Hardfork Utility Functions For The Message Data-structure

Table of Contents

Introduction
Module Contents
- Functions
Module Details
- prepare_message

Introduction

Message specific functions used in this frontierhomestead version of specification.

Module Contents

Functions

prepare_message

Execute a transaction against the provided environment.

Module Details

prepare_message

prepare_message(caller, target, value, data, gas, env, code_address=None, should_transfer_value=True)

Execute a transaction against the provided environment.

Parameters

caller – Address which initiated the transaction
target – Address whose code will be executed
value – Value to be transferred.
data – Array of bytes provided to the code in target.
gas – Gas provided for the code in target.
env – Environment for the Ethereum Virtual Machine.
code_address – This is usually same as the target address except when an alternative accounts code needs to be executed. eg. CALLCODE calling a precompile.
should_transfer_value – if True ETH should be transferred while executing a message call.

Returns

message – Items containing contract creation or message call specific data.

Return type

ethereum.frontier.vm.Message

ethereum.homestead.vm.Message

def prepare_message(
    caller: Address,
    target: Union[Bytes0, Address],
    value: U256,
    data: Bytes,
    gas: Uint,
    env: Environment,
    code_address: Optional[Address] = None,
should_transfer_value: bool = True,
) -> Message:
    if isinstance(target, Bytes0):
        current_target = compute_contract_address(
            caller,
            get_account(env.state, caller).nonce - U256(1),
        )
        msg_data = Bytes(b"")
        code = data
    elif isinstance(target, Address):
        current_target = target
        msg_data = data
        code = get_account(env.state, target).code
        if code_address is None:
            code_address = target
    else:
        raise AssertionError("Target must be address or empty bytes")

    return Message(
        caller=caller,
        target=target,
        gas=gas,
        value=value,
        data=msg_data,
        code=code,
        depth=Uint(0),
        current_target=current_target,
        code_address=code_address,
        should_transfer_value=should_transfer_value,
        parent_evm=None,
    )