xhs-note-crawling/python/py/Lib/site-packages/uncompyle6/scanners/scanner30.py

#  Copyright (c) 2016-2017, 2020-2021 by Rocky Bernstein
"""
Python 3.0 bytecode scanner/deparser

This sets up opcodes Python's 3.0 and calls a generalized
scanner routine for Python 3.
"""

from __future__ import print_function

import xdis
from xdis import instruction_size

# bytecode verification, verify(), uses JUMP_OPs from here
from xdis.opcodes import opcode_30 as opc

from uncompyle6.scanners.scanner3 import Scanner3

JUMP_TF = frozenset([opc.JUMP_IF_FALSE, opc.JUMP_IF_TRUE])


class Scanner30(Scanner3):
    def __init__(self, show_asm=None, is_pypy=False):
        Scanner3.__init__(self, (3, 0), show_asm, is_pypy)
        return

    pass

    def detect_control_flow(self, offset, targets, inst_index):
        """
        Detect structures and their boundaries to fix optimized jumps
        Python 3.0 is more like Python 2.6 than it is Python 3.x.
        So we have a special routine here.
        """

        code = self.code
        op = self.insts[inst_index].opcode

        # Detect parent structure
        parent = self.structs[0]
        start = parent["start"]
        end = parent["end"]

        # Pick innermost parent for our offset
        for struct in self.structs:
            current_start = struct["start"]
            current_end = struct["end"]
            if (current_start <= offset < current_end) and (
                current_start >= start and current_end <= end
            ):
                start = current_start
                end = current_end
                parent = struct

        if op == self.opc.SETUP_LOOP:
            # We categorize loop types: 'for', 'while', 'while 1' with
            # possibly suffixes '-loop' and '-else'
            # Try to find the jump_back instruction of the loop.
            # It could be a return instruction.

            start += instruction_size(op, self.opc)
            target = self.get_target(offset)
            end = self.restrict_to_parent(target, parent)
            self.setup_loops[target] = offset

            if target != end:
                self.fixed_jumps[offset] = end

            (line_no, next_line_byte) = self.lines[offset]
            jump_back = self.last_instr(
                start, end, self.opc.JUMP_ABSOLUTE, next_line_byte, False
            )

            if jump_back:
                jump_forward_offset = xdis.next_offset(
                    code[jump_back], self.opc, jump_back
                )
            else:
                jump_forward_offset = None

            return_val_offset1 = self.prev[self.prev[end]]

            if (
                jump_back
                and jump_back != self.prev_op[end]
                and self.is_jump_forward(jump_forward_offset)
            ):
                if code[self.prev_op[end]] == self.opc.RETURN_VALUE or (
                    code[self.prev_op[end]] == self.opc.POP_BLOCK
                    and code[return_val_offset1] == self.opc.RETURN_VALUE
                ):
                    jump_back = None
            if not jump_back:
                # loop suite ends in return
                jump_back = self.last_instr(start, end, self.opc.RETURN_VALUE)
                if not jump_back:
                    return

                jb_inst = self.get_inst(jump_back)
                jump_back = self.next_offset(jb_inst.opcode, jump_back)

                if_offset = None
                if code[self.prev_op[next_line_byte]] not in JUMP_TF:
                    if_offset = self.prev[next_line_byte]
                if if_offset:
                    loop_type = "while"
                    self.ignore_if.add(if_offset)
                else:
                    loop_type = "for"
                target = next_line_byte
                end = jump_back + 3
            else:
                if self.get_target(jump_back) >= next_line_byte:
                    jump_back = self.last_instr(
                        start, end, self.opc.JUMP_ABSOLUTE, start, False
                    )

                jb_inst = self.get_inst(jump_back)

                jb_next_offset = self.next_offset(jb_inst.opcode, jump_back)
                if end > jb_next_offset and self.is_jump_forward(end):
                    if self.is_jump_forward(jb_next_offset):
                        if self.get_target(jump_back + 4) == self.get_target(end):
                            self.fixed_jumps[offset] = jump_back + 4
                            end = jb_next_offset
                elif target < offset:
                    self.fixed_jumps[offset] = jump_back + 4
                    end = jb_next_offset

                target = self.get_target(jump_back)

