add ydb deps

1 files changed, 775 insertions, 0 deletions

diff --git a/contrib/tools/python3/src/Lib/dis.py b/contrib/tools/python3/src/Lib/dis.py
new file mode 100644
index 0000000000..5bf52c3e6d
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/dis.py
@@ -0,0 +1,775 @@
+"""Disassembler of Python byte code into mnemonics."""
+
+import sys
+import types
+import collections
+import io
+
+from opcode import *
+from opcode import (
+    __all__ as _opcodes_all,
+    _cache_format,
+    _inline_cache_entries,
+    _nb_ops,
+    _specializations,
+    _specialized_instructions,
+)
+
+__all__ = ["code_info", "dis", "disassemble", "distb", "disco",
+           "findlinestarts", "findlabels", "show_code",
+           "get_instructions", "Instruction", "Bytecode"] + _opcodes_all
+del _opcodes_all
+
+_have_code = (types.MethodType, types.FunctionType, types.CodeType,
+              classmethod, staticmethod, type)
+
+FORMAT_VALUE = opmap['FORMAT_VALUE']
+FORMAT_VALUE_CONVERTERS = (
+    (None, ''),
+    (str, 'str'),
+    (repr, 'repr'),
+    (ascii, 'ascii'),
+)
+MAKE_FUNCTION = opmap['MAKE_FUNCTION']
+MAKE_FUNCTION_FLAGS = ('defaults', 'kwdefaults', 'annotations', 'closure')
+
+LOAD_CONST = opmap['LOAD_CONST']
+LOAD_GLOBAL = opmap['LOAD_GLOBAL']
+BINARY_OP = opmap['BINARY_OP']
+JUMP_BACKWARD = opmap['JUMP_BACKWARD']
+
+CACHE = opmap["CACHE"]
+
+_all_opname = list(opname)
+_all_opmap = dict(opmap)
+_empty_slot = [slot for slot, name in enumerate(_all_opname) if name.startswith("<")]
+for spec_op, specialized in zip(_empty_slot, _specialized_instructions):
+    # fill opname and opmap
+    _all_opname[spec_op] = specialized
+    _all_opmap[specialized] = spec_op
+
+deoptmap = {
+    specialized: base for base, family in _specializations.items() for specialized in family
+}
+
+def _try_compile(source, name):
+    """Attempts to compile the given source, first as an expression and
+       then as a statement if the first approach fails.
+
+       Utility function to accept strings in functions that otherwise
+       expect code objects
+    """
+    try:
+        c = compile(source, name, 'eval')
+    except SyntaxError:
+        c = compile(source, name, 'exec')
+    return c
+
+def dis(x=None, *, file=None, depth=None, show_caches=False, adaptive=False):
+    """Disassemble classes, methods, functions, and other compiled objects.
+
+    With no argument, disassemble the last traceback.
+
+    Compiled objects currently include generator objects, async generator
+    objects, and coroutine objects, all of which store their code object
+    in a special attribute.
+    """
+    if x is None:
+        distb(file=file, show_caches=show_caches, adaptive=adaptive)
+        return
+    # Extract functions from methods.
+    if hasattr(x, '__func__'):
+        x = x.__func__
+    # Extract compiled code objects from...
+    if hasattr(x, '__code__'):  # ...a function, or
+        x = x.__code__
+    elif hasattr(x, 'gi_code'):  #...a generator object, or
+        x = x.gi_code
+    elif hasattr(x, 'ag_code'):  #...an asynchronous generator object, or
+        x = x.ag_code
+    elif hasattr(x, 'cr_code'):  #...a coroutine.
+        x = x.cr_code
+    # Perform the disassembly.
