Ethereum Virtual Machine (EVM) Logging Instructions

Introduction

Implementations of the EVM logging instructions.

Module Contents

Functions

log_n

Appends a log entry, having num_topics topics, to the evm logs.

Attributes

log0

log1

log2

log3

log4

Module Details

log_n

log_n(evm: ethereum.london.vm.Evm, num_topics: ethereum.base_types.U256)None

Appends a log entry, having num_topics topics, to the evm logs.

This will also expand the memory if the data (required by the log entry) corresponding to the memory is not accessible.

Parameters
  • evm – The current EVM frame.

  • num_topics – The number of topics to be included in the log entry.

def log_n(evm: Evm, num_topics: U256) -> None:
    # STACK
    memory_start_index = pop(evm.stack)
    size = pop(evm.stack)

    topics = []
    for _ in range(num_topics):
        topic = pop(evm.stack).to_be_bytes32()
        topics.append(topic)

    # GAS
    extend_memory = calculate_gas_extend_memory(
        evm.memory, [(memory_start_index, size)]
    )
    charge_gas(
        evm,
        GAS_LOG
        + GAS_LOG_DATA * size
        + GAS_LOG_TOPIC * num_topics
        + extend_memory.cost,
    )

    # OPERATION
    evm.memory += b"\x00" * extend_memory.expand_by
    ensure(not evm.message.is_static, WriteInStaticContext)
    log_entry = Log(
        address=evm.message.current_target,
        topics=tuple(topics),
        data=memory_read_bytes(evm.memory, memory_start_index, size),
    )

    evm.logs = evm.logs + (log_entry,)

    # PROGRAM COUNTER
    evm.pc += 1

log0

log0
log0 = partial(log_n, num_topics=0)

log1

log1
log1 = partial(log_n, num_topics=1)

log2

log2
log2 = partial(log_n, num_topics=2)

log3

log3
log3 = partial(log_n, num_topics=3)

log4

log4
log4 = partial(log_n, num_topics=4)