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Annotation of OpenXM_contrib/gmp/mpn/generic/set_str.c, Revision 1.1.1.2

1.1       maekawa     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
                      3:    limb vector pointed to by RES_PTR.  Return the number of limbs in
                      4:    RES_PTR.
                      5:
1.1.1.2 ! maekawa     6: Copyright (C) 1991, 1992, 1993, 1994, 1996, 2000 Free Software Foundation,
        !             7: Inc.
1.1       maekawa     8:
                      9: This file is part of the GNU MP Library.
                     10:
                     11: The GNU MP Library is free software; you can redistribute it and/or modify
1.1.1.2 ! maekawa    12: it under the terms of the GNU Lesser General Public License as published by
        !            13: the Free Software Foundation; either version 2.1 of the License, or (at your
1.1       maekawa    14: option) any later version.
                     15:
                     16: The GNU MP Library is distributed in the hope that it will be useful, but
                     17: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
1.1.1.2 ! maekawa    18: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
1.1       maekawa    19: License for more details.
                     20:
1.1.1.2 ! maekawa    21: You should have received a copy of the GNU Lesser General Public License
1.1       maekawa    22: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     23: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     24: MA 02111-1307, USA. */
                     25:
                     26: #include "gmp.h"
                     27: #include "gmp-impl.h"
                     28:
                     29: mp_size_t
1.1.1.2 ! maekawa    30: #if __STDC__
        !            31: mpn_set_str (mp_ptr xp, const unsigned char *str, size_t str_len, int base)
        !            32: #else
1.1       maekawa    33: mpn_set_str (xp, str, str_len, base)
                     34:      mp_ptr xp;
                     35:      const unsigned char *str;
                     36:      size_t str_len;
                     37:      int base;
1.1.1.2 ! maekawa    38: #endif
1.1       maekawa    39: {
                     40:   mp_size_t size;
                     41:   mp_limb_t big_base;
                     42:   int indigits_per_limb;
                     43:   mp_limb_t res_digit;
                     44:
                     45:   big_base = __mp_bases[base].big_base;
                     46:   indigits_per_limb = __mp_bases[base].chars_per_limb;
                     47:
                     48: /*   size = str_len / indigits_per_limb + 1;  */
                     49:
                     50:   size = 0;
                     51:
                     52:   if ((base & (base - 1)) == 0)
                     53:     {
                     54:       /* The base is a power of 2.  Read the input string from
                     55:         least to most significant character/digit.  */
                     56:
                     57:       const unsigned char *s;
                     58:       int next_bitpos;
                     59:       int bits_per_indigit = big_base;
                     60:
                     61:       res_digit = 0;
                     62:       next_bitpos = 0;
                     63:
                     64:       for (s = str + str_len - 1; s >= str; s--)
                     65:        {
                     66:          int inp_digit = *s;
                     67:
                     68:          res_digit |= (mp_limb_t) inp_digit << next_bitpos;
                     69:          next_bitpos += bits_per_indigit;
                     70:          if (next_bitpos >= BITS_PER_MP_LIMB)
                     71:            {
                     72:              xp[size++] = res_digit;
                     73:              next_bitpos -= BITS_PER_MP_LIMB;
                     74:              res_digit = inp_digit >> (bits_per_indigit - next_bitpos);
                     75:            }
                     76:        }
                     77:
                     78:       if (res_digit != 0)
                     79:        xp[size++] = res_digit;
                     80:     }
                     81:   else
                     82:     {
                     83:       /* General case.  The base is not a power of 2.  */
                     84:
                     85:       size_t i;
                     86:       int j;
                     87:       mp_limb_t cy_limb;
                     88:
                     89:       for (i = indigits_per_limb; i < str_len; i += indigits_per_limb)
                     90:        {
                     91:          res_digit = *str++;
                     92:          if (base == 10)
                     93:            { /* This is a common case.
                     94:                 Help the compiler to avoid multiplication.  */
                     95:              for (j = 1; j < indigits_per_limb; j++)
                     96:                res_digit = res_digit * 10 + *str++;
                     97:            }
                     98:          else
                     99:            {
                    100:              for (j = 1; j < indigits_per_limb; j++)
                    101:                res_digit = res_digit * base + *str++;
                    102:            }
                    103:
                    104:          if (size == 0)
                    105:            {
                    106:              if (res_digit != 0)
                    107:                {
                    108:                  xp[0] = res_digit;
                    109:                  size = 1;
                    110:                }
                    111:            }
                    112:          else
                    113:            {
                    114:              cy_limb = mpn_mul_1 (xp, xp, size, big_base);
                    115:              cy_limb += mpn_add_1 (xp, xp, size, res_digit);
                    116:              if (cy_limb != 0)
                    117:                xp[size++] = cy_limb;
                    118:            }
                    119:        }
                    120:
                    121:       big_base = base;
                    122:       res_digit = *str++;
                    123:       if (base == 10)
                    124:        { /* This is a common case.
                    125:             Help the compiler to avoid multiplication.  */
                    126:          for (j = 1; j < str_len - (i - indigits_per_limb); j++)
                    127:            {
                    128:              res_digit = res_digit * 10 + *str++;
                    129:              big_base *= 10;
                    130:            }
                    131:        }
                    132:       else
                    133:        {
                    134:          for (j = 1; j < str_len - (i - indigits_per_limb); j++)
                    135:            {
                    136:              res_digit = res_digit * base + *str++;
                    137:              big_base *= base;
                    138:            }
                    139:        }
                    140:
                    141:       if (size == 0)
                    142:        {
                    143:          if (res_digit != 0)
                    144:            {
                    145:              xp[0] = res_digit;
                    146:              size = 1;
                    147:            }
                    148:        }
                    149:       else
                    150:        {
                    151:          cy_limb = mpn_mul_1 (xp, xp, size, big_base);
                    152:          cy_limb += mpn_add_1 (xp, xp, size, res_digit);
                    153:          if (cy_limb != 0)
                    154:            xp[size++] = cy_limb;
                    155:        }
                    156:     }
                    157:
                    158:   return size;
                    159: }