ethereum.constantinople.vm.instructions.control_flow

Ethereum Virtual Machine (EVM) Control Flow Instructions ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

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

Introduction

Implementations of the EVM control flow instructions.

stop

Stop further execution of EVM code.

Parameters

evm : The current EVM frame.

def stop(​evm: Evm​) -> None:
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    """
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    Stop further execution of EVM code.
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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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    """
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    # STACK
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    pass
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    # GAS
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    pass
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    # OPERATION
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    evm.running = False
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

jump

Alter the program counter to the location specified by the top of the stack.

Parameters

evm : The current EVM frame.

def jump(​evm: Evm​) -> None:
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    """
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    Alter the program counter to the location specified by the top of the
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    stack.
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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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    """
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    # STACK
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    jump_dest = Uint(pop(evm.stack))
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    # GAS
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    charge_gas(evm, GAS_MID)
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    # OPERATION
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    if jump_dest not in evm.valid_jump_destinations:
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        raise InvalidJumpDestError
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    # PROGRAM COUNTER
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    evm.pc = Uint(jump_dest)

jumpi

Alter the program counter to the specified location if and only if a condition is true. If the condition is not true, then the program counter would increase only by 1.

Parameters

evm : The current EVM frame.

def jumpi(​evm: Evm​) -> None:
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    """
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    Alter the program counter to the specified location if and only if a
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    condition is true. If the condition is not true, then the program counter
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    would increase only by 1.
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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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    """
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    # STACK
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    jump_dest = Uint(pop(evm.stack))
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    conditional_value = pop(evm.stack)
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    # GAS
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    charge_gas(evm, GAS_HIGH)
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    # OPERATION
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    if conditional_value == 0:
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        destination = evm.pc + Uint(1)
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    elif jump_dest not in evm.valid_jump_destinations:
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        raise InvalidJumpDestError
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    else:
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        destination = jump_dest
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    # PROGRAM COUNTER
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    evm.pc = destination

pc

Push onto the stack the value of the program counter after reaching the current instruction and without increasing it for the next instruction.

Parameters

evm : The current EVM frame.

def pc(​evm: Evm​) -> None:
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    """
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    Push onto the stack the value of the program counter after reaching the
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    current instruction and without increasing it for the next instruction.
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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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    """
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    # STACK
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    pass
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    # GAS
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    charge_gas(evm, GAS_BASE)
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    # OPERATION
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    push(evm.stack, U256(evm.pc))
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

gas_left

Push the amount of available gas (including the corresponding reduction for the cost of this instruction) onto the stack.

Parameters

evm : The current EVM frame.

def gas_left(​evm: Evm​) -> None:
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    """
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    Push the amount of available gas (including the corresponding reduction
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    for the cost of this instruction) onto the stack.
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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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    """
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    # STACK
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    pass
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    # GAS
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    charge_gas(evm, GAS_BASE)
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    # OPERATION
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    push(evm.stack, U256(evm.gas_left))
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

jumpdest

Mark a valid destination for jumps. This is a noop, present only to be used by JUMP and JUMPI opcodes to verify that their jump is valid.

Parameters

evm : The current EVM frame.

def jumpdest(​evm: Evm​) -> None:
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    """
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    Mark a valid destination for jumps. This is a noop, present only
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    to be used by `JUMP` and `JUMPI` opcodes to verify that their jump is
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    valid.
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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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    """
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    # STACK
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    pass
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    # GAS
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    charge_gas(evm, GAS_JUMPDEST)
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    # OPERATION
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    pass
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)