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Annotation of OpenXM_contrib/gmp/mpn/generic/set_str.c, Revision 1.1.1.1

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

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