+    if hasattr(x, '__dict__'):  # Class or module
+        items = sorted(x.__dict__.items())
+        for name, x1 in items:
+            if isinstance(x1, _have_code):
+                print("Disassembly of %s:" % name, file=file)
+                try:
+                    dis(x1, file=file, depth=depth, show_caches=show_caches, adaptive=adaptive)
+                except TypeError as msg:
+                    print("Sorry:", msg, file=file)
+                print(file=file)
+    elif hasattr(x, 'co_code'): # Code object
+        _disassemble_recursive(x, file=file, depth=depth, show_caches=show_caches, adaptive=adaptive)
+    elif isinstance(x, (bytes, bytearray)): # Raw bytecode
+        _disassemble_bytes(x, file=file, show_caches=show_caches)
+    elif isinstance(x, str):    # Source code
+        _disassemble_str(x, file=file, depth=depth, show_caches=show_caches, adaptive=adaptive)
+    else:
+        raise TypeError("don't know how to disassemble %s objects" %
+                        type(x).__name__)
+
+def distb(tb=None, *, file=None, show_caches=False, adaptive=False):
+    """Disassemble a traceback (default: last traceback)."""
+    if tb is None:
+        try:
+            tb = sys.last_traceback
+        except AttributeError:
+            raise RuntimeError("no last traceback to disassemble") from None
+        while tb.tb_next: tb = tb.tb_next
+    disassemble(tb.tb_frame.f_code, tb.tb_lasti, file=file, show_caches=show_caches, adaptive=adaptive)
+
+# The inspect module interrogates this dictionary to build its
+# list of CO_* constants. It is also used by pretty_flags to
+# turn the co_flags field into a human readable list.
+COMPILER_FLAG_NAMES = {
+     1: "OPTIMIZED",
+     2: "NEWLOCALS",
+     4: "VARARGS",
+     8: "VARKEYWORDS",
+    16: "NESTED",
+    32: "GENERATOR",
+    64: "NOFREE",
+   128: "COROUTINE",
+   256: "ITERABLE_COROUTINE",
+   512: "ASYNC_GENERATOR",
+}
+
+def pretty_flags(flags):
+    """Return pretty representation of code flags."""
+    names = []
+    for i in range(32):
+        flag = 1<<i
+        if flags & flag:
+            names.append(COMPILER_FLAG_NAMES.get(flag, hex(flag)))
+            flags ^= flag
+            if not flags:
+                break
+    else:
+        names.append(hex(flags))
+    return ", ".join(names)
+
+class _Unknown:
+    def __repr__(self):
+        return "<unknown>"
+
+# Sentinel to represent values that cannot be calculated
+UNKNOWN = _Unknown()
+
+def _get_code_object(x):
+    """Helper to handle methods, compiled or raw code objects, and strings."""
+    # Extract functions from methods.
+    if hasattr(x, '__func__'):
+        x = x.__func__
+    # Extract compiled code objects from...
+    if hasattr(x, '__code__'):  # ...a function, or
+        x = x.__code__
+    elif hasattr(x, 'gi_code'):  #...a generator object, or
+        x = x.gi_code
+    elif hasattr(x, 'ag_code'):  #...an asynchronous generator object, or
+        x = x.ag_code
+    elif hasattr(x, 'cr_code'):  #...a coroutine.
+        x = x.cr_code
+    # Handle source code.
+    if isinstance(x, str):
+        x = _try_compile(x, "<disassembly>")
+    # By now, if we don't have a code object, we can't disassemble x.
+    if hasattr(x, 'co_code'):
+        return x
+    raise TypeError("don't know how to disassemble %s objects" %
+                    type(x).__name__)
+
+def _deoptop(op):
+    name = _all_opname[op]
+    return _all_opmap[deoptmap[name]] if name in deoptmap else op
+
+def _get_code_array(co, adaptive):
+    return co._co_code_adaptive if adaptive else co.co_code
+
+def code_info(x):
+    """Formatted details of methods, functions, or code."""
