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480 lines
17 KiB
Python
480 lines
17 KiB
Python
"""Disassembler of Python byte code into mnemonics."""
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import sys
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import types
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import collections
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import io
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from opcode import *
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from opcode import __all__ as _opcodes_all
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__all__ = ["code_info", "dis", "disassemble", "distb", "disco",
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"findlinestarts", "findlabels", "show_code",
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"get_instructions", "Instruction", "Bytecode"] + _opcodes_all
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del _opcodes_all
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_have_code = (types.MethodType, types.FunctionType, types.CodeType, type)
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def _try_compile(source, name):
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"""Attempts to compile the given source, first as an expression and
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then as a statement if the first approach fails.
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Utility function to accept strings in functions that otherwise
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expect code objects
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"""
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try:
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c = compile(source, name, 'eval')
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except SyntaxError:
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c = compile(source, name, 'exec')
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return c
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def dis(x=None, *, file=None):
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"""Disassemble classes, methods, functions, generators, or code.
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With no argument, disassemble the last traceback.
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"""
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if x is None:
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distb(file=file)
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return
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if hasattr(x, '__func__'): # Method
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x = x.__func__
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if hasattr(x, '__code__'): # Function
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x = x.__code__
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if hasattr(x, 'gi_code'): # Generator
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x = x.gi_code
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if hasattr(x, '__dict__'): # Class or module
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items = sorted(x.__dict__.items())
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for name, x1 in items:
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if isinstance(x1, _have_code):
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print("Disassembly of %s:" % name, file=file)
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try:
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dis(x1, file=file)
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except TypeError as msg:
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print("Sorry:", msg, file=file)
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print(file=file)
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elif hasattr(x, 'co_code'): # Code object
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disassemble(x, file=file)
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elif isinstance(x, (bytes, bytearray)): # Raw bytecode
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_disassemble_bytes(x, file=file)
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elif isinstance(x, str): # Source code
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_disassemble_str(x, file=file)
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else:
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raise TypeError("don't know how to disassemble %s objects" %
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type(x).__name__)
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def distb(tb=None, *, file=None):
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"""Disassemble a traceback (default: last traceback)."""
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if tb is None:
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try:
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tb = sys.last_traceback
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except AttributeError:
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raise RuntimeError("no last traceback to disassemble")
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while tb.tb_next: tb = tb.tb_next
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disassemble(tb.tb_frame.f_code, tb.tb_lasti, file=file)
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# The inspect module interrogates this dictionary to build its
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# list of CO_* constants. It is also used by pretty_flags to
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# turn the co_flags field into a human readable list.
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COMPILER_FLAG_NAMES = {
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1: "OPTIMIZED",
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2: "NEWLOCALS",
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4: "VARARGS",
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8: "VARKEYWORDS",
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16: "NESTED",
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32: "GENERATOR",
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64: "NOFREE",
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}
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def pretty_flags(flags):
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"""Return pretty representation of code flags."""
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names = []
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for i in range(32):
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flag = 1<<i
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if flags & flag:
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names.append(COMPILER_FLAG_NAMES.get(flag, hex(flag)))
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flags ^= flag
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if not flags:
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break
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else:
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names.append(hex(flags))
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return ", ".join(names)
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def _get_code_object(x):
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"""Helper to handle methods, functions, generators, strings and raw code objects"""
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if hasattr(x, '__func__'): # Method
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x = x.__func__
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if hasattr(x, '__code__'): # Function
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x = x.__code__
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if hasattr(x, 'gi_code'): # Generator
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x = x.gi_code
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if isinstance(x, str): # Source code
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x = _try_compile(x, "<disassembly>")
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if hasattr(x, 'co_code'): # Code object
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return x
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raise TypeError("don't know how to disassemble %s objects" %
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type(x).__name__)
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def code_info(x):
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"""Formatted details of methods, functions, or code."""
