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cpython/Lib/dis.py

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"""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']
FOR_ITER = opmap['FOR_ITER']
LOAD_ATTR = opmap['LOAD_ATTR']
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
elif deop == LOAD_ATTR:
argval, argrepr = _get_name_info(arg//2, get_name)
if (arg & 1) and argrepr:
argrepr = "NULL|self + " + 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
if deop == FOR_ITER:
argval += 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>>4]
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:
if i == 0:
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 in hasarg:
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:
deop = _deoptop(op)
if deop in hasjrel:
if _is_backward_jump(deop):
arg = -arg
label = offset + 2 + arg*2
if deop == FOR_ITER:
label += 2
elif deop 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']
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()
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