                if code[target] in (self.opc.FOR_ITER, self.opc.GET_ITER):
                    loop_type = "for"
                else:
                    loop_type = "while"
                    test = self.prev_op[next_line_byte]

                    if test == offset:
                        loop_type = "while 1"
                    elif self.code[test] in self.opc.JUMP_OPs:
                        self.ignore_if.add(test)
                        test_target = self.get_target(test)
                        if test_target > (jump_back + 3):
                            jump_back = test_target
                self.not_continue.add(jump_back)
            self.loops.append(target)
            self.structs.append(
                {"type": loop_type + "-loop", "start": target, "end": jump_back}
            )
            after_jump_offset = xdis.next_offset(code[jump_back], self.opc, jump_back)
            if self.get_inst(after_jump_offset).opname == "POP_TOP":
                after_jump_offset = xdis.next_offset(
                    code[after_jump_offset], self.opc, after_jump_offset
                )
            if after_jump_offset != end:
                self.structs.append(
                    {
                        "type": loop_type + "-else",
                        "start": after_jump_offset,
                        "end": end,
                    }
                )
        elif op in self.pop_jump_tf:
            start = offset + instruction_size(op, self.opc)
            target = self.get_target(offset)
            rtarget = self.restrict_to_parent(target, parent)
            prev_op = self.prev_op

            # Do not let jump to go out of parent struct bounds
            if target != rtarget and parent["type"] == "and/or":
                self.fixed_jumps[offset] = rtarget
                return

            # Does this jump to right after another conditional jump that is
            # not myself?  If so, it's part of a larger conditional.
            # rocky: if we have a conditional jump to the next instruction, then
            # possibly I am "skipping over" a "pass" or null statement.

            if (
                (code[prev_op[target]] in self.pop_jump_if_pop)
                and (target > offset)
                and prev_op[target] != offset
            ):
                self.fixed_jumps[offset] = prev_op[target]
                self.structs.append(
                    {"type": "and/or", "start": start, "end": prev_op[target]}
                )
                return

            # The op offset just before the target jump offset is important
            # in making a determination of what we have. Save that.
            pre_rtarget = prev_op[rtarget]

            # Is it an "and" inside an "if" or "while" block
            if op == opc.JUMP_IF_FALSE:

                # Search for another JUMP_IF_FALSE targeting the same op,
                # in current statement, starting from current offset, and filter
                # everything inside inner 'or' jumps and midline ifs
                match = self.rem_or(
                    start, self.next_stmt[offset], opc.JUMP_IF_FALSE, target
                )

                # If we still have any offsets in set, start working on it
                if match:
                    is_jump_forward = self.is_jump_forward(pre_rtarget)
                    if (
                        is_jump_forward
                        and pre_rtarget not in self.stmts
                        and self.restrict_to_parent(
                            self.get_target(pre_rtarget), parent
                        )
                        == rtarget
                    ):
                        if (
                            code[prev_op[pre_rtarget]] == self.opc.JUMP_ABSOLUTE
                            and self.remove_mid_line_ifs([offset])
                            and target == self.get_target(prev_op[pre_rtarget])
                            and (
                                prev_op[pre_rtarget] not in self.stmts
                                or self.get_target(prev_op[pre_rtarget])
                                > prev_op[pre_rtarget]
                            )
                            and 1
                            == len(
                                self.remove_mid_line_ifs(
                                    self.rem_or(
                                        start, prev_op[pre_rtarget], JUMP_TF, target
                                    )
                                )
                            )
                        ):
                            pass
                        elif (
                            code[prev_op[pre_rtarget]] == self.opc.RETURN_VALUE
                            and self.remove_mid_line_ifs([offset])
                            and 1
                            == (
                                len(
                                    set(
                                        self.remove_mid_line_ifs(
                                            self.rem_or(
                                                start,
                                                prev_op[pre_rtarget],
                                                JUMP_TF,
                                                target,
                                            )
                                        )
                                    )
                                    | set(
                                        self.remove_mid_line_ifs(
                                            self.rem_or(
                                                start,
                                                prev_op[pre_rtarget],
                                                (
                                                    opc.JUMP_IF_FALSE,
                                                    opc.JUMP_IF_TRUE,
                                                    opc.JUMP_ABSOLUTE,
                                                ),
                                                pre_rtarget,
                                                True,
                                            )
                                        )
                                    )
                                )
                            )
                        ):
                            pass
                        else:
                            fix = None
                            jump_ifs = self.inst_matches(
                                start, self.next_stmt[offset], opc.JUMP_IF_FALSE
                            )
                            last_jump_good = True
                            for j in jump_ifs:
                                if target == self.get_target(j):
                                    # FIXME: remove magic number
                                    if self.lines[j].next == j + 3 and last_jump_good:
                                        fix = j
                                        break
                                else:
                                    last_jump_good = False
                            self.fixed_jumps[offset] = fix or match[-1]
                            return
                    else:
                        self.fixed_jumps[offset] = match[-1]
                        return
            # op == JUMP_IF_TRUE
            else:
                next = self.next_stmt[offset]
                if prev_op[next] == offset:
                    pass
                elif self.is_jump_forward(next) and target == self.get_target(next):
                    if code[prev_op[next]] == opc.JUMP_IF_FALSE:
                        if (
                            code[next] == self.opc.JUMP_FORWARD
                            or target != rtarget
                            or code[prev_op[pre_rtarget]]
                            not in (self.opc.JUMP_ABSOLUTE, self.opc.RETURN_VALUE)
                        ):
                            self.fixed_jumps[offset] = prev_op[next]
                            return
                elif (
                    code[next] == self.opc.JUMP_ABSOLUTE
                    and self.is_jump_forward(target)
                    and self.get_target(target) == self.get_target(next)
                ):
                    self.fixed_jumps[offset] = prev_op[next]
                    return

