diff options
Diffstat (limited to 'mpn/generic/set_str.c')
| -rw-r--r-- | mpn/generic/set_str.c | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/mpn/generic/set_str.c b/mpn/generic/set_str.c new file mode 100644 index 000000000..154b4b096 --- /dev/null +++ b/mpn/generic/set_str.c @@ -0,0 +1,154 @@ +/* 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; +} |