python-uncompyle6/uncompyle6/scanner.py

#  Copyright (c) 2016, 2018-2024 by Rocky Bernstein
#  Copyright (c) 2005 by Dan Pascu <dan@windowmaker.org>
#  Copyright (c) 2000-2002 by hartmut Goebel <h.goebel@crazy-compilers.com>
#  Copyright (c) 1999 John Aycock
#
#  This program is free software: you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation, either version 3 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
"""
scanner/ingestion module. From here we call various version-specific
scanners, e.g. for Python 2.7 or 3.4.
"""

from abc import ABC
from array import array
from collections import namedtuple
from types import ModuleType
from typing import Optional, Union

import xdis
from xdis import (
    Bytecode,
    canonic_python_version,
    code2num,
    extended_arg_val,
    instruction_size,
    next_offset,
)
from xdis.version_info import IS_PYPY, version_tuple_to_str

from uncompyle6.scanners.tok import Token

# The byte code versions we support.
# Note: these all have to be tuples of 2 ints
PYTHON_VERSIONS = frozenset(
    (
        (1, 0),
        (1, 1),
        (1, 3),
        (1, 4),
        (1, 5),
        (1, 6),
        (2, 1),
        (2, 2),
        (2, 3),
        (2, 4),
        (2, 5),
        (2, 6),
        (2, 7),
        (3, 0),
        (3, 1),
        (3, 2),
        (3, 3),
        (3, 4),
        (3, 5),
        (3, 6),
        (3, 7),
        (3, 8),
    )
)

CANONIC2VERSION = dict(
    (canonic_python_version[version_tuple_to_str(python_version)], python_version)
    for python_version in PYTHON_VERSIONS
)

# Magic changed mid version for Python 3.5.2. Compatibility was added for
# the older 3.5 interpreter magic.
CANONIC2VERSION["3.5.2"] = 3.5


# FIXME: DRY
L65536 = 65536


def long(num):
    return num


CONST_COLLECTIONS = ("CONST_LIST", "CONST_SET", "CONST_DICT", "CONST_MAP")


class Code:
    """
    Class for representing code-objects.

    This is similar to the original code object, but additionally
    the diassembled code is stored in the attribute '_tokens'.
    """

    def __init__(self, co, scanner, classname=None, show_asm=None):
        # Full initialization is given below, but for linters
        # well set up some initial values.
        self.co_code = None  # Really either bytes for >= 3.0 and string in < 3.0

        for i in dir(co):
            if i.startswith("co_"):
                setattr(self, i, getattr(co, i))
        self._tokens, self._customize = scanner.ingest(co, classname, show_asm=show_asm)


class Scanner(ABC):
    def __init__(self, version: tuple, show_asm=None, is_pypy=False):
        self.version = version
        self.show_asm = show_asm
        self.is_pypy = is_pypy

        # Temoorary initialization.
        self.opc = ModuleType("uninitialized")

        if version[:2] in PYTHON_VERSIONS:
            v_str = f"""opcode_{version_tuple_to_str(version, start=0, end=2, delimiter="")}"""
            if is_pypy:
                v_str += "pypy"
            exec(f"""from xdis.opcodes import {v_str}""")
            exec("self.opc = %s" % v_str)
        else:
            raise TypeError(
                "%s is not a Python version I know about"
                % version_tuple_to_str(version)
            )

        self.opname = self.opc.opname

        # FIXME: This weird Python2 behavior is not Python3
        self.resetTokenClass()

    def bound_collection_from_tokens(self, tokens, t, i, collection_type):
        count = t.attr
        assert isinstance(count, int)

        assert count <= i

        if collection_type == "CONST_DICT":
            # constant dictionaries work via BUILD_CONST_KEY_MAP and
            # handle the values() like sets and lists.
            # However, the keys() are an LOAD_CONST of the keys.
            # adjust offset to account for this
            count += 1

        # For small lists don't bother
        if count < 5:
            return None

        collection_start = i - count

        for j in range(collection_start, i):
            if tokens[j].kind not in (
                "LOAD_CONST",
                "LOAD_FAST",
                "LOAD_GLOBAL",
                "LOAD_NAME",
            ):
                return None

        collection_enum = CONST_COLLECTIONS.index(collection_type)