            # Don't add a struct for a while test, it's already taken care of
            if offset in self.ignore_if:
                return

            if (
                code[pre_rtarget] == self.opc.JUMP_ABSOLUTE
                and pre_rtarget in self.stmts
                and pre_rtarget != offset
                and prev_op[pre_rtarget] != offset
                and not (
                    code[rtarget] == self.opc.JUMP_ABSOLUTE
                    and code[rtarget + 3] == self.opc.POP_BLOCK
                    and code[prev_op[pre_rtarget]] != self.opc.JUMP_ABSOLUTE
                )
            ):
                rtarget = pre_rtarget

            # Does the "jump if" jump beyond a jump op?
            # That is, we have something like:
            #  JUMP_IF_FALSE HERE
            #  ...
            # JUMP_FORWARD
            # HERE:
            #
            # If so, this can be block inside an "if" statement
            # or a conditional assignment like:
            #   x = 1 if x else 2
            #
            # There are other contexts we may need to consider
            # like whether the target is "END_FINALLY"
            # or if the condition jump is to a forward location
            if self.is_jump_forward(pre_rtarget):
                if_end = self.get_target(pre_rtarget, 0)

                # If the jump target is back, we are looping
                if if_end < pre_rtarget and (
                    code[prev_op[if_end]] == self.opc.SETUP_LOOP
                ):
                    if if_end > start:
                        return

                self.restrict_to_parent(if_end, parent)

                self.structs.append(
                    {"type": "if-then", "start": start, "end": pre_rtarget}
                )
                self.not_continue.add(pre_rtarget)

