byte swapping

git-svn-id: svn://svn.coreboot.org/coreboot/trunk@1406 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1

src/include/swab.h

@@ -0,0 +1,33 @@
+#ifndef _SWAB_H
+#define _SWAB_H
+
+/*
+ * linux/byteorder/swab.h
+ * Byte-swapping, independently from CPU endianness
+ *	swabXX[ps]?(foo)
+ *
+ * Francois-Rene Rideau <fare@tunes.org> 19971205
+ *    separated swab functions from cpu_to_XX,
+ *    to clean up support for bizarre-endian architectures.
+ *
+ * See asm-i386/byteorder.h and suches for examples of how to provide
+ * architecture-dependent optimized versions
+ *
+ */
+
+/* casts are necessary for constants, because we never know how for sure
+ * how U/UL/ULL map to __u16, __u32, __u64. At least not in a portable way.
+ */
+#define swab16(x) \
+	((unsigned short)( \
+		(((unsigned short)(x) & (unsigned short)0x00ffU) << 8) | \
+		(((unsigned short)(x) & (unsigned short)0xff00U) >> 8) ))
+
+#define swab32(x) \
+	((unsigned int)( \
+		(((unsigned int)(x) & (unsigned int)0x000000ffUL) << 24) | \
+		(((unsigned int)(x) & (unsigned int)0x0000ff00UL) <<  8) | \
+		(((unsigned int)(x) & (unsigned int)0x00ff0000UL) >>  8) | \
+		(((unsigned int)(x) & (unsigned int)0xff000000UL) >> 24) ))
+
+#endif /* _SWAB_H */