ethereum.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: U256​) -> None:
32
    """
33
    Appends a log entry, having `num_topics` topics, to the evm logs.
34
35
    This will also expand the memory if the data (required by the log entry)
36
    corresponding to the memory is not accessible.
37
38
    Parameters
39
    ----------
40
    evm :
41
        The current EVM frame.
42
    num_topics :
43
        The number of topics to be included in the log entry.
44
45
    """
46
    # STACK
47
    memory_start_index = pop(evm.stack)
48
    size = pop(evm.stack)
49
50
    topics = []
51
    for _ in range(num_topics):
52
        topic = pop(evm.stack).to_be_bytes32()
53
        topics.append(topic)
54
55
    # GAS
56
    extend_memory = calculate_gas_extend_memory(
57
        evm.memory, [(memory_start_index, size)]
58
    )
59
    charge_gas(
60
        evm,
61
        GAS_LOG
62
        + GAS_LOG_DATA * Uint(size)
63
        + GAS_LOG_TOPIC * Uint(num_topics)
64
        + extend_memory.cost,
65
    )
66
67
    # OPERATION
68
    evm.memory += b"\x00" * extend_memory.expand_by
69
    log_entry = Log(
70
        address=evm.message.current_target,
71
        topics=tuple(topics),
72
        data=memory_read_bytes(evm.memory, memory_start_index, size),
73
    )
74
75
    evm.logs = evm.logs + (log_entry,)
76
77
    # PROGRAM COUNTER
78
    evm.pc += Uint(1)

log0

81
log0 = partial(log_n, num_topics=0)

log1

82
log1 = partial(log_n, num_topics=1)

log2

83
log2 = partial(log_n, num_topics=2)

log3

84
log3 = partial(log_n, num_topics=3)

log4

85
log4 = partial(log_n, num_topics=4)