代币标准--ERC1155协议源码解析
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ERC1155多代币标准
ERC1155结合了ERC20和ERC721的能力,这是一个标准接口,支持开发同质化的、半同质化的、非同质化的代币和其他配置的通用智能合约。
IERC1155接口
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC1155/IERC1155.sol)
pragma solidity ^0.8.0;
import "../../utils/introspection/IERC165.sol";
// IERC1155接口同样继承了IERC165接口
interface IERC1155 is IERC165
TransferSingle事件
// 转移代币后触发事件,记录转移信息
event TransferSingle(address indexed operator, address indexed from, address indexed to, uint256 id, uint256 value);
TransferBatch事件
// 批量转移代币后触发事件,记录转移信息
event TransferBatch(
address indexed operator,
address indexed from,
address indexed to,
uint256[] ids,
uint256[] values
);
ApprovalForAll事件
// 授权approve后触发事件,记录授权信息
event ApprovalForAll(address indexed account, address indexed operator, bool approved);
URI事件
// URI的值改变时触发该事件,记录信息
event URI(string value, uint256 indexed id);
balanceOf函数
// 获取account账户对应代币id拥有的数量
function balanceOf(address account, uint256 id) external view returns (uint256);
balanceOfBatch函数
// 获取账户列表对用的token余额,相当于多次balanceOf
function balanceOfBatch(address[] calldata accounts, uint256[] calldata ids)
external
view
returns (uint256[] memory);
setApprovalForAll函数
// 设置给operate的授权
function setApprovalForAll(address operator, bool approved) external;
isApprovedForAll函数
// 判断operate是否有account账号的授权
function isApprovedForAll(address account, address operator) external view returns (bool);
safeTransferFrom函数
// 从from账户转移amount数量的代币id到to地址
function safeTransferFrom(
address from,
address to,
uint256 id,
uint256 amount,
bytes calldata data
) external;
safeBatchTransferFrom函数
// 批量转移token,相当于调用多次safeTransfer
function safeBatchTransferFrom(
address from,
address to,
uint256[] calldata ids,
uint256[] calldata amounts,
bytes calldata data
) external;
ERC1155
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC1155/ERC1155.sol)
pragma solidity ^0.8.0;
import "./IERC1155.sol";
import "./IERC1155Receiver.sol";
import "./extensions/IERC1155MetadataURI.sol";
import "../../utils/Address.sol";
import "../../utils/Context.sol";
import "../../utils/introspection/ERC165.sol";
contract ERC1155 is Context, ERC165, IERC1155, IERC1155MetadataURI
using Address for address;
// 代币id与拥有者地址及其该代币余额的映射
mapping(uint256 => mapping(address => uint256)) private _balances;
// 地址之间的授权状态的映射
mapping(address => mapping(address => bool)) private _operatorApprovals;
// 相同类型的代币 _uri是一致的
string private _uri;
// 构造函数 初始化uri
constructor(string memory uri_)
_setURI(uri_);
supportsInterface函数
// 检查合约是否实现该接口
function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool)
return
interfaceId == type(IERC1155).interfaceId ||
interfaceId == type(IERC1155MetadataURI).interfaceId ||
super.supportsInterface(interfaceId);
uri函数
// 获取代币的uri,uri指向是代币的元数据,例如图片信息
function uri(uint256) public view virtual override returns (string memory)
return _uri;
balanceOf函数
// 获取account地址的id代币的数量
function balanceOf(address account, uint256 id) public view virtual override returns (uint256)
// 检查account不为空地址
require(account != address(0), "ERC1155: address zero is not a valid owner");
return _balances[id][account];
balanceOfBatch函数
// 返回account账号列表对应的id代币的数量
function balanceOfBatch(address[] memory accounts, uint256[] memory ids)
public
view
virtual
override
returns (uint256[] memory)
// 检查账号列表长度与代币id列表长度一致
