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From: Craig Rodrigues <rodrigc@FreeBSD.org>
Date: Fri, 10 Jun 2011 01:13:15 +0000 (UTC)
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Subject: svn commit: r222908 - head/lib/libstand
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Author: rodrigc
Date: Fri Jun 10 01:13:15 2011
New Revision: 222908
URL: http://svn.freebsd.org/changeset/base/222908

Log:
  Obtain bswap64() function implementation from
  version 1.3 of src/common/lib/libc/gen/bswap64.c in NetBSD.
  
  Obtained from: NetBSD

Modified:
  head/lib/libstand/bswap.c

Modified: head/lib/libstand/bswap.c
==============================================================================
--- head/lib/libstand/bswap.c	Thu Jun  9 23:12:23 2011	(r222907)
+++ head/lib/libstand/bswap.c	Fri Jun 10 01:13:15 2011	(r222908)
@@ -8,7 +8,7 @@ __FBSDID("$FreeBSD$");
 
 #if defined(LIBC_SCCS) && !defined(lint)
 static char *rcsid = "$NetBSD: bswap32.c,v 1.1 1997/10/09 15:42:33 bouyer Exp $";
-static char *rcsid = "$NetBSD: bswap64.c,v 1.1 1997/10/09 15:42:33 bouyer Exp $";
+static char *rcsid = "$NetBSD: bswap64.c,v 1.3 2009/03/16 05:59:21 cegger Exp $";
 #endif
 
 #include <sys/types.h>
@@ -30,12 +30,28 @@ bswap32(u_int32_t x)
 
 u_int64_t
 bswap64(u_int64_t x)
-{  
-	u_int32_t *p = (u_int32_t*)&x;
-	u_int32_t t;
-	t = bswap32(p[0]);
-	p[0] = bswap32(p[1]);
-	p[1] = t;
-	return x;
-}   
-
+{
+#ifdef _LP64
+	/*
+	 * Assume we have wide enough registers to do it without touching
+	 * memory.
+	 */
+	return  ( (x << 56) & 0xff00000000000000UL ) |
+		( (x << 40) & 0x00ff000000000000UL ) |
+		( (x << 24) & 0x0000ff0000000000UL ) |
+		( (x <<  8) & 0x000000ff00000000UL ) |
+		( (x >>  8) & 0x00000000ff000000UL ) |
+		( (x >> 24) & 0x0000000000ff0000UL ) |
+		( (x >> 40) & 0x000000000000ff00UL ) |
+		( (x >> 56) & 0x00000000000000ffUL );
+#else
+	/*
+	 * Split the operation in two 32bit steps.
+	 */
+	u_int32_t tl, th;
+
+	th = bswap32((u_int32_t)(x & 0x00000000ffffffffULL));
+	tl = bswap32((u_int32_t)((x >> 32) & 0x00000000ffffffffULL));
+	return ((u_int64_t)th << 32) | tl;
+#endif
+}