1 files changed, 16 insertions, 14 deletions

diff --git a/src/zlsh.c b/src/zlsh.c
index b631c1a..2a76fbc 100644
--- a/src/zlsh.c
+++ b/src/zlsh.c
@@ -19,25 +19,27 @@ zlsh(z_t a, z_t b, size_t bits)
 
 	chars = FLOOR_BITS_TO_CHARS(bits);
 	bits = BITS_IN_LAST_CHAR(bits);
-	cbits = BITS_PER_CHAR - 1 - bits;
+	cbits = BITS_PER_CHAR - bits;
 
-	a->used = b->used + chars;
-	ENSURE_SIZE(a, a->used);
+	ENSURE_SIZE(a, b->used + chars);
 	if (a == b)
-		zmemmove(a->chars + chars, b->chars, a->used);
+		zmemmove(a->chars + chars, b->chars, b->used);
 	else
-		zmemcpy(a->chars + chars, b->chars, a->used);
+		zmemcpy(a->chars + chars, b->chars, b->used);
 	zmemset(a->chars, 0, chars);
+	a->used = b->used + chars;
 
-	for (i = chars; i < a->used; i++) {
-		carry[~i & 1] = a->chars[i] >> cbits;
-		a->chars[i] <<= bits;
-		a->chars[i] |= carry[i & 1];
-	}
-	if (carry[i & 1]) {
-		ENSURE_SIZE(a, a->alloced << 1);
-		a->chars[i] = carry[i & 1];
-		a->used++;
+	if (bits) { /* This if statement is very important in C. */
+		for (i = chars; i < a->used; i++) {
+			carry[~i & 1] = a->chars[i] >> cbits;
+			a->chars[i] <<= bits;
+			a->chars[i] |= carry[i & 1];
+		}
+		if (carry[i & 1]) {
+			ENSURE_SIZE(a, a->used + 1);
+			a->chars[i] = carry[i & 1];
+			a->used++;
+		}
 	}
 
 	SET_SIGNUM(a, zsignum(b));