require(accounts.length == ids.length, "ERC1155: accounts and ids length mismatch");
// 创建一个列表长度与account相同
uint256[] memory batchBalances = new uint256[](accounts.length);
// 获取账号对应的代币id的数量
for (uint256 i = 0; i < accounts.length; ++i)
batchBalances[i] = balanceOf(accounts[i], ids[i]);
return batchBalances;
setApprovalForAll函数
// 设置对operate的授权approve状态
function setApprovalForAll(address operator, bool approved) public virtual override
// 调用_setApprovalForAll函数
_setApprovalForAll(_msgSender(), operator, approved);
isApprovedForAll函数
// 获取account地址对operate地址的授权状态
function isApprovedForAll(address account, address operator) public view virtual override returns (bool)
return _operatorApprovals[account][operator];
safeTransferFrom函数
// 转移mount数量的id代币 从from地址到to地址
function safeTransferFrom(
address from,
address to,
uint256 id,
uint256 amount,
bytes memory data
) public virtual override
// 检查from是否是合约调用者地址,或者from账号有approve授权给合约调用者
require(
from == _msgSender() || isApprovedForAll(from, _msgSender()),
"ERC1155: caller is not token owner or approved"
);
// 调用_safeTransferFrom函数,转移代币
_safeTransferFrom(from, to, id, amount, data);
safeBatchTransferFrom函数
// 批量转移代币
function safeBatchTransferFrom(
address from,
address to,
uint256[] memory ids,
uint256[] memory amounts,
bytes memory data
) public virtual override
// 检查from是否是合约调用者地址,或者from账号有approve授权给合约调用者
require(
from == _msgSender() || isApprovedForAll(from, _msgSender()),
"ERC1155: caller is not token owner or approved"
);
// 调用_safeBatchTransferFrom函数转移代币
_safeBatchTransferFrom(from, to, ids, amounts, data);
_safeTransferFrom函数
// 转移mount数量的id代币 从from地址到to地址
function _safeTransferFrom(
address from,
address to,
uint256 id,
uint256 amount,
bytes memory data
) internal virtual
// 检查to地址是否为空地址
require(to != address(0), "ERC1155: transfer to the zero address");
// 获取当前合约调用者地址
address operator = _msgSender();
// 获取id列表,该列表只有一个元素 ids[0] = id
uint256[] memory ids = _asSingletonArray(id);
// 获取amount列表该列表只有一个元素 amounts[0] = amount
uint256[] memory amounts = _asSingletonArray(amount);
// 转移代币前执行的函数
_beforeTokenTransfer(operator, from, to, ids, amounts, data);
// 获取from地址的id代币数量
uint256 fromBalance = _balances[id][from];
// 检查 from地址的id代币数量fromBalance 是否大于等于要转移的数量amount
require(fromBalance >= amount, "ERC1155: insufficient balance for transfer");
// 减去转移走的数量 重新写入代币数量
unchecked
_balances[id][from] = fromBalance - amount;
// 加上得到的代币数量,重新写入值
_balances[id][to] += amount;
// 触发转移单个代币时间,记录信息
emit TransferSingle(operator, from, to, id, amount);
// 代币转移后执行函数
_afterTokenTransfer(operator, from, to, ids, amounts, data);
// 检查接收的合约地址是否实现IERC1155Receiver接口
_doSafeTransferAcceptanceCheck(operator, from, to, id, amount, data);
_safeBatchTransferFrom函数
function _safeBatchTransferFrom(
address from,
address to,
uint256[] memory ids,
uint256[] memory amounts,
bytes memory data
) internal virtual
// 检查账号列表长度与代币id列表长度一致
require(ids.length == amounts.length, "ERC1155: ids and amounts length mismatch");
// 检查to地址是否为空地址
require(to != address(0), "ERC1155: transfer to the zero address");
// 获取当前合约调用者地址
address operator = _msgSender();
// 代币转移前执行函数
_beforeTokenTransfer(operator, from, to, ids, amounts, data);
for (uint256 i = 0; i < ids.length; ++i)
// 获取代币id
uint256 id = ids[i];
// 获取转移数量值
uint256 amount = amounts[i];
// 获取当前账号与代币对应数量
uint256 fromBalance = _balances[id][from];