        # If we go there all instructions before tokens[i] are LOAD_CONST and we can replace
        # add a boundary marker and change LOAD_CONST to something else
        new_tokens = tokens[:-count]
        start_offset = tokens[collection_start].offset
        new_tokens.append(
            Token(
                opname="COLLECTION_START",
                attr=collection_enum,
                pattr=collection_type,
                offset="%s_0" % start_offset,
                has_arg=True,
                opc=self.opc,
                has_extended_arg=False,
            )
        )
        for j in range(collection_start, i):
            if tokens[j] == "LOAD_CONST":
                opname = "ADD_VALUE"
            else:
                opname = "ADD_VALUE_VAR"
            new_tokens.append(
                Token(
                    opname=opname,
                    attr=tokens[j].attr,
                    pattr=tokens[j].pattr,
                    offset=tokens[j].offset,
                    has_arg=True,
                    linestart=tokens[j].linestart,
                    opc=self.opc,
                    has_extended_arg=False,
                )
            )
        new_tokens.append(
            Token(
                opname="BUILD_%s" % collection_type,
                attr=t.attr,
                pattr=t.pattr,
                offset=t.offset,
                has_arg=t.has_arg,
                linestart=t.linestart,
                opc=t.opc,
                has_extended_arg=False,
            )
        )
        return new_tokens

    def build_instructions(self, co):
        """
        Create a list of instructions (a structured object rather than
        an array of bytes) and store that in self.insts
        """
        # FIXME: remove this when all subsidiary functions have been removed.
        # We should be able to get everything from the self.insts list.
        self.code = array("B", co.co_code)

        bytecode = Bytecode(co, self.opc)
        self.build_prev_op()
        self.insts = self.remove_extended_args(list(bytecode))
        self.lines = self.build_lines_data(co)
        self.offset2inst_index = {}
        for i, inst in enumerate(self.insts):
            self.offset2inst_index[inst.offset] = i

        return bytecode

    def build_lines_data(self, code_obj):
        """
        Generate various line-related helper data.
        """

        # Offset: lineno pairs, only for offsets which start line.
        # Locally we use list for more convenient iteration using indices
        linestarts = list(self.opc.findlinestarts(code_obj))
        self.linestarts = dict(linestarts)
        if not self.linestarts:
            return []

        # 'List-map' which shows line number of current op and offset of
        # first op on following line, given offset of op as index
        lines = []
        LineTuple = namedtuple("LineTuple", ["l_no", "next"])

        # Iterate through available linestarts, and fill
        # the data for all code offsets encountered until
        # last linestart offset
        _, prev_line_no = linestarts[0]
        offset = 0
        for start_offset, line_no in linestarts[1:]:
            while offset < start_offset:
                lines.append(LineTuple(prev_line_no, start_offset))
                offset += 1
            prev_line_no = line_no

        # Fill remaining offsets with reference to last line number
        # and code length as start offset of following non-existing line
        codelen = len(self.code)
        while offset < codelen:
            lines.append(LineTuple(prev_line_no, codelen))
            offset += 1
        return lines

    def build_prev_op(self):
        """
        Compose 'list-map' which allows to jump to previous
        op, given offset of current op as index.
        """
        code = self.code
        codelen = len(code)
        # 2.x uses prev 3.x uses prev_op. Sigh
        # Until we get this sorted out.
        self.prev = self.prev_op = [0]
        for offset in self.op_range(0, codelen):
            op = code[offset]
            for _ in range(instruction_size(op, self.opc)):
                self.prev_op.append(offset)

    def is_jump_forward(self, offset: int) -> bool:
        """
        Return True if the code at offset is some sort of jump forward.
        That is, it is ether "JUMP_FORWARD" or an absolute jump that
        goes forward.
        """
        opname = self.get_inst(offset).opname
        if opname == "JUMP_FORWARD":
            return True
        if opname != "JUMP_ABSOLUTE":
            return False
        return offset < self.get_target(offset)

    def ingest(self, co, classname=None, code_objects={}, show_asm=None):
        """
        Code to tokenize disassembly. Subclasses must implement this.
        """
        raise NotImplementedError("This method should have been implemented")

    def prev_offset(self, offset: int) -> int:
        return self.insts[self.offset2inst_index[offset] - 1].offset

    def get_inst(self, offset: int):
        # Instructions can get moved as a result of EXTENDED_ARGS removal.
        # So if "offset" is not in self.offset2inst_index, then
        # we assume that it was an instruction moved back.
        # We check that assumption though by looking at
        # self.code's opcode.
        if offset not in self.offset2inst_index:
            offset -= instruction_size(self.opc.EXTENDED_ARG, self.opc)
            assert self.code[offset] == self.opc.EXTENDED_ARG
        return self.insts[self.offset2inst_index[offset]]

    def get_target(self, offset: int, extended_arg: int = 0) -> int:
        """
        Get next instruction offset for op located at given <offset>.
        NOTE: extended_arg is no longer used
        """
        inst = self.get_inst(offset)
        if inst.opcode in self.opc.JREL_OPS | self.opc.JABS_OPS:
            target = inst.argval
        else:
            # No jump offset, so use fall-through offset
            target = next_offset(inst.opcode, self.opc, inst.offset)
        return target

    def get_argument(self, pos: int):
        arg = self.code[pos + 1] + self.code[pos + 2] * 256
        return arg

    def next_offset(self, op, offset: int) -> int:
        return xdis.next_offset(op, self.opc, offset)

    def first_instr(self, start: int, end: int, instr, target=None, exact=True):
        """
        Find the first <instr> in the block from start to end.
        <instr> is any python bytecode instruction or a list of opcodes
        If <instr> is an opcode with a target (like a jump), a target
        destination can be specified which must match precisely if exact
        is True, or if exact is False, the instruction which has a target
        closest to <target> will be returned.

