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