/* mpi-bit.c - MPI bit level functions * Copyright (C) 1998, 1999, 2001, 2002, 2006 Free Software Foundation, Inc. * Copyright (C) 2013 g10 Code GmbH * * This file is part of Libgcrypt. * * Libgcrypt is free software; you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License as * published by the Free Software Foundation; either version 2.1 of * the License, or (at your option) any later version. * * Libgcrypt is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */ #include #include #include #include "mpi-internal.h" #include "longlong.h" #ifdef MPI_INTERNAL_NEED_CLZ_TAB #ifdef __STDC__ const #endif unsigned char _gcry_clz_tab[] = { 0,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5, 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6, 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, }; #endif #define A_LIMB_1 ((mpi_limb_t)1) /**************** * Sometimes we have MSL (most significant limbs) which are 0; * this is for some reasons not good, so this function removes them. */ void _gcry_mpi_normalize( gcry_mpi_t a ) { if( mpi_is_opaque(a) ) return; for( ; a->nlimbs && !a->d[a->nlimbs-1]; a->nlimbs-- ) ; } /**************** * Return the number of bits in A. */ unsigned int _gcry_mpi_get_nbits (gcry_mpi_t a) { unsigned n; if( mpi_is_opaque(a) ) { return a->sign; /* which holds the number of bits */ } _gcry_mpi_normalize( a ); if( a->nlimbs ) { mpi_limb_t alimb = a->d[a->nlimbs-1]; if( alimb ) count_leading_zeros( n, alimb ); else n = BITS_PER_MPI_LIMB; n = BITS_PER_MPI_LIMB - n + (a->nlimbs-1) * BITS_PER_MPI_LIMB; } else n = 0; return n; } /**************** * Test whether bit N is set. */ int _gcry_mpi_test_bit( gcry_mpi_t a, unsigned int n ) { unsigned int limbno, bitno; mpi_limb_t limb; limbno = n / BITS_PER_MPI_LIMB; bitno = n % BITS_PER_MPI_LIMB; if( limbno >= a->nlimbs ) return 0; /* too far left: this is a 0 */ limb = a->d[limbno]; return (limb & (A_LIMB_1 << bitno))? 1: 0; } /**************** * Set bit N of A. */ void _gcry_mpi_set_bit( gcry_mpi_t a, unsigned int n ) { unsigned int i, limbno, bitno; if (mpi_is_immutable (a)) { mpi_immutable_failed (); return; } limbno = n / BITS_PER_MPI_LIMB; bitno = n % BITS_PER_MPI_LIMB; if ( limbno >= a->nlimbs ) { for (i=a->nlimbs; i < a->alloced; i++) a->d[i] = 0; mpi_resize (a, limbno+1 ); a->nlimbs = limbno+1; } a->d[limbno] |= (A_LIMB_1<= a->nlimbs ) { for (i=a->nlimbs; i < a->alloced; i++) a->d[i] = 0; mpi_resize (a, limbno+1 ); a->nlimbs = limbno+1; } a->d[limbno] |= (A_LIMB_1<d[limbno] &= ~(A_LIMB_1 << bitno); a->nlimbs = limbno+1; } /**************** * clear bit N of A and all bits above */ void _gcry_mpi_clear_highbit( gcry_mpi_t a, unsigned int n ) { unsigned int limbno, bitno; if (mpi_is_immutable (a)) { mpi_immutable_failed (); return; } limbno = n / BITS_PER_MPI_LIMB; bitno = n % BITS_PER_MPI_LIMB; if( limbno >= a->nlimbs ) return; /* not allocated, therefore no need to clear bits :-) */ for( ; bitno < BITS_PER_MPI_LIMB; bitno++ ) a->d[limbno] &= ~(A_LIMB_1 << bitno); a->nlimbs = limbno+1; } /**************** * Clear bit N of A. */ void _gcry_mpi_clear_bit( gcry_mpi_t a, unsigned int n ) { unsigned int limbno, bitno; if (mpi_is_immutable (a)) { mpi_immutable_failed (); return; } limbno = n / BITS_PER_MPI_LIMB; bitno = n % BITS_PER_MPI_LIMB; if (limbno >= a->nlimbs) return; /* Don't