Git initHEAD2.0_alphamaster2.0alpha1.0_post

1 files changed, 536 insertions, 0 deletions

diff --git a/mpi/mpih-div.c b/mpi/mpih-div.c
new file mode 100644
index 0000000..1e962a1
--- /dev/null
+++ b/mpi/mpih-div.c
@@ -0,0 +1,536 @@
+/* mpihelp-div.c  -  MPI helper functions
+ *	Copyright (C) 1994, 1996 Free Software Foundation, Inc.
+ *	Copyright (C) 1998, 1999 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+ * 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"
+
+#ifndef UMUL_TIME
+#define UMUL_TIME 1
+#endif
+#ifndef UDIV_TIME
+#define UDIV_TIME UMUL_TIME
+#endif
+
+/* FIXME: We should be using invert_limb (or invert_normalized_limb)
+ * here (not udiv_qrnnd).
+ */
+
+mpi_limb_t
+mpihelp_mod_1(mpi_ptr_t dividend_ptr, mpi_size_t dividend_size,
+				      mpi_limb_t divisor_limb)
+{
+    mpi_size_t i;
+    mpi_limb_t n1, n0, r;
+    int dummy;
+
+    /* Botch: Should this be handled at all?  Rely on callers?	*/
+    if( !dividend_size )
+	return 0;
+
+    /* If multiplication is much faster than division, and the
+     * dividend is large, pre-invert the divisor, and use
+     * only multiplications in the inner loop.
+     *
+     * This test should be read:
+     *	 Does it ever help to use udiv_qrnnd_preinv?
+     *	   && Does what we save compensate for the inversion overhead?
+     */
+    if( UDIV_TIME > (2 * UMUL_TIME + 6)
+	&& (UDIV_TIME - (2 * UMUL_TIME + 6)) * dividend_size > UDIV_TIME ) {
+	int normalization_steps;
+
+	count_leading_zeros( normalization_steps, divisor_limb );
+	if( normalization_steps ) {
+	    mpi_limb_t divisor_limb_inverted;
+
+	    divisor_limb <<= normalization_steps;
+
+	    /* Compute (2**2N - 2**N * DIVISOR_LIMB) / DIVISOR_LIMB.  The
+	     * result is a (N+1)-bit approximation to 1/DIVISOR_LIMB, with the
+	     * most significant bit (with weight 2**N) implicit.
+	     *
+	     * Special case for DIVISOR_LIMB == 100...000.
+	     */
+	    if( !(divisor_limb << 1) )
+		divisor_limb_inverted = ~(mpi_limb_t)0;
+	    else
+		udiv_qrnnd(divisor_limb_inverted, dummy,
+			   -divisor_limb, 0, divisor_limb);
+
+	    n1 = dividend_ptr[dividend_size - 1];
+	    r = n1 >> (BITS_PER_MPI_LIMB - normalization_steps);
+
+	    /* Possible optimization:
+	     * if (r == 0
+	     * && divisor_limb > ((n1 << normalization_steps)
+	     *		       | (dividend_ptr[dividend_size - 2] >> ...)))
+	     * ...one division less...
+	     */
+	    for( i = dividend_size - 2; i >= 0; i--) {
+		n0 = dividend_ptr[i];
+		UDIV_QRNND_PREINV(dummy, r, r,
+				   ((n1 << normalization_steps)
+			  | (n0 >> (BITS_PER_MPI_LIMB - normalization_steps))),
+			  divisor_limb, divisor_limb_inverted);
+		n1 = n0;
+	    }
+	    UDIV_QRNND_PREINV(dummy, r, r,
+			      n1 << normalization_steps,
+			      divisor_limb, divisor_limb_inverted);
+	    return r >> normalization_steps;
+	}
+	else {
+	    mpi_limb_t divisor_limb_inverted;
+
+	    /* Compute (2**2N - 2**N * DIVISOR_LIMB) / DIVISOR_LIMB.  The
+	     * result is a (N+1)-bit approximation to 1/DIVISOR_LIMB, with the
+	     * most significant bit (with weight 2**N) implicit.
