| 1 | #!/usr/bin/env python2
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| 2 | """
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| 3 | umask_osh.py - Implements the umask builtin, including parsing
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| 4 | """
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| 5 | from __future__ import print_function
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| 6 |
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| 7 | from _devbuild.gen.runtime_asdl import cmd_value
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| 8 | from core import vm
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| 9 | from frontend import flag_util
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| 10 | from mycpp.mylib import print_stderr
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| 11 |
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| 12 | import posix_ as posix
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| 13 |
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| 14 | from typing import List, Tuple
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| 15 |
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