The contract folder

The base for smart contract support in Blockchain Development Kit (BDK).

This subchapter contains a brief overview of each one of the components inside the src/contract folder.

ABI

The abi.h file contains the ABI namespace - helper functions for handling Solidity ABI types and data natively, as well as the encoding and decoding of said data, also used for C++ <-> EVM inter-operability.

BaseContract

The contract.h file contains the BaseContract class - the base from which all smart contracts are derived - as well as the ContractGlobals and ContractLocals helper classes that provide access to global and local variables, respectively, for those contracts to work.

ContractFactory

The contractfactory.h file contains the ContractFactory namespace - helper functions for aiding contract creation, typically used by ContractManager.

ContractHost

The contracthost.h file contains the ContractHost class - responsible for managing a single chain of contract execution from beginning to end (including nested calls), including the EVMC host implementation for EVM contracts, holding the execution stack and commit/revert during or at the end of the call (via ContractStack), and allowing both C++ and EVM contract calls and inter-operability.

ContractManager

The contractmanager.h contains the ContractManager class - responsible solely for creating and deploying contracts, passing their ownership to State when done.

ContractStack

The contractstack.h file contains the ContractStack class - responsible for managing temporary data from contract nested call chains, such as used SafeVariables and altered balances, acting as the one who effectively decides whether those changes are committed or reverted during a contract call. Only one instance of ContractStack is spawned per ContractHost during a call - this ensures the contract call lifecycle is properly contained and state data doesn't spill over other calls.

CustomContracts

The customcontracts.h file contains a tuple that holds all the registered contracts within the blockchain. It is also used as a reference for generating the ABI of said contracts.

DynamicContract

The dynamiccontract.h file contains the DynamicContract class - the base from which all Dynamic Contracts are derived (while BaseContract is mainly used for Protocol Contracts).

Event and EventManager

The event.h file contains the Event and EventManager classes, as well as the EventContainer typedef for indexing - they represent the subset of contract functionality related to Solidity events.

Event is responsible for abstracting a Solidity event's structure and data, while EventManager is responsible for maintaining all emitted events within the blockchain. Events are supported for both C++ and EVM contracts.

The variables subfolder

The variables subfolder contains implementations for SafeVariables - special classes that abstract safe versions of variables used within contracts.

The templates subfolder

The templates subfolder contains several contracts used as templates, examples and for internal testing purposes. It's also meant to be the folder where user-coded contracts are stored.