base/guid_posix.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/guid.h"
   6
   7 #include "base/rand_util.h"
   8 #include "base/strings/stringprintf.h"
   9
  10 namespace base {
  11
  12 std::string GenerateGUID() {
  13   uint64 sixteen_bytes[2] = { base::RandUint64(), base::RandUint64() };
  14
  15   // Set the GUID to version 4 as described in RFC 4122, section 4.4.
  16   // The format of GUID version 4 must be xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx,
  17   // where y is one of [8, 9, A, B].
  18
  19   // Clear the version bits and set the version to 4:
  20   sixteen_bytes[0] &= 0xffffffffffff0fffULL;
  21   sixteen_bytes[0] |= 0x0000000000004000ULL;
  22
  23   // Set the two most significant bits (bits 6 and 7) of the
  24   // clock_seq_hi_and_reserved to zero and one, respectively:
  25   sixteen_bytes[1] &= 0x3fffffffffffffffULL;
  26   sixteen_bytes[1] |= 0x8000000000000000ULL;
  27
  28   return RandomDataToGUIDString(sixteen_bytes);
  29 }
  30
  31 // TODO(cmasone): Once we're comfortable this works, migrate Windows code to
  32 // use this as well.
  33 std::string RandomDataToGUIDString(const uint64 bytes[2]) {
  34   return StringPrintf("%08X-%04X-%04X-%04X-%012llX",
  35                       static_cast<unsigned int>(bytes[0] >> 32),
  36                       static_cast<unsigned int>((bytes[0] >> 16) & 0x0000ffff),
  37                       static_cast<unsigned int>(bytes[0] & 0x0000ffff),
  38                       static_cast<unsigned int>(bytes[1] >> 48),
  39                       bytes[1] & 0x0000ffffffffffffULL);
  40 }
  41
  42 }  // namespace guid