[v2,06/10] qemu/bitops.h: add bitrev8 implementation

Commit Message

Mark Cave-Ayland June 25, 2021, 6:53 a.m. UTC

This will be required for an upcoming checksum calculation.

Signed-off-by: Mark Cave-Ayland <[e-mail]>
---
 include/qemu/bitops.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

Comments

Philippe Mathieu-Daudé July 1, 2021, 9:46 p.m. UTC | #1

On 6/25/21 8:53 AM, Mark Cave-Ayland wrote:
> This will be required for an upcoming checksum calculation.
> 
> Signed-off-by: Mark Cave-Ayland <[e-mail]>
> ---
>  include/qemu/bitops.h | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)

Reviewed-by: Philippe Mathieu-Daudé <[e-mail]>

Patch

diff --git a/include/qemu/bitops.h b/include/qemu/bitops.h
index 03213ce952..110c56e099 100644
--- a/include/qemu/bitops.h
+++ b/include/qemu/bitops.h
@@ -618,4 +618,26 @@  static inline uint64_t half_unshuffle64(uint64_t x)
     return x;
 }
 
+/**
+ * bitrev8:
+ * @x: 8-bit value to be reversed
+ *
+ * Given an input value with bits::
+ *
+ *   ABCDEFGH
+ *
+ * return the value with its bits reversed from left to right::
+ *
+ *   HGFEDCBA
+ *
+ * Returns: the bit-reversed value.
+ */
+static inline uint8_t bitrev8(uint8_t x)
+{
+    x = ((x >> 1) & 0x55) | ((x << 1) & 0xaa);
+    x = ((x >> 2) & 0x33) | ((x << 2) & 0xcc);
+    x = (x >> 4) | (x << 4) ;
+    return x;
+}
+
 #endif