mappingTest.sol

pragma solidity ^0.4.11;

contract mappingTest{
    struct entry{
        uint index;
        bytes32 value;
    }
    
    mapping(address => entry) internal map;
    address[] internal keylist; // for check out how many keys in map
    
    function add(address _key, bytes32 _value) public {
        entry en = map[_key];
        en.value = _value;
        
        if(en.index > 0){ //exist
            return;
        } else {
            keylist.push(_key);
            uint keylistIndex = keylist.length - 1 ;
            en.index = keylistIndex + 1 ;
        }
    }
    
    function del(address _key) public {
        delete map[_key];
    }
    
    function contain() public returns(bool){ // exist
        return map[_key].index > 0 ;
    }
    
    function checkoutlen() view public returns(uint){
        return uint(keylist.length); // ? is this 형변환?
    }
    
    function remove(address _key) public {
        entry en = map[_key];
        require(en.index != 0);
        require(!(en.index >= keylist.length));
        
        // 맨 뒤에 있는 걸 삭제할 인덱스에 넣고 크기 줄이는 작업
        uint keylistIndex = en.index - 1;
        uint lastIndex = keylist.length - 1;
        map[keylist[lastIndex]].index = en.index;
        keylist[keylistIndex] = keylist[lastIndex];
        keylist.length--;
        delete map[_key];
    }
    
    function show(address _key) constant returns(bytes32){
        return map[_key]
    }
}