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return _format_code_info(_get_code_object(x))
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def _format_code_info(co):
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lines = []
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lines.append("Name: %s" % co.co_name)
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lines.append("Filename: %s" % co.co_filename)
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lines.append("Argument count: %s" % co.co_argcount)
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lines.append("Kw-only arguments: %s" % co.co_kwonlyargcount)
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lines.append("Number of locals: %s" % co.co_nlocals)
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lines.append("Stack size: %s" % co.co_stacksize)
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lines.append("Flags: %s" % pretty_flags(co.co_flags))
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if co.co_consts:
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lines.append("Constants:")
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for i_c in enumerate(co.co_consts):
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lines.append("%4d: %r" % i_c)
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if co.co_names:
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lines.append("Names:")
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for i_n in enumerate(co.co_names):
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lines.append("%4d: %s" % i_n)
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if co.co_varnames:
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lines.append("Variable names:")
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for i_n in enumerate(co.co_varnames):
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lines.append("%4d: %s" % i_n)
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if co.co_freevars:
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lines.append("Free variables:")
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for i_n in enumerate(co.co_freevars):
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lines.append("%4d: %s" % i_n)
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if co.co_cellvars:
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lines.append("Cell variables:")
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for i_n in enumerate(co.co_cellvars):
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lines.append("%4d: %s" % i_n)
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return "\n".join(lines)
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def show_code(co, *, file=None):
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"""Print details of methods, functions, or code to *file*.
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If *file* is not provided, the output is printed on stdout.
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"""
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print(code_info(co), file=file)
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_Instruction = collections.namedtuple("_Instruction",
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"opname opcode arg argval argrepr offset starts_line is_jump_target")
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class Instruction(_Instruction):
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"""Details for a bytecode operation
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Defined fields:
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opname - human readable name for operation
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opcode - numeric code for operation
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arg - numeric argument to operation (if any), otherwise None
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argval - resolved arg value (if known), otherwise same as arg
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argrepr - human readable description of operation argument
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offset - start index of operation within bytecode sequence
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starts_line - line started by this opcode (if any), otherwise None
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is_jump_target - True if other code jumps to here, otherwise False
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"""
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def _disassemble(self, lineno_width=3, mark_as_current=False):
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"""Format instruction details for inclusion in disassembly output
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*lineno_width* sets the width of the line number field (0 omits it)
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*mark_as_current* inserts a '-->' marker arrow as part of the line
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"""
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fields = []
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# Column: Source code line number
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if lineno_width:
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if self.starts_line is not None:
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lineno_fmt = "%%%dd" % lineno_width
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fields.append(lineno_fmt % self.starts_line)
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else:
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fields.append(' ' * lineno_width)
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# Column: Current instruction indicator
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if mark_as_current:
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fields.append('-->')
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else:
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fields.append(' ')
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# Column: Jump target marker
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if self.is_jump_target:
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fields.append('>>')
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else:
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fields.append(' ')
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# Column: Instruction offset from start of code sequence
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fields.append(repr(self.offset).rjust(4))
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# Column: Opcode name
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fields.append(self.opname.ljust(20))
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# Column: Opcode argument
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if self.arg is not None:
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fields.append(repr(self.arg).rjust(5))
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# Column: Opcode argument details
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if self.argrepr:
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fields.append('(' + self.argrepr + ')')
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return ' '.join(fields).rstrip()
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def get_instructions(x, *, first_line=None):
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"""Iterator for the opcodes in methods, functions or code
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Generates a series of Instruction named tuples giving the details of
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each operations in the supplied code.
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If *first_line* is not None, it indicates the line number that should
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be reported for the first source line in the disassembled code.
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Otherwise, the source line information (if any) is taken directly from
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the disassembled code object.
