crypto: lib - Move mpi into lib/crypto

[thirdparty/linux.git] / lib / crypto / mpi / generic_mpih-add1.c

diff --git a/lib/crypto/mpi/generic_mpih-add1.c b/lib/crypto/mpi/generic_mpih-add1.c
new file mode 100644 (file)
index 0000000..299308b
--- /dev/null
+++ b/lib/crypto/mpi/generic_mpih-add1.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* mpihelp-add_1.c  -  MPI helper functions
+ * Copyright (C) 1994, 1996, 1997, 1998,
+ *               2000 Free Software Foundation, Inc.
+ *
+ * This file is part of GnuPG.
+ *
+ * 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 "mpi-internal.h"
+#include "longlong.h"
+
+mpi_limb_t
+mpihelp_add_n(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
+             mpi_ptr_t s2_ptr, mpi_size_t size)
+{
+       mpi_limb_t x, y, cy;
+       mpi_size_t j;
+
+       /* The loop counter and index J goes from -SIZE to -1.  This way
+          the loop becomes faster.  */
+       j = -size;
+
+       /* Offset the base pointers to compensate for the negative indices. */
+       s1_ptr -= j;
+       s2_ptr -= j;
+       res_ptr -= j;
+
+       cy = 0;
+       do {
+               y = s2_ptr[j];
+               x = s1_ptr[j];
+               y += cy;        /* add previous carry to one addend */
+               cy = y < cy;    /* get out carry from that addition */
+               y += x;         /* add other addend */
+               cy += y < x;    /* get out carry from that add, combine */
+               res_ptr[j] = y;
+       } while (++j);
+
+       return cy;
+}