diff options
Diffstat (limited to 'external/nettle-3.3/nettle/bignum.c')
| -rw-r--r-- | external/nettle-3.3/nettle/bignum.c | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/external/nettle-3.3/nettle/bignum.c b/external/nettle-3.3/nettle/bignum.c new file mode 100644 index 0000000..b58726f --- /dev/null +++ b/external/nettle-3.3/nettle/bignum.c @@ -0,0 +1,186 @@ +/* bignum.c + + Bignum operations that are missing from gmp. + + Copyright (C) 2001 Niels Möller + + This file is part of GNU Nettle. + + GNU Nettle is free software: you can redistribute it and/or + modify it under the terms of either: + + * the GNU Lesser General Public License as published by the Free + Software Foundation; either version 3 of the License, or (at your + option) any later version. + + or + + * the GNU General Public License as published by the Free + Software Foundation; either version 3 of the License, or (at your + option) any later version. + + or both in parallel, as here. + + GNU Nettle 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 + General Public License for more details. + + You should have received copies of the GNU General Public License and + the GNU Lesser General Public License along with this program. If + not, see http://www.gnu.org/licenses/. +*/ + +#if HAVE_CONFIG_H +# include "config.h" +#endif + +#include <assert.h> +#include <string.h> + +#include "bignum.h" + +/* Two's complement negation means that -x = ~x + 1, ~x = -(x+1), + * and we use that x = ~~x = ~(-x-1). + * + * Examples: + * + * x ~x = -x+1 ~~x = x + * -1 0 ff + * -2 1 fe + * -7f 7e 81 + * -80 7f 80 + * -81 80 ff7f + */ + +/* Including extra sign bit, if needed. Also one byte for zero. */ +size_t +nettle_mpz_sizeinbase_256_s(const mpz_t x) +{ + if (mpz_sgn(x) >= 0) + return 1 + mpz_sizeinbase(x, 2) / 8; + else + { + /* We'll output ~~x, so we need as many bits as for ~x */ + size_t size; + mpz_t c; + + mpz_init(c); + mpz_com(c, x); /* Same as c = - x - 1 = |x| + 1 */ + size = 1 + mpz_sizeinbase(c,2) / 8; + mpz_clear(c); + + return size; + } +} + +size_t +nettle_mpz_sizeinbase_256_u(const mpz_t x) +{ + return (mpz_sizeinbase(x,2) + 7) / 8; +} + +static void +nettle_mpz_to_octets(size_t length, uint8_t *s, + const mpz_t x, uint8_t sign) +{ + uint8_t *dst = s + length - 1; + size_t size = mpz_size(x); + size_t i; + + for (i = 0; i<size; i++) + { + mp_limb_t limb = mpz_getlimbn(x, i); + size_t j; + + for (j = 0; length && j < sizeof(mp_limb_t); j++) + { + *dst-- = sign ^ (limb & 0xff); + limb >>= 8; + length--; + } + } + + if (length) + memset(s, sign, length); +} + +void +nettle_mpz_get_str_256(size_t length, uint8_t *s, const mpz_t x) +{ + if (!length) + { + /* x must be zero */ + assert(!mpz_sgn(x)); + return; + } + + if (mpz_sgn(x) >= 0) + { + assert(nettle_mpz_sizeinbase_256_u(x) <= length); + nettle_mpz_to_octets(length, s, x, 0); + } + else + { + mpz_t c; + mpz_init(c); + mpz_com(c, x); + + assert(nettle_mpz_sizeinbase_256_u(c) <= length); + nettle_mpz_to_octets(length, s, c, 0xff); + + mpz_clear(c); + } +} + +/* Converting from strings */ + +/* mpz_import was introduced in GMP-4.1 */ +#define nettle_mpz_from_octets(x, length, s) \ + mpz_import((x), (length), 1, 1, 0, 0, (s)) + +void +nettle_mpz_set_str_256_u(mpz_t x, + size_t length, const uint8_t *s) +{ + nettle_mpz_from_octets(x, length, s); +} + +void +nettle_mpz_init_set_str_256_u(mpz_t x, + size_t length, const uint8_t *s) +{ + mpz_init(x); + nettle_mpz_from_octets(x, length, s); +} + +void +nettle_mpz_set_str_256_s(mpz_t x, + size_t length, const uint8_t *s) +{ + if (!length) + { + mpz_set_ui(x, 0); + return; + } + + nettle_mpz_from_octets(x, length, s); + + if (s[0] & 0x80) + { + mpz_t t; + + mpz_init_set_ui(t, 1); + mpz_mul_2exp(t, t, length*8); + mpz_sub(x, x, t); + mpz_clear(t); + } +} + +void +nettle_mpz_init_set_str_256_s(mpz_t x, + size_t length, const uint8_t *s) +{ + mpz_init(x); + nettle_mpz_set_str_256_s(x, length, s); +} |