/* mpi-div.c  -  MPI functions *	Copyright (C) 1994, 1996 Free Software Foundation, Inc. *	Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc. * * This file is part of GnuPG. * * GnuPG is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * GnuPG 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 General Public License for more details. * * You should have received a copy of the GNU 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. *	 The GNU MP Library itself is published under the LGPL; *	 however I decided to publish this code under the plain GPL. */ #include <linux/string.h>#include "mpi-internal.h"#include "longlong.h" int mpi_fdiv_r(MPI rem, MPI dividend, MPI divisor){	int rc = -ENOMEM;	int divisor_sign = divisor->sign;	MPI 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) {		if (mpi_copy(&temp_divisor, divisor) < 0)			goto nomem;		divisor = temp_divisor;	} 	if (mpi_tdiv_qr(NULL, rem, dividend, divisor) < 0)		goto nomem;	if (((divisor_sign ? 1 : 0) ^ (dividend->sign ? 1 : 0)) && rem->nlimbs)		if (mpi_add(rem, rem, divisor) < 0)			goto nomem; 	rc = 0; nomem:	if (temp_divisor)		mpi_free(temp_divisor);	return rc;} /**************** * Division rounding the quotient towards -infinity. * The remainder gets the same sign as the denominator. * rem is optional */ ulong mpi_fdiv_r_ui(MPI rem, MPI dividend, ulong divisor){	mpi_limb_t rlimb; 	rlimb = mpihelp_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;} int mpi_fdiv_q(MPI quot, MPI dividend, MPI divisor){	MPI tmp = mpi_alloc(mpi_get_nlimbs(quot));	if (!tmp)		return -ENOMEM;	mpi_fdiv_qr(quot, tmp, dividend, divisor);	mpi_free(tmp);	return 0;} int mpi_fdiv_qr(MPI quot, MPI rem, MPI dividend, MPI divisor){	int divisor_sign = divisor->sign;	MPI temp_divisor = NULL; 	if (quot == divisor || rem == divisor) {		if (mpi_copy(&temp_divisor, divisor) < 0)			return -ENOMEM;		divisor = temp_divisor;	} 	if (mpi_tdiv_qr(quot, rem, dividend, divisor) < 0)		goto nomem; 	if ((divisor_sign ^ dividend->sign) && rem->nlimbs) {		if (mpi_sub_ui(quot, quot, 1) < 0)			goto nomem;		if (mpi_add(rem, rem, divisor) < 0)			goto nomem;	} 	if (temp_divisor)		mpi_free(temp_divisor); 	return 0; nomem:	mpi_free(temp_divisor);	return -ENOMEM;} /* 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. */ int mpi_tdiv_r(MPI rem, MPI num, MPI den){	return mpi_tdiv_qr(NULL, rem, num, den);} int mpi_tdiv_qr(MPI quot, MPI rem, MPI num, MPI den){	int rc = -ENOMEM;	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];	int markidx = 0; 	if (!dsize)		return -EINVAL; 	memset(marker, 0, sizeof(marker)); 	/* 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;	if (mpi_resize(rem, rsize) < 0)		goto nomem; 	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 0;	} 	if (quot)		if (mpi_resize(quot, qsize) < 0)			goto nomem; 	/* 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 = mpihelp_divmod_1(qp, np, nsize, dp[0]);			qsize -= qp[qsize - 1] == 0;			quot->nlimbs = qsize;			quot->sign = sign_quotient;		} else			rlimb = mpihelp_mod_1(np, nsize, dp[0]);		rp[0] = rlimb;		rsize = rlimb != 0 ? 1 : 0;		rem->nlimbs = rsize;		rem->sign = sign_remainder;		return 0;	} 	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.  */			np = marker[markidx++] = mpi_alloc_limb_space(nsize);			if (!np)				goto nomem;			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.  */		tp = marker[markidx++] = mpi_alloc_limb_space(dsize);		if (!tp)			goto nomem;		mpihelp_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 = mpihelp_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; 			tp = marker[markidx++] = mpi_alloc_limb_space(dsize);			if (!tp)				goto nomem;			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 = mpihelp_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) {		mpihelp_rshift(rp, rp, rsize, normalization_steps);		rsize -= rp[rsize - 1] == 0 ? 1 : 0;	} 	rem->nlimbs = rsize;	rem->sign = sign_remainder; 	rc = 0;nomem:	while (markidx)		mpi_free_limb_space(marker[--markidx]);	return rc;} int mpi_tdiv_q_2exp(MPI w, MPI u, unsigned 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; 		if (RESIZE_IF_NEEDED(w, wsize) < 0)			return -ENOMEM;		wp = w->d;		up = u->d; 		count %= BITS_PER_MPI_LIMB;		if (count) {			mpihelp_rshift(wp, up + limb_cnt, wsize, count);			wsize -= !wp[wsize - 1];		} else {			MPN_COPY_INCR(wp, up + limb_cnt, wsize);		} 		w->nlimbs = wsize;	}	return 0;} /**************** * Check whether dividend is divisible by divisor * (note: divisor must fit into a limb) */int mpi_divisible_ui(MPI dividend, ulong divisor){	return !mpihelp_mod_1(dividend->d, dividend->nlimbs, divisor);}