source/libs/gmp/gmp-src/mpn/generic/set_str.c

   1 /* mpn_set_str (mp_ptr res_ptr, const char *str, size_t str_len, int base) --
   2    Convert a STR_LEN long base BASE byte string pointed to by STR to a limb
   3    vector pointed to by RES_PTR.  Return the number of limbs in RES_PTR.
   4
   5    Contributed to the GNU project by Torbjorn Granlund.
   6
   7    THE FUNCTIONS IN THIS FILE, EXCEPT mpn_set_str, ARE INTERNAL WITH A MUTABLE
   8    INTERFACE.  IT IS ONLY SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES.  IN
   9    FACT, IT IS ALMOST GUARANTEED THAT THEY WILL CHANGE OR DISAPPEAR IN A FUTURE
  10    GNU MP RELEASE.
  11
  12 Copyright 1991-1994, 1996, 2000-2002, 2004, 2006-2008, 2012, 2013 Free
  13 Software Foundation, Inc.
  14
  15 This file is part of the GNU MP Library.
  16
  17 The GNU MP Library is free software; you can redistribute it and/or modify
  18 it under the terms of either:
  19
  20   * the GNU Lesser General Public License as published by the Free
  21     Software Foundation; either version 3 of the License, or (at your
  22     option) any later version.
  23
  24 or
  25
  26   * the GNU General Public License as published by the Free Software
  27     Foundation; either version 2 of the License, or (at your option) any
  28     later version.
  29
  30 or both in parallel, as here.
  31
  32 The GNU MP Library is distributed in the hope that it will be useful, but
  33 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  34 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  35 for more details.
  36
  37 You should have received copies of the GNU General Public License and the
  38 GNU Lesser General Public License along with the GNU MP Library.  If not,
  39 see https://www.gnu.org/licenses/.  */
  40
  41
  42 /* TODO:
  43
  44       Perhaps do not compute the highest power?
  45       Instead, multiply twice by the 2nd highest power:
  46
  47                _______
  48               |_______|  hp
  49               |_______|  pow
  50        _______________
  51       |_______________|  final result
  52
  53
  54                _______
  55               |_______|  hp
  56                   |___|  pow[-1]
  57            ___________
  58           |___________|  intermediate result
  59                   |___|  pow[-1]
  60        _______________
  61       |_______________|  final result
  62
  63       Generalizing that idea, perhaps we should make powtab contain successive
  64       cubes, not squares.
  65 */
  66
  67 #include "gmp.h"
  68 #include "gmp-impl.h"
  69 #include "longlong.h"
  70
  71 mp_size_t
  72 mpn_set_str (mp_ptr rp, const unsigned char *str, size_t str_len, int base)
  73 {
  74   if (POW2_P (base))
  75     {
  76       /* The base is a power of 2.  Read the input string from least to most
  77          significant character/digit.  */
  78
  79       const unsigned char *s;
  80       int next_bitpos;
  81       mp_limb_t res_digit;
  82       mp_size_t size;
  83       int bits_per_indigit = mp_bases[base].big_base;
  84
  85       size = 0;
  86       res_digit = 0;
  87       next_bitpos = 0;
  88
  89       for (s = str + str_len - 1; s >= str; s--)
  90         {
  91           int inp_digit = *s;
  92
  93           res_digit |= ((mp_limb_t) inp_digit << next_bitpos) & GMP_NUMB_MASK;
  94           next_bitpos += bits_per_indigit;
  95           if (next_bitpos >= GMP_NUMB_BITS)
  96             {
  97               rp[size++] = res_digit;
  98               next_bitpos -= GMP_NUMB_BITS;
  99               res_digit = inp_digit >> (bits_per_indigit - next_bitpos);
 100             }
 101         }
 102
 103       if (res_digit != 0)
 104         rp[size++] = res_digit;
 105       return size;
 106     }
 107
 108   if (BELOW_THRESHOLD (str_len, SET_STR_PRECOMPUTE_THRESHOLD))
