id:BSN_2021
公众号：BSN研习社
目标：跟大家一块去研究下1155标准中提供的案例
章节流程：
- 核心文件
- 核心方法
- 汇总
在eip-1155中看到如下图所示一段内容，并提供了一个案例，因此今天跟大家去研究一下内部的实现细节。
一、核心文件
其主要涉及两个文件ERC1155MixedFungibleMintable.sol和ERC1155MixedFungible .sol，如下：
- 文件ERC1155MixedFungible .sol内容如下：
pragma solidity ^0.5.0;
import "./ERC1155.sol";
/**
@dev Extension to ERC1155 for Mixed Fungible and Non-Fungible Items support
The main benefit is sharing of common type information, just like you do when
creating a fungible id.
*/
contract ERC1155MixedFungible is ERC1155 {
// Use a split bit implementation. Store the type in the upper 128 bits..
// 十进制：115792089237316195423570985008687907852929702298719625575994209400481361428480
// 十六进制：ffffffffffffffffffffffffffffffff00000000000000000000000000000000
// 二进制：
// 11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
// 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
uint256 public constant TYPE_MASK = uint256(uint128(~0)) << 128;
// ..and the non-fungible index in the lower 128
// 十进制:340282366920938463463374607431768211455
// 十六进制:ffffffffffffffffffffffffffffffff
// 二进制:
// 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
// 11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
uint256 public constant NF_INDEX_MASK = uint128(~0);
// The top bit is a flag to tell if this is a NFI.
// 十进制: 57896044618658097711785492504343953926634992332820282019728792003956564819968
// 十六进制: 8000000000000000000000000000000000000000000000000000000000000000
// 二进制:
// 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
// 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
uint256 public constant TYPE_NF_BIT = 1 << 255;
mapping (uint256 => address) nfOwners;
// Only to make code clearer. Should not be functions
function isNonFungible(uint256 _id) public pure returns(bool) {
return _id & TYPE_NF_BIT == TYPE_NF_BIT;
}
function isFungible(uint256 _id) public pure returns(bool) {
return _id & TYPE_NF_BIT == 0;
}
function getNonFungibleIndex(uint256 _id) public pure returns(uint256) {
return _id & NF_INDEX_MASK;
}
function getNonFungibleBaseType(uint256 _id) public pure returns(uint256) {
return _id & TYPE_MASK;
}
function isNonFungibleBaseType(uint256 _id) public pure returns(bool) {
// A base type has the NF bit but does not have an index.
return (_id & TYPE_NF_BIT == TYPE_NF_BIT) && (_id & NF_INDEX_MASK == 0);
}
function isNonFungibleItem(uint256 _id) public pure returns(bool) {
// A base type has the NF bit but does has an index.
return (_id & TYPE_NF_BIT == TYPE_NF_BIT) && (_id & NF_INDEX_MASK != 0);
}
function ownerOf(uint256 _id) public view returns (address) {
return nfOwners[_id];
}
// override
function safeTransferFrom(address _from, address _to, uint256 _id, uint256 _value, bytes calldata _data) external {
require(_to != address(0x0), "cannot send to zero address");
require(_from == msg.sender || operatorApproval[_from][msg.sender] == true, "Need operator approval for 3rd party transfers.");
if (isNonFungible(_id)) {
require(nfOwners[_id] == _from);
nfOwners[_id] = _to;
// You could keep balance of NF type in base type id like so:
// uint256 baseType = getNonFungibleBaseType(_id);
// balances[baseType][_from] = balances[baseType][_from].sub(_value);
// balances[baseType][_to] = balances[baseType][_to].add(_value);
} else {
balances[_id][_from] = balances[_id][_from].sub(_value);
balances[_id][_to] = balances[_id][_to].add(_value);
}
emit TransferSingle(msg.sender, _from, _to, _id, _value);
if (_to.isContract()) {
_doSafeTransferAcceptanceCheck(msg.sender, _from, _to, _id, _value, _data);
}
}
// override
function safeBatchTransferFrom(address _from, address _to, uint256[] calldata _ids, uint256[] calldata _values, bytes calldata _data) external {
require(_to != address(0x0), "cannot send to zero address");
require(_ids.length == _values.length, "Array length must match");
// Only supporting a global operator approval allows us to do only 1 check and not to touch storage to handle allowances.
