Move net/base/sys_byteorder.h to base/sys_byteorder.h

base/sys_byteorder.h

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This is a convenience header to pull in the platform-specific
+// headers that define functions for byte-order conversion,
+// particularly: ntohs(), htons(), ntohl(), htonl(). Prefer including
+// this file instead of directly writing the #if / #else, since it
+// avoids duplicating the platform-specific selections.
+// This header also provides ntoh_64() and hton_64() for byte-order conversion
+// for 64-bit integers.
+
+#ifndef BASE_SYS_BYTEORDER_H_
+#define BASE_SYS_BYTEORDER_H_
+
+#include "build/build_config.h"
+
+#if defined(OS_WIN)
+#include <winsock2.h>
+#else
+#include <arpa/inet.h>
+#endif
+
+// Include headers to provide bswap for all platforms.
+#if defined(COMPILER_MSVC)
+#include <stdlib.h>
+#define bswap_16(x) _byteswap_ushort(x)

[brettw, 2011/12/21 17:48:14]

Did we consider writing real inline functions rather than #defines for this? I'd
prefer base::ByteSwap() (could be overloaded for 16, 32, and 64-bit types). Or
would this mess something up because the swaps are some kind of intrinsics?

[Ilya Sherman, 2011/12/21 19:43:08]

+hclam, who originally added these, and probably has better insight into this
question

[Ryan Sleevi, 2011/12/21 19:49:10]

wtc is probably a better candidate, as he reviewed and suggested the use of
these functions.

Definitely for MSVC, they are compiler intrinsics. I haven't checked the object
code to see if putting them in an inline function would interfere with the
intrinsics, but I would suspect it would all optimize out properly at even the
most basic of optimizations.

[wtc, 2011/12/23 00:37:22]

No, we didn't consider writing real inline functions.  It
was an oversignt.

[Ilya Sherman, 2011/12/23 02:31:29]

Ok, wrote these as real inline functions instead.  There aren't any clients of
BaseSwap() other than the ntoh and hton functions, so I only defined the 64-bit
one.

I also renamed the "ntoh_64" and "hton_64" functions to be "ntohll" and
"htonll", as that is more consistent with the names "ntohs", "htons", "ntohl",
and "htonl" for the 16- and 32-bit versions of these functions.

+#define bswap_32(x) _byteswap_ulong(x)
+#define bswap_64(x) _byteswap_uint64(x)
+#elif defined(OS_MACOSX)
+#include <libkern/OSByteOrder.h>
+#define bswap_16(x) OSSwapInt16(x)
+#define bswap_32(x) OSSwapInt32(x)
+#define bswap_64(x) OSSwapInt64(x)
+#elif defined(OS_OPENBSD)
+#include <sys/endian.h>
+#define bswap_16(x) swap16(x)
+#define bswap_32(x) swap32(x)
+#define bswap_64(x) swap64(x)
+#else
+#include <byteswap.h>
+#endif
+
+#if defined(ARCH_CPU_LITTLE_ENDIAN)
+#define ntoh_64(x) bswap_64(x)
+#define hton_64(x) bswap_64(x)
+#else
+#define ntoh_64(x) (x)
+#define hton_64(x) (x)
+#endif
+
+#endif  // BASE_SYS_BYTEORDER_H_