+    return _format_code_info(_get_code_object(x))
+
+def _format_code_info(co):
+    lines = []
+    lines.append("Name:              %s" % co.co_name)
+    lines.append("Filename:          %s" % co.co_filename)
+    lines.append("Argument count:    %s" % co.co_argcount)
+    lines.append("Positional-only arguments: %s" % co.co_posonlyargcount)
+    lines.append("Kw-only arguments: %s" % co.co_kwonlyargcount)
+    lines.append("Number of locals:  %s" % co.co_nlocals)
+    lines.append("Stack size:        %s" % co.co_stacksize)
+    lines.append("Flags:             %s" % pretty_flags(co.co_flags))
+    if co.co_consts:
+        lines.append("Constants:")
+        for i_c in enumerate(co.co_consts):
+            lines.append("%4d: %r" % i_c)
+    if co.co_names:
+        lines.append("Names:")
+        for i_n in enumerate(co.co_names):
+            lines.append("%4d: %s" % i_n)
+    if co.co_varnames:
+        lines.append("Variable names:")
+        for i_n in enumerate(co.co_varnames):
+            lines.append("%4d: %s" % i_n)
+    if co.co_freevars:
+        lines.append("Free variables:")
+        for i_n in enumerate(co.co_freevars):
+            lines.append("%4d: %s" % i_n)
+    if co.co_cellvars:
+        lines.append("Cell variables:")
+        for i_n in enumerate(co.co_cellvars):
+            lines.append("%4d: %s" % i_n)
+    return "\n".join(lines)
+
+def show_code(co, *, file=None):
+    """Print details of methods, functions, or code to *file*.
+
+    If *file* is not provided, the output is printed on stdout.
+    """
+    print(code_info(co), file=file)
+
+Positions = collections.namedtuple(
+    'Positions',
+    [
+        'lineno',
+        'end_lineno',
+        'col_offset',
+        'end_col_offset',
+    ],
+    defaults=[None] * 4
+)
+
+_Instruction = collections.namedtuple(
+    "_Instruction",
+    [
+        'opname',
+        'opcode',
+        'arg',
+        'argval',
+        'argrepr',
+        'offset',
+        'starts_line',
+        'is_jump_target',
+        'positions'
+    ],
+    defaults=[None]
+)
+
+_Instruction.opname.__doc__ = "Human readable name for operation"
+_Instruction.opcode.__doc__ = "Numeric code for operation"
+_Instruction.arg.__doc__ = "Numeric argument to operation (if any), otherwise None"
+_Instruction.argval.__doc__ = "Resolved arg value (if known), otherwise same as arg"
+_Instruction.argrepr.__doc__ = "Human readable description of operation argument"
+_Instruction.offset.__doc__ = "Start index of operation within bytecode sequence"
+_Instruction.starts_line.__doc__ = "Line started by this opcode (if any), otherwise None"
+_Instruction.is_jump_target.__doc__ = "True if other code jumps to here, otherwise False"
+_Instruction.positions.__doc__ = "dis.Positions object holding the span of source code covered by this instruction"
+
+_ExceptionTableEntry = collections.namedtuple("_ExceptionTableEntry",
+    "start end target depth lasti")
+
+_OPNAME_WIDTH = 20
+_OPARG_WIDTH = 5
+
+class Instruction(_Instruction):
+    """Details for a bytecode operation
+
+       Defined fields:
+         opname - human readable name for operation
+         opcode - numeric code for operation
+         arg - numeric argument to operation (if any), otherwise None
+         argval - resolved arg value (if known), otherwise same as arg
+         argrepr - human readable description of operation argument
+         offset - start index of operation within bytecode sequence
+         starts_line - line started by this opcode (if any), otherwise None
+         is_jump_target - True if other code jumps to here, otherwise False
+         positions - Optional dis.Positions object holding the span of source code
+                     covered by this instruction
+    """
+
+    def _disassemble(self, lineno_width=3, mark_as_current=False, offset_width=4):
+        """Format instruction details for inclusion in disassembly output
+
+        *lineno_width* sets the width of the line number field (0 omits it)
+        *mark_as_current* inserts a '-->' marker arrow as part of the line
+        *offset_width* sets the width of the instruction offset field
+        """
+        fields = []
+        # Column: Source code line number
+        if lineno_width:
+            if self.starts_line is not None:
+                lineno_fmt = "%%%dd" % lineno_width
+                fields.append(lineno_fmt % self.starts_line)
+            else:
+                fields.append(' ' * lineno_width)
+        # Column: Current instruction indicator
+        if mark_as_current:
+            fields.append('-->')
+        else:
+            fields.append('   ')
+        # Column: Jump target marker
+        if self.is_jump_target:
+            fields.append('>>')
+        else:
+            fields.append('  ')
+        # Column: Instruction offset from start of code sequence
+        fields.append(repr(self.offset).rjust(offset_width))
+        # Column: Opcode name
+        fields.append(self.opname.ljust(_OPNAME_WIDTH))
+        # Column: Opcode argument
+        if self.arg is not None:
+            fields.append(repr(self.arg).rjust(_OPARG_WIDTH))
+            # Column: Opcode argument details
+            if self.argrepr:
+                fields.append('(' + self.argrepr + ')')
+        return ' '.join(fields).rstrip()
+
+
+def get_instructions(x, *, first_line=None, show_caches=False, adaptive=False):
+    """Iterator for the opcodes in methods, functions or code
+
+    Generates a series of Instruction named tuples giving the details of
+    each operations in the supplied code.
