ethereum.spurious_dragon.vm.instructions.arithmetic

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

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

Introduction

Implementations of the EVM Arithmetic instructions.

add

Adds the top two elements of the stack together, and pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def add(​evm: Evm​) -> None:
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    """
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    Adds the top two elements of the stack together, and pushes the result back
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    on 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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    x = pop(evm.stack)
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    y = pop(evm.stack)
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    # GAS
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    charge_gas(evm, GAS_VERY_LOW)
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    # OPERATION
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    result = x.wrapping_add(y)
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

sub

Subtracts the top two elements of the stack, and pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def sub(​evm: Evm​) -> None:
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    """
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    Subtracts the top two elements of the stack, and pushes the result back
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    on 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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    x = pop(evm.stack)
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    y = pop(evm.stack)
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    # GAS
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    charge_gas(evm, GAS_VERY_LOW)
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    # OPERATION
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    result = x.wrapping_sub(y)
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

mul

Multiply the top two elements of the stack, and pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def mul(​evm: Evm​) -> None:
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    """
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    Multiply the top two elements of the stack, and pushes the result back
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    on 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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    x = pop(evm.stack)
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    y = pop(evm.stack)
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    # GAS
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    charge_gas(evm, GAS_LOW)
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    # OPERATION
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    result = x.wrapping_mul(y)
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

div

Integer division of the top two elements of the stack. Pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def div(​evm: Evm​) -> None:
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    """
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    Integer division of the top two elements of the stack. Pushes the result
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    back on 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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    dividend = pop(evm.stack)
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    divisor = pop(evm.stack)
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    # GAS
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    charge_gas(evm, GAS_LOW)
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    # OPERATION
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    if divisor == 0:
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        quotient = U256(0)
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    else:
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        quotient = dividend // divisor
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    push(evm.stack, quotient)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

U255_CEIL_VALUE

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U255_CEIL_VALUE = 2**255

sdiv

Signed integer division of the top two elements of the stack. Pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def sdiv(​evm: Evm​) -> None:
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    """
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    Signed integer division of the top two elements of the stack. Pushes the
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    result back on 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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    dividend = pop(evm.stack).to_signed()
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    divisor = pop(evm.stack).to_signed()
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    # GAS
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    charge_gas(evm, GAS_LOW)
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    # OPERATION
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    if divisor == 0:
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        quotient = 0
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    elif dividend == -U255_CEIL_VALUE and divisor == -1:
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        quotient = -U255_CEIL_VALUE
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    else:
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        sign = get_sign(dividend * divisor)
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        quotient = sign * (abs(dividend) // abs(divisor))
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    push(evm.stack, U256.from_signed(quotient))
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

mod

Modulo remainder of the top two elements of the stack. Pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def mod(​evm: Evm​) -> None:
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    """
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    Modulo remainder of the top two elements of the stack. Pushes the result
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    back on 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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    x = pop(evm.stack)
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    y = pop(evm.stack)
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    # GAS
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    charge_gas(evm, GAS_LOW)
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    # OPERATION
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    if y == 0:
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        remainder = U256(0)
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    else:
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        remainder = x % y
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    push(evm.stack, remainder)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

smod

Signed modulo remainder of the top two elements of the stack. Pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def smod(​evm: Evm​) -> None:
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    """
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    Signed modulo remainder of the top two elements of the stack. Pushes the
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    result back on 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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    x = pop(evm.stack).to_signed()
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    y = pop(evm.stack).to_signed()
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    # GAS
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    charge_gas(evm, GAS_LOW)
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    # OPERATION
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    if y == 0:
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        remainder = 0
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    else:
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        remainder = get_sign(x) * (abs(x) % abs(y))
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    push(evm.stack, U256.from_signed(remainder))
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

addmod

Modulo addition of the top 2 elements with the 3rd element. Pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def addmod(​evm: Evm​) -> None:
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    """
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    Modulo addition of the top 2 elements with the 3rd element. Pushes the
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    result back on 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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    x = Uint(pop(evm.stack))
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    y = Uint(pop(evm.stack))
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    z = 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 z == 0:
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        result = U256(0)
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    else:
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        result = U256((x + y) % z)
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

mulmod

Modulo multiplication of the top 2 elements with the 3rd element. Pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def mulmod(​evm: Evm​) -> None:
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    """
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    Modulo multiplication of the top 2 elements with the 3rd element. Pushes
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    the result back on 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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    x = Uint(pop(evm.stack))
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    y = Uint(pop(evm.stack))
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    z = 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 z == 0:
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        result = U256(0)
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    else:
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        result = U256((x * y) % z)
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

exp

Exponential operation of the top 2 elements. Pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def exp(​evm: Evm​) -> None:
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    """
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    Exponential operation of the top 2 elements. Pushes the result back on
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    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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    base = Uint(pop(evm.stack))
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    exponent = Uint(pop(evm.stack))
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    # GAS
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    # This is equivalent to 1 + floor(log(y, 256)). But in python the log
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    # function is inaccurate leading to wrong results.
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    exponent_bits = exponent.bit_length()
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    exponent_bytes = (exponent_bits + Uint(7)) // Uint(8)
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    charge_gas(
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        evm, GAS_EXPONENTIATION + GAS_EXPONENTIATION_PER_BYTE * exponent_bytes
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    )
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    # OPERATION
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    result = U256(pow(base, exponent, Uint(U256.MAX_VALUE) + Uint(1)))
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

signextend

Sign extend operation. In other words, extend a signed number which fits in N bytes to 32 bytes.

Parameters

evm : The current EVM frame.

def signextend(​evm: Evm​) -> None:
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    """
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    Sign extend operation. In other words, extend a signed number which
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    fits in N bytes to 32 bytes.
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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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    byte_num = pop(evm.stack)
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    value = pop(evm.stack)
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    # GAS
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    charge_gas(evm, GAS_LOW)
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    # OPERATION
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    if byte_num > U256(31):
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        # Can't extend any further
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        result = value
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    else:
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        # U256(0).to_be_bytes() gives b'' instead b'\x00'.
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        value_bytes = bytes(value.to_be_bytes32())
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        # Now among the obtained value bytes, consider only
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        # N `least significant bytes`, where N is `byte_num + 1`.
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        value_bytes = value_bytes[31 - int(byte_num) :]
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        sign_bit = value_bytes[0] >> 7
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        if sign_bit == 0:
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            result = U256.from_be_bytes(value_bytes)
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        else:
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            num_bytes_prepend = U256(32) - (byte_num + U256(1))
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            result = U256.from_be_bytes(
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                bytearray([0xFF] * num_bytes_prepend) + value_bytes
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            )
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)