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-rw-r--r--lib/mpi/mpi-bit.c217
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diff --git a/lib/mpi/mpi-bit.c b/lib/mpi/mpi-bit.c
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+/* mpi-bit.c - MPI bit level fucntions
+ * 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+
+#include "mpi-internal.h"
+#include "longlong.h"
+
+#define A_LIMB_1 ((mpi_limb_t) 1)
+
+/****************
+ * Sometimes we have MSL (most significant limbs) which are 0;
+ * this is for some reasons not good, so this function removes them.
+ */
+void mpi_normalize(MPI a)
+{
+ for (; a->nlimbs && !a->d[a->nlimbs - 1]; a->nlimbs--)
+ ;
+}
+
+/****************
+ * Return the number of bits in A.
+ */
+unsigned mpi_get_nbits(MPI a)
+{
+ unsigned n;
+
+ mpi_normalize(a);
+
+ if (a->nlimbs) {
+ mpi_limb_t alimb = a->d[a->nlimbs - 1];
+ if (alimb)
+ count_leading_zeros(n, alimb);
+ else
+ n = BITS_PER_MPI_LIMB;
+ n = BITS_PER_MPI_LIMB - n + (a->nlimbs - 1) * BITS_PER_MPI_LIMB;
+ } else
+ n = 0;
+ return n;
+}
+EXPORT_SYMBOL_GPL(mpi_get_nbits);
+
+/****************
+ * Test whether bit N is set.
+ */
+int mpi_test_bit(MPI a, unsigned n)
+{
+ unsigned limbno, bitno;
+ mpi_limb_t limb;
+
+ limbno = n / BITS_PER_MPI_LIMB;
+ bitno = n % BITS_PER_MPI_LIMB;
+
+ if (limbno >= a->nlimbs)
+ return 0; /* too far left: this is a 0 */
+ limb = a->d[limbno];
+ return (limb & (A_LIMB_1 << bitno)) ? 1 : 0;
+}
+
+/****************
+ * Set bit N of A.
+ */
+int mpi_set_bit(MPI a, unsigned n)
+{
+ unsigned limbno, bitno;
+
+ limbno = n / BITS_PER_MPI_LIMB;
+ bitno = n % BITS_PER_MPI_LIMB;
+
+ if (limbno >= a->nlimbs) { /* resize */
+ if (a->alloced >= limbno)
+ if (mpi_resize(a, limbno + 1) < 0)
+ return -ENOMEM;
+ a->nlimbs = limbno + 1;
+ }
+ a->d[limbno] |= (A_LIMB_1 << bitno);
+ return 0;
+}
+
+/****************
+ * Set bit N of A. and clear all bits above
+ */
+int mpi_set_highbit(MPI a, unsigned n)
+{
+ unsigned limbno, bitno;
+
+ limbno = n / BITS_PER_MPI_LIMB;
+ bitno = n % BITS_PER_MPI_LIMB;
+
+ if (limbno >= a->nlimbs) { /* resize */
+ if (a->alloced >= limbno)
+ if (mpi_resize(a, limbno + 1) < 0)
+ return -ENOMEM;
+ a->nlimbs = limbno + 1;
+ }
+ a->d[limbno] |= (A_LIMB_1 << bitno);
+ for (bitno++; bitno < BITS_PER_MPI_LIMB; bitno++)
+ a->d[limbno] &= ~(A_LIMB_1 << bitno);
+ a->nlimbs = limbno + 1;
+ return 0;
+}
+
+/****************
+ * clear bit N of A and all bits above
+ */
+void mpi_clear_highbit(MPI a, unsigned n)
+{
+ unsigned limbno, bitno;
+
+ limbno = n / BITS_PER_MPI_LIMB;
+ bitno = n % BITS_PER_MPI_LIMB;
+
+ if (limbno >= a->nlimbs)
+ return; /* not allocated, so need to clear bits :-) */
+
+ for (; bitno < BITS_PER_MPI_LIMB; bitno++)
+ a->d[limbno] &= ~(A_LIMB_1 << bitno);
+ a->nlimbs = limbno + 1;
+}
+
+/****************
+ * Clear bit N of A.
+ */
+void mpi_clear_bit(MPI a, unsigned n)
+{
+ unsigned limbno, bitno;
+
+ limbno = n / BITS_PER_MPI_LIMB;
+ bitno = n % BITS_PER_MPI_LIMB;
+
+ if (limbno >= a->nlimbs)
+ return; /* don't need to clear this bit, it's to far to left */
+ a->d[limbno] &= ~(A_LIMB_1 << bitno);
+}
+
+/****************
+ * Shift A by N bits to the right
+ * FIXME: should use alloc_limb if X and A are same.
+ */
+int mpi_rshift(MPI x, MPI a, unsigned n)
+{
+ mpi_ptr_t xp;
+ mpi_size_t xsize;
+
+ xsize = a->nlimbs;
+ x->sign = a->sign;
+ if (RESIZE_IF_NEEDED(x, (size_t) xsize) < 0)
+ return -ENOMEM;
+ xp = x->d;
+
+ if (xsize) {
+ mpihelp_rshift(xp, a->d, xsize, n);
+ MPN_NORMALIZE(xp, xsize);
+ }
+ x->nlimbs = xsize;
+ return 0;
+}
+
+/****************
+ * Shift A by COUNT limbs to the left
+ * This is used only within the MPI library
+ */
+int mpi_lshift_limbs(MPI a, unsigned int count)
+{
+ mpi_ptr_t ap = a->d;
+ int n = a->nlimbs;
+ int i;
+
+ if (!count || !n)
+ return 0;
+
+ if (RESIZE_IF_NEEDED(a, n + count) < 0)
+ return -ENOMEM;
+
+ for (i = n - 1; i >= 0; i--)
+ ap[i + count] = ap[i];
+ for (i = 0; i < count; i++)
+ ap[i] = 0;
+ a->nlimbs += count;
+ return 0;
+}
+
+/****************
+ * Shift A by COUNT limbs to the right
+ * This is used only within the MPI library
+ */
+void mpi_rshift_limbs(MPI a, unsigned int count)
+{
+ mpi_ptr_t ap = a->d;
+ mpi_size_t n = a->nlimbs;
+ unsigned int i;
+
+ if (count >= n) {
+ a->nlimbs = 0;
+ return;
+ }
+
+ for (i = 0; i < n - count; i++)
+ ap[i] = ap[i + count];
+ ap[i] = 0;
+ a->nlimbs -= count;
+}