+
+    If *first_line* is not None, it indicates the line number that should
+    be reported for the first source line in the disassembled code.
+    Otherwise, the source line information (if any) is taken directly from
+    the disassembled code object.
+    """
+    co = _get_code_object(x)
+    linestarts = dict(findlinestarts(co))
+    if first_line is not None:
+        line_offset = first_line - co.co_firstlineno
+    else:
+        line_offset = 0
+    return _get_instructions_bytes(_get_code_array(co, adaptive),
+                                   co._varname_from_oparg,
+                                   co.co_names, co.co_consts,
+                                   linestarts, line_offset,
+                                   co_positions=co.co_positions(),
+                                   show_caches=show_caches)
+
+def _get_const_value(op, arg, co_consts):
+    """Helper to get the value of the const in a hasconst op.
+
+       Returns the dereferenced constant if this is possible.
+       Otherwise (if it is a LOAD_CONST and co_consts is not
+       provided) returns the dis.UNKNOWN sentinel.
+    """
+    assert op in hasconst
+
+    argval = UNKNOWN
+    if op == LOAD_CONST:
+        if co_consts is not None:
+            argval = co_consts[arg]
+    return argval
+
+def _get_const_info(op, arg, co_consts):
+    """Helper to get optional details about const references
+
+       Returns the dereferenced constant and its repr if the value
+       can be calculated.
+       Otherwise returns the sentinel value dis.UNKNOWN for the value
+       and an empty string for its repr.
+    """
+    argval = _get_const_value(op, arg, co_consts)
+    argrepr = repr(argval) if argval is not UNKNOWN else ''
+    return argval, argrepr
+
+def _get_name_info(name_index, get_name, **extrainfo):
+    """Helper to get optional details about named references
+
+       Returns the dereferenced name as both value and repr if the name
+       list is defined.
+       Otherwise returns the sentinel value dis.UNKNOWN for the value
+       and an empty string for its repr.
+    """
+    if get_name is not None:
+        argval = get_name(name_index, **extrainfo)
+        return argval, argval
+    else:
+        return UNKNOWN, ''
+
+def _parse_varint(iterator):
+    b = next(iterator)
+    val = b & 63
+    while b&64:
+        val <<= 6
+        b = next(iterator)
+        val |= b&63
+    return val
+
+def _parse_exception_table(code):
+    iterator = iter(code.co_exceptiontable)
+    entries = []
+    try:
+        while True:
+            start = _parse_varint(iterator)*2
+            length = _parse_varint(iterator)*2
+            end = start + length
+            target = _parse_varint(iterator)*2
+            dl = _parse_varint(iterator)
+            depth = dl >> 1
+            lasti = bool(dl&1)
+            entries.append(_ExceptionTableEntry(start, end, target, depth, lasti))
+    except StopIteration:
+        return entries
+
+def _is_backward_jump(op):
+    return 'JUMP_BACKWARD' in opname[op]
+
+def _get_instructions_bytes(code, varname_from_oparg=None,
+                            names=None, co_consts=None,
+                            linestarts=None, line_offset=0,
+                            exception_entries=(), co_positions=None,
+                            show_caches=False):
+    """Iterate over the instructions in a bytecode string.
+
+    Generates a sequence of Instruction namedtuples giving the details of each
+    opcode.  Additional information about the code's runtime environment
+    (e.g. variable names, co_consts) can be specified using optional
+    arguments.
