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
GenerateGUID()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.
RandomDataToGUIDString(const uint64 bytes[2])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
43