// 检查余额是否大于转移数量
require(fromBalance >= amount, "ERC1155: insufficient balance for transfer");
// 减去转移数量,重新写入值
unchecked
_balances[id][from] = fromBalance - amount;
// 加上转移数量,重新写入值
_balances[id][to] += amount;
// 触发转移单个代币事件,记录信息
emit TransferBatch(operator, from, to, ids, amounts);
// 代币转移后执行函数
_afterTokenTransfer(operator, from, to, ids, amounts, data);
// 检查接收的合约地址是否实现IERC1155Receiver接口
_doSafeBatchTransferAcceptanceCheck(operator, from, to, ids, amounts, data);
_setURI函数
// 设置新uri地址
function _setURI(string memory newuri) internal virtual
_uri = newuri;
_mint函数
// 铸造amount数量id代币给to地址
function _mint(
address to,
uint256 id,
uint256 amount,
bytes memory data
) internal virtual
// 检查to是否是空地址
require(to != address(0), "ERC1155: mint to the zero address");
// 获取合约调用者地址
address operator = _msgSender();
// 获取id列表,该列表只有一个元素 ids[0] = id
uint256[] memory ids = _asSingletonArray(id);
// 获取amount列表该列表只有一个元素 amounts[0] = amount
uint256[] memory amounts = _asSingletonArray(amount);
// 代币转移前执行函数
_beforeTokenTransfer(operator, address(0), to, ids, amounts, data);
// 增加代币余额
_balances[id][to] += amount;
// 触发转移单个代币事件,记录信息
emit TransferSingle(operator, address(0), to, id, amount);
// 代币转移后执行函数
_afterTokenTransfer(operator, address(0), to, ids, amounts, data);
// 检查接收的合约地址是否实现IERC1155Receiver接口
_doSafeTransferAcceptanceCheck(operator, address(0), to, id, amount, data);
_mintBatch函数
// 铸造amounts列表对应ids列表代币给to地址
function _mintBatch(
address to,
uint256[] memory ids,
uint256[] memory amounts,
bytes memory data
) internal virtual
// 检查to是否是空地址
require(to != address(0), "ERC1155: mint to the zero address");
// 检查账号列表长度与代币id列表长度一致
require(ids.length == amounts.length, "ERC1155: ids and amounts length mismatch");
// 获取当前合约调用者地址
address operator = _msgSender();
// 代币转移前执行函数
_beforeTokenTransfer(operator, address(0), to, ids, amounts, data);
// 增加代币余额
for (uint256 i = 0; i < ids.length; i++)
_balances[ids[i]][to] += amounts[i];
// 触发转移单个代币事件,记录信息
emit TransferBatch(operator, address(0), to, ids, amounts);
// 代币转移后执行函数
_afterTokenTransfer(operator, address(0), to, ids, amounts, data);
// 检查接收的合约地址是否实现IERC1155Receiver接口
_doSafeBatchTransferAcceptanceCheck(operator, address(0), to, ids, amounts, data);
_burn函数
//销毁from地址的id代币
function _burn(
address from,
uint256 id,
uint256 amount
) internal virtual
// 检查from地址 不为空地址
require(from != address(0), "ERC1155: burn from the zero address");
// 获取当前合约调用者地址
address operator = _msgSender();
// 获取id列表,该列表只有一个元素 ids[0] = id
uint256[] memory ids = _asSingletonArray(id);
// 获取amount列表该列表只有一个元素 amounts[0] = amount
uint256[] memory amounts = _asSingletonArray(amount);
// 代币转移前执行函数
_beforeTokenTransfer(operator, from, address(0), ids, amounts, "");
// 获取from账号id代币余额
uint256 fromBalance = _balances[id][from];
// 检查余额是否大于等于销毁数量
require(fromBalance >= amount, "ERC1155: burn amount exceeds balance");
// 减去销毁数量,重新写入值
unchecked
_balances[id][from] = fromBalance - amount;
// 触发转移单个代币事件,记录信息
emit TransferSingle(operator, from, address(0), id, amount);
// 代币转移后执行函数
_afterTokenTransfer(operator, from, address(0), ids, amounts, "");
_burnBatch函数
// 批量销毁地址拥有的各种id代币
function _burnBatch(
address from,
uint256[] memory ids,
uint256[] memory amounts
) internal virtual
// 检查from地址 不为空地址
require(from != address(0), "ERC1155: burn from the zero address");
// 检查账号列表长度与代币id列表长度一致
