## File: bn_mp_expt_d_ex.c

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libtommath 1.1.0-3
 `12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879` ``````#include "tommath_private.h" #ifdef BN_MP_EXPT_D_EX_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 */ /* calculate c = a**b using a square-multiply algorithm */ int mp_expt_d_ex(const mp_int *a, mp_digit b, mp_int *c, int fast) { int res; unsigned int x; mp_int g; if ((res = mp_init_copy(&g, a)) != MP_OKAY) { return res; } /* set initial result */ mp_set(c, 1uL); if (fast != 0) { while (b > 0u) { /* if the bit is set multiply */ if ((b & 1u) != 0u) { if ((res = mp_mul(c, &g, c)) != MP_OKAY) { mp_clear(&g); return res; } } /* square */ if (b > 1u) { if ((res = mp_sqr(&g, &g)) != MP_OKAY) { mp_clear(&g); return res; } } /* shift to next bit */ b >>= 1; } } else { for (x = 0; x < (unsigned)DIGIT_BIT; x++) { /* square */ if ((res = mp_sqr(c, c)) != MP_OKAY) { mp_clear(&g); return res; } /* if the bit is set multiply */ if ((b & ((mp_digit)1 << (DIGIT_BIT - 1))) != 0u) { if ((res = mp_mul(c, &g, c)) != MP_OKAY) { mp_clear(&g); return res; } } /* shift to next bit */ b <<= 1; } } /* if ... else */ mp_clear(&g); return MP_OKAY; } #endif /* ref: HEAD -> master, tag: v1.1.0 */ /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */ /* commit time: 2019-01-28 20:32:32 +0100 */ ``````