Fixing issues with alignment, undefined behaviour and endianness in the FieldTrial::HashName functi…

base/sys_byteorder.h

 // Copyright (c) 2012 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 header defines cross-platform ByteSwap() implementations for 16, 32 and
 // 64-bit values, and NetToHostXX() / HostToNextXX() functions equivalent to
 // the traditional ntohX() and htonX() functions.
 // Use the functions defined here rather than using the platform-specific
 // functions directly.
 
@@ skipping 51 matching lines @@
   return _byteswap_uint64(x);
 #elif defined(OS_MACOSX)
   return OSSwapInt64(x);
 #elif defined(OS_OPENBSD)
   return swap64(x);
 #else
   return bswap_64(x);
 #endif
 }
 
+// Converts the bytes in |x| from host order (endianness) to little endian, and
+// returns the result.
+inline uint16 ByteSwapToLE16(uint16 x) {
+#if defined(ARCH_CPU_LITTLE_ENDIAN)
+  return x;
+#else
+  return ByteSwap(x);
+#endif
+}
+inline uint32 ByteSwapToLE32(uint32 x) {
+#if defined(ARCH_CPU_LITTLE_ENDIAN)
+  return x;
+#else
+  return ByteSwap(x);
+#endif
+}
+inline uint64 ByteSwapToLE64(uint64 x) {
+#if defined(ARCH_CPU_LITTLE_ENDIAN)
+  return x;
+#else
+  return ByteSwap(x);
+#endif

[Ilya Sherman, 2012/04/13 20:19:20]

Hmm, why are you adding these functions rather than just using HostToNet32()? 
Is it important that the bytes be in little-endian order rather than in
big-endian order?

[jwd, 2012/04/13 20:33:44]

We decided that we wanted the values in little-endian because of the existing
data and some arguments about the servers being mostly little-endian right now
anyway. 
On 2012/04/13 20:19:20, Ilya Sherman wrote:

[Ilya Sherman, 2012/04/13 21:27:33]

Ok, fair enough.  Thanks :)

+}
+
 // Converts the bytes in |x| from network to host order (endianness), and
 // returns the result.
 inline uint16 NetToHost16(uint16 x) {
 #if defined(ARCH_CPU_LITTLE_ENDIAN)
   return ByteSwap(x);
 #else
   return x;
 #endif
 }
 inline uint32 NetToHost32(uint32 x) {
@@ skipping 32 matching lines @@
   return ByteSwap(x);
 #else
   return x;
 #endif
 }
 
 }  // namespace base
 
 
 #endif  // BASE_SYS_BYTEORDER_H_