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      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 <stddef.h>
      8 #include <stdint.h>
      9 
     10 #include "base/rand_util.h"
     11 #include "base/strings/string_util.h"
     12 #include "base/strings/stringprintf.h"
     13 
     14 namespace base {
     15 
     16 namespace {
     17 
     18 bool IsLowerHexDigit(char c) {
     19   return (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f');
     20 }
     21 
     22 bool IsValidGUIDInternal(const base::StringPiece& guid, bool strict) {
     23   const size_t kGUIDLength = 36U;
     24   if (guid.length() != kGUIDLength)
     25     return false;
     26 
     27   for (size_t i = 0; i < guid.length(); ++i) {
     28     char current = guid[i];
     29     if (i == 8 || i == 13 || i == 18 || i == 23) {
     30       if (current != '-')
     31         return false;
     32     } else {
     33       if ((strict && !IsLowerHexDigit(current)) || !IsHexDigit(current))
     34         return false;
     35     }
     36   }
     37 
     38   return true;
     39 }
     40 
     41 }  // namespace
     42 
     43 std::string GenerateGUID() {
     44   uint64_t sixteen_bytes[2] = {base::RandUint64(), base::RandUint64()};
     45 
     46   // Set the GUID to version 4 as described in RFC 4122, section 4.4.
     47   // The format of GUID version 4 must be xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx,
     48   // where y is one of [8, 9, A, B].
     49 
     50   // Clear the version bits and set the version to 4:
     51   sixteen_bytes[0] &= 0xffffffffffff0fffULL;
     52   sixteen_bytes[0] |= 0x0000000000004000ULL;
     53 
     54   // Set the two most significant bits (bits 6 and 7) of the
     55   // clock_seq_hi_and_reserved to zero and one, respectively:
     56   sixteen_bytes[1] &= 0x3fffffffffffffffULL;
     57   sixteen_bytes[1] |= 0x8000000000000000ULL;
     58 
     59   return RandomDataToGUIDString(sixteen_bytes);
     60 }
     61 
     62 bool IsValidGUID(const base::StringPiece& guid) {
     63   return IsValidGUIDInternal(guid, false /* strict */);
     64 }
     65 
     66 bool IsValidGUIDOutputString(const base::StringPiece& guid) {
     67   return IsValidGUIDInternal(guid, true /* strict */);
     68 }
     69 
     70 std::string RandomDataToGUIDString(const uint64_t bytes[2]) {
     71   return StringPrintf("%08x-%04x-%04x-%04x-%012llx",
     72                       static_cast<unsigned int>(bytes[0] >> 32),
     73                       static_cast<unsigned int>((bytes[0] >> 16) & 0x0000ffff),
     74                       static_cast<unsigned int>(bytes[0] & 0x0000ffff),
     75                       static_cast<unsigned int>(bytes[1] >> 48),
     76                       bytes[1] & 0x0000ffffffffffffULL);
     77 }
     78 
     79 }  // namespace base
     80