require(ids.length == amounts.length, "ERC1155: ids and amounts length mismatch");
// 获取当前合约调用者地址
address operator = _msgSender();
// 代币转移前执行函数
_beforeTokenTransfer(operator, from, address(0), ids, amounts, "");
// 销毁代币
for (uint256 i = 0; i < ids.length; i++)
// 获取代币id
uint256 id = ids[i];
// 获取销毁数量
uint256 amount = amounts[i];
// 获取代币余额
uint256 fromBalance = _balances[id][from];
// 检查余额是否大于等于销毁数量
require(fromBalance >= amount, "ERC1155: burn amount exceeds balance");
// 减去转销毁量,重新写入值
unchecked
_balances[id][from] = fromBalance - amount;
// 触发批量转移代币事件,记录信息
emit TransferBatch(operator, from, address(0), ids, amounts);
// 代币转移后执行函数
_afterTokenTransfer(operator, from, address(0), ids, amounts, "");
_setApprovalForAll函数
// 设置owner对operate的授权状态
function _setApprovalForAll(
address owner,
address operator,
bool approved
) internal virtual
// 检查 owner地址和operate地址是否相同
require(owner != operator, "ERC1155: setting approval status for self");
// 设置对operate的授权approve状态
_operatorApprovals[owner][operator] = approved;
// 触发授权事件
emit ApprovalForAll(owner, operator, approved);
_beforeTokenTransfer函数
// 代币转移前函数
function _beforeTokenTransfer(
address operator,
address from,
address to,
uint256[] memory ids,
uint256[] memory amounts,
bytes memory data
) internal virtual
_afterTokenTransfer函数
// 代币转移后执行函数
function _afterTokenTransfer(
address operator,
address from,
address to,
uint256[] memory ids,
uint256[] memory amounts,
bytes memory data
) internal virtual
_doSafeTransferAcceptanceCheck函数
// 如果to是普通地址则返回ture,如果to是合约地址则检查该合约是否实现onERC1155Received接口
function _doSafeTransferAcceptanceCheck(
address operator,
address from,
address to,
uint256 id,
uint256 amount,
bytes memory data
) private
if (to.isContract())
try IERC1155Receiver(to).onERC1155Received(operator, from, id, amount, data) returns (bytes4 response)
if (response != IERC1155Receiver.onERC1155Received.selector)
revert("ERC1155: ERC1155Receiver rejected tokens");
catch Error(string memory reason)
revert(reason);
catch
revert("ERC1155: transfer to non-ERC1155Receiver implementer");
_doSafeBatchTransferAcceptanceCheck函数
// 如果to是普通地址则返回ture,如果to是合约地址则检查该合约是否实现onERC1155Received接口
function _doSafeBatchTransferAcceptanceCheck(
address operator,
address from,
address to,
uint256[] memory ids,
uint256[] memory amounts,
bytes memory data
) private
if (to.isContract())
try IERC1155Receiver(to).onERC1155BatchReceived(operator, from, ids, amounts, data) returns (
bytes4 response
)
if (response != IERC1155Receiver.onERC1155BatchReceived.selector)
revert("ERC1155: ERC1155Receiver rejected tokens");
catch Error(string memory reason)
revert(reason);
catch
revert("ERC1155: transfer to non-ERC1155Receiver implementer");
_asSingletonArray函数
// 返回包含单个元素的列表
function _asSingletonArray(uint256 element) private pure returns (uint256[] memory)
uint256[] memory array = new uint256[](1);
array[0] = element;
return array;
剖析非同质化代币ERC721-全面解析ERC721标准
什么是ERC-721?现在我们看到的各种加密猫猫狗狗都是基于ERC-721创造出来的,每只都是一个独一无二的ERC-721代币,不过ERC-721在区块链世界远不止猫猫狗狗,它更大的想象空间在于将物理世界的资产映射到区块链上。本文就来剖析下什么是ERC721.ERC721是什么
在创建代币一篇,我们讲到过ERC20代币,
和ERC20一样,ERC721同样是一个代币标准,ERC721官方简要解释是Non-Fungible Tokens,简写为NFTs,多翻译为非同质代币。
ERC721 是由Dieter Shirley 在2017年9月提出。Dieter Shirley 正是谜恋猫CryptoKitties背后的公司Axiom Zen的技术总监。因此谜恋猫也是第一个实现了ERC721 标准的去中心化应用。ERC721号提议已经被以太坊作为标准接受,但该标准仍处于草稿阶段。本文介绍的ERC721标准基于最新(2018/03/23官方提议。
那怎么理解非同质代币呢?
