## File: bn_mp_div_2d.c

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libtommath 1.1.0-3
 `1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283` ``````#include "tommath_private.h" #ifdef BN_MP_DIV_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 right by a certain bit count (store quotient in c, optional remainder in d) */ int mp_div_2d(const mp_int *a, int b, mp_int *c, mp_int *d) { mp_digit D, r, rr; int x, res; /* if the shift count is <= 0 then we do no work */ if (b <= 0) { res = mp_copy(a, c); if (d != NULL) { mp_zero(d); } return res; } /* copy */ if ((res = mp_copy(a, c)) != MP_OKAY) { return res; } /* 'a' should not be used after here - it might be the same as d */ /* get the remainder */ if (d != NULL) { if ((res = mp_mod_2d(a, b, d)) != MP_OKAY) { return res; } } /* shift by as many digits in the bit count */ if (b >= DIGIT_BIT) { mp_rshd(c, b / DIGIT_BIT); } /* shift any bit count < DIGIT_BIT */ D = (mp_digit)(b % DIGIT_BIT); if (D != 0u) { mp_digit *tmpc, mask, shift; /* mask */ mask = ((mp_digit)1 << D) - 1uL; /* shift for lsb */ shift = (mp_digit)DIGIT_BIT - D; /* alias */ tmpc = c->dp + (c->used - 1); /* carry */ r = 0; for (x = c->used - 1; x >= 0; x--) { /* get the lower bits of this word in a temp */ rr = *tmpc & mask; /* shift the current word and mix in the carry bits from the previous word */ *tmpc = (*tmpc >> D) | (r << shift); --tmpc; /* set the carry to the carry bits of the current word found above */ r = rr; } } 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 */ ``````