linearRevoke.sol

/*
• Zeppelin Audit
• Draft for a proof of concept code on how to make the revoke function of the BeamBalanceStore 
• linear on the size of the policy array. 
•  DO NOT USE IN PRODUCTION
*/

function linearRevoke(string memory  _policyIdentifier)  public returns (bool _revoked) {
    bytes32 _hash = keccak256(abi.encodePacked(_policyIdentifier));
    uint256 i = 0;
    uint256 timesFound = 0;
    /* 
       Note that the loop will end the travelsal one element before the last one.
       This is to avoid accessing an element out of bound (see the assigment below) 
    */
    while (i+timesFound < policies.length-1) {
        if (policies[i] == _hash) {
            // solium-enable zeppelin/no-arithmetic-operations
            timesFound++;
        }
        else {
            i++;
        }
        // solium-enable zeppelin/no-arithmetic-operations
        /* 
           Here is were the removal of the elements and shifting of array elements occurs. 
           Note that if timesFound==0 this statement does nothing but when timesFound>0 the element found 
           will be overwritten with a subsequent element in the array.
        */   
        policies[i] = policies[i+timesFound];
    }
    
    // Check whether the last element is also an ocurrence 
    if (policies[i] == _hash) {
        // solium-enable zeppelin/no-arithmetic-operations
        timesFound++;
    }

    // Reduces the size of the array according to the number of elements found
    policies.length-=timesFound;
            
    if (timesFound>0) {
        // If a policy if found, call reauthorize to rebuild the authorization mapping
        reAuthorize();
        // Inform that the policy was found
        _revoked = true;
        emit Revoked(msg.sender, _policyIdentifier);
    }
    else {
        // If not inform that the policy was not found
        _revoked = false;
        emit NotRevoked(msg.sender, _policyIdentifier);
    }
}