Precompiles

Polaris Ethereum supports the execution of stateless and stateful precompiled contracts.

Stateless Precompiles

Stateless precompiles run completely in the EVM and do not rely on state from the native host chain. Go-ethereum provides implementations of several stateless precompiles at hardcoded addresses here. More stateless precompiles can be added by adhering to the StatelessImpl, defined in interfaces.go.

If no custom precompiles are added by the host chain, the default precompile plugin will execute the stateless precompiles.

Stateful Precompiles

Stateful Precompiles are run in the host chain's native execution environment. This is enabled via injecting a Precompile Plugin from the host chain.

Stateful Precompiles can be implemented by adhering to the StatefulImpl interface, defined in interfaces.go. Below are the suggested steps to follow (more details in method.go):

1) Define a Solidity interface with the methods that you want implemented via a precompile.
2) Build a Go precompile contract, which implements the interface's methods.
    A) This precompile contract should expose the ABI's `Methods`, which can be generated via
    Go-Ethereum's abi package. These methods are of type `abi.Method`.
    B) This precompile contract should also expose the `Method`s. A `Method` includes the
    `executable`, which is the direct implementation of a corresponding ABI method, and the ABI signature. Do NOT provide the `AbiMethod` as
    this field will be automatically populated.

Examples of stateful precompiles that run in a Cosmos SDK-based host chain can be found in the precompile directory.