qemu/bitops.h: add bitrev8 implementation

This will be required for an upcoming checksum calculation.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Tested-by: Finn Thain <fthain@linux-m68k.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210625065401.30170-7-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

diff --git a/include/qemu/bitops.h b/include/qemu/bitops.h
index 03213ce..110c56e 100644 (file)
--- 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