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-rw-r--r--libtommath/bn_mp_signed_rsh.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/libtommath/bn_mp_signed_rsh.c b/libtommath/bn_mp_signed_rsh.c
new file mode 100644
index 0000000..8d8d841
--- /dev/null
+++ b/libtommath/bn_mp_signed_rsh.c
@@ -0,0 +1,22 @@
+#include "tommath_private.h"
+#ifdef BN_MP_SIGNED_RSH_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* shift right by a certain bit count with sign extension */
+mp_err mp_signed_rsh(const mp_int *a, int b, mp_int *c)
+{
+ mp_err res;
+ if (a->sign == MP_ZPOS) {
+ return mp_div_2d(a, b, c, NULL);
+ }
+
+ res = mp_add_d(a, 1uL, c);
+ if (res != MP_OKAY) {
+ return res;
+ }
+
+ res = mp_div_2d(c, b, c, NULL);
+ return (res == MP_OKAY) ? mp_sub_d(c, 1uL, c) : res;
+}
+#endif