initially checkin

1 files changed, 88 insertions, 0 deletions

diff --git a/mpi/mpi-scan.c b/mpi/mpi-scan.c
new file mode 100644
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--- /dev/null
+++ b/mpi/mpi-scan.c
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+/* mpi-scan.c  -  MPI 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"
+
+/****************
+ * 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( MPI a, unsigned index )
+{
+    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 == index )
+		return (limb >> j*8) & 0xff;
+    }
+    return -1;
+}
+
+
+/****************
+ * Put a value at position INDEX into A. index counts from lsb to msb
+ */
+void
+mpi_putbyte( MPI a, unsigned index, int c )
+{
+    int i, j;
+    unsigned n;
+    mpi_ptr_t ap;
+    mpi_limb_t limb;
+
+#if BYTES_PER_MPI_LIMB != 4
+  #error please enhance this function, its ugly - i know.
+#endif
+    c &= 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 == index ) {
+		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);
+		if( a->nlimbs <= i )
+		    a->nlimbs = i+1;
+		ap[i] = limb;
+		return;
+	    }
+    }
+    abort(); /* index out of range */
+}
+