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/* mpn_set_str (mp_ptr res_ptr, const char *str, size_t str_len, int base)
-- Convert a STR_LEN long base BASE byte string pointed to by STR to a
limb vector pointed to by RES_PTR. Return the number of limbs in
RES_PTR.
Copyright (C) 1991, 1992, 1993, 1994, 1996 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
License for more details.
You should have received a copy of the GNU Library General Public License
along with the GNU MP Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include "gmp.h"
#include "gmp-impl.h"
mp_size_t
mpn_set_str (xp, str, str_len, base)
mp_ptr xp;
const unsigned char *str;
size_t str_len;
int base;
{
mp_size_t size;
mp_limb_t big_base;
int indigits_per_limb;
mp_limb_t res_digit;
big_base = __mp_bases[base].big_base;
indigits_per_limb = __mp_bases[base].chars_per_limb;
/* size = str_len / indigits_per_limb + 1; */
size = 0;
if ((base & (base - 1)) == 0)
{
/* The base is a power of 2. Read the input string from
least to most significant character/digit. */
const unsigned char *s;
int next_bitpos;
int bits_per_indigit = big_base;
res_digit = 0;
next_bitpos = 0;
for (s = str + str_len - 1; s >= str; s--)
{
int inp_digit = *s;
res_digit |= (mp_limb_t) inp_digit << next_bitpos;
next_bitpos += bits_per_indigit;
if (next_bitpos >= BITS_PER_MP_LIMB)
{
xp[size++] = res_digit;
next_bitpos -= BITS_PER_MP_LIMB;
res_digit = inp_digit >> (bits_per_indigit - next_bitpos);
}
}
if (res_digit != 0)
xp[size++] = res_digit;
}
else
{
/* General case. The base is not a power of 2. */
size_t i;
int j;
mp_limb_t cy_limb;
for (i = indigits_per_limb; i < str_len; i += indigits_per_limb)
{
res_digit = *str++;
if (base == 10)
{ /* This is a common case.
Help the compiler to avoid multiplication. */
for (j = 1; j < indigits_per_limb; j++)
res_digit = res_digit * 10 + *str++;
}
else
{
for (j = 1; j < indigits_per_limb; j++)
res_digit = res_digit * base + *str++;
}
if (size == 0)
{
if (res_digit != 0)
{
xp[0] = res_digit;
size = 1;
}
}
else
{
cy_limb = mpn_mul_1 (xp, xp, size, big_base);
cy_limb += mpn_add_1 (xp, xp, size, res_digit);
if (cy_limb != 0)
xp[size++] = cy_limb;
}
}
big_base = base;
res_digit = *str++;
if (base == 10)
{ /* This is a common case.
Help the compiler to avoid multiplication. */
for (j = 1; j < str_len - (i - indigits_per_limb); j++)
{
res_digit = res_digit * 10 + *str++;
big_base *= 10;
}
}
else
{
for (j = 1; j < str_len - (i - indigits_per_limb); j++)
{
res_digit = res_digit * base + *str++;
big_base *= base;
}
}
if (size == 0)
{
if (res_digit != 0)
{
xp[0] = res_digit;
size = 1;
}
}
else
{
cy_limb = mpn_mul_1 (xp, xp, size, big_base);
cy_limb += mpn_add_1 (xp, xp, size, res_digit);
if (cy_limb != 0)
xp[size++] = cy_limb;
}
}
return size;
}
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