Unstructured storage demo (mapping to value types)

SimpleMappingDemo.sol

pragma solidity 0.4.24;

contract SimpleMappingDemo {
    
    bytes32 internal constant SHARES_MAPPING_POSITION = keccak256("org.test.storagedemo.shares");
    
    function getShares(address _address) public view returns (uint256) {
        return _getShares(_address, SHARES_MAPPING_POSITION);
    }
    
    function setShares(address _address, uint256 _shares) public {
        _setShares(_address, _shares, SHARES_MAPPING_POSITION);
    }
    
    function _getShares(address _address, bytes32 _sharesSlot) internal view returns (uint256 result) {
        assembly {
            // using scratch space
            mstore(0, _address)
            mstore(32, _sharesSlot)
            let hash := keccak256(0, 64)
            result := sload(hash)
        }
    }
    
    function _setShares(address _address, uint256 _shares, bytes32 _sharesSlot) internal {
        assembly {
            // using scratch space
            mstore(0, _address)
            mstore(32, _sharesSlot)
            let hash := keccak256(0, 64)
            sstore(hash, _shares)
        }
    }
}