diff options
Diffstat (limited to 'libtommath/bn_mp_dr_reduce.c')
| -rw-r--r-- | libtommath/bn_mp_dr_reduce.c | 100 |
1 files changed, 48 insertions, 52 deletions
diff --git a/libtommath/bn_mp_dr_reduce.c b/libtommath/bn_mp_dr_reduce.c index c85ee77..77de433 100644 --- a/libtommath/bn_mp_dr_reduce.c +++ b/libtommath/bn_mp_dr_reduce.c @@ -1,4 +1,4 @@ -#include <tommath_private.h> +#include "tommath_private.h" #ifdef BN_MP_DR_REDUCE_C /* LibTomMath, multiple-precision integer library -- Tom St Denis * @@ -9,10 +9,7 @@ * Michael Fromberger but has been written from scratch with * additional optimizations in place. * - * The library is free for all purposes without any express - * guarantee it works. - * - * Tom St Denis, tstdenis82@gmail.com, http://libtom.org + * SPDX-License-Identifier: Unlicense */ /* reduce "x" in place modulo "n" using the Diminished Radix algorithm. @@ -29,68 +26,67 @@ * * Input x must be in the range 0 <= x <= (n-1)**2 */ -int -mp_dr_reduce (mp_int * x, mp_int * n, mp_digit k) +int mp_dr_reduce(mp_int *x, const mp_int *n, mp_digit k) { - int err, i, m; - mp_word r; - mp_digit mu, *tmpx1, *tmpx2; + int err, i, m; + mp_word r; + mp_digit mu, *tmpx1, *tmpx2; - /* m = digits in modulus */ - m = n->used; + /* m = digits in modulus */ + m = n->used; - /* ensure that "x" has at least 2m digits */ - if (x->alloc < (m + m)) { - if ((err = mp_grow (x, m + m)) != MP_OKAY) { - return err; - } - } + /* ensure that "x" has at least 2m digits */ + if (x->alloc < (m + m)) { + if ((err = mp_grow(x, m + m)) != MP_OKAY) { + return err; + } + } -/* top of loop, this is where the code resumes if - * another reduction pass is required. - */ + /* top of loop, this is where the code resumes if + * another reduction pass is required. + */ top: - /* aliases for digits */ - /* alias for lower half of x */ - tmpx1 = x->dp; + /* aliases for digits */ + /* alias for lower half of x */ + tmpx1 = x->dp; - /* alias for upper half of x, or x/B**m */ - tmpx2 = x->dp + m; + /* alias for upper half of x, or x/B**m */ + tmpx2 = x->dp + m; - /* set carry to zero */ - mu = 0; + /* set carry to zero */ + mu = 0; - /* compute (x mod B**m) + k * [x/B**m] inline and inplace */ - for (i = 0; i < m; i++) { - r = (((mp_word)*tmpx2++) * (mp_word)k) + *tmpx1 + mu; + /* compute (x mod B**m) + k * [x/B**m] inline and inplace */ + for (i = 0; i < m; i++) { + r = ((mp_word)*tmpx2++ * (mp_word)k) + *tmpx1 + mu; *tmpx1++ = (mp_digit)(r & MP_MASK); mu = (mp_digit)(r >> ((mp_word)DIGIT_BIT)); - } + } - /* set final carry */ - *tmpx1++ = mu; + /* set final carry */ + *tmpx1++ = mu; - /* zero words above m */ - for (i = m + 1; i < x->used; i++) { + /* zero words above m */ + for (i = m + 1; i < x->used; i++) { *tmpx1++ = 0; - } + } - /* clamp, sub and return */ - mp_clamp (x); + /* clamp, sub and return */ + mp_clamp(x); - /* if x >= n then subtract and reduce again - * Each successive "recursion" makes the input smaller and smaller. - */ - if (mp_cmp_mag (x, n) != MP_LT) { - if ((err = s_mp_sub(x, n, x)) != MP_OKAY) { - return err; - } - goto top; - } - return MP_OKAY; + /* if x >= n then subtract and reduce again + * Each successive "recursion" makes the input smaller and smaller. + */ + if (mp_cmp_mag(x, n) != MP_LT) { + if ((err = s_mp_sub(x, n, x)) != MP_OKAY) { + return err; + } + goto top; + } + return MP_OKAY; } #endif -/* ref: $Format:%D$ */ -/* git commit: $Format:%H$ */ -/* commit time: $Format:%ai$ */ +/* ref: HEAD -> master, tag: v1.1.0 */ +/* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */ +/* commit time: 2019-01-28 20:32:32 +0100 */ |