diff options
Diffstat (limited to 'grub-core/lib/libgcrypt/mpi/mpi-div.c')
| -rw-r--r-- | grub-core/lib/libgcrypt/mpi/mpi-div.c | 355 |
1 files changed, 355 insertions, 0 deletions
diff --git a/grub-core/lib/libgcrypt/mpi/mpi-div.c b/grub-core/lib/libgcrypt/mpi/mpi-div.c new file mode 100644 index 0000000..a6ee300 --- /dev/null +++ b/grub-core/lib/libgcrypt/mpi/mpi-div.c @@ -0,0 +1,355 @@ +/* mpi-div.c - MPI functions + * Copyright (C) 1994, 1996, 1998, 2001, 2002, + * 2003 Free Software Foundation, Inc. + * + * 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 + * + * Note: This code is heavily based on the GNU MP Library. + * Actually it's the same code with only minor changes in the + * way the data is stored; this is to support the abstraction + * of an optional secure memory allocation which may be used + * to avoid revealing of sensitive data due to paging etc. + */ + +#include <config.h> +#include <stdio.h> +#include <stdlib.h> +#include "mpi-internal.h" +#include "longlong.h" +#include "g10lib.h" + + +void +_gcry_mpi_fdiv_r( gcry_mpi_t rem, gcry_mpi_t dividend, gcry_mpi_t divisor ) +{ + int divisor_sign = divisor->sign; + gcry_mpi_t temp_divisor = NULL; + + /* We need the original value of the divisor after the remainder has been + * preliminary calculated. We have to copy it to temporary space if it's + * the same variable as REM. */ + if( rem == divisor ) { + temp_divisor = mpi_copy( divisor ); + divisor = temp_divisor; + } + + _gcry_mpi_tdiv_r( rem, dividend, divisor ); + + if( ((divisor_sign?1:0) ^ (dividend->sign?1:0)) && rem->nlimbs ) + gcry_mpi_add( rem, rem, divisor); + + if( temp_divisor ) + mpi_free(temp_divisor); +} + + + +/**************** + * Division rounding the quotient towards -infinity. + * The remainder gets the same sign as the denominator. + * rem is optional + */ + +ulong +_gcry_mpi_fdiv_r_ui( gcry_mpi_t rem, gcry_mpi_t dividend, ulong divisor ) +{ + mpi_limb_t rlimb; + + rlimb = _gcry_mpih_mod_1( dividend->d, dividend->nlimbs, divisor ); + if( rlimb && dividend->sign ) + rlimb = divisor - rlimb; + + if( rem ) { + rem->d[0] = rlimb; + rem->nlimbs = rlimb? 1:0; + } + return rlimb; +} + + +void +_gcry_mpi_fdiv_q( gcry_mpi_t quot, gcry_mpi_t dividend, gcry_mpi_t divisor ) +{ + gcry_mpi_t tmp = mpi_alloc( mpi_get_nlimbs(quot) ); + _gcry_mpi_fdiv_qr( quot, tmp, dividend, divisor); + mpi_free(tmp); +} + +void +_gcry_mpi_fdiv_qr( gcry_mpi_t quot, gcry_mpi_t rem, gcry_mpi_t dividend, gcry_mpi_t divisor ) +{ + int divisor_sign = divisor->sign; + gcry_mpi_t temp_divisor = NULL; + + if( quot == divisor || rem == divisor ) { + temp_divisor = mpi_copy( divisor ); + divisor = temp_divisor; + } + + _gcry_mpi_tdiv_qr( quot, rem, dividend, divisor ); + + if( (divisor_sign ^ dividend->sign) && rem->nlimbs ) { + gcry_mpi_sub_ui( quot, quot, 1 ); + gcry_mpi_add( rem, rem, divisor); + } + + if( temp_divisor ) + mpi_free(temp_divisor); +} + + +/* If den == quot, den needs temporary storage. + * If den == rem, den needs temporary storage. + * If num == quot, num needs temporary storage. + * If den has temporary storage, it can be normalized while being copied, + * i.e no extra storage should be allocated. + */ + +void +_gcry_mpi_tdiv_r( gcry_mpi_t rem, gcry_mpi_t num, gcry_mpi_t den) +{ + _gcry_mpi_tdiv_qr(NULL, rem, num, den ); +} + +void +_gcry_mpi_tdiv_qr( gcry_mpi_t quot, gcry_mpi_t rem, gcry_mpi_t num, gcry_mpi_t den) +{ + mpi_ptr_t np, dp; + mpi_ptr_t qp, rp; + mpi_size_t nsize = num->nlimbs; + mpi_size_t dsize = den->nlimbs; + mpi_size_t qsize, rsize; + mpi_size_t sign_remainder = num->sign; + mpi_size_t sign_quotient = num->sign ^ den->sign; + unsigned normalization_steps; + mpi_limb_t q_limb; + mpi_ptr_t marker[5]; + unsigned int marker_nlimbs[5]; + int markidx=0; + + /* Ensure space is enough for quotient and remainder. + * We need space for an extra limb in the remainder, because it's + * up-shifted (normalized) below. */ + rsize = nsize + 1; + mpi_resize( rem, rsize); + + qsize = rsize - dsize; /* qsize cannot be bigger than this. */ + if( qsize <= 0 ) { + if( num != rem ) { + rem->nlimbs = num->nlimbs; + rem->sign = num->sign; + MPN_COPY(rem->d, num->d, nsize); + } + if( quot ) { + /* This needs to follow the assignment to rem, in case the + * numerator and quotient are the same. */ + quot->nlimbs = 0; + quot->sign = 0; + } + return; + } + + if( quot ) + mpi_resize( quot, qsize); + + /* Read pointers here, when reallocation is finished. */ + np = num->d; + dp = den->d; + rp = rem->d; + + /* Optimize division by a single-limb divisor. */ + if( dsize == 1 ) { + mpi_limb_t rlimb; + if( quot ) { + qp = quot->d; + rlimb = _gcry_mpih_divmod_1( qp, np, nsize, dp[0] ); + qsize -= qp[qsize - 1] == 0; + quot->nlimbs = qsize; + quot->sign = sign_quotient; + } + else + rlimb = _gcry_mpih_mod_1( np, nsize, dp[0] ); + rp[0] = rlimb; + rsize = rlimb != 0?1:0; + rem->nlimbs = rsize; + rem->sign = sign_remainder; + return; + } + + + if( quot ) { + qp = quot->d; + /* Make sure QP and NP point to different objects. Otherwise the + * numerator would be gradually overwritten by the quotient limbs. */ + if(qp == np) { /* Copy NP object to temporary space. */ + marker_nlimbs[markidx] = nsize; + np = marker[markidx++] = mpi_alloc_limb_space(nsize, + mpi_is_secure(quot)); + MPN_COPY(np, qp, nsize); + } + } + else /* Put quotient at top of remainder. */ + qp = rp + dsize; + + count_leading_zeros( normalization_steps, dp[dsize - 1] ); + + /* Normalize the denominator, i.e. make its most significant bit set by + * shifting it NORMALIZATION_STEPS bits to the left. Also shift the + * numerator the same number of steps (to keep the quotient the same!). + */ + if( normalization_steps ) { + mpi_ptr_t tp; + mpi_limb_t nlimb; + + /* Shift up the denominator setting the most significant bit of + * the most significant word. Use temporary storage not to clobber + * the original contents of the denominator. */ + marker_nlimbs[markidx] = dsize; + tp = marker[markidx++] = mpi_alloc_limb_space(dsize,mpi_is_secure(den)); + _gcry_mpih_lshift( tp, dp, dsize, normalization_steps ); + dp = tp; + + /* Shift up the numerator, possibly introducing a new most + * significant word. Move the shifted numerator in the remainder + * meanwhile. */ + nlimb = _gcry_mpih_lshift(rp, np, nsize, normalization_steps); + if( nlimb ) { + rp[nsize] = nlimb; + rsize = nsize + 1; + } + else + rsize = nsize; + } + else { + /* The denominator is already normalized, as required. Copy it to + * temporary space if it overlaps with the quotient or remainder. */ + if( dp == rp || (quot && (dp == qp))) { + mpi_ptr_t tp; + + marker_nlimbs[markidx] = dsize; + tp = marker[markidx++] = mpi_alloc_limb_space(dsize, + mpi_is_secure(den)); + MPN_COPY( tp, dp, dsize ); + dp = tp; + } + + /* Move the numerator to the remainder. */ + if( rp != np ) + MPN_COPY(rp, np, nsize); + + rsize = nsize; + } + + q_limb = _gcry_mpih_divrem( qp, 0, rp, rsize, dp, dsize ); + + if( quot ) { + qsize = rsize - dsize; + if(q_limb) { + qp[qsize] = q_limb; + qsize += 1; + } + + quot->nlimbs = qsize; + quot->sign = sign_quotient; + } + + rsize = dsize; + MPN_NORMALIZE (rp, rsize); + + if( normalization_steps && rsize ) { + _gcry_mpih_rshift(rp, rp, rsize, normalization_steps); + rsize -= rp[rsize - 1] == 0?1:0; + } + + rem->nlimbs = rsize; + rem->sign = sign_remainder; + while( markidx ) + { + markidx--; + _gcry_mpi_free_limb_space (marker[markidx], marker_nlimbs[markidx]); + } +} + +void +_gcry_mpi_tdiv_q_2exp( gcry_mpi_t w, gcry_mpi_t u, unsigned int count ) +{ + mpi_size_t usize, wsize; + mpi_size_t limb_cnt; + + usize = u->nlimbs; + limb_cnt = count / BITS_PER_MPI_LIMB; + wsize = usize - limb_cnt; + if( limb_cnt >= usize ) + w->nlimbs = 0; + else { + mpi_ptr_t wp; + mpi_ptr_t up; + + RESIZE_IF_NEEDED( w, wsize ); + wp = w->d; + up = u->d; + + count %= BITS_PER_MPI_LIMB; + if( count ) { + _gcry_mpih_rshift( wp, up + limb_cnt, wsize, count ); + wsize -= !wp[wsize - 1]; + } + else { + MPN_COPY_INCR( wp, up + limb_cnt, wsize); + } + + w->nlimbs = wsize; + } +} + +/**************** + * Check whether dividend is divisible by divisor + * (note: divisor must fit into a limb) + */ +int +_gcry_mpi_divisible_ui(gcry_mpi_t dividend, ulong divisor ) +{ + return !_gcry_mpih_mod_1( dividend->d, dividend->nlimbs, divisor ); +} + + +void +gcry_mpi_div (gcry_mpi_t quot, gcry_mpi_t rem, gcry_mpi_t dividend, gcry_mpi_t divisor, int round) +{ + if (!round) + { + if (!rem) + { + gcry_mpi_t tmp = mpi_alloc (mpi_get_nlimbs(quot)); + _gcry_mpi_tdiv_qr (quot, tmp, dividend, divisor); + mpi_free (tmp); + } + else + _gcry_mpi_tdiv_qr (quot, rem, dividend, divisor); + } + else if (round < 0) + { + if (!rem) + _gcry_mpi_fdiv_q (quot, dividend, divisor); + else if (!quot) + _gcry_mpi_fdiv_r (rem, dividend, divisor); + else + _gcry_mpi_fdiv_qr (quot, rem, dividend, divisor); + } + else + log_bug ("mpi rounding to ceiling not yet implemented\n"); +} |