text: // Copyright (c) Microsoft. All rights reserved.
  // Licensed under the MIT license. See LICENSE file in the project root for full license information.
  
  #include <stdlib.h>
  #include <stdint.h>
  #include "azure_c_shared_utility/uniqueid.h"
  #include "azure_c_shared_utility/xlogging.h"
  #include <time.h>
  
  MU_DEFINE_ENUM_STRINGS(UNIQUEID_RESULT, UNIQUEID_RESULT_VALUES);
  
  static const char tochar[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
  static void generate128BitUUID(unsigned char* arrayOfByte)
  {
      size_t arrayIndex;
  
      for (arrayIndex = 0; arrayIndex < 16; arrayIndex++)
      {
          arrayOfByte[arrayIndex] = (unsigned char)rand();
      }
  
      //
      // Stick in the version field for random uuid.
      //
      arrayOfByte[7] &= 0x0f; //clear the bit field
      arrayOfByte[7] |= 0x40; //set the ones we care about
  
      //
      // Stick in the variant field for the random uuid.
      //
      arrayOfByte[8] &= 0xf3; // Clear
      arrayOfByte[8] |= 0x08; // Set
  
  }
  
  // TODO: The User will need to call srand before calling this function
  UNIQUEID_RESULT UniqueId_Generate(char* uid, size_t len)
  {
      UNIQUEID_RESULT result;
      unsigned char arrayOfChar[16];
  
      /* Codes_SRS_UNIQUEID_07_002: [If uid is NULL then UniqueId_Generate shall return UNIQUEID_INVALID_ARG] */
      /* Codes_SRS_UNIQUEID_07_003: [If len is less then 37 then UniqueId_Generate shall return UNIQUEID_INVALID_ARG] */
      if (uid == NULL || len < 37)
      {
          result = UNIQUEID_INVALID_ARG;
          LogError("Buffer Size is Null or length is less then 37 bytes");
      }
      else 
      {
          size_t arrayIndex;
          size_t shiftCount;
          size_t characterPosition = 0;
  
          /* Codes_SRS_UNIQUEID_07_001: [UniqueId_Generate shall create a unique Id 36 character long string.] */
          generate128BitUUID(arrayOfChar);
          for (arrayIndex = 0; arrayIndex < 16; arrayIndex++)
          {
              for (shiftCount = 0; shiftCount <= 1; shiftCount++)
              {
                  char hexChar = tochar[arrayOfChar[arrayIndex] & 0xf];
                  if ((characterPosition == 8) || (characterPosition == 13) || (characterPosition == 18) || (characterPosition == 23))
                  {
                      uid[characterPosition] = '-';
                      characterPosition++;
                  }
                  uid[characterPosition] = hexChar;
                  characterPosition++;
                  arrayOfChar[arrayIndex] = arrayOfChar[arrayIndex] >> 4;
              }
          }
          uid[characterPosition] = 0;
          result = UNIQUEID_OK;
      }
      return result;
  }
  