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construct_str.c

解説を見る。

#include "multiprec.h"
#include <string.h>
#include <math.h>


inline void
ymp_assign_string(mp_ref_t self, 
                  const char *psz, char **endptr, unsigned radix)
{
  if (radix > 36)
    ymp_error("文字列からの変換の基数が大きすぎる: %u", radix);

  switch (*psz)
    {
    case '-':
      ++psz;
      self->sign = negative_sign;
      break;
    case '+':
      ++psz; /* no break */
    default:
      self->sign = positive_sign;
    }

  if (radix == 0)
    {
      if (*psz != '0') radix = 10;
      else switch (*++psz)
        {
        case 'B': case 'b': radix = 2; ++psz; break;
        case 'Q': case 'q': radix = 4; ++psz; break;
        case 'O': case 'o': radix = 8; ++psz; break;
        case 'D': case 'd': radix = 10; ++psz; break;
        case 'X': case 'x': radix = 16; ++psz; break;
        default: radix = 8; break;
        }
    }

  ymp_reserve(self, ceil(strlen(psz)*(log(radix)/log(MULTIPREC_RADIX)))+1);

  self->used = 0; self->digits[0] = 0;
  for ( ; *psz; ++psz)
    {
      digit_t c;
      switch (*psz)
        {
        case '0': c = 0; break; case '1': c = 1; break;
        case '2': c = 2; break; case '3': c = 3; break;
        case '4': c = 4; break; case '5': c = 5; break;
        case '6': c = 6; break; case '7': c = 7; break;
        case '8': c = 8; break; case '9': c = 9; break;
        case 'A': case 'a': c = 10; break;
        case 'B': case 'b': c = 11; break;
        case 'C': case 'c': c = 12; break;
        case 'D': case 'd': c = 13; break;
        case 'E': case 'e': c = 14; break;
        case 'F': case 'f': c = 15; break;
        case 'G': case 'g': c = 16; break;
        case 'H': case 'h': c = 17; break;
        case 'I': case 'i': c = 18; break;
        case 'J': case 'j': c = 19; break;
        case 'K': case 'k': c = 20; break;
        case 'L': case 'l': c = 21; break;
        case 'M': case 'm': c = 22; break;
        case 'N': case 'n': c = 23; break;
        case 'O': case 'o': c = 24; break;
        case 'P': case 'p': c = 25; break;
        case 'Q': case 'q': c = 26; break;
        case 'R': case 'r': c = 27; break;
        case 'S': case 's': c = 28; break;
        case 'T': case 't': c = 29; break;
        case 'U': case 'u': c = 30; break;
        case 'V': case 'v': c = 31; break;
        case 'W': case 'w': c = 32; break;
        case 'X': case 'x': c = 33; break;
        case 'Y': case 'y': c = 34; break;
        case 'Z': case 'z': c = 35; break;

        case '_': continue;
        default: c = 127;
        }
      if (c >= radix) break;

      ymp_reserve(self, self->used+1);
      self->used
        = ymp_mulabs_digit(self->digits, self->digits, radix, self->used);
      self->used
        = ymp_addabs(self->digits, self->digits, &c, self->used, 1);
    }
  
  if (endptr) *endptr = (char*)psz;
}

void
ymp_initialize_by_string(mp_ref_t self, 
                         const char *psz, char **endptr, unsigned radix)
{
  ymp_initialize(self);
  ymp_assign_string(self, psz, endptr, radix);
}

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