## File: bn_mp_mul_2d.c

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libtommath 1.1.0-3
 `12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182` ``````#include "tommath_private.h" #ifdef BN_MP_MUL_2D_C /* LibTomMath, multiple-precision integer library -- Tom St Denis * * LibTomMath is a library that provides multiple-precision * integer arithmetic as well as number theoretic functionality. * * The library was designed directly after the MPI library by * Michael Fromberger but has been written from scratch with * additional optimizations in place. * * SPDX-License-Identifier: Unlicense */ /* shift left by a certain bit count */ int mp_mul_2d(const mp_int *a, int b, mp_int *c) { mp_digit d; int res; /* copy */ if (a != c) { if ((res = mp_copy(a, c)) != MP_OKAY) { return res; } } if (c->alloc < (c->used + (b / DIGIT_BIT) + 1)) { if ((res = mp_grow(c, c->used + (b / DIGIT_BIT) + 1)) != MP_OKAY) { return res; } } /* shift by as many digits in the bit count */ if (b >= DIGIT_BIT) { if ((res = mp_lshd(c, b / DIGIT_BIT)) != MP_OKAY) { return res; } } /* shift any bit count < DIGIT_BIT */ d = (mp_digit)(b % DIGIT_BIT); if (d != 0u) { mp_digit *tmpc, shift, mask, r, rr; int x; /* bitmask for carries */ mask = ((mp_digit)1 << d) - (mp_digit)1; /* shift for msbs */ shift = (mp_digit)DIGIT_BIT - d; /* alias */ tmpc = c->dp; /* carry */ r = 0; for (x = 0; x < c->used; x++) { /* get the higher bits of the current word */ rr = (*tmpc >> shift) & mask; /* shift the current word and OR in the carry */ *tmpc = ((*tmpc << d) | r) & MP_MASK; ++tmpc; /* set the carry to the carry bits of the current word */ r = rr; } /* set final carry */ if (r != 0u) { c->dp[(c->used)++] = r; } } mp_clamp(c); return MP_OKAY; } #endif /* ref: HEAD -> master, tag: v1.1.0 */ /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */ /* commit time: 2019-01-28 20:32:32 +0100 */ ``````