aa9bc17601
BMakefiles and other bits will follow. Requested by: Andrey Chernov Made world by: Chuck Robey
155 lines
3.7 KiB
C
155 lines
3.7 KiB
C
/* mpn_set_str (mp_ptr res_ptr, const char *str, size_t str_len, int base)
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-- Convert a STR_LEN long base BASE byte string pointed to by STR to a
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limb vector pointed to by RES_PTR. Return the number of limbs in
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RES_PTR.
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Copyright (C) 1991, 1992, 1993, 1994, 1996 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Library General Public License as published by
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the Free Software Foundation; either version 2 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
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License for more details.
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You should have received a copy of the GNU Library General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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mp_size_t
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mpn_set_str (xp, str, str_len, base)
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mp_ptr xp;
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const unsigned char *str;
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size_t str_len;
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int base;
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{
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mp_size_t size;
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mp_limb_t big_base;
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int indigits_per_limb;
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mp_limb_t res_digit;
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big_base = __mp_bases[base].big_base;
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indigits_per_limb = __mp_bases[base].chars_per_limb;
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/* size = str_len / indigits_per_limb + 1; */
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size = 0;
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if ((base & (base - 1)) == 0)
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{
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/* The base is a power of 2. Read the input string from
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least to most significant character/digit. */
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const unsigned char *s;
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int next_bitpos;
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int bits_per_indigit = big_base;
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res_digit = 0;
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next_bitpos = 0;
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for (s = str + str_len - 1; s >= str; s--)
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{
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int inp_digit = *s;
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res_digit |= (mp_limb_t) inp_digit << next_bitpos;
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next_bitpos += bits_per_indigit;
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if (next_bitpos >= BITS_PER_MP_LIMB)
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{
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xp[size++] = res_digit;
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next_bitpos -= BITS_PER_MP_LIMB;
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res_digit = inp_digit >> (bits_per_indigit - next_bitpos);
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}
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}
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if (res_digit != 0)
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xp[size++] = res_digit;
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}
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else
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{
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/* General case. The base is not a power of 2. */
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size_t i;
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int j;
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mp_limb_t cy_limb;
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for (i = indigits_per_limb; i < str_len; i += indigits_per_limb)
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{
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res_digit = *str++;
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if (base == 10)
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{ /* This is a common case.
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Help the compiler to avoid multiplication. */
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for (j = 1; j < indigits_per_limb; j++)
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res_digit = res_digit * 10 + *str++;
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}
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else
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{
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for (j = 1; j < indigits_per_limb; j++)
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res_digit = res_digit * base + *str++;
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}
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if (size == 0)
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{
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if (res_digit != 0)
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{
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xp[0] = res_digit;
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size = 1;
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}
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}
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else
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{
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cy_limb = mpn_mul_1 (xp, xp, size, big_base);
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cy_limb += mpn_add_1 (xp, xp, size, res_digit);
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if (cy_limb != 0)
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xp[size++] = cy_limb;
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}
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}
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big_base = base;
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res_digit = *str++;
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if (base == 10)
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{ /* This is a common case.
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Help the compiler to avoid multiplication. */
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for (j = 1; j < str_len - (i - indigits_per_limb); j++)
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{
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res_digit = res_digit * 10 + *str++;
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big_base *= 10;
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}
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}
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else
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{
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for (j = 1; j < str_len - (i - indigits_per_limb); j++)
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{
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res_digit = res_digit * base + *str++;
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big_base *= base;
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}
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}
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if (size == 0)
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{
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if (res_digit != 0)
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{
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xp[0] = res_digit;
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size = 1;
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}
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}
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else
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{
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cy_limb = mpn_mul_1 (xp, xp, size, big_base);
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cy_limb += mpn_add_1 (xp, xp, size, res_digit);
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if (cy_limb != 0)
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xp[size++] = cy_limb;
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}
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}
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return size;
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}
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