ethereum.constantinople.vm.instructions.logethereum.istanbul.vm.instructions.log

Ethereum Virtual Machine (EVM) Logging Instructions ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. contents:: Table of Contents :backlinks: none :local:

Introduction

Implementations of the EVM logging instructions.

log_n

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:
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    """
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    Appends a log entry, having `num_topics` topics, to the evm logs.
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    This will also expand the memory if the data (required by the log entry)
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    corresponding to the memory is not accessible.
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    Parameters
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    ----------
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    evm :
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        The current EVM frame.
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    num_topics :
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        The number of topics to be included in the log entry.
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    """
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    # STACK
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    memory_start_index = pop(evm.stack)
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    size = pop(evm.stack)
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    topics = []
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    for _ in range(num_topics):
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        topic = pop(evm.stack).to_be_bytes32()
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        topics.append(topic)
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    # GAS
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    extend_memory = calculate_gas_extend_memory(
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        evm.memory, [(memory_start_index, size)]
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    )
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    charge_gas(
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        evm,
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        GAS_LOG
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        + GAS_LOG_DATA * size
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        + GAS_LOG_TOPIC * num_topics
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        + extend_memory.cost,
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    )
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    # OPERATION
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    evm.memory += b"\x00" * extend_memory.expand_by
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    if evm.message.is_static:
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        raise WriteInStaticContext
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    log_entry = Log(
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        address=evm.message.current_target,
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        topics=tuple(topics),
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        data=memory_read_bytes(evm.memory, memory_start_index, size),
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    )
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    evm.logs = evm.logs + (log_entry,)
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    # PROGRAM COUNTER
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    evm.pc += 1

log0

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log0 = partial(log_n, num_topics=0)

log1

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log1 = partial(log_n, num_topics=1)

log2

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log2 = partial(log_n, num_topics=2)

log3

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log3 = partial(log_n, num_topics=3)

log4

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log4 = partial(log_n, num_topics=4)