硬核深度解析:BAYC“无聊猿” 源码中的随机偏移逻辑与公平性博弈

{  "image": "ipfs://QmRRPWG96cmgTn2qSzjwr2qvfNEuhunv6FNeMFGa9bx6mQ",  "attributes": [    {      "trait_type": "Earring",      "value": "Silver Hoop"    },    {      "trait_type": "Background",      "value": "Orange"    },    {      "trait_type": "Fur",      "value": "Robot"    },    {      "trait_type": "Clothes",      "value": "Striped Tee"    },    {      "trait_type": "Mouth",      "value": "Discomfort"    },    {      "trait_type": "Eyes",      "value": "X Eyes"    }  ]}

contract BoredApeYachtClub is ERC721, Ownable {    using SafeMath for uint256;    string public BAYC_PROVENANCE = "";  //hash承诺，把所有图片人为排定一个初始顺序，并且把图片的hash摘要进行拼接、再算出总的hash摘要上链进行承诺    uint256 public startingIndexBlock; //揭示阶段初始区块编号    uint256 public startingIndex;  //偏移量，即随机种子    uint256 public constant apePrice = 80000000000000000; //0.08 ETH 发行价格    uint public constant maxApePurchase = 20;  //每次最多mint 20个    uint256 public MAX_APES;  //最大发行量 10000    bool public saleIsActive = false;  //宣发期 -> 正式发售    uint256 public REVEAL_TIMESTAMP; //揭示时间。    constructor(string memory name, string memory symbol, uint256 maxNftSupply, uint256 saleStart) ERC721(name, symbol) {        MAX_APES = maxNftSupply;        REVEAL_TIMESTAMP = saleStart + (86400 * 9); //开始发售9天之后为揭示时间    }    function withdraw() public onlyOwner {  //项目方提取赚的发行收益        uint balance = address(this).balance;        msg.sender.transfer(balance);    }    /**     * Set some Bored Apes aside     */    function reserveApes() public onlyOwner { //项目方自己mint保留30个。            uint supply = totalSupply();        uint i;        for (i = 0; i < 30; i++) {            _safeMint(msg.sender, supply + i);        }    }    /**     * DM Gargamel in Discord that you're standing right behind him.      */    function setRevealTimestamp(uint256 revealTimeStamp) public onlyOwner {        REVEAL_TIMESTAMP = revealTimeStamp;    }     /*         * Set provenance once it's calculated 项目方设置承诺    */    function setProvenanceHash(string memory provenanceHash) public onlyOwner {        BAYC_PROVENANCE = provenanceHash;    }    function setBaseURI(string memory baseURI) public onlyOwner { //项目方设置bashUrl        _setBaseURI(baseURI);    }    /*    * Pause sale if active, make active if paused    */    function flipSaleState() public onlyOwner { //切换状态        saleIsActive = !saleIsActive;    }    /**    * Mints Bored Apes 批量铸造NFT    */    function mintApe(uint numberOfTokens) public payable {        require(saleIsActive, "Sale must be active to mint Ape"); //是否已到开放mint时间        require(numberOfTokens <= maxApePurchase, "Can only mint 20 tokens at a time"); //每次最多mint 20个        require(totalSupply().add(numberOfTokens) <= MAX_APES, "Purchase would exceed max supply of Apes"); //是否超过总供给数量        require(apePrice.mul(numberOfTokens) <= msg.value, "Ether value sent is not correct"); //发送来的eth要超过初始发行价格        for(uint i = 0; i < numberOfTokens; i++) { //批量mint            uint mintIndex = totalSupply();            if (totalSupply() < MAX_APES) {                _safeMint(msg.sender, mintIndex);            }        }        // If we haven't set the starting index and this is either 1) the last saleable token or 2) the first token to be sold after        // the end of pre-sale, set the starting index block         if (startingIndexBlock == 0 && (totalSupply() == MAX_APES || block.timestamp >= REVEAL_TIMESTAMP)) {            startingIndexBlock = block.number;  //全卖完了或者到揭示时间了，那么就把这时候的block.number设置为startingIndexBlock        }     }    /**     * Set the starting index for the collection 允许任何人调用可以防止项目方拖延reveal     */    function setStartingIndex() public {  //startingIndexBlock确定了，startingIndex也就确定了        require(startingIndex == 0, "Starting index is already set");        require(startingIndexBlock != 0, "Starting index block must be set"); //startingIndexBlock要先被设置，要么通过mintApe，要么通过emergencySetStartingIndexBlock        startingIndex = uint(blockhash(startingIndexBlock)) % MAX_APES;  //计算startingIndex的算法        // Just a sanity case in the worst case if this function is called late (EVM only stores last 256 block hashes)        ///startingIndexBlock设置之后，过了255个区块才有人调用setStartingIndex，但项目方应该避免这种兜底情况发生。        if (block.number.sub(startingIndexBlock) > 255) {              startingIndex = uint(blockhash(block.number - 1)) % MAX_APES;        }        // Prevent default sequence        if (startingIndex == 0) {            startingIndex = startingIndex.add(1);  //如果刚好区块编号整除MAX_APES，那强制改成1        }    }    /**     * Set the starting index block for the collection, essentially unblocking     * setting starting index     */    function emergencySetStartingIndexBlock() public onlyOwner { //如果mintApe的时候没能设置startingIndexBlock（9天没卖完、且到9天了也没人mint触发），项目方可以手动设置。        require(startingIndex == 0, "Starting index is already set");        startingIndexBlock = block.number;    }}

/*** DM Gargamel in Discord that you're standing right behind him. */function setRevealTimestamp(uint256 revealTimeStamp) public onlyOwner {   REVEAL_TIMESTAMP = revealTimeStamp;}