非同质代表独一无二,谜恋猫为例,每只猫都被赋予拥有基因,是独一无二的(一只猫就是一个NFTs),猫之间是不能置换的。这种独特性使得某些稀有猫具有收藏价值,也因此受到追捧。
ERC20代币是可置换的,且可细分为N份(1 = 10 * 0.1), 而ERC721的Token最小的单位为1,无法再分割。
如果同一个集合的两个物品具有不同的特征,这两个物品是非同质的,而同质是某个部分或数量可以被另一个同等部分或数量所代替。
非同质性其实广泛存在于我们的生活中,如图书馆的每一本,宠物商店的每一只宠物,歌手所演唱的歌曲,花店里不同的花等等,因此ERC721合约必定有广泛的应用场景。通过这样一个标准,也可建立跨功能的NFTs管理和销售平台(就像有支持ERC20的交易所和钱包一样),使生态更加强大。
ERC721标准
ERC721最为一个合约标准,提供了在实现ERC721代币时必须要遵守的协议,要求每个ERC721标准合约需要实现ERC721及ERC165接口,接口定义如下:
pragma solidity ^0.4.20;
interface ERC721 /* is ERC165 */ {
event Transfer(address indexed _from, address indexed _to, uint256 _tokenId);
event Approval(address indexed _owner, address indexed _approved, uint256 _tokenId);
event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);
function balanceOf(address _owner) external view returns (uint256);
function ownerOf(uint256 _tokenId) external view returns (address);
function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) external payable;
function safeTransferFrom(address _from, address _to, uint256 _tokenId) external payable;
function transferFrom(address _from, address _to, uint256 _tokenId) external payable;
function approve(address _approved, uint256 _tokenId) external payable;
function setApprovalForAll(address _operator, bool _approved) external;
function getApproved(uint256 _tokenId) external view returns (address);
function isApprovedForAll(address _owner, address _operator) external view returns (bool);
}
接口说明:
- balanceOf(): 返回由_owner 持有的NFTs的数量。
- ownerOf(): 返回tokenId代币持有者的地址。
- approve(): 授予地址_to具有_tokenId的控制权,方法成功后需触发Approval 事件。
- setApprovalForAll(): 授予地址_operator具有所有NFTs的控制权,成功后需触发ApprovalForAll事件。
-
getApproved()、isApprovedForAll(): 用来查询授权。
- safeTransferFrom(): 转移NFT所有权,一次成功的转移操作必须发起 Transer 事件。函数的实现需要做一下几种检查:
- 调用者msg.sender应该是当前tokenId的所有者或被授权的地址
- _from 必须是 _tokenId的所有者
- _tokenId 应该是当前合约正在监测的NFTs 中的任何一个
- _to 地址不应该为 0
- 如果_to 是一个合约应该调用其onERC721Received方法, 并且检查其返回值,如果返回值不为
bytes4(keccak256("onERC721Received(address,uint256,bytes)"))
抛出异常。
一个可接收NFT的合约必须实现ERC721TokenReceiver接口:interface ERC721TokenReceiver { /// @return `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))` function onERC721Received(address _from, uint256 _tokenId, bytes data) external returns(bytes4); }
- transferFrom(): 用来转移NFTs, 方法成功后需触发Transfer事件。调用者自己确认_to地址能正常接收NFT,否则将丢失此NFT。此函数实现时需要检查上面条件的前4条。
ERC165 标准
ERC721标准同时要求必须符合ERC165标准 ,其接口如下:
interface ERC165 {
function supportsInterface(bytes4 interfaceID) external view returns (bool);
