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      1 // Copyright (c) 2006, Google Inc.
      2 // All rights reserved.
      3 //
      4 // Redistribution and use in source and binary forms, with or without
      5 // modification, are permitted provided that the following conditions are
      6 // met:
      7 //
      8 //     * Redistributions of source code must retain the above copyright
      9 // notice, this list of conditions and the following disclaimer.
     10 //     * Redistributions in binary form must reproduce the above
     11 // copyright notice, this list of conditions and the following disclaimer
     12 // in the documentation and/or other materials provided with the
     13 // distribution.
     14 //     * Neither the name of Google Inc. nor the names of its
     15 // contributors may be used to endorse or promote products derived from
     16 // this software without specific prior written permission.
     17 //
     18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29 
     30 #include "common/linux/guid_creator.h"
     31 
     32 #include <assert.h>
     33 #include <pthread.h>
     34 #include <stdio.h>
     35 #include <stdlib.h>
     36 #include <time.h>
     37 #include <unistd.h>
     38 
     39 //
     40 // GUIDGenerator
     41 //
     42 // This class is used to generate random GUID.
     43 // Currently use random number to generate a GUID since Linux has
     44 // no native GUID generator. This should be OK since we don't expect
     45 // crash to happen very offen.
     46 //
     47 class GUIDGenerator {
     48  public:
     49   static uint32_t BytesToUInt32(const uint8_t bytes[]) {
     50     return ((uint32_t) bytes[0]
     51             | ((uint32_t) bytes[1] << 8)
     52             | ((uint32_t) bytes[2] << 16)
     53             | ((uint32_t) bytes[3] << 24));
     54   }
     55 
     56   static void UInt32ToBytes(uint8_t bytes[], uint32_t n) {
     57     bytes[0] = n & 0xff;
     58     bytes[1] = (n >> 8) & 0xff;
     59     bytes[2] = (n >> 16) & 0xff;
     60     bytes[3] = (n >> 24) & 0xff;
     61   }
     62 
     63   static bool CreateGUID(GUID *guid) {
     64     InitOnce();
     65     guid->data1 = random();
     66     guid->data2 = (uint16_t)(random());
     67     guid->data3 = (uint16_t)(random());
     68     UInt32ToBytes(&guid->data4[0], random());
     69     UInt32ToBytes(&guid->data4[4], random());
     70     return true;
     71   }
     72 
     73  private:
     74   static void InitOnce() {
     75     pthread_once(&once_control, &InitOnceImpl);
     76   }
     77 
     78   static void InitOnceImpl() {
     79     srandom(time(NULL));
     80   }
     81 
     82   static pthread_once_t once_control;
     83 };
     84 
     85 pthread_once_t GUIDGenerator::once_control = PTHREAD_ONCE_INIT;
     86 
     87 bool CreateGUID(GUID *guid) {
     88   return GUIDGenerator::CreateGUID(guid);
     89 }
     90 
     91 // Parse guid to string.
     92 bool GUIDToString(const GUID *guid, char *buf, int buf_len) {
     93   // Should allow more space the the max length of GUID.
     94   assert(buf_len > kGUIDStringLength);
     95   int num = snprintf(buf, buf_len, kGUIDFormatString,
     96                      guid->data1, guid->data2, guid->data3,
     97                      GUIDGenerator::BytesToUInt32(&(guid->data4[0])),
     98                      GUIDGenerator::BytesToUInt32(&(guid->data4[4])));
     99   if (num != kGUIDStringLength)
    100     return false;
    101 
    102   buf[num] = '\0';
    103   return true;
    104 }
    105