1 files changed, 136 insertions, 0 deletions

diff --git a/lib/mpi/mpi-scan.c b/lib/mpi/mpi-scan.c
new file mode 100644
index 000000000000..b2da5ad96199
--- /dev/null
+++ b/lib/mpi/mpi-scan.c
@@ -0,0 +1,136 @@
+/* mpi-scan.c  -  MPI functions
+ * 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
+ */
+
+#include "mpi-internal.h"
+#include "longlong.h"
+
+/****************
+ * Scan through an mpi and return byte for byte. a -1 is returned to indicate
+ * the end of the mpi. Scanning is done from the lsb to the msb, returned
+ * values are in the range of 0 .. 255.
+ *
+ * FIXME: This code is VERY ugly!
+ */
+int mpi_getbyte(const MPI a, unsigned idx)
+{
+        int i, j;
+        unsigned n;
+        mpi_ptr_t ap;
+        mpi_limb_t limb;
+
+        ap = a->d;
+        for (n = 0, i = 0; i < a->nlimbs; i++) {
+                limb = ap[i];
+                for (j = 0; j < BYTES_PER_MPI_LIMB; j++, n++)
+                        if (n == idx)
+                                return (limb >> j * 8) & 0xff;
+        }
+        return -1;
+}
+
+/****************
+ * Put a value at position IDX into A. idx counts from lsb to msb
+ */
+void mpi_putbyte(MPI a, unsigned idx, int xc)
+{
+        int i, j;
+        unsigned n;
+        mpi_ptr_t ap;
+        mpi_limb_t limb, c;
+
+        c = xc & 0xff;
+        ap = a->d;
+        for (n = 0, i = 0; i < a->alloced; i++) {
+                limb = ap[i];
+                for (j = 0; j < BYTES_PER_MPI_LIMB; j++, n++)
+                        if (n == idx) {
+#if BYTES_PER_MPI_LIMB == 4
+                                if (j == 0)
+                                        limb = (limb & 0xffffff00) | c;
+                                else if (j == 1)
+                                        limb = (limb & 0xffff00ff) | (c << 8);
+                                else if (j == 2)
+                                        limb = (limb & 0xff00ffff) | (c << 16);
+                                else
+                                        limb = (limb & 0x00ffffff) | (c << 24);
+#elif BYTES_PER_MPI_LIMB == 8
+                                if (j == 0)
+                                        limb = (limb & 0xffffffffffffff00) | c;
+                                else if (j == 1)
+                                        limb =
+                                            (limb & 0xffffffffffff00ff) | (c <<
+                                                                           8);
+                                else if (j == 2)
+                                        limb =
+                                            (limb & 0xffffffffff00ffff) | (c <<
+                                                                           16);
+                                else if (j == 3)
+                                        limb =
+                                            (limb & 0xffffffff00ffffff) | (c <<
+                                                                           24);
+                                else if (j == 4)
+                                        limb =
+                                            (limb & 0xffffff00ffffffff) | (c <<
+                                                                           32);
+                                else if (j == 5)
+                                        limb =
+                                            (limb & 0xffff00ffffffffff) | (c <<
+                                                                           40);
+                                else if (j == 6)
+                                        limb =
+                                            (limb & 0xff00ffffffffffff) | (c <<
+                                                                           48);
+                                else
+                                        limb =
+                                            (limb & 0x00ffffffffffffff) | (c <<
+                                                                           56);
+#else
+#error please enhance this function, its ugly - i know.
+#endif
+                                if (a->nlimbs <= i)
+                                        a->nlimbs = i + 1;
+                                ap[i] = limb;
+                                return;
+                        }
+        }
+        log_bug("index out of range\n");
+}
+
+/****************
+ * Count the number of zerobits at the low end of A
+ */
+unsigned mpi_trailing_zeros(const MPI a)
+{
+        unsigned n, count = 0;
+
+        for (n = 0; n < a->nlimbs; n++) {
+                if (a->d[n]) {
+                        unsigned nn;
+                        mpi_limb_t alimb = a->d[n];
+
+                        count_trailing_zeros(nn, alimb);
+                        count += nn;
+                        break;
+                }
+                count += BITS_PER_MPI_LIMB;
+        }
+        return count;
+
+}