+
+    """
+    co_positions = co_positions or iter(())
+    get_name = None if names is None else names.__getitem__
+    labels = set(findlabels(code))
+    for start, end, target, _, _ in exception_entries:
+        for i in range(start, end):
+            labels.add(target)
+    starts_line = None
+    for offset, op, arg in _unpack_opargs(code):
+        if linestarts is not None:
+            starts_line = linestarts.get(offset, None)
+            if starts_line is not None:
+                starts_line += line_offset
+        is_jump_target = offset in labels
+        argval = None
+        argrepr = ''
+        positions = Positions(*next(co_positions, ()))
+        deop = _deoptop(op)
+        if arg is not None:
+            #  Set argval to the dereferenced value of the argument when
+            #  available, and argrepr to the string representation of argval.
+            #    _disassemble_bytes needs the string repr of the
+            #    raw name index for LOAD_GLOBAL, LOAD_CONST, etc.
+            argval = arg
+            if deop in hasconst:
+                argval, argrepr = _get_const_info(deop, arg, co_consts)
+            elif deop in hasname:
+                if deop == LOAD_GLOBAL:
+                    argval, argrepr = _get_name_info(arg//2, get_name)
+                    if (arg & 1) and argrepr:
+                        argrepr = "NULL + " + argrepr
+                else:
+                    argval, argrepr = _get_name_info(arg, get_name)
+            elif deop in hasjabs:
+                argval = arg*2
+                argrepr = "to " + repr(argval)
+            elif deop in hasjrel:
+                signed_arg = -arg if _is_backward_jump(deop) else arg
+                argval = offset + 2 + signed_arg*2
+                argrepr = "to " + repr(argval)
+            elif deop in haslocal or deop in hasfree:
+                argval, argrepr = _get_name_info(arg, varname_from_oparg)
+            elif deop in hascompare:
+                argval = cmp_op[arg]
+                argrepr = argval
+            elif deop == FORMAT_VALUE:
+                argval, argrepr = FORMAT_VALUE_CONVERTERS[arg & 0x3]
+                argval = (argval, bool(arg & 0x4))
+                if argval[1]:
+                    if argrepr:
+                        argrepr += ', '
+                    argrepr += 'with format'
+            elif deop == MAKE_FUNCTION:
+                argrepr = ', '.join(s for i, s in enumerate(MAKE_FUNCTION_FLAGS)
+                                    if arg & (1<<i))
+            elif deop == BINARY_OP:
+                _, argrepr = _nb_ops[arg]
+        yield Instruction(_all_opname[op], op,
+                          arg, argval, argrepr,
+                          offset, starts_line, is_jump_target, positions)
+        caches = _inline_cache_entries[deop]
+        if not caches:
+            continue
+        if not show_caches:
+            # We still need to advance the co_positions iterator:
+            for _ in range(caches):
+                next(co_positions, ())
+            continue
+        for name, size in _cache_format[opname[deop]].items():
+            for i in range(size):
+                offset += 2
+                # Only show the fancy argrepr for a CACHE instruction when it's
+                # the first entry for a particular cache value and the
+                # instruction using it is actually quickened:
+                if i == 0 and op != deop:
+                    data = code[offset: offset + 2 * size]
+                    argrepr = f"{name}: {int.from_bytes(data, sys.byteorder)}"
+                else:
+                    argrepr = ""
+                yield Instruction(
+                    "CACHE", CACHE, 0, None, argrepr, offset, None, False,
+                    Positions(*next(co_positions, ()))
+                )
+
+def disassemble(co, lasti=-1, *, file=None, show_caches=False, adaptive=False):
+    """Disassemble a code object."""
