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 // Copyright (c) 2006, Google Inc.

 // All rights reserved.

 //

 // Redistribution and use in source and binary forms, with or without

 // modification, are permitted provided that the following conditions are

 // met:

 //

 //     * Redistributions of source code must retain the above copyright

 // notice, this list of conditions and the following disclaimer.

 //     * Redistributions in binary form must reproduce the above

 // copyright notice, this list of conditions and the following disclaimer

 // in the documentation and/or other materials provided with the

 // distribution.

 //     * Neither the name of Google Inc. nor the names of its

 // contributors may be used to endorse or promote products derived from

 // this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 #include "common/linux/guid_creator.h"

 #include <assert.h>

 #include <pthread.h>

 #include <stdio.h>

 #include <stdlib.h>

 #include <time.h>

 #include <unistd.h>

 //

 // GUIDGenerator

 //

 // This class is used to generate random GUID.

 // Currently use random number to generate a GUID since Linux has

 // no native GUID generator. This should be OK since we don't expect

 // crash to happen very offen.

 //

 class GUIDGenerator {

  public:

   static uint32_t BytesToUInt32(const uint8_t bytes[]) {

     return ((uint32_t) bytes[0]

             | ((uint32_t) bytes[1] << 8)

             | ((uint32_t) bytes[2] << 16)

             | ((uint32_t) bytes[3] << 24));

   }

   static void UInt32ToBytes(uint8_t bytes[], uint32_t n) {

     bytes[0] = n & 0xff;

     bytes[1] = (n >> 8) & 0xff;

     bytes[2] = (n >> 16) & 0xff;

     bytes[3] = (n >> 24) & 0xff;

   }

   static bool CreateGUID(GUID *guid) {

     InitOnce();

     guid->data1 = random();

     guid->data2 = (uint16_t)(random());

     guid->data3 = (uint16_t)(random());

     UInt32ToBytes(&guid->data4[0], random());

     UInt32ToBytes(&guid->data4[4], random());

     return true;

   }

  private:

   static void InitOnce() {

     pthread_once(&once_control, &InitOnceImpl);

   }

   static void InitOnceImpl() {

     srandom(time(NULL));

   }

   static pthread_once_t once_control;

 };

 pthread_once_t GUIDGenerator::once_control = PTHREAD_ONCE_INIT;

 bool CreateGUID(GUID *guid) {

   return GUIDGenerator::CreateGUID(guid);

 }

 // Parse guid to string.

 bool GUIDToString(const GUID *guid, char *buf, int buf_len) {

   // Should allow more space the the max length of GUID.

   assert(buf_len > kGUIDStringLength);

   int num = snprintf(buf, buf_len, kGUIDFormatString,

                      guid->data1, guid->data2, guid->data3,

                      GUIDGenerator::BytesToUInt32(&(guid->data4[0])),

                      GUIDGenerator::BytesToUInt32(&(guid->data4[4])));

   if (num != kGUIDStringLength)

     return false;

   buf[num] = '\0';

   return true;

 }