Precompiled C++ engine

Precompiled contracts provide a way to use C++The method of writing contracts, which separates contract logic from data, has better performance than solidity contracts, and can be upgraded by modifying the underlying code。

Precompiled contracts vs. Solidity contracts

Precompiled contracts advantages:

• Access more: Based on this framework, users can access the local DB storage state and implement any logic they need。

• Better performance: Since the precompiled contract implemented on C++, the code will be compiled in POTOS, and the underlying layer without entering the EVM for execution, which can have better performance.

• Easy to start: Developers can use C++ to develop your own precompiled contracts to quickly implement the required business logic without learning the Solidity language.

Table Name	Precompiled Contracts	Solidity Contract
Address	Fixed address, defined in code	Determine when deploying
Contract Code	Data is stored in tables, separated from contracts, and contract logic can be upgraded	Contract variables and data are stored in the MPT tree
Execute	C++Low-level execution for higher performance and parallelism	EVM virtual machine, serial execution

Module Architecture

The architecture of Precompiled is shown in the following figure. The block validator determines the type based on the address of the called contract when executing the transaction。Addresses 1-4 represent Ethereum precompiled contracts, addresses 0x1000-0x10000 are C++Precompiled contracts, other addresses are EVM contracts。

Key Processes

• When executing a precompiled contract, you first need to get the object of the precompiled contract based on the contract address。

• Each precompiled contract object implements the ‘call’ interface, where the specific logic of the precompiled contract is implemented。

• ‘call’ obtains the ‘Function Selector’ and parameters according to the abi code of the transaction, and then executes the corresponding logic。

    graph LR
        Start(Commencement) --> branch1{Precompiled Contracts?}
        branch1 --> Yes --> op1[Get contract object by address]
        branch1 --> No --> op2[EVM]
        op1 --> op3[Parse Call Function and Parameters]
        op3 --> End(Return execution result)
        op2 --> End(Return execution result)

Precompiled contracts in POTOS

POTOS provides several useful precompiled contracts. These contracts are implemented in the platform itself as a native implementation, which means they are part of the POTOS node.

For embracing EVM ecology, the precompiled contracts from address 0x01 through 0x0A are the same as those in any EVM compatible blockchain. The precompiled contracts from address 0x1000 through 0xfffff are C++ precompiled contracts, which are implemented in the POTOS node.

The following table lists the precompiled contracts provided by POTOS.

Address	Name	Description
0x01	ecrecover	Recover the public key from the signature and hash value
0x02	sha256	Calculate the SHA256 hash value
0x03	ripemd160	Calculate the RIPEMD160 hash value
0x04	identity	Return the input data
0x05	modexp	Calculate the modular exponentiation
0x06	alt_bn128_add	Calculate the addition of the alt_bn128 curve
0x07	alt_bn128_mul	Calculate the multiplication of the alt_bn128 curve
0x08	alt_bn128_pairing	Calculate the pairing of the alt_bn128 curve
0x09	blake2f	Calculate the BLAKE2F hash value
0x0A	kzg	Calculate the KZG proof verification to a given value at a given point. For more information, see EIP-4844.
0x1000	SystemConfig	Configuration management of blockchain system
0x1001	Table	Accessing table contract logic
0x1002	TableManager	Table Contract Management
0x1003	ConsensusManager	Manage the stauts of nodes
0x1005	AuthManager	Contract-based permission control
0x1009	KVTable	Accessing kv table contract logic
0x100a	Crypto	Provide cryptographic interface
0x100c	DAGTransfer	Provide DAG Transfer Test Contract
0x100e	BFS	BFS System Contract Interface
0x100f	Cast	Easy way to cast solidity trival type
0x1010	Sharding	Block sharding execution management
0x1011	Balance	Balance of accounts management
0x10001	AuthManager	Authority Governance Committee Contract
0x5003	Paillier	Paillier crypto interfaces
0x5004	GroupSign	Group Signature interfaces
0x5005	RingSign	Ring Signature interfaces
0x5100	ZKP	ZKP System Contract