Update head to match stable 1.0

mpi/mpi-div.c

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+/* 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 <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "mpi-internal.h"
+#include "longlong.h"
+
+
+
+void
+mpi_fdiv_r( MPI rem, MPI dividend, MPI divisor )
+{
+    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 ) {
+	temp_divisor = mpi_copy( divisor );
+	divisor = temp_divisor;
+    }
+
+    mpi_tdiv_r( rem, dividend, divisor );
+
+    if( ((divisor_sign?1:0) ^ (dividend->sign?1:0)) && rem->nlimbs )
+	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
+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;
+}
+
+
+void
+mpi_fdiv_q( MPI quot, MPI dividend, MPI divisor )
+{
+    MPI tmp = mpi_alloc( mpi_get_nlimbs(quot) );
+    mpi_fdiv_qr( quot, tmp, dividend, divisor);
+    mpi_free(tmp);
+}
+
+void
+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 ) {
+	temp_divisor = mpi_copy( divisor );
+	divisor = temp_divisor;
+    }
+
+    mpi_tdiv_qr( quot, rem, dividend, divisor );
+
+    if( (divisor_sign ^ dividend->sign) && rem->nlimbs ) {
+	mpi_sub_ui( quot, quot, 1 );
+	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
+mpi_tdiv_r( MPI rem, MPI num, MPI den)
+{
+    mpi_tdiv_qr(NULL, rem, num, den );
+}
+
+void
+mpi_tdiv_qr( MPI quot, MPI rem, MPI num, MPI 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];
+    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 = 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;
+    }
+
+
+    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,
+							  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.  */
+	tp = marker[markidx++] = mpi_alloc_limb_space(dsize,mpi_is_secure(den));
+	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, 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 = 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;
+    while( markidx )
+	mpi_free_limb_space(marker[--markidx]);
+}
+
+void
+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;
+
+	RESIZE_IF_NEEDED( w, wsize );
+	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;
+    }
+}
+
+/****************
+ * 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 );
+}
+