ethereum.homestead.vm.instructions.bitwise

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

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

Introduction

Implementations of the EVM bitwise instructions.

bitwise_and

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

Parameters

evm : The current EVM frame.

def bitwise_and(​evm: Evm​) -> None:
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    """
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    Bitwise AND operation of the top 2 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)
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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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    push(evm.stack, x & y)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

bitwise_or

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

Parameters

evm : The current EVM frame.

def bitwise_or(​evm: Evm​) -> None:
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    """
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    Bitwise OR operation of the top 2 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)
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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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    push(evm.stack, x | y)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

bitwise_xor

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

Parameters

evm : The current EVM frame.

def bitwise_xor(​evm: Evm​) -> None:
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    """
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    Bitwise XOR operation of the top 2 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)
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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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    push(evm.stack, x ^ y)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

bitwise_not

Bitwise NOT operation of the top element of the stack. Pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def bitwise_not(​evm: Evm​) -> None:
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    """
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    Bitwise NOT operation of the top element 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)
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    # GAS
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    charge_gas(evm, GAS_VERY_LOW)
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    # OPERATION
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    push(evm.stack, ~x)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

get_byte

For a word (defined by next top element of the stack), retrieve the Nth byte (0-indexed and defined by top element of stack) from the left (most significant) to right (least significant).

Parameters

evm : The current EVM frame.

def get_byte(​evm: Evm​) -> None:
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    """
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    For a word (defined by next top element of the stack), retrieve the
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    Nth byte (0-indexed and defined by top element of stack) from the
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    left (most significant) to right (least significant).
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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_index = pop(evm.stack)
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    word = 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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    if byte_index >= U256(32):
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        result = U256(0)
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    else:
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        extra_bytes_to_right = U256(31) - byte_index
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        # Remove the extra bytes in the right
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        word = word >> (extra_bytes_to_right * U256(8))
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        # Remove the extra bytes in the left
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        word = word & U256(0xFF)
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        result = word
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)