properly implement msmouse-like sensitivity, separate from speedHEADmaster

1 files changed, 14 insertions, 5 deletions

diff --git a/utils.h b/utils.h
index 9b9db2a..e1258c9 100644
--- a/utils.h
+++ b/utils.h
@@ -60,7 +60,17 @@ static unsigned scaleu(unsigned x, unsigned srcmax, unsigned dstmax);
 	"div bx" /* ax = dx:ax / srcmax */\
 	__parm [ax] [bx] [cx] \
 	__value [ax] \
-	__modify [ax dx]
+	__modify exact [ax dx]
+
+/** Map x linearly from range [0, srcmax] to [0, 2^dstmax].
+ *  Equivalent to above, but uses shift instead of division. */
+static unsigned scaleu_shift(unsigned x, unsigned char srcmax, unsigned dstmax);
+#pragma aux scaleu_shift = \
+	"mul dx" /* dx:ax = x * dstmax */ \
+	"shrd ax, dx, cl" /* ax = dx:ax / 2^srcmax */ \
+	__parm [ax] [cl] [dx] \
+	__value [ax] \
+	__modify exact [ax dx]
 
 /** Map x linearly from range [0, srcmax] to [0, dstmax].
  *  Equivalent of (x * dstmax) / srcmax but with 32-bit signed precision. */
@@ -70,12 +80,11 @@ static int scalei(int x, int srcmax, int dstmax);
 	"idiv bx" /* ax = dx:ax / srcmax */ \
 	__parm [ax] [bx] [cx] \
 	__value [ax] \
-	__modify [ax dx]
+	__modify exact [ax dx]
 
 /** Map x linearly from range [0, srcmax] to [0, dstmax].
- *  Equivalent of (x * dstmax) / srcmax but with 32-bit signed precision.
- *  Division remainder is returned in rem, which should be reused
- *  in future calls to reduce rounding error. */
+ *  Equivalent to scalei, but the division remainder is returned in rem,
+ *  which can be reused in future calls to reduce rounding error. */
 static int scalei_rem(int x, int srcmax, int dstmax, short *rem);
 #pragma aux scalei_rem = \
 	"imul cx"       /* dx:ax = x * dstmax */ \