+	     *
+	     * Special case for DIVISOR_LIMB == 100...000.
+	     */
+	    if( !(divisor_limb << 1) )
+		divisor_limb_inverted = ~(mpi_limb_t)0;
+	    else
+		udiv_qrnnd(divisor_limb_inverted, dummy,
+			    -divisor_limb, 0, divisor_limb);
+
+	    i = dividend_size - 1;
+	    r = dividend_ptr[i];
+
+	    if( r >= divisor_limb )
+		r = 0;
+	    else
+		i--;
+
+	    for( ; i >= 0; i--) {
+		n0 = dividend_ptr[i];
+		UDIV_QRNND_PREINV(dummy, r, r,
+				  n0, divisor_limb, divisor_limb_inverted);
+	    }
+	    return r;
+	}
+    }
+    else {
+	if( UDIV_NEEDS_NORMALIZATION ) {
+	    int normalization_steps;
+
+	    count_leading_zeros(normalization_steps, divisor_limb);
+	    if( normalization_steps ) {
+		divisor_limb <<= normalization_steps;
+
+		n1 = dividend_ptr[dividend_size - 1];
+		r = n1 >> (BITS_PER_MPI_LIMB - normalization_steps);
+
+		/* Possible optimization:
+		 * if (r == 0
+		 * && divisor_limb > ((n1 << normalization_steps)
+		 *		   | (dividend_ptr[dividend_size - 2] >> ...)))
+		 * ...one division less...
+		 */
+		for(i = dividend_size - 2; i >= 0; i--) {
+		    n0 = dividend_ptr[i];
+		    udiv_qrnnd (dummy, r, r,
+				((n1 << normalization_steps)
+			 | (n0 >> (BITS_PER_MPI_LIMB - normalization_steps))),
+			 divisor_limb);
+		    n1 = n0;
+		}
+		udiv_qrnnd (dummy, r, r,
+			    n1 << normalization_steps,
+			    divisor_limb);
+		return r >> normalization_steps;
+	    }
+	}
+	/* No normalization needed, either because udiv_qrnnd doesn't require
+	 * it, or because DIVISOR_LIMB is already normalized.  */
+	i = dividend_size - 1;
+	r = dividend_ptr[i];
+
+	if(r >= divisor_limb)
+	    r = 0;
+	else
+	    i--;
+
+	for(; i >= 0; i--) {
+	    n0 = dividend_ptr[i];
+	    udiv_qrnnd (dummy, r, r, n0, divisor_limb);
+	}
+	return r;
+    }
+}
+
+/* Divide num (NP/NSIZE) by den (DP/DSIZE) and write
+ * the NSIZE-DSIZE least significant quotient limbs at QP
+ * and the DSIZE long remainder at NP.	If QEXTRA_LIMBS is
+ * non-zero, generate that many fraction bits and append them after the
+ * other quotient limbs.
+ * Return the most significant limb of the quotient, this is always 0 or 1.
+ *
+ * Preconditions:
+ * 0. NSIZE >= DSIZE.
+ * 1. The most significant bit of the divisor must be set.
+ * 2. QP must either not overlap with the input operands at all, or
+ *    QP + DSIZE >= NP must hold true.	(This means that it's
+ *    possible to put the quotient in the high part of NUM, right after the
+ *    remainder in NUM.
+ * 3. NSIZE >= DSIZE, even if QEXTRA_LIMBS is non-zero.
