ethereum.forks.frontier.vm.instructions.logethereum.forks.homestead.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: int​) -> None:
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    <snip>
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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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        GasCosts.OPCODE_LOG_BASE
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        + GasCosts.OPCODE_LOG_DATA_PER_BYTE * Uint(size)
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        + GasCosts.OPCODE_LOG_TOPIC * Uint(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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    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 += Uint(1)

log0

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log0: Callable[[Evm], None] = partial(log_n, num_topics=0)

log1

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log1: Callable[[Evm], None] = partial(log_n, num_topics=1)

log2

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log2: Callable[[Evm], None] = partial(log_n, num_topics=2)

log3

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log3: Callable[[Evm], None] = partial(log_n, num_topics=3)

log4

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log4: Callable[[Evm], None] = partial(log_n, num_topics=4)