1 files changed, 51 insertions, 0 deletions
diff --git a/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_lshd.c b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_lshd.c
new file mode 100644
index 00000000000..82345809cc0
--- /dev/null
+++ b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_lshd.c
@@ -0,0 +1,51 @@
+#include "tommath_private.h"
+#ifdef BN_MP_LSHD_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* shift left a certain amount of digits */
+mp_err mp_lshd(mp_int *a, int b)
+{
+   int x;
+   mp_err err;
+   mp_digit *top, *bottom;
+
+   /* if its less than zero return */
+   if (b <= 0) {
+      return MP_OKAY;
+   }
+   /* no need to shift 0 around */
+   if (MP_IS_ZERO(a)) {
+      return MP_OKAY;
+   }
+
+   /* grow to fit the new digits */
+   if (a->alloc < (a->used + b)) {
+      if ((err = mp_grow(a, a->used + b)) != MP_OKAY) {
+         return err;
+      }
+   }
+
+   /* increment the used by the shift amount then copy upwards */
+   a->used += b;
+
+   /* top */
+   top = a->dp + a->used - 1;
+
+   /* base */
+   bottom = (a->dp + a->used - 1) - b;
+
+   /* much like mp_rshd this is implemented using a sliding window
+    * except the window goes the otherway around.  Copying from
+    * the bottom to the top.  see bn_mp_rshd.c for more info.
+    */
+   for (x = a->used - 1; x >= b; x--) {
+      *top-- = *bottom--;
+   }
+
+   /* zero the lower digits */
+   MP_ZERO_DIGITS(a->dp, b);
+
+   return MP_OKAY;
+}
+#endif