 109     return mpn_bc_set_str (rp, str, str_len, base);
 110   else
 111     {
 112       mp_ptr powtab_mem, tp;
 113       powers_t powtab[GMP_LIMB_BITS];
 114       int chars_per_limb;
 115       mp_size_t size;
 116       mp_size_t un;
 117       TMP_DECL;
 118
 119       TMP_MARK;
 120
 121       chars_per_limb = mp_bases[base].chars_per_limb;
 122
 123       un = str_len / chars_per_limb + 1;
 124
 125       /* Allocate one large block for the powers of big_base.  */
 126       powtab_mem = TMP_BALLOC_LIMBS (mpn_dc_set_str_powtab_alloc (un));
 127
 128       mpn_set_str_compute_powtab (powtab, powtab_mem, un, base);
 129
 130       tp = TMP_BALLOC_LIMBS (mpn_dc_set_str_itch (un));
 131       size = mpn_dc_set_str (rp, str, str_len, powtab, tp);
 132
 133       TMP_FREE;
 134       return size;
 135     }
 136 }
 137
 138 void
 139 mpn_set_str_compute_powtab (powers_t *powtab, mp_ptr powtab_mem, mp_size_t un, int base)
 140 {
 141   mp_ptr powtab_mem_ptr;
 142   long i, pi;
 143   mp_size_t n;
 144   mp_ptr p, t;
 145   mp_limb_t big_base;
 146   int chars_per_limb;
 147   size_t digits_in_base;
 148   mp_size_t shift;
 149
 150   powtab_mem_ptr = powtab_mem;
 151
 152   chars_per_limb = mp_bases[base].chars_per_limb;
 153   big_base = mp_bases[base].big_base;
 154
 155   p = powtab_mem_ptr;
 156   powtab_mem_ptr += 1;
 157
 158   digits_in_base = chars_per_limb;
 159
 160   p[0] = big_base;
 161   n = 1;
 162
 163   count_leading_zeros (i, un - 1);
 164   i = GMP_LIMB_BITS - 1 - i;
 165
 166   powtab[i].p = p;
 167   powtab[i].n = n;
 168   powtab[i].digits_in_base = digits_in_base;
 169   powtab[i].base = base;
 170   powtab[i].shift = 0;
 171
 172   shift = 0;
 173   for (pi = i - 1; pi >= 0; pi--)
 174     {
 175       t = powtab_mem_ptr;
 176       powtab_mem_ptr += 2 * n;
 177
 178       ASSERT_ALWAYS (powtab_mem_ptr < powtab_mem + mpn_dc_set_str_powtab_alloc (un));
 179
 180       mpn_sqr (t, p, n);
 181       n = 2 * n - 1; n += t[n] != 0;
 182       digits_in_base *= 2;
 183 #if 1
 184       if ((((un - 1) >> pi) & 2) == 0)
 185         {
 186           mpn_divexact_1 (t, t, n, big_base);
 187           n -= t[n - 1] == 0;
 188           digits_in_base -= chars_per_limb;
 189         }
 190 #else
 191       if (CLEVER_CONDITION_1 ())
 192         {
 193           /* perform adjustment operation of previous */
 194           cy = mpn_mul_1 (p, p, n, big_base);
 195         }
 196       if (CLEVER_CONDITION_2 ())
 197         {
 198           /* perform adjustment operation of new */
 199           cy = mpn_mul_1 (t, t, n, big_base);
 200         }
 201 #endif
 202       shift *= 2;
 203       /* Strip low zero limbs, but be careful to keep the result divisible by
 204          big_base.  */
 205       while (t[0] == 0 && (t[1] & ((big_base & -big_base) - 1)) == 0)
 206         {
 207           t++;
 208           n--;
 209           shift++;
 210         }
 211       p = t;
 212       powtab[pi].p = p;
 213       powtab[pi].n = n;
 214       powtab[pi].digits_in_base = digits_in_base;
 215       powtab[pi].base = base;
 216       powtab[pi].shift = shift;
 217     }
 218 }
 219
 220 mp_size_t
 221 mpn_dc_set_str (mp_ptr rp, const unsigned char *str, size_t str_len,
 222                 const powers_t *powtab, mp_ptr tp)
 223 {
 224   size_t len_lo, len_hi;
 225   mp_limb_t cy;
 226   mp_size_t ln, hn, n, sn;
 227
 228   len_lo = powtab->digits_in_base;
 229
 230   if (str_len <= len_lo)
 231     {
 232       if (BELOW_THRESHOLD (str_len, SET_STR_DC_THRESHOLD))
 233         return mpn_bc_set_str (rp, str, str_len, powtab->base);
 234       else
 235         return mpn_dc_set_str (rp, str, str_len, powtab + 1, tp);
 236     }
 237
 238   len_hi = str_len - len_lo;
 239   ASSERT (len_lo >= len_hi);
 240
 241   if (BELOW_THRESHOLD (len_hi, SET_STR_DC_THRESHOLD))