}
ERC165同样是一个合约标准,这个标准要求合约提供其实现了哪些接口,这样再与合约进行交互的时候可以先调用此接口进行查询。
interfaceID为函数选择器,计算方式有两种,如:bytes4(keccak256(‘supportsInterface(bytes4)‘));
或ERC165.supportsInterface.selector
,多个函数的接口ID为函数选择器的异或值。
关于ERC165,这里不深入介绍,有兴趣的同学可以阅读官方提案。
可选实现接口:ERC721Metadata
ERC721Metadata 接口用于提供合约的元数据:name , symbol 及 URI(NFT所对应的资源)。
其接口定义如下:
interface ERC721Metadata /* is ERC721 */ {
function name() external pure returns (string _name);
function symbol() external pure returns (string _symbol);
function tokenURI(uint256 _tokenId) external view returns (string);
}
接口说明:
- name(): 返回合约名字,尽管是可选,但强烈建议实现,即便是返回空字符串。
- symbol(): 返回合约代币符号,尽管是可选,但强烈建议实现,即便是返回空字符串。
- tokenURI(): 返回_tokenId所对应的外部资源文件的URI(通常是IPFS或HTTP(S)路径)。外部资源文件需要包含名字、描述、图片,其格式的要求如下:
{ "title": "Asset Metadata", "type": "object", "properties": { "name": { "type": "string", "description": "Identifies the asset to which this NFT represents", }, "description": { "type": "string", "description": "Describes the asset to which this NFT represents", }, "image": { "type": "string", "description": "A URI pointing to a resource with mime type image/* representing the asset to which this NFT represents. Consider making any images at a width between 320 and 1080 pixels and aspect ratio between 1.91:1 and 4:5 inclusive.", } } }
tokenURI通常是被web3调用,以便在应用层做相应的查询和展示。
可选实现接口:ERC721Enumerable
ERC721Enumerable的主要目的是提高合约中NTF的可访问性,其接口定义如下:
interface ERC721Enumerable /* is ERC721 */ {
function totalSupply() external view returns (uint256);
function tokenByIndex(uint256 _index) external view returns (uint256);
function tokenOfOwnerByIndex(address _owner, uint256 _index) external view returns (uint256);
}
接口说明:
- totalSupply(): 返回NFT总量
- tokenByIndex(): 通过索引返回对应的tokenId。
- tokenOfOwnerByIndex(): 所有者可以一次拥有多个的NFT, 此函数返回_owner拥有的NFT列表中对应索引的tokenId。
补充说明
NTF IDs
NTF ID,即tokenId,在合约中用唯一的uint265进行标识,每个NFT的ID在智能合约的生命周期内不允许改变。推荐的实现方式有:
- 从0开始,每新加一个NFT,NTF ID加1
- 使用sha3后uuid 转换为 NTF ID
与ERC-20的兼容性
ERC721标准尽可能遵循 ERC-20 的语义,但由于同质代币与非同质代币之间的根本差异,并不能完全兼容ERC-20。
交易、挖矿、销毁
在实现transter相关接口时除了满足上面的的条件外,我们可以根据需要添加自己的逻辑,如加入黑名单等。
同时挖矿、销毁尽管不是标准的一部分,我们可以根据需要实现。
参考实现
参考实现为订阅用户专有福利,请订阅我的小专栏:区块链技术查看。
## 参考文献 1. [EIPS-165](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md) 2. [EIPS-721](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md) 3. [深入浅出区块链](https://learnblockchain.cn/) - 系统学习区块链,打造最好的区块链技术博客。以上是关于代币标准--ERC1155协议源码解析的主要内容,如果未能解决你的问题,请参考以下文章