add initial support for 2nd wheel & 4-5 mouse buttons

1 files changed, 7 insertions, 0 deletions

diff --git a/utils.h b/utils.h
index 715294e..9b9db2a 100644
--- a/utils.h
+++ b/utils.h
@@ -92,4 +92,11 @@ static int scalei_rem(int x, int srcmax, int dstmax, short *rem);
 	__value [ax] \
 	__modify [ax cx dx si]
 
+/** Sign extend x from b bits to 16. */
+static inline int16_t sign_extend(int16_t x, int b)
+{
+	int m = 16 - b;
+	return (x << m) >> m;
+}
+
 #endif