require(_from == msg.sender || operatorApproval[_from][msg.sender] == true, "Need operator approval for 3rd party transfers.");
for (uint256 i = 0; i < _ids.length; ++i) {
// Cache value to local variable to reduce read costs.
uint256 id = _ids[i];
uint256 value = _values[i];
if (isNonFungible(id)) {
require(nfOwners[id] == _from);
nfOwners[id] = _to;
} else {
balances[id][_from] = balances[id][_from].sub(value);
balances[id][_to] = value.add(balances[id][_to]);
}
}
emit TransferBatch(msg.sender, _from, _to, _ids, _values);
if (_to.isContract()) {
_doSafeBatchTransferAcceptanceCheck(msg.sender, _from, _to, _ids, _values, _data);
}
}
function balanceOf(address _owner, uint256 _id) external view returns (uint256) {
if (isNonFungibleItem(_id))
return nfOwners[_id] == _owner ? 1 : 0;
return balances[_id][_owner];
}
function balanceOfBatch(address[] calldata _owners, uint256[] calldata _ids) external view returns (uint256[] memory) {
require(_owners.length == _ids.length);
uint256[] memory balances_ = new uint256[](_owners.length);
for (uint256 i = 0; i < _owners.length; ++i) {
uint256 id = _ids[i];
if (isNonFungibleItem(id)) {
balances_[i] = nfOwners[id] == _owners[i] ? 1 : 0;
} else {
balances_[i] = balances[id][_owners[i]];
}
}
return balances_;
}
}
- 文件ERC1155MixedFungibleMintable.sol内容如下：
pragma solidity ^0.5.0;
import "./ERC1155MixedFungible.sol";
/**
@dev Mintable form of ERC1155
Shows how easy it is to mint new items
*/
contract ERC1155MixedFungibleMintable is ERC1155MixedFungible {
uint256 nonce;
mapping (uint256 => address) public creators;
mapping (uint256 => uint256) public maxIndex;
modifier creatorOnly(uint256 _id) {
require(creators[_id] == msg.sender);
_;
}
// This function only creates the type.
function create(
string calldata _uri,
bool _isNF)
external returns(uint256 _type) {
// Store the type in the upper 128 bits
_type = (++nonce << 128);
// Set a flag if this is an NFI.
if (_isNF)
_type = _type | TYPE_NF_BIT;
// This will allow restricted access to creators.
creators[_type] = msg.sender;
// emit a Transfer event with Create semantic to help with discovery.
emit TransferSingle(msg.sender, address(0x0), address(0x0), _type, 0);
if (bytes(_uri).length > 0)
emit URI(_uri, _type);
}
function mintNonFungible(uint256 _type, address[] calldata _to) external creatorOnly(_type) {
// No need to check this is a nf type rather than an id since
// creatorOnly() will only let a type pass through.
require(isNonFungible(_type));
// Index are 1-based.
uint256 index = maxIndex[_type] + 1;
maxIndex[_type] = _to.length.add(maxIndex[_type]);
for (uint256 i = 0; i < _to.length; ++i) {
address dst = _to[i];
uint256 id = _type | index + i;
nfOwners[id] = dst;
// You could use base-type id to store NF type balances if you wish.