+ */
+
+mpi_limb_t
+mpihelp_divrem( mpi_ptr_t qp, mpi_size_t qextra_limbs,
+		mpi_ptr_t np, mpi_size_t nsize,
+		mpi_ptr_t dp, mpi_size_t dsize)
+{
+    mpi_limb_t most_significant_q_limb = 0;
+
+    switch(dsize) {
+      case 0:
+	/* We are asked to divide by zero, so go ahead and do it!  (To make
+	   the compiler not remove this statement, return the value.)  */
+	return 1 / dsize;
+
+      case 1:
+	{
+	    mpi_size_t i;
+	    mpi_limb_t n1;
+	    mpi_limb_t d;
+
+	    d = dp[0];
+	    n1 = np[nsize - 1];
+
+	    if( n1 >= d ) {
+		n1 -= d;
+		most_significant_q_limb = 1;
+	    }
+
+	    qp += qextra_limbs;
+	    for( i = nsize - 2; i >= 0; i--)
+		udiv_qrnnd( qp[i], n1, n1, np[i], d );
+	    qp -= qextra_limbs;
+
+	    for( i = qextra_limbs - 1; i >= 0; i-- )
+		udiv_qrnnd (qp[i], n1, n1, 0, d);
+
+	    np[0] = n1;
+	}
+	break;
+
+      case 2:
+	{
+	    mpi_size_t i;
+	    mpi_limb_t n1, n0, n2;
+	    mpi_limb_t d1, d0;
+
+	    np += nsize - 2;
+	    d1 = dp[1];
+	    d0 = dp[0];
+	    n1 = np[1];
+	    n0 = np[0];
+
+	    if( n1 >= d1 && (n1 > d1 || n0 >= d0) ) {
+		sub_ddmmss (n1, n0, n1, n0, d1, d0);
+		most_significant_q_limb = 1;
+	    }
+
+	    for( i = qextra_limbs + nsize - 2 - 1; i >= 0; i-- ) {
+		mpi_limb_t q;
+		mpi_limb_t r;
+
+		if( i >= qextra_limbs )
+		    np--;
+		else
+		    np[0] = 0;
+
+		if( n1 == d1 ) {
+		    /* Q should be either 111..111 or 111..110.  Need special
+		     * treatment of this rare case as normal division would
+		     * give overflow.  */
+		    q = ~(mpi_limb_t)0;
+
+		    r = n0 + d1;
+		    if( r < d1 ) {   /* Carry in the addition? */
+			add_ssaaaa( n1, n0, r - d0, np[0], 0, d0 );
+			qp[i] = q;
+			continue;
+		    }
+		    n1 = d0 - (d0 != 0?1:0);
+		    n0 = -d0;
+		}
+		else {
+		    udiv_qrnnd (q, r, n1, n0, d1);
+		    umul_ppmm (n1, n0, d0, q);
+		}
+
+		n2 = np[0];
+	      q_test:
+		if( n1 > r || (n1 == r && n0 > n2) ) {
+		    /* The estimated Q was too large.  */
+		    q--;
+		    sub_ddmmss (n1, n0, n1, n0, 0, d0);
+		    r += d1;
+		    if( r >= d1 )    /* If not carry, test Q again.  */
+			goto q_test;
+		}
+
+		qp[i] = q;
+		sub_ddmmss (n1, n0, r, n2, n1, n0);
+	    }
+	    np[1] = n1;
+	    np[0] = n0;
+	}
+	break;
+
+      default:
+	{
+	    mpi_size_t i;
+	    mpi_limb_t dX, d1, n0;
+
+	    np += nsize - dsize;
+	    dX = dp[dsize - 1];
+	    d1 = dp[dsize - 2];
+	    n0 = np[dsize - 1];
+
+	    if( n0 >= dX ) {
+		if(n0 > dX || mpihelp_cmp(np, dp, dsize - 1) >= 0 ) {
+		    mpihelp_sub_n(np, np, dp, dsize);
+		    n0 = np[dsize - 1];
+		    most_significant_q_limb = 1;
+		}
+	    }
+
+	    for( i = qextra_limbs + nsize - dsize - 1; i >= 0; i--) {
+		mpi_limb_t q;
+		mpi_limb_t n1, n2;
+		mpi_limb_t cy_limb;
+
+		if( i >= qextra_limbs ) {
+		    np--;
+		    n2 = np[dsize];
+		}
+		else {
+		    n2 = np[dsize - 1];
+		    MPN_COPY_DECR (np + 1, np, dsize - 1);
