## File: bn_mp_lshd.c

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libtommath 1.1.0-3
 `1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768` ``````#include "tommath_private.h" #ifdef BN_MP_LSHD_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 a certain amount of digits */ int mp_lshd(mp_int *a, int b) { int x, res; /* if its less than zero return */ if (b <= 0) { return MP_OKAY; } /* no need to shift 0 around */ if (mp_iszero(a) == MP_YES) { return MP_OKAY; } /* grow to fit the new digits */ if (a->alloc < (a->used + b)) { if ((res = mp_grow(a, a->used + b)) != MP_OKAY) { return res; } } { mp_digit *top, *bottom; /* increment the used by the shift amount then copy upwards */ a->used += b; /* top */ top = a->dp + a->used - 1; /* base */ bottom = (a->dp + a->used - 1) - b; /* much like mp_rshd this is implemented using a sliding window * except the window goes the otherway around. Copying from * the bottom to the top. see bn_mp_rshd.c for more info. */ for (x = a->used - 1; x >= b; x--) { *top-- = *bottom--; } /* zero the lower digits */ top = a->dp; for (x = 0; x < b; x++) { *top++ = 0; } } return MP_OKAY; } #endif /* ref: HEAD -> master, tag: v1.1.0 */ /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */ /* commit time: 2019-01-28 20:32:32 +0100 */ ``````