Subject: Re: [PATCH] block-sha1: Windows declares ntohl() in winsock2.h

From: Sebastian Schuberth <[email-masked]>
Date: Tue, 18 Aug 2009 12:45:53 +0200

> This is a minimal fix to compile block-sha1 on Windows. I did not do any
> benchmarks whether the implementation of ntohl() is actually faster than
> bytewise access and shifts.

As ntohl()/htonl() are function calls (that internally do shifts), I 
doubt they're faster than the shift macros, though I haven't measured 
it. However, I do not suggest to go for the macros on Windows/Intel, but 
to apply the following patch on top of your patch:

 From 34402f0e5691ca46cd63c930eef8fc9cadf80493 Mon Sep 17 00:00:00 2001
From: Sebastian Schuberth <[email-masked]>
Date: Tue, 18 Aug 2009 12:33:35 +0200
Subject: [PATCH] block-sha1: On Intel, use bswap built-in in favor of 
ntohl()/htonl()

On Windows/Intel, ntohl()/htonl() are function calls that do shifts to 
swap the
byte order. Using the native bswap instruction boths gets rid of the 
shifts and
the function call overhead to gain some performance.

Signed-off-by: Sebastian Schuberth <[email-masked]>
---
  block-sha1/sha1.c |   15 ++++++++++-----
  1 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/block-sha1/sha1.c b/block-sha1/sha1.c
index f2830c0..07f2937 100644
--- a/block-sha1/sha1.c
+++ b/block-sha1/sha1.c
@@ -66,15 +66,20 @@

  /*
   * Performance might be improved if the CPU architecture is OK with
- * unaligned 32-bit loads and a fast ntohl() is available.
+ * unaligned 32-bit loads and a fast ntohl() is available. On Intel,
+ * use the bswap built-in to get rid of the function call overhead.
   * Otherwise fall back to byte loads and shifts which is portable,
   * and is faster on architectures with memory alignment issues.
   */

-#if defined(__i386__) || defined(__x86_64__) || \
-    defined(__ppc__) || defined(__ppc64__) || \
-    defined(__powerpc__) || defined(__powerpc64__) || \
-    defined(__s390__) || defined(__s390x__)
+#if defined(__i386__) || defined(__x86_64__)
+
+#define get_be32(p)	__builtin_bswap32(*(unsigned int *)(p))
+#define put_be32(p, v)	do { *(unsigned int *)(p) = 
__builtin_bswap32(v); } while (0)
+
+#elif defined(__ppc__) || defined(__ppc64__) || \
+      defined(__powerpc__) || defined(__powerpc64__) || \
+      defined(__s390__) || defined(__s390x__)

  #define get_be32(p)	ntohl(*(unsigned int *)(p))
  #define put_be32(p, v)	do { *(unsigned int *)(p) = htonl(v); } while (0)
-- 
1.6.4.169.g64d5.dirty