如何将DAI从DSR (/ MakerDao)中仅使用合同而不是Dapp前端退出？

Question

我目前正在通过MakerDao (https://oasis.app/save)测试Oasis。在将一些DAI转换成DSR后，用户可以赚取储蓄，只要他们愿意，就可以使用Dapp前端退出按钮提取他们的资金(转换回DAI)。

我喜欢这个想法，但在更多的戴之前，我想知道如何在不使用前端的情况下与合同进行交互。

有人能告诉我如何只使用合同代码来提取所有的储蓄吗？所以不使用绿洲的前端。我想知道我需要调用哪个函数(S)，以及作为输入需要填充什么。

下面是部署在储户帐户上的合同代码：

pragma solidity ^0.4.23;

contract DSAuthority {
    function canCall(
        address src, address dst, bytes4 sig
    ) public view returns (bool);
}

contract DSAuthEvents {
    event LogSetAuthority (address indexed authority);
    event LogSetOwner     (address indexed owner);
}

contract DSAuth is DSAuthEvents {
    DSAuthority  public  authority;
    address      public  owner;

    constructor() public {
        owner = msg.sender;
        emit LogSetOwner(msg.sender);
    }

    function setOwner(address owner_)
        public
        auth
    {
        owner = owner_;
        emit LogSetOwner(owner);
    }

    function setAuthority(DSAuthority authority_)
        public
        auth
    {
        authority = authority_;
        emit LogSetAuthority(authority);
    }

    modifier auth {
        require(isAuthorized(msg.sender, msg.sig));
        _;
    }

    function isAuthorized(address src, bytes4 sig) internal view returns (bool) {
        if (src == address(this)) {
            return true;
        } else if (src == owner) {
            return true;
        } else if (authority == DSAuthority(0)) {
            return false;
        } else {
            return authority.canCall(src, this, sig);
        }
    }
}

contract DSNote {
    event LogNote(
        bytes4   indexed  sig,
        address  indexed  guy,
        bytes32  indexed  foo,
        bytes32  indexed  bar,
        uint              wad,
        bytes             fax
    ) anonymous;

    modifier note {
        bytes32 foo;
        bytes32 bar;

        assembly {
            foo := calldataload(4)
            bar := calldataload(36)
        }

        emit LogNote(msg.sig, msg.sender, foo, bar, msg.value, msg.data);

        _;
    }
}

// DSProxy
// Allows code execution using a persistant identity This can be very
// useful to execute a sequence of atomic actions. Since the owner of
// the proxy can be changed, this allows for dynamic ownership models
// i.e. a multisig
contract DSProxy is DSAuth, DSNote {
    DSProxyCache public cache;  // global cache for contracts

    constructor(address _cacheAddr) public {
        require(setCache(_cacheAddr));
    }

    function() public payable {
    }

    // use the proxy to execute calldata _data on contract _code
    function execute(bytes _code, bytes _data)
        public
        payable
        returns (address target, bytes32 response)
    {
        target = cache.read(_code);
        if (target == 0x0) {
            // deploy contract & store its address in cache
            target = cache.write(_code);
        }

        response = execute(target, _data);
    }

    function execute(address _target, bytes _data)
        public
        auth
        note
        payable
        returns (bytes32 response)
    {
        require(_target != 0x0);

        // call contract in current context
        assembly {
            let succeeded := delegatecall(sub(gas, 5000), _target, add(_data, 0x20), mload(_data), 0, 32)
            response := mload(0)      // load delegatecall output
            switch iszero(succeeded)
            case 1 {
                // throw if delegatecall failed
                revert(0, 0)
            }
        }
    }

    //set new cache
    function setCache(address _cacheAddr)
        public
        auth
        note
        returns (bool)
    {
        require(_cacheAddr != 0x0);        // invalid cache address
        cache = DSProxyCache(_cacheAddr);  // overwrite cache
        return true;
    }
}

// DSProxyFactory
// This factory deploys new proxy instances through build()
// Deployed proxy addresses are logged
contract DSProxyFactory {
    event Created(address indexed sender, address indexed owner, address proxy, address cache);
    mapping(address=>bool) public isProxy;
    DSProxyCache public cache = new DSProxyCache();

    // deploys a new proxy instance
    // sets owner of proxy to caller
    function build() public returns (DSProxy proxy) {
        proxy = build(msg.sender);
    }

    // deploys a new proxy instance
    // sets custom owner of proxy
    function build(address owner) public returns (DSProxy proxy) {
        proxy = new DSProxy(cache);
        emit Created(msg.sender, owner, address(proxy), address(cache));
        proxy.setOwner(owner);
        isProxy[proxy] = true;
    }
}

// DSProxyCache
// This global cache stores addresses of contracts previously deployed
// by a proxy. This saves gas from repeat deployment of the same
// contracts and eliminates blockchain bloat.

// By default, all proxies deployed from the same factory store
// contracts in the same cache. The cache a proxy instance uses can be
// changed.  The cache uses the sha3 hash of a contract's bytecode to
// lookup the address
contract DSProxyCache {
    mapping(bytes32 => address) cache;

    function read(bytes _code) public view returns (address) {
        bytes32 hash = keccak256(_code);
        return cache[hash];
    }

    function write(bytes _code) public returns (address target) {
        assembly {
            target := create(0, add(_code, 0x20), mload(_code))
            switch iszero(extcodesize(target))
            case 1 {
                // throw if contract failed to deploy
                revert(0, 0)
            }
        }
        bytes32 hash = keccak256(_code);
        cache[hash] = target;
    }
}

来源：https://etherscan.io/address/0xad01c274961a55a493991e1f63e0c362aabf6705#code

当单击Dapp上的退出按钮时，似乎调用了execute()函数，但我不知道什么是bytes _data。Metamask为这个参数显示了一个很长的输入(228个字节)，但我不知道它意味着什么，如果需要的话，人们如何自己猜测它。有人知道准确地调用什么以及作为输入应该填写什么吗？

作为一个分散的应用程序，如果由于任何原因前端不可用(维护、更新.)，这将非常有用。一个人想要回他的钱。

谢谢您:)

Answer 1

但我不明白什么是bytes _data

它是一个编码的函数调用，它在函数execute中执行(通过程序集)。

下面是一个编码函数调用的示例：

bytes4 selector = bytes4(uint256(keccak256("someFunc(address,uint256,bool)") >> 224));
bytes memory data = abi.encodeWithSelector(selector, someAddress, someUint256, someBool);

当然，上面的编码是在链上(在合同中)执行的，而您需要计算离链(例如，web3.js脚本)中的相同内容，然后将其传递给合同的函数。

Answer 2

万一绿洲网站消失了怎么办？因为我的硬币被委托给一份困难的合同，我的硬币是否处于危险之中？

这就是为什么我也想知道如何才能只使用合同代码来提取我的储蓄。

从上面的答案看，似乎很复杂，我不知道如何生成该数据字段。也许有人可以一步一步地描述水电部合同的相互作用，以退出绿洲DSR合同？