## File: bn_mp_lshd.c

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libtommath 0.42.0-1
 `12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667` ``````#include #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. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, tomstdenis@gmail.com, http://libtom.org */ /* 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; } /* grow to fit the new digits */ if (a->alloc < a->used + b) { if ((res = mp_grow (a, a->used + b)) != MP_OKAY) { return res; } } { register 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 /* \$Source\$ */ /* \$Revision: 0.41 \$ */ /* \$Date: 2007-04-18 09:58:18 +0000 \$ */ ``````