1 files changed, 333 insertions, 0 deletions
diff --git a/lib/mpi/mpi-div.c b/lib/mpi/mpi-div.c
new file mode 100644
index 00000000000..c3087d1390c
--- /dev/null
+++ b/lib/mpi/mpi-div.c
@@ -0,0 +1,333 @@
+/* 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;
+
+	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);
+			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);
+}