// balances[_type][dst] = quantity.add(balances[_type][dst]);
emit TransferSingle(msg.sender, address(0x0), dst, id, 1);
if (dst.isContract()) {
_doSafeTransferAcceptanceCheck(msg.sender, msg.sender, dst, id, 1, '');
}
}
}
function mintFungible(uint256 _id, address[] calldata _to, uint256[] calldata _quantities) external creatorOnly(_id) {
require(isFungible(_id));
for (uint256 i = 0; i < _to.length; ++i) {
address to = _to[i];
uint256 quantity = _quantities[i];
// Grant the items to the caller
balances[_id][to] = quantity.add(balances[_id][to]);
// Emit the Transfer/Mint event.
// the 0x0 source address implies a mint
// It will also provide the circulating supply info.
emit TransferSingle(msg.sender, address(0x0), to, _id, quantity);
if (to.isContract()) {
_doSafeTransferAcceptanceCheck(msg.sender, msg.sender, to, _id, quantity, '');
}
}
}
}
二、核心方法
先看一下几个内置的状态变量，如下：
TYPE_NF_BIT= 100xxx000 000xxx000
TYPE_MASK= 111xxx111 000xxx000
NF_INDEX_MASK=000xxx000 111xxx111
主要的几个方法，详解如下：
创建类型 create(string calldata _uri,bool _isNF)：
关键逻辑：首先，通过nonce自增然后左移128位生成_type 类别唯一标识（tokenid）。接下来，判断是否是非同质化，是则与TYPE_NF_BIT按位或（注：其结果最高位标识为1开头），否则直接返回_type。
示例：前128位，后128位。
nft_type：100xxx001 000xxx000；
ft_type: 000xxx001 000xxx000；铸造非同质化 mintNonFungible(uint256 _type, address[] calldata _to)
关键逻辑：首先，要求_type符合非同质化条件，即判断_type按位与TYPE_NF_BIT是否等于TYPE_NF_BIT。接下来，获取最新的索引值index，然后根据规则（将_type与index+i按位或）生成唯一标识，并与对应的address进行映射。
示例：
非同质化条件：100xxx001 000xxx000 & TYPE_NF_BIT == TYPE_NF_BIT ；
生成tokenId的规则：id = _type | index +i。即 100xxx001 000xxx000 | 001 => 100xxx001 000xxx001 ；铸造同质化mintFungible(uint256 _id, address[] calldata _to, uint256[] calldata _quantities)
关键逻辑：首先，要求符合同质化条件，即判断_type按位与TYPE_NF_BIT是否等于0；接下来，计算最新的数量，并与对应的address进行映射。
示例：
同质化条件：000xxx001 000xxx000 & TYPE_NF_BIT == 0；转移 safeTransferFrom(address _from, address _to, uint256 _id, uint256 _value, bytes calldata _data)
关键逻辑：根据_id判断是否是非同质化标识，即判断_type按位与TYPE_NF_BIT是否等于TYPE_NF_BIT，然后返回对应的结果。
获取余额balanceOf(address _owner, uint256 _id) external view returns (uint256)
关键逻辑：根据_id判断是否是非同质化标识，即判断_id按位与TYPE_NF_BIT是否等于TYPE_NF_BIT，并且_id按位与NF_INDEX_MASK 等于零。然后返回对应的结果。注：非同质化的数量为0或1；
三、汇总
关键的几个方法看完后，可以发现技术上没有太大的难度，主要是运用了标识位拆分（Split ID bits）以及位运算进行巧妙的设计。即将tokenid uint256分为两部分（前128位和后128位）。当非同质化时前128位标识类型，后面128为代表索引或id，即<uint128: base token id><uint128: index of non-fungible>。当同质化时前128位标识id，后128位为零，即<uint128: base token id><uint128: zero>；
通俗点的来说，当调用create方法时，非同质化生成的为类别（或系列）标识，然后再生成该类别下的唯一标识，即nf-tokenID。同质化生成的即为唯一标识,即f-tokenID。
引用资源地址：
https://eips.ethereum.org/EIPS/eip-1155
https://github.com/enjin/erc-1155
