Using Precompiled Contracts¶

Tags: “Precompiled Contracts” “BFS” “CRUD”

FISCO BCOS 3.0 follows the FISCO BCOS 2.0 version of the precompiled contract。In the future, we will also try to abstract the existing typical business scenarios and develop them into pre-compiled contract templates as the basic capability provided by the underlying layer to help users use FISCO BCOS in their business faster and more conveniently。

Principles of Precompiled Contracts and FISCO BCOS 2.0+Similar to the version, users can refer to the link when studying its principles: FISCO BCOS Precompiled Contract Architecture。

Advantages of Precompiled Contracts¶

Access to distributed storage interfacesBased on this framework, users can access the local DB storage state and implement any logic they need。

Better performanceSince the implementation is C++The code will be compiled in the underlying layer without entering the EVM for execution, which can have better performance。

Get started without learning Solidity languageBased on FISCO BCOSPrecompiledcontract framework, developers can use C++Develop your own pre-compiled contracts to quickly implement the required business logic without learning the Solidity language。

FISCO BCOS 3.x Precompiled Contracts and Addresses¶

Currently, the Solidity contract only supports the address type of 20 bytes as the calling object, while Liquid supports the address of the string to call the contract, so the address of the precompiled contract is divided into two versions: Solidity and Liquid。

Addresses in this table are for Solidity contracts only。

Address	合同	Description
0x1000	SystemConfigPrecompiled	Realize configuration management of group system parameters
0x1002	TableManagerPrecompiled	Table Contract Management
0x1003	ConsensusPrecompiled	Group node and node identity management
0x1005	AuthManagerPrecompiled	Contract-based permission control
0x100a	CryptoPrecompiled	Provide cryptographic interface
0x100c	DAGTransferPrecompiled	Provide DAG Transfer Test Contract
0x100e	BFSPrecompiled	BFS System Contract Interface
0x10001	AuthManagerPrecompiled	Authority Governance Committee Contract
0x5004	GroupSignPrecompiled	Group Signature System Contract
0x5005	RingSignPrecompield	Ring Signature System Contract
0x5100	ZKPPrecompiled	ZKP System Contract

The BFS paths in the following table are only used for webankblockchain-liquid (WBC-Liquid) contracts。

BFS Path	合同	Description
/sys/status	SystemConfigPrecompiled	Realize configuration management of group system parameters
/sys/table_Manager	TableManagerPrecompiled	Table Contract Management
/sys/consensus	ConsensusPrecompiled	Group node and node identity management
/sys/auth	AuthManagerPrecompiled	Contract-based permission control
/sys/crypto_tools	CryptoPrecompiled	Provide cryptographic interface
/sys/dag_test	DAGTransferPrecompiled	Provide DAG Transfer Test Contract
/sys/bfs	BFSPrecompiled	BFS System Contract Interface
/sys/group_sig	GroupSignPrecompiled	Group Signature System Contract
/sys/ring_sig	RingSignPrecompield	Ring Signature System Contract
/sys/discrete_zkp	ZKPPrecompiled	ZKP System Contract

How to use the FISCO BCOS precompiled contract interface¶

The steps for a smart contract to invoke a precompiled contract are similar to those for invoking a normal contract, as follows

Introduction of interface declarations: Introduction of pre-compiled contract contract files, or declaration of interfaces in the same smart contract file；
Specify the contract address: According to the address table of the precompiled contract, use the corresponding address when initializing the object； -Call the object interface: After initializing the object, use the object to call the method interface；

The following uses the Table contract as an example to call the Table interface:

Introduction of interface declarations

Place the Table.sol contract in the TableTest.sol peer directory and introduce Table.sol in the TableTest.sol contract file. The code is as follows:
```
pragma solidity >=0.6.10 <0.8.20;
pragma experimental ABIEncoderV2;
import "./Table.sol";
```
Specify Contract Address

Initializes the ‘TableManager’ object by specifying the address of the ‘TableManager’
```
TableManager constant tm =  TableManager(address(0x1002));
```

Call the object interface

Call the initialized ‘TableManager’ object interface to create a ‘Table’ contract object

Table table;
string constant TABLE_NAME = "t_test";
constructor () public{
    / / Create the t _ test table. The primary key of the table is id, and the other fields are name and age
    string[] memory columnNames = new string[](2);
    columnNames[0] = "name";
    columnNames[1] = "age";
    TableInfo memory tf = TableInfo("id", columnNames);
    tm.createTable(TABLE_NAME, tf);
    
    / / Get the real address, which is stored in the contract
    address t_address = tm.openTable(TABLE_NAME);
    require(t_address!=address(0x0),"");
    table = Table(t_address);
}