+    linestarts = dict(findlinestarts(co))
+    exception_entries = _parse_exception_table(co)
+    _disassemble_bytes(_get_code_array(co, adaptive),
+                       lasti, co._varname_from_oparg,
+                       co.co_names, co.co_consts, linestarts, file=file,
+                       exception_entries=exception_entries,
+                       co_positions=co.co_positions(), show_caches=show_caches)
+
+def _disassemble_recursive(co, *, file=None, depth=None, show_caches=False, adaptive=False):
+    disassemble(co, file=file, show_caches=show_caches, adaptive=adaptive)
+    if depth is None or depth > 0:
+        if depth is not None:
+            depth = depth - 1
+        for x in co.co_consts:
+            if hasattr(x, 'co_code'):
+                print(file=file)
+                print("Disassembly of %r:" % (x,), file=file)
+                _disassemble_recursive(
+                    x, file=file, depth=depth, show_caches=show_caches, adaptive=adaptive
+                )
+
+def _disassemble_bytes(code, lasti=-1, varname_from_oparg=None,
+                       names=None, co_consts=None, linestarts=None,
+                       *, file=None, line_offset=0, exception_entries=(),
+                       co_positions=None, show_caches=False):
+    # Omit the line number column entirely if we have no line number info
+    show_lineno = bool(linestarts)
+    if show_lineno:
+        maxlineno = max(linestarts.values()) + line_offset
+        if maxlineno >= 1000:
+            lineno_width = len(str(maxlineno))
+        else:
+            lineno_width = 3
+    else:
+        lineno_width = 0
+    maxoffset = len(code) - 2
+    if maxoffset >= 10000:
+        offset_width = len(str(maxoffset))
+    else:
+        offset_width = 4
+    for instr in _get_instructions_bytes(code, varname_from_oparg, names,
+                                         co_consts, linestarts,
+                                         line_offset=line_offset,
+                                         exception_entries=exception_entries,
+                                         co_positions=co_positions,
+                                         show_caches=show_caches):
+        new_source_line = (show_lineno and
+                           instr.starts_line is not None and
+                           instr.offset > 0)
+        if new_source_line:
+            print(file=file)
+        is_current_instr = instr.offset == lasti
+        print(instr._disassemble(lineno_width, is_current_instr, offset_width),
+              file=file)
+    if exception_entries:
+        print("ExceptionTable:", file=file)
+        for entry in exception_entries:
+            lasti = " lasti" if entry.lasti else ""
+            end = entry.end-2
+            print(f"  {entry.start} to {end} -> {entry.target} [{entry.depth}]{lasti}", file=file)
+
+def _disassemble_str(source, **kwargs):
+    """Compile the source string, then disassemble the code object."""
+    _disassemble_recursive(_try_compile(source, '<dis>'), **kwargs)
+
+disco = disassemble                     # XXX For backwards compatibility
+
+
+# Rely on C `int` being 32 bits for oparg
+_INT_BITS = 32
+# Value for c int when it overflows
+_INT_OVERFLOW = 2 ** (_INT_BITS - 1)
+
+def _unpack_opargs(code):
+    extended_arg = 0
+    caches = 0
+    for i in range(0, len(code), 2):
+        # Skip inline CACHE entries:
+        if caches:
+            caches -= 1
+            continue
+        op = code[i]
+        deop = _deoptop(op)
+        caches = _inline_cache_entries[deop]
+        if deop >= HAVE_ARGUMENT:
+            arg = code[i+1] | extended_arg
+            extended_arg = (arg << 8) if deop == EXTENDED_ARG else 0
+            # The oparg is stored as a signed integer
+            # If the value exceeds its upper limit, it will overflow and wrap
+            # to a negative integer
+            if extended_arg >= _INT_OVERFLOW:
+                extended_arg -= 2 * _INT_OVERFLOW
+        else:
+            arg = None
+            extended_arg = 0
+        yield (i, op, arg)
+
+def findlabels(code):
+    """Detect all offsets in a byte code which are jump targets.
+
+    Return the list of offsets.
+
+    """
+    labels = []
+    for offset, op, arg in _unpack_opargs(code):
+        if arg is not None:
+            if op in hasjrel:
+                if _is_backward_jump(op):
+                    arg = -arg
+                label = offset + 2 + arg*2
+            elif op in hasjabs:
+                label = arg*2
+            else:
+                continue
+            if label not in labels:
+                labels.append(label)
+    return labels
+
+def findlinestarts(code):
+    """Find the offsets in a byte code which are start of lines in the source.
+
+    Generate pairs (offset, lineno)
+    """
+    lastline = None
+    for start, end, line in code.co_lines():
+        if line is not None and line != lastline:
+            lastline = line
+            yield start, line
+    return
+
+def _find_imports(co):
+    """Find import statements in the code
+
+    Generate triplets (name, level, fromlist) where
+    name is the imported module and level, fromlist are
+    the corresponding args to __import__.