+		    np[0] = 0;
+		}
+
+		if( n0 == dX ) {
+		    /* This might over-estimate q, but it's probably not worth
+		     * the extra code here to find out.  */
+		    q = ~(mpi_limb_t)0;
+		}
+		else {
+		    mpi_limb_t r;
+
+		    udiv_qrnnd(q, r, n0, np[dsize - 1], dX);
+		    umul_ppmm(n1, n0, d1, q);
+
+		    while( n1 > r || (n1 == r && n0 > np[dsize - 2])) {
+			q--;
+			r += dX;
+			if( r < dX ) /* I.e. "carry in previous addition?" */
+			    break;
+			n1 -= n0 < d1;
+			n0 -= d1;
+		    }
+		}
+
+		/* Possible optimization: We already have (q * n0) and (1 * n1)
+		 * after the calculation of q.	Taking advantage of that, we
+		 * could make this loop make two iterations less.  */
+		cy_limb = mpihelp_submul_1(np, dp, dsize, q);
+
+		if( n2 != cy_limb ) {
+		    mpihelp_add_n(np, np, dp, dsize);
+		    q--;
+		}
+
+		qp[i] = q;
+		n0 = np[dsize - 1];
+	    }
+	}
+    }
+
+    return most_significant_q_limb;
+}
+
+
+/****************
+ * Divide (DIVIDEND_PTR,,DIVIDEND_SIZE) by DIVISOR_LIMB.
+ * Write DIVIDEND_SIZE limbs of quotient at QUOT_PTR.
+ * Return the single-limb remainder.
+ * There are no constraints on the value of the divisor.
+ *
+ * QUOT_PTR and DIVIDEND_PTR might point to the same limb.
+ */
+
+mpi_limb_t
+mpihelp_divmod_1( mpi_ptr_t quot_ptr,
+		  mpi_ptr_t dividend_ptr, mpi_size_t dividend_size,
+		  mpi_limb_t divisor_limb)
+{
+    mpi_size_t i;
+    mpi_limb_t n1, n0, r;
+    int dummy;
+
+    if( !dividend_size )
+	return 0;
+
+    /* If multiplication is much faster than division, and the
+     * dividend is large, pre-invert the divisor, and use
+     * only multiplications in the inner loop.
+     *
+     * This test should be read:
+     * Does it ever help to use udiv_qrnnd_preinv?
+     * && Does what we save compensate for the inversion overhead?
+     */
+    if( UDIV_TIME > (2 * UMUL_TIME + 6)
+	&& (UDIV_TIME - (2 * UMUL_TIME + 6)) * dividend_size > UDIV_TIME ) {
+	int normalization_steps;
+
+	count_leading_zeros( normalization_steps, divisor_limb );
+	if( normalization_steps ) {
+	    mpi_limb_t divisor_limb_inverted;
+
+	    divisor_limb <<= normalization_steps;
+
+	    /* Compute (2**2N - 2**N * DIVISOR_LIMB) / DIVISOR_LIMB.  The
+	     * result is a (N+1)-bit approximation to 1/DIVISOR_LIMB, with the
+	     * most significant bit (with weight 2**N) implicit.
+	     */
+	    /* Special case for DIVISOR_LIMB == 100...000.  */
+	    if( !(divisor_limb << 1) )
+		divisor_limb_inverted = ~(mpi_limb_t)0;
+	    else
+		udiv_qrnnd(divisor_limb_inverted, dummy,
+			   -divisor_limb, 0, divisor_limb);
+
+	    n1 = dividend_ptr[dividend_size - 1];
+	    r = n1 >> (BITS_PER_MPI_LIMB - normalization_steps);
+
+	    /* Possible optimization:
+	     * if (r == 0
+	     * && divisor_limb > ((n1 << normalization_steps)
+	     *		       | (dividend_ptr[dividend_size - 2] >> ...)))
