n = hn + powtab->n + sn;

  return n - (rp[n - 1] == 0);

}

mp_size_t

mpn_bc_set_str (mp_ptr rp, const unsigned char *str, size_t str_len, int base)

{

  mp_size_t size;

  size_t i;

  long j;

  mp_limb_t cy_limb;

  mp_limb_t big_base;

  int chars_per_limb;

  mp_limb_t res_digit;

  ASSERT (base >= 2);

  ASSERT (base < numberof (mp_bases));

  ASSERT (str_len >= 1);

  big_base = mp_bases[base].big_base;

  chars_per_limb = mp_bases[base].chars_per_limb;

  size = 0;

  for (i = chars_per_limb; i < str_len; i += chars_per_limb)

    {

      res_digit = *str++;

      if (base == 10)

  { /* This is a common case.

       Help the compiler to avoid multiplication.  */

    for (j = MP_BASES_CHARS_PER_LIMB_10 - 1; j != 0; j--)

      res_digit = res_digit * 10 + *str++;

  }

      else

  {

    for (j = chars_per_limb - 1; j != 0; j--)

      res_digit = res_digit * base + *str++;

  }

      if (size == 0)

  {

    if (res_digit != 0)

      {

        rp[0] = res_digit;

        size = 1;

      }

  }

      else

  {

#if HAVE_NATIVE_mpn_mul_1c

    cy_limb = mpn_mul_1c (rp, rp, size, big_base, res_digit);

#else

    cy_limb = mpn_mul_1 (rp, rp, size, big_base);

    cy_limb += mpn_add_1 (rp, rp, size, res_digit);

#endif

    if (cy_limb != 0)

      rp[size++] = cy_limb;

  }

    }

  big_base = base;

  res_digit = *str++;

  if (base == 10)

    { /* This is a common case.

   Help the compiler to avoid multiplication.  */

      for (j = str_len - (i - MP_BASES_CHARS_PER_LIMB_10) - 1; j > 0; j--)

  {

    res_digit = res_digit * 10 + *str++;

    big_base *= 10;

  }

    }

  else

    {

      for (j = str_len - (i - chars_per_limb) - 1; j > 0; j--)

  {

    res_digit = res_digit * base + *str++;

    big_base *= base;

  }

    }

  if (size == 0)

    {

      if (res_digit != 0)

  {

    rp[0] = res_digit;

    size = 1;

  }

    }

  else

    {

#if HAVE_NATIVE_mpn_mul_1c

      cy_limb = mpn_mul_1c (rp, rp, size, big_base, res_digit);

#else

      cy_limb = mpn_mul_1 (rp, rp, size, big_base);

      cy_limb += mpn_add_1 (rp, rp, size, res_digit);

#endif

      if (cy_limb != 0)

  rp[size++] = cy_limb;

    }

  return size;

}