        Return index to it or None if not found.
        """
        code = self.code
        assert start >= 0 and end <= len(code)

        if not isinstance(instr, list):
            instr = [instr]

        result_offset = None
        current_distance = len(code)
        for offset in self.op_range(start, end):
            op = code[offset]
            if op in instr:
                if target is None:
                    return offset
                dest = self.get_target(offset)
                if dest == target:
                    return offset
                elif not exact:
                    new_distance = abs(target - dest)
                    if new_distance < current_distance:
                        current_distance = new_distance
                        result_offset = offset
        return result_offset

    def last_instr(
        self, start: int, end: int, instr, target=None, exact=True
    ) -> Optional[int]:
        """
        Find the last <instr> in the block from start to end.
        <instr> is any python bytecode instruction or a list of opcodes
        If <instr> is an opcode with a target (like a jump), a target
        destination can be specified which must match precisely if exact
        is True, or if exact is False, the instruction which has a target
        closest to <target> will be returned.

        Return index to it or None if not found.
        """

        code = self.code
        # Make sure requested positions do not go out of
        # code bounds
        if not (start >= 0 and end <= len(code)):
            return None

        if not isinstance(instr, list):
            instr = [instr]

        result_offset = None
        current_distance = self.insts[-1].offset - self.insts[0].offset
        extended_arg = 0
        # FIXME: use self.insts rather than code[]
        for offset in self.op_range(start, end):
            op = code[offset]

            if op == self.opc.EXTENDED_ARG:
                arg = code2num(code, offset + 1) | extended_arg
                extended_arg = extended_arg_val(self.opc, arg)
                continue

            if op in instr:
                if target is None:
                    result_offset = offset
                else:
                    dest = self.get_target(offset, extended_arg)
                    if dest == target:
                        current_distance = 0
                        result_offset = offset
                    elif not exact:
                        new_distance = abs(target - dest)
                        if new_distance <= current_distance:
                            current_distance = new_distance
                            result_offset = offset
                            pass
                        pass
                    pass
                pass
            extended_arg = 0
            pass
        return result_offset

    def inst_matches(self, start, end, instr, target=None, include_beyond_target=False):
        """
        Find all `instr` in the block from start to end.
        `instr` is a Python opcode or a list of opcodes
        If `instr` is an opcode with a target (like a jump), a target
        destination can be specified which must match precisely.

        Return a list with indexes to them or [] if none found.
        """
        try:
            None in instr
        except Exception:
            instr = [instr]

        first = self.offset2inst_index[start]
        result = []
        for inst in self.insts[first:]:
            if inst.opcode in instr:
                if target is None:
                    result.append(inst.offset)
                else:
                    t = self.get_target(inst.offset)
                    if include_beyond_target and t >= target:
                        result.append(inst.offset)
                    elif t == target:
                        result.append(inst.offset)
                        pass
                    pass
                pass
            if inst.offset >= end:
                break
            pass

        # FIXME: put in a test
        # check = self.all_instr(start, end, instr, target, include_beyond_target)
        # assert result == check

        return result

    # FIXME: this is broken on 3.6+. Replace remaining (2.x-based) calls
    # with inst_matches

    def all_instr(
        self, start: int, end: int, instr, target=None, include_beyond_target=False
    ):
        """
        Find all `instr` in the block from start to end.
        `instr` is any Python opcode or a list of opcodes
        If `instr` is an opcode with a target (like a jump), a target
        destination can be specified which must match precisely.

        Return a list with indexes to them or [] if none found.
        """

        code = self.code
        assert start >= 0 and end <= len(code)

        try:
            None in instr
        except:
            instr = [instr]

        result = []
        extended_arg = 0
        for offset in self.op_range(start, end):
            op = code[offset]

            if op == self.opc.EXTENDED_ARG:
                arg = code2num(code, offset + 1) | extended_arg
                extended_arg = extended_arg_val(self.opc, arg)
                continue

            if op in instr:
                if target is None:
                    result.append(offset)
                else:
                    t = self.get_target(offset, extended_arg)
                    if include_beyond_target and t >= target:
                        result.append(offset)
                    elif t == target:
                        result.append(offset)
                        pass
                    pass
                pass
            extended_arg = 0
            pass

        return result

    def opname_for_offset(self, offset):
        return self.opc.opname[self.code[offset]]