+    """
+    IMPORT_NAME = opmap['IMPORT_NAME']
+    LOAD_CONST = opmap['LOAD_CONST']
+
+    consts = co.co_consts
+    names = co.co_names
+    opargs = [(op, arg) for _, op, arg in _unpack_opargs(co.co_code)
+                  if op != EXTENDED_ARG]
+    for i, (op, oparg) in enumerate(opargs):
+        if op == IMPORT_NAME and i >= 2:
+            from_op = opargs[i-1]
+            level_op = opargs[i-2]
+            if (from_op[0] in hasconst and level_op[0] in hasconst):
+                level = _get_const_value(level_op[0], level_op[1], consts)
+                fromlist = _get_const_value(from_op[0], from_op[1], consts)
+                yield (names[oparg], level, fromlist)
+
+def _find_store_names(co):
+    """Find names of variables which are written in the code
+
+    Generate sequence of strings
+    """
+    STORE_OPS = {
+        opmap['STORE_NAME'],
+        opmap['STORE_GLOBAL']
+    }
+
+    names = co.co_names
+    for _, op, arg in _unpack_opargs(co.co_code):
+        if op in STORE_OPS:
+            yield names[arg]
+
+
+class Bytecode:
+    """The bytecode operations of a piece of code
+
+    Instantiate this with a function, method, other compiled object, string of
+    code, or a code object (as returned by compile()).
+
+    Iterating over this yields the bytecode operations as Instruction instances.
+    """
+    def __init__(self, x, *, first_line=None, current_offset=None, show_caches=False, adaptive=False):
+        self.codeobj = co = _get_code_object(x)
+        if first_line is None:
+            self.first_line = co.co_firstlineno
+            self._line_offset = 0
+        else:
+            self.first_line = first_line
+            self._line_offset = first_line - co.co_firstlineno
+        self._linestarts = dict(findlinestarts(co))
+        self._original_object = x
+        self.current_offset = current_offset
+        self.exception_entries = _parse_exception_table(co)
+        self.show_caches = show_caches
+        self.adaptive = adaptive
+
+    def __iter__(self):
+        co = self.codeobj
+        return _get_instructions_bytes(_get_code_array(co, self.adaptive),
+                                       co._varname_from_oparg,
+                                       co.co_names, co.co_consts,
+                                       self._linestarts,
+                                       line_offset=self._line_offset,
+                                       exception_entries=self.exception_entries,
+                                       co_positions=co.co_positions(),
+                                       show_caches=self.show_caches)
+
+    def __repr__(self):
+        return "{}({!r})".format(self.__class__.__name__,
+                                 self._original_object)
+
+    @classmethod
+    def from_traceback(cls, tb, *, show_caches=False, adaptive=False):
+        """ Construct a Bytecode from the given traceback """
+        while tb.tb_next:
+            tb = tb.tb_next
+        return cls(
+            tb.tb_frame.f_code, current_offset=tb.tb_lasti, show_caches=show_caches, adaptive=adaptive
+        )
+
+    def info(self):
+        """Return formatted information about the code object."""
+        return _format_code_info(self.codeobj)
+
+    def dis(self):
+        """Return a formatted view of the bytecode operations."""
+        co = self.codeobj
+        if self.current_offset is not None:
+            offset = self.current_offset
+        else:
+            offset = -1
+        with io.StringIO() as output:
+            _disassemble_bytes(_get_code_array(co, self.adaptive),
+                               varname_from_oparg=co._varname_from_oparg,
+                               names=co.co_names, co_consts=co.co_consts,
+                               linestarts=self._linestarts,
+                               line_offset=self._line_offset,
+                               file=output,
+                               lasti=offset,
+                               exception_entries=self.exception_entries,
+                               co_positions=co.co_positions(),
+                               show_caches=self.show_caches)
+            return output.getvalue()
+
+
+def _test():
+    """Simple test program to disassemble a file."""
+    import argparse
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('infile', type=argparse.FileType('rb'), nargs='?', default='-')
+    args = parser.parse_args()
+    with args.infile as infile:
+        source = infile.read()
+    code = compile(source, args.infile.name, "exec")
+    dis(code)
+
+if __name__ == "__main__":
+    _test()