swd: Improve parity calculation and move it to types.h

[openocd.git] / src / helper / types.h

diff --git a/src/helper/types.h b/src/helper/types.h
index 210d3c3e92fd3d2f1354e8eb0066a41da9a703cd..3f0724c3a65c429f3052094459a46e8493b2cea9 100644 (file)
--- a/src/helper/types.h
+++ b/src/helper/types.h
@@ -270,6 +270,25 @@ static inline void buf_bswap32(uint8_t *dst, const uint8_t *src, size_t len)
        }
 }
 
+/**
+ * Calculate the (even) parity of a 32-bit datum.
+ * @param x The datum.
+ * @return 1 if the number of set bits in x is odd, 0 if it is even.
+ */
+static inline int parity_u32(uint32_t x)
+{
+#ifdef __GNUC__
+       return __builtin_parityl(x);
+#else
+       x ^= x >> 16;
+       x ^= x >> 8;
+       x ^= x >> 4;
+       x ^= x >> 2;
+       x ^= x >> 1;
+       return x & 1;
+#endif
+}
+
 #if defined(__ECOS)
 
 /* eCos plain lacks these definition... A series of upstream patches