    def op_name(self, op):
        return self.opc.opname[op]

    def op_range(self, start, end):
        """
        Iterate through positions of opcodes, skipping
        arguments.
        """
        while start < end:
            yield start
            start += instruction_size(self.code[start], self.opc)

    def remove_extended_args(self, instructions):
        """Go through instructions removing extended ARG.
        get_instruction_bytes previously adjusted the operand values
        to account for these"""
        new_instructions = []
        last_was_extarg = False
        n = len(instructions)
        for i, inst in enumerate(instructions):
            if (
                inst.opname == "EXTENDED_ARG"
                and i + 1 < n
                and instructions[i + 1].opname != "MAKE_FUNCTION"
            ):
                last_was_extarg = True
                starts_line = inst.starts_line
                is_jump_target = inst.is_jump_target
                offset = inst.offset
                continue
            if last_was_extarg:
                # j = self.stmts.index(inst.offset)
                # self.lines[j] = offset

                new_inst = inst._replace(
                    starts_line=starts_line,
                    is_jump_target=is_jump_target,
                    offset=offset,
                )
                inst = new_inst
                if i < n:
                    new_prev = self.prev_op[instructions[i].offset]
                    j = instructions[i + 1].offset
                    old_prev = self.prev_op[j]
                    while self.prev_op[j] == old_prev and j < n:
                        self.prev_op[j] = new_prev
                        j += 1

            last_was_extarg = False
            new_instructions.append(inst)
        return new_instructions

    def remove_mid_line_ifs(self, ifs):
        """
        Go through passed offsets, filtering ifs
        located somewhere mid-line.
        """

        # FIXME: this doesn't work for Python 3.6+

        filtered = []
        for i in ifs:
            # For each offset, if line number of current and next op
            # is the same
            if self.lines[i].l_no == self.lines[i + 3].l_no:
                # Skip last op on line if it is some sort of POP_JUMP.
                if self.code[self.prev[self.lines[i].next]] in (
                    self.opc.PJIT,
                    self.opc.PJIF,
                ):
                    continue
            filtered.append(i)
        return filtered

    def resetTokenClass(self):
        return self.setTokenClass(Token)

    def restrict_to_parent(self, target: int, parent) -> int:
        """Restrict target to parent structure boundaries."""
        if not (parent["start"] < target < parent["end"]):
            target = parent["end"]
        return target

    def setTokenClass(self, tokenClass: Token) -> Token:
        self.Token = tokenClass
        return self.Token


def get_scanner(version: Union[str, tuple], is_pypy=False, show_asm=None) -> Scanner:
    """
    Import the right scanner module for ``version`` and return the Scanner class
    in that module.
    """
    # If version is a string, turn that into the corresponding float.
    if isinstance(version, str):
        if version not in canonic_python_version:
            raise RuntimeError(f"Unknown Python version in xdis {version}")
        canonic_version = canonic_python_version[version]
        if canonic_version not in CANONIC2VERSION:
            raise RuntimeError(
                f"Unsupported Python version {version} (canonic {canonic_version})"
            )
        version = CANONIC2VERSION[canonic_version]

    # Pick up appropriate scanner
    if version[:2] in PYTHON_VERSIONS:
        v_str = version_tuple_to_str(version, start=0, end=2, delimiter="")
        try:
            import importlib

            if is_pypy:
                scan = importlib.import_module("uncompyle6.scanners.pypy%s" % v_str)
            else:
                scan = importlib.import_module("uncompyle6.scanners.scanner%s" % v_str)
            if False:
                print(scan)  # Avoid unused scan
        except ImportError:
            if is_pypy:
                exec(
                    "import uncompyle6.scanners.pypy%s as scan" % v_str,
                    locals(),
                    globals(),
                )
            else:
                exec(
                    "import uncompyle6.scanners.scanner%s as scan" % v_str,
                    locals(),
                    globals(),
                )
        if is_pypy:
            scanner = eval(
                "scan.ScannerPyPy%s(show_asm=show_asm)" % v_str, locals(), globals()
            )
        else:
            scanner = eval(
                "scan.Scanner%s(show_asm=show_asm)" % v_str, locals(), globals()
            )
    else:
        raise RuntimeError(
            f"Unsupported Python version, {version_tuple_to_str(version)}, for decompilation"
        )
    return scanner


if __name__ == "__main__":
    import inspect

    co = inspect.currentframe().f_code
    # scanner = get_scanner('2.7.13', True)
    # scanner = get_scanner(sys.version[:5], False)
    from xdis.version_info import PYTHON_VERSION_TRIPLE

    scanner = get_scanner(PYTHON_VERSION_TRIPLE, IS_PYPY, True)
    tokens, customize = scanner.ingest(co, {}, show_asm="after")