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 <stdint.h>
8
9 #include "base/rand_util.h"
10 #include "base/strings/stringprintf.h"
11
12 namespace base {
13
GenerateGUID()14 std::string GenerateGUID() {
15 uint64_t sixteen_bytes[2] = {base::RandUint64(), base::RandUint64()};
16
17 // Set the GUID to version 4 as described in RFC 4122, section 4.4.
18 // The format of GUID version 4 must be xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx,
19 // where y is one of [8, 9, A, B].
20
21 // Clear the version bits and set the version to 4:
22 sixteen_bytes[0] &= 0xffffffffffff0fffULL;
23 sixteen_bytes[0] |= 0x0000000000004000ULL;
24
25 // Set the two most significant bits (bits 6 and 7) of the
26 // clock_seq_hi_and_reserved to zero and one, respectively:
27 sixteen_bytes[1] &= 0x3fffffffffffffffULL;
28 sixteen_bytes[1] |= 0x8000000000000000ULL;
29
30 return RandomDataToGUIDString(sixteen_bytes);
31 }
32
33 // TODO(cmasone): Once we're comfortable this works, migrate Windows code to
34 // use this as well.
RandomDataToGUIDString(const uint64_t bytes[2])35 std::string RandomDataToGUIDString(const uint64_t bytes[2]) {
36 return StringPrintf("%08X-%04X-%04X-%04X-%012llX",
37 static_cast<unsigned int>(bytes[0] >> 32),
38 static_cast<unsigned int>((bytes[0] >> 16) & 0x0000ffff),
39 static_cast<unsigned int>(bytes[0] & 0x0000ffff),
40 static_cast<unsigned int>(bytes[1] >> 48),
41 bytes[1] & 0x0000ffffffffffffULL);
42 }
43
44 } // namespace base
45