                # if rtarget < end and (
                #         code[rtarget] not in (self.opc.END_FINALLY,
                #                               self.opc.JUMP_ABSOLUTE) and
                #         code[prev_op[pre_rtarget]] not in (self.opc.POP_EXCEPT,
                #                                         self.opc.END_FINALLY)):
                #     self.structs.append({'type': 'else',
                #                          'start': rtarget,
                #                          'end': end})
                #     self.else_start[rtarget] = end
            elif self.is_jump_back(pre_rtarget, 0):
                self.structs.append(
                    {"type": "if-then", "start": start, "end": pre_rtarget}
                )
                self.not_continue.add(pre_rtarget)
            elif code[pre_rtarget] in (self.opc.RETURN_VALUE, self.opc.BREAK_LOOP):
                self.structs.append({"type": "if-then", "start": start, "end": rtarget})
                # It is important to distinguish if this return is inside some sort
                # except block return
                jump_prev = prev_op[offset]
                if self.is_pypy and code[jump_prev] == self.opc.COMPARE_OP:
                    if self.opc.cmp_op[code[jump_prev + 1]] == "exception-match":
                        return
                if self.version >= (3, 5):
                    # Python 3.5 may remove as dead code a JUMP
                    # instruction after a RETURN_VALUE. So we check
                    # based on seeing SETUP_EXCEPT various places.
                    if code[rtarget] == self.opc.SETUP_EXCEPT:
                        return
                    # Check that next instruction after pops and jump is
                    # not from SETUP_EXCEPT
                    next_op = rtarget
                    if code[next_op] == self.opc.POP_BLOCK:
                        next_op += instruction_size(self.code[next_op], self.opc)
                    if code[next_op] == self.opc.JUMP_ABSOLUTE:
                        next_op += instruction_size(self.code[next_op], self.opc)
                    if next_op in targets:
                        for try_op in targets[next_op]:
                            come_from_op = code[try_op]
                            if come_from_op == self.opc.SETUP_EXCEPT:
                                return
                            pass
                    pass
                if code[pre_rtarget] == self.opc.RETURN_VALUE:
                    if self.version == (3, 0):
                        next_op = rtarget
                        if code[next_op] == self.opc.POP_TOP:
                            next_op = rtarget
                        for block in self.structs:
                            if (
                                block["type"] == "while-loop"
                                and block["end"] == next_op
                            ):
                                return
                        next_op += instruction_size(self.code[next_op], self.opc)
                        if code[next_op] == self.opc.POP_BLOCK:
                            return
                    self.return_end_ifs.add(pre_rtarget)
                else:
                    self.fixed_jumps[offset] = rtarget
                    self.not_continue.add(pre_rtarget)

        elif op == self.opc.SETUP_EXCEPT:
            target = self.get_target(offset)
            end = self.restrict_to_parent(target, parent)
            self.fixed_jumps[offset] = end
        elif op == self.opc.SETUP_FINALLY:
            target = self.get_target(offset)
            end = self.restrict_to_parent(target, parent)
            self.fixed_jumps[offset] = end
        elif op in self.jump_if_pop:
            target = self.get_target(offset)
            if target > offset:
                unop_target = self.last_instr(
                    offset, target, self.opc.JUMP_FORWARD, target
                )
                if unop_target and code[unop_target + 3] != self.opc.ROT_TWO:
                    self.fixed_jumps[offset] = unop_target
                else:
                    self.fixed_jumps[offset] = self.restrict_to_parent(target, parent)
                    pass
                pass
        elif self.version >= (3, 5):
            # 3.5+ has Jump optimization which too often causes RETURN_VALUE to get
            # misclassified as RETURN_END_IF. Handle that here.
            # In RETURN_VALUE, JUMP_ABSOLUTE, RETURN_VALUE is never RETURN_END_IF
            if op == self.opc.RETURN_VALUE:
                if (
                    offset + 1 < len(code)
                    and code[offset + 1] == self.opc.JUMP_ABSOLUTE
                    and offset in self.return_end_ifs
                ):
                    self.return_end_ifs.remove(offset)
                    pass
                pass
            elif op == self.opc.JUMP_FORWARD:
                # If we have:
                #   JUMP_FORWARD x, [non-jump, insns], RETURN_VALUE, x:
                # then RETURN_VALUE is not RETURN_END_IF
                rtarget = self.get_target(offset)
                rtarget_prev = self.prev[rtarget]
                if (
                    code[rtarget_prev] == self.opc.RETURN_VALUE
                    and rtarget_prev in self.return_end_ifs
                ):
                    i = rtarget_prev
                    while i != offset:
                        if code[i] in [opc.JUMP_FORWARD, opc.JUMP_ABSOLUTE]:
                            return
                        i = self.prev[i]
                    self.return_end_ifs.remove(rtarget_prev)
                pass
        return


if __name__ == "__main__":
    from xdis.version_info import PYTHON_VERSION_TRIPLE, version_tuple_to_str

    if PYTHON_VERSION_TRIPLE[:2] == (3, 0):
        import inspect

        co = inspect.currentframe().f_code  # type: ignore
        tokens, customize = Scanner30().ingest(co)
        for t in tokens:
            print(t.format())
        pass
    else:
        print("Need to be Python 3.0 to demo; I am version %s" % version_tuple_to_str())