1  //SPDX-License-Identifier: MIT
  2  pragma solidity >= 0.4.15 < 0.9.0;
  3  
  4  library AssertAddress {
  5  
  6      // Constant: ADDRESS_NULL
  7      // The null address: 0
  8      address constant ADDRESS_NULL = 0x0000000000000000000000000000000000000000;
  9  
 10      /*
 11          Event: TestEvent
 12  
 13          Fired when an assertion is made.
 14  
 15          Params:
 16              result (bool) - Whether or not the assertion holds.
 17              message (string) - A message to display if the assertion does not hold.
 18      */
 19      event TestEvent(bool indexed result, string message);
 20  
 21      // ************************************** address **************************************
 22  
 23      /*
 24          Function: equal(address)
 25  
 26          Assert that two addresses are equal.
 27  
 28          : A == B
 29  
 30          Params:
 31              A (address) - The first address.
 32              B (address) - The second address.
 33              message (string) - A message that is sent if the assertion fails.
 34  
 35          Returns:
 36              result (bool) - The result.
 37      */
 38      function equal(address a, address b, string memory message) public returns (bool result) {
 39          result = (a == b);
 40          _report(result, message);
 41      }
 42      /*
 43          Function: notEqual(address)
 44  
 45          Assert that two addresses are not equal.
 46  
 47          : A != B
 48  
 49          Params:
 50              A (address) - The first address.
 51              B (address) - The second address.
 52              message (string) - A message that is sent if the assertion fails.
 53  
 54          Returns:
 55              result (bool) - The result.
 56      */
 57      function notEqual(address a, address b, string memory message) public returns (bool result) {
 58          result = (a != b);
 59           _report(result, message);
 60      }
 61  
 62      /*
 63          Function: isZero(address)
 64  
 65          Assert that an address is zero.
 66  
 67          : addr == ADDRESS_NULL
 68  
 69          Params:
 70              addr (address) - The address.
 71              message (string) - A message that is sent if the assertion fails.
 72  
 73          Returns:
 74              result (bool) - The result.
 75      */
 76      function isZero(address addr, string memory message) public returns (bool result) {
 77          result = (addr == ADDRESS_NULL);
 78          _report(result, message);
 79      }
 80  
 81      /*
 82          Function: isNotZero(address)
 83  
 84          Assert that an address is not zero.
 85  
 86          : addr != ADDRESS_NULL
 87  
 88          Params:
 89              addr (address) - The address.
 90              message (string) - A message that is sent if the assertion fails.
 91  
 92          Returns:
 93              result (bool) - The result.
 94      */
 95      function isNotZero(address addr, string memory message) public returns (bool result) {
 96          result = (addr != ADDRESS_NULL);
 97          _report(result, message);
 98      }
 99  
100      /******************************** internal ********************************/
101  
102          /*
103              Function: _report
104  
105              Internal function for triggering <TestEvent>.
106  
107              Params:
108                  result (bool) - The test result (true or false).
109                  message (string) - The message that is sent if the assertion fails.
110          */
111      function _report(bool result, string memory message) internal {
112          if(result)
113              emit TestEvent(true, "");
114          else
115              emit TestEvent(false, message);
116      }
117  }