 242     hn = mpn_bc_set_str (tp, str, len_hi, powtab->base);
 243   else
 244     hn = mpn_dc_set_str (tp, str, len_hi, powtab + 1, rp);
 245
 246   sn = powtab->shift;
 247
 248   if (hn == 0)
 249     {
 250       /* Zero +1 limb here, to avoid reading an allocated but uninitialised
 251          limb in mpn_incr_u below.  */
 252       MPN_ZERO (rp, powtab->n + sn + 1);
 253     }
 254   else
 255     {
 256       if (powtab->n > hn)
 257         mpn_mul (rp + sn, powtab->p, powtab->n, tp, hn);
 258       else
 259         mpn_mul (rp + sn, tp, hn, powtab->p, powtab->n);
 260       MPN_ZERO (rp, sn);
 261     }
 262
 263   str = str + str_len - len_lo;
 264   if (BELOW_THRESHOLD (len_lo, SET_STR_DC_THRESHOLD))
 265     ln = mpn_bc_set_str (tp, str, len_lo, powtab->base);
 266   else
 267     ln = mpn_dc_set_str (tp, str, len_lo, powtab + 1, tp + powtab->n + sn + 1);
 268
 269   if (ln != 0)
 270     {
 271       cy = mpn_add_n (rp, rp, tp, ln);
 272       mpn_incr_u (rp + ln, cy);
 273     }
 274   n = hn + powtab->n + sn;
 275   return n - (rp[n - 1] == 0);
 276 }
 277
 278 mp_size_t
 279 mpn_bc_set_str (mp_ptr rp, const unsigned char *str, size_t str_len, int base)
 280 {
 281   mp_size_t size;
 282   size_t i;
 283   long j;
 284   mp_limb_t cy_limb;
 285
 286   mp_limb_t big_base;
 287   int chars_per_limb;
 288   mp_limb_t res_digit;
 289
 290   ASSERT (base >= 2);
 291   ASSERT (base < numberof (mp_bases));
 292   ASSERT (str_len >= 1);
 293
 294   big_base = mp_bases[base].big_base;
 295   chars_per_limb = mp_bases[base].chars_per_limb;
 296
 297   size = 0;
 298   for (i = chars_per_limb; i < str_len; i += chars_per_limb)
 299     {
 300       res_digit = *str++;
 301       if (base == 10)
 302         { /* This is a common case.
 303              Help the compiler to avoid multiplication.  */
 304           for (j = MP_BASES_CHARS_PER_LIMB_10 - 1; j != 0; j--)
 305             res_digit = res_digit * 10 + *str++;
 306         }
 307       else
 308         {
 309           for (j = chars_per_limb - 1; j != 0; j--)
 310             res_digit = res_digit * base + *str++;
 311         }
 312
 313       if (size == 0)
 314         {
 315           if (res_digit != 0)
 316             {
 317               rp[0] = res_digit;
 318               size = 1;
 319             }
 320         }
 321       else
 322         {
 323 #if HAVE_NATIVE_mpn_mul_1c
 324           cy_limb = mpn_mul_1c (rp, rp, size, big_base, res_digit);
 325 #else
 326           cy_limb = mpn_mul_1 (rp, rp, size, big_base);
 327           cy_limb += mpn_add_1 (rp, rp, size, res_digit);
 328 #endif
 329           if (cy_limb != 0)
 330             rp[size++] = cy_limb;
 331         }
 332     }
 333
 334   big_base = base;
 335   res_digit = *str++;
 336   if (base == 10)
 337     { /* This is a common case.
 338          Help the compiler to avoid multiplication.  */
 339       for (j = str_len - (i - MP_BASES_CHARS_PER_LIMB_10) - 1; j > 0; j--)
 340         {
 341           res_digit = res_digit * 10 + *str++;
 342           big_base *= 10;
 343         }
 344     }
 345   else
 346     {
 347       for (j = str_len - (i - chars_per_limb) - 1; j > 0; j--)
 348         {
 349           res_digit = res_digit * base + *str++;
 350           big_base *= base;
 351         }
 352     }
 353
 354   if (size == 0)
 355     {
 356       if (res_digit != 0)
 357         {
 358           rp[0] = res_digit;
 359           size = 1;
 360         }
 361     }
 362   else
 363     {
 364 #if HAVE_NATIVE_mpn_mul_1c
 365       cy_limb = mpn_mul_1c (rp, rp, size, big_base, res_digit);
 366 #else
 367       cy_limb = mpn_mul_1 (rp, rp, size, big_base);
 368       cy_limb += mpn_add_1 (rp, rp, size, res_digit);
 369 #endif
 370       if (cy_limb != 0)
 371         rp[size++] = cy_limb;
 372     }
 373   return size;
 374 }