+	     * ...one division less...
+	     */
+	    for( i = dividend_size - 2; i >= 0; i--) {
+		n0 = dividend_ptr[i];
+		UDIV_QRNND_PREINV( quot_ptr[i + 1], r, r,
+				   ((n1 << normalization_steps)
+			 | (n0 >> (BITS_PER_MPI_LIMB - normalization_steps))),
+			      divisor_limb, divisor_limb_inverted);
+		n1 = n0;
+	    }
+	    UDIV_QRNND_PREINV( quot_ptr[0], r, r,
+			       n1 << normalization_steps,
+			       divisor_limb, divisor_limb_inverted);
+	    return r >> normalization_steps;
+	}
+	else {
+	    mpi_limb_t divisor_limb_inverted;
+
+	    /* Compute (2**2N - 2**N * DIVISOR_LIMB) / DIVISOR_LIMB.  The
+	     * result is a (N+1)-bit approximation to 1/DIVISOR_LIMB, with the
+	     * most significant bit (with weight 2**N) implicit.
+	     */
+	    /* Special case for DIVISOR_LIMB == 100...000.  */
+	    if( !(divisor_limb << 1) )
+		divisor_limb_inverted = ~(mpi_limb_t) 0;
+	    else
+		udiv_qrnnd(divisor_limb_inverted, dummy,
+			   -divisor_limb, 0, divisor_limb);
+
+	    i = dividend_size - 1;
+	    r = dividend_ptr[i];
+
+	    if( r >= divisor_limb )
+		r = 0;
+	    else
+		quot_ptr[i--] = 0;
+
+	    for( ; i >= 0; i-- ) {
+		n0 = dividend_ptr[i];
+		UDIV_QRNND_PREINV( quot_ptr[i], r, r,
+				   n0, divisor_limb, divisor_limb_inverted);
+	    }
+	    return r;
+	}
+    }
+    else {
+	if(UDIV_NEEDS_NORMALIZATION) {
+	    int normalization_steps;
+
+	    count_leading_zeros (normalization_steps, divisor_limb);
+	    if( normalization_steps ) {
+		divisor_limb <<= normalization_steps;
+
+		n1 = dividend_ptr[dividend_size - 1];
+		r = n1 >> (BITS_PER_MPI_LIMB - normalization_steps);
+
+		/* Possible optimization:
+		 * if (r == 0
+		 * && divisor_limb > ((n1 << normalization_steps)
+		 *		   | (dividend_ptr[dividend_size - 2] >> ...)))
+		 * ...one division less...
+		 */
+		for( i = dividend_size - 2; i >= 0; i--) {
+		    n0 = dividend_ptr[i];
+		    udiv_qrnnd (quot_ptr[i + 1], r, r,
+			     ((n1 << normalization_steps)
+			 | (n0 >> (BITS_PER_MPI_LIMB - normalization_steps))),
+				divisor_limb);
+		    n1 = n0;
+		}
+		udiv_qrnnd (quot_ptr[0], r, r,
+			    n1 << normalization_steps,
+			    divisor_limb);
+		return r >> normalization_steps;
+	    }
+	}
+	/* No normalization needed, either because udiv_qrnnd doesn't require
+	 * it, or because DIVISOR_LIMB is already normalized.  */
+	i = dividend_size - 1;
+	r = dividend_ptr[i];
+
+	if(r >= divisor_limb)
+	    r = 0;
+	else
+	    quot_ptr[i--] = 0;
+
+	for(; i >= 0; i--) {
+	    n0 = dividend_ptr[i];
+	    udiv_qrnnd( quot_ptr[i], r, r, n0, divisor_limb );
+	}
+	return r;
+    }
+}