need to clear this bit, it's far too left. */ a->d[limbno] &= ~(A_LIMB_1 << bitno); } /**************** * Shift A by COUNT limbs to the right * This is used only within the MPI library */ void _gcry_mpi_rshift_limbs( gcry_mpi_t a, unsigned int count ) { mpi_ptr_t ap = a->d; mpi_size_t n = a->nlimbs; unsigned int i; if (mpi_is_immutable (a)) { mpi_immutable_failed (); return; } if (count >= n) { a->nlimbs = 0; return; } for( i = 0; i < n - count; i++ ) ap[i] = ap[i+count]; ap[i] = 0; a->nlimbs -= count; } /* * Shift A by N bits to the right. */ void _gcry_mpi_rshift ( gcry_mpi_t x, gcry_mpi_t a, unsigned int n ) { mpi_size_t xsize; unsigned int i; unsigned int nlimbs = (n/BITS_PER_MPI_LIMB); unsigned int nbits = (n%BITS_PER_MPI_LIMB); if (mpi_is_immutable (x)) { mpi_immutable_failed (); return; } if ( x == a ) { /* In-place operation. */ if ( nlimbs >= x->nlimbs ) { x->nlimbs = 0; return; } if (nlimbs) { for (i=0; i < x->nlimbs - nlimbs; i++ ) x->d[i] = x->d[i+nlimbs]; x->d[i] = 0; x->nlimbs -= nlimbs; } if ( x->nlimbs && nbits ) _gcry_mpih_rshift ( x->d, x->d, x->nlimbs, nbits ); } else if ( nlimbs ) { /* Copy and shift by more or equal bits than in a limb. */ xsize = a->nlimbs; x->sign = a->sign; RESIZE_IF_NEEDED (x, xsize); x->nlimbs = xsize; for (i=0; i < a->nlimbs; i++ ) x->d[i] = a->d[i]; x->nlimbs = i; if ( nlimbs >= x->nlimbs ) { x->nlimbs = 0; return; } if (nlimbs) { for (i=0; i < x->nlimbs - nlimbs; i++ ) x->d[i] = x->d[i+nlimbs]; x->d[i] = 0; x->nlimbs -= nlimbs; } if ( x->nlimbs && nbits ) _gcry_mpih_rshift ( x->d, x->d, x->nlimbs, nbits ); } else { /* Copy and shift by less than bits in a limb. */ xsize = a->nlimbs; x->sign = a->sign; RESIZE_IF_NEEDED (x, xsize); x->nlimbs = xsize; if ( xsize ) { if (nbits ) _gcry_mpih_rshift (x->d, a->d, x->nlimbs, nbits ); else { /* The rshift helper function is not specified for NBITS==0, thus we do a plain copy here. */ for (i=0; i < x->nlimbs; i++ ) x->d[i] = a->d[i]; } } } MPN_NORMALIZE (x->d, x->nlimbs); } /**************** * Shift A by COUNT limbs to the left * This is used only within the MPI library */ void _gcry_mpi_lshift_limbs (gcry_mpi_t a, unsigned int count) { mpi_ptr_t ap; int n = a->nlimbs; int i; if (!count || !n) return; RESIZE_IF_NEEDED (a, n+count); ap = a->d; for (i = n-1; i >= 0; i--) ap[i+count] = ap[i]; for (i=0; i < count; i++ ) ap[i] = 0; a->nlimbs += count; } /* * Shift A by N bits to the left. */ void _gcry_mpi_lshift ( gcry_mpi_t x, gcry_mpi_t a, unsigned int n ) { unsigned int nlimbs = (n/BITS_PER_MPI_LIMB); unsigned int nbits = (n%BITS_PER_MPI_LIMB); if (mpi_is_immutable (x)) { mpi_immutable_failed (); return; } if (x == a && !n) return; /* In-place shift with an amount of zero. */ if ( x != a ) { /* Copy A to X. */ unsigned int alimbs = a->nlimbs; int asign = a->sign; mpi_ptr_t xp, ap; RESIZE_IF_NEEDED (x, alimbs+nlimbs+1); xp = x->d; ap = a->d; MPN_COPY (xp, ap, alimbs); x->nlimbs = alimbs; x->flags = a->flags; x->sign = asign; } if (nlimbs && !nbits) { /* Shift a full number of limbs. */ _gcry_mpi_lshift_limbs (x, nlimbs); } else if (n) { /* We use a very dump approach: Shift left by the number of limbs plus one and than fix it up by an rshift. */ _gcry_mpi_lshift_limbs (x, nlimbs+1); mpi_rshift (x, x, BITS_PER_MPI_LIMB - nbits); } MPN_NORMALIZE (x->d, x->nlimbs); }