1 files changed, 94 insertions, 0 deletions
diff --git a/mpi/mpih-shift.c b/mpi/mpih-shift.c
new file mode 100644
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+++ b/mpi/mpih-shift.c
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+/* mpihelp-shift.c  -  MPI helper functions
+ *	Copyright (c) 1997 by Werner Koch (dd9jn)
+ *
+ * This file is part of G10.
+ *
+ * G10 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.
+ *
+ * G10 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 <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "mpi-internal.h"
+
+/* Shift U (pointed to by UP and USIZE digits long) CNT bits to the left
+ * and store the USIZE least significant digits of the result at WP.
+ * Return the bits shifted out from the most significant digit.
+ *
+ * Argument constraints:
+ * 1. 0 < CNT < BITS_PER_MP_LIMB
+ * 2. If the result is to be written over the input, WP must be >= UP.
+ */
+
+mpi_limb_t
+mpihelp_lshift( mpi_ptr_t wp, mpi_ptr_t up, mpi_size_t usize,
+					    unsigned int cnt)
+{
+    mpi_limb_t high_limb, low_limb;
+    unsigned sh_1, sh_2;
+    mpi_size_t i;
+    mpi_limb_t retval;
+
+    sh_1 = cnt;
+    wp += 1;
+    sh_2 = BITS_PER_MPI_LIMB - sh_1;
+    i = usize - 1;
+    low_limb = up[i];
+    retval = low_limb >> sh_2;
+    high_limb = low_limb;
+    while( --i >= 0 ) {
+	low_limb = up[i];
+	wp[i] = (high_limb << sh_1) | (low_limb >> sh_2);
+	high_limb = low_limb;
+    }
+    wp[i] = high_limb << sh_1;
+
+    return retval;
+}
+
+
+/* Shift U (pointed to by UP and USIZE limbs long) CNT bits to the right
+ * and store the USIZE least significant limbs of the result at WP.
+ * The bits shifted out to the right are returned.
+ *
+ * Argument constraints:
+ * 1. 0 < CNT < BITS_PER_MP_LIMB
+ * 2. If the result is to be written over the input, WP must be <= UP.
+ */
+
+mpi_limb_t
+mpihelp_rshift( mpi_ptr_t wp, mpi_ptr_t up, mpi_size_t usize, unsigned cnt)
+{
+    mpi_limb_t high_limb, low_limb;
+    unsigned sh_1, sh_2;
+    mpi_size_t i;
+    mpi_limb_t retval;
+
+    sh_1 = cnt;
+    wp -= 1;
+    sh_2 = BITS_PER_MPI_LIMB - sh_1;
+    high_limb = up[0];
+    retval = high_limb << sh_2;
+    low_limb = high_limb;
+    for( i=1; i < usize; i++) {
+	high_limb = up[i];
+	wp[i] = (low_limb >> sh_1) | (high_limb << sh_2);
+	low_limb = high_limb;
+    }
+    wp[i] = low_limb >> sh_1;
+
+    return retval;
+}
+