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"""
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co = _get_code_object(x)
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cell_names = co.co_cellvars + co.co_freevars
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linestarts = dict(findlinestarts(co))
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if first_line is not None:
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line_offset = first_line - co.co_firstlineno
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else:
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line_offset = 0
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return _get_instructions_bytes(co.co_code, co.co_varnames, co.co_names,
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co.co_consts, cell_names, linestarts,
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line_offset)
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def _get_const_info(const_index, const_list):
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"""Helper to get optional details about const references
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Returns the dereferenced constant and its repr if the constant
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list is defined.
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Otherwise returns the constant index and its repr().
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"""
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argval = const_index
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if const_list is not None:
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argval = const_list[const_index]
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return argval, repr(argval)
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def _get_name_info(name_index, name_list):
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"""Helper to get optional details about named references
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Returns the dereferenced name as both value and repr if the name
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list is defined.
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Otherwise returns the name index and its repr().
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"""
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argval = name_index
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if name_list is not None:
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argval = name_list[name_index]
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argrepr = argval
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else:
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argrepr = repr(argval)
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return argval, argrepr
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def _get_instructions_bytes(code, varnames=None, names=None, constants=None,
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cells=None, linestarts=None, line_offset=0):
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"""Iterate over the instructions in a bytecode string.
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Generates a sequence of Instruction namedtuples giving the details of each
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opcode. Additional information about the code's runtime environment
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(e.g. variable names, constants) can be specified using optional
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arguments.
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"""
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labels = findlabels(code)
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extended_arg = 0
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starts_line = None
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free = None
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# enumerate() is not an option, since we sometimes process
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# multiple elements on a single pass through the loop
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n = len(code)
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i = 0
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while i < n:
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op = code[i]
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offset = i
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if linestarts is not None:
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starts_line = linestarts.get(i, None)
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if starts_line is not None:
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starts_line += line_offset
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is_jump_target = i in labels
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i = i+1
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arg = None
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argval = None
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argrepr = ''
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if op >= HAVE_ARGUMENT:
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arg = code[i] + code[i+1]*256 + extended_arg
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extended_arg = 0
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i = i+2
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if op == EXTENDED_ARG:
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extended_arg = arg*65536
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# Set argval to the dereferenced value of the argument when
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# availabe, and argrepr to the string representation of argval.
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# _disassemble_bytes needs the string repr of the
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# raw name index for LOAD_GLOBAL, LOAD_CONST, etc.
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argval = arg
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if op in hasconst:
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argval, argrepr = _get_const_info(arg, constants)
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elif op in hasname:
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argval, argrepr = _get_name_info(arg, names)
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elif op in hasjrel:
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argval = i + arg
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argrepr = "to " + repr(argval)
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elif op in haslocal:
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argval, argrepr = _get_name_info(arg, varnames)
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elif op in hascompare:
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argval = cmp_op[arg]
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argrepr = argval
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elif op in hasfree:
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argval, argrepr = _get_name_info(arg, cells)
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elif op in hasnargs:
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argrepr = "%d positional, %d keyword pair" % (code[i-2], code[i-1])
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yield Instruction(opname[op], op,
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arg, argval, argrepr,
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offset, starts_line, is_jump_target)
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def disassemble(co, lasti=-1, *, file=None):
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"""Disassemble a code object."""
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cell_names = co.co_cellvars + co.co_freevars
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linestarts = dict(findlinestarts(co))
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_disassemble_bytes(co.co_code, lasti, co.co_varnames, co.co_names,
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co.co_consts, cell_names, linestarts, file=file)
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def _disassemble_bytes(code, lasti=-1, varnames=None, names=None,
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constants=None, cells=None, linestarts=None,
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*, file=None, line_offset=0):
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# Omit the line number column entirely if we have no line number info
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show_lineno = linestarts is not None
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# TODO?: Adjust width upwards if max(linestarts.values()) >= 1000?
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lineno_width = 3 if show_lineno else 0
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for instr in _get_instructions_bytes(code, varnames, names,
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constants, cells, linestarts,
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line_offset=line_offset):
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new_source_line = (show_lineno and
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instr.starts_line is not None and
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instr.offset > 0)
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if new_source_line:
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print(file=file)
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is_current_instr = instr.offset == lasti
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print(instr._disassemble(lineno_width, is_current_instr), file=file)
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def _disassemble_str(source, *, file=None):
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"""Compile the source string, then disassemble the code object."""
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disassemble(_try_compile(source, '<dis>'), file=file)
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disco = disassemble # XXX For backwards compatibility
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def findlabels(code):
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"""Detect all offsets in a byte code which are jump targets.
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Return the list of offsets.
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"""
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labels = []
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# enumerate() is not an option, since we sometimes process
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# multiple elements on a single pass through the loop
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n = len(code)
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i = 0
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while i < n:
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op = code[i]
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i = i+1
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if op >= HAVE_ARGUMENT:
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arg = code[i] + code[i+1]*256
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i = i+2
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label = -1
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if op in hasjrel:
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label = i+arg
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elif op in hasjabs:
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label = arg
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if label >= 0:
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if label not in labels:
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labels.append(label)
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return labels
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def findlinestarts(code):
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"""Find the offsets in a byte code which are start of lines in the source.
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Generate pairs (offset, lineno) as described in Python/compile.c.
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"""
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byte_increments = list(code.co_lnotab[0::2])
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line_increments = list(code.co_lnotab[1::2])
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lastlineno = None
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lineno = code.co_firstlineno
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addr = 0
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for byte_incr, line_incr in zip(byte_increments, line_increments):
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if byte_incr:
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if lineno != lastlineno:
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yield (addr, lineno)
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lastlineno = lineno
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addr += byte_incr
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lineno += line_incr
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if lineno != lastlineno:
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yield (addr, lineno)
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class Bytecode:
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"""The bytecode operations of a piece of code
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Instantiate this with a function, method, string of code, or a code object
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(as returned by compile()).
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Iterating over this yields the bytecode operations as Instruction instances.
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"""
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def __init__(self, x, *, first_line=None, current_offset=None):
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self.codeobj = co = _get_code_object(x)
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if first_line is None:
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self.first_line = co.co_firstlineno
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self._line_offset = 0
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else:
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self.first_line = first_line
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self._line_offset = first_line - co.co_firstlineno
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self._cell_names = co.co_cellvars + co.co_freevars
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self._linestarts = dict(findlinestarts(co))
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self._original_object = x
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self.current_offset = current_offset
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def __iter__(self):
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co = self.codeobj
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return _get_instructions_bytes(co.co_code, co.co_varnames, co.co_names,
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co.co_consts, self._cell_names,
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self._linestarts,
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line_offset=self._line_offset)
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def __repr__(self):
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return "{}({!r})".format(self.__class__.__name__,
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self._original_object)
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@classmethod
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def from_traceback(cls, tb):
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""" Construct a Bytecode from the given traceback """
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while tb.tb_next:
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tb = tb.tb_next
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return cls(tb.tb_frame.f_code, current_offset=tb.tb_lasti)
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def info(self):
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"""Return formatted information about the code object."""
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return _format_code_info(self.codeobj)
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def dis(self):
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"""Return a formatted view of the bytecode operations."""
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co = self.codeobj
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if self.current_offset is not None:
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offset = self.current_offset
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else:
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offset = -1
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with io.StringIO() as output:
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_disassemble_bytes(co.co_code, varnames=co.co_varnames,
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names=co.co_names, constants=co.co_consts,
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cells=self._cell_names,
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linestarts=self._linestarts,
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line_offset=self._line_offset,
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file=output,
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lasti=offset)
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return output.getvalue()
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def _test():
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"""Simple test program to disassemble a file."""
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import argparse
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parser = argparse.ArgumentParser()
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parser.add_argument('infile', type=argparse.FileType(), nargs='?', default='-')
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args = parser.parse_args()
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with args.infile as infile:
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source = infile.read()
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code = compile(source, args.infile.name, "exec")
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dis(code)
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if __name__ == "__main__":
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_test()
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