## File: bn_mp_sqrt.c

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libtommath 1.1.0-3
 `1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980` ``````#include "tommath_private.h" #ifdef BN_MP_SQRT_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 */ /* this function is less generic than mp_n_root, simpler and faster */ int mp_sqrt(const mp_int *arg, mp_int *ret) { int res; mp_int t1, t2; /* must be positive */ if (arg->sign == MP_NEG) { return MP_VAL; } /* easy out */ if (mp_iszero(arg) == MP_YES) { mp_zero(ret); return MP_OKAY; } if ((res = mp_init_copy(&t1, arg)) != MP_OKAY) { return res; } if ((res = mp_init(&t2)) != MP_OKAY) { goto E2; } /* First approx. (not very bad for large arg) */ mp_rshd(&t1, t1.used/2); /* t1 > 0 */ if ((res = mp_div(arg, &t1, &t2, NULL)) != MP_OKAY) { goto E1; } if ((res = mp_add(&t1, &t2, &t1)) != MP_OKAY) { goto E1; } if ((res = mp_div_2(&t1, &t1)) != MP_OKAY) { goto E1; } /* And now t1 > sqrt(arg) */ do { if ((res = mp_div(arg, &t1, &t2, NULL)) != MP_OKAY) { goto E1; } if ((res = mp_add(&t1, &t2, &t1)) != MP_OKAY) { goto E1; } if ((res = mp_div_2(&t1, &t1)) != MP_OKAY) { goto E1; } /* t1 >= sqrt(arg) >= t2 at this point */ } while (mp_cmp_mag(&t1, &t2) == MP_GT); mp_exch(&t1, ret); E1: mp_clear(&t2); E2: mp_clear(&t1); return res; } #endif /* ref: HEAD -> master, tag: v1.1.0 */ /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */ /* commit time: 2019-01-28 20:32:32 +0100 */ ``````