From 1412dac6805f7e2e5e1e8a7d89ba57abf062bdb9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dag-Erling=20Sm=C3=B8rgrav?= <des@des.no>
Date: Mon, 29 Dec 2014 23:20:26 +0000
Subject: [PATCH] Shifting any number by zero places is a no-op, but so is
 shifting zero by any number of places.

---
 lib/mpi/mpi_shift.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/mpi/mpi_shift.c b/lib/mpi/mpi_shift.c
index f058eff..789d0dd 100644
--- a/lib/mpi/mpi_shift.c
+++ b/lib/mpi/mpi_shift.c
@@ -42,8 +42,8 @@ mpi_lshift(cryb_mpi *X, unsigned int c)
 {
 	unsigned int cl, i;
 
-	/* zero shift */
-	if (c == 0)
+	/* operands are zero */
+	if (c == 0 || X->msb == 0)
 		return (0);
 	/* make room */
 	if (mpi_grow(X, X->msb + c) != 0)
@@ -79,8 +79,8 @@ mpi_rshift(cryb_mpi *X, unsigned int c)
 {
 	unsigned int cl, i;
 
-	/* zero shift */
-	if (c == 0)
+	/* operands are zero */
+	if (c == 0 || X->msb == 0)
 		return (0);
 	/* shift wider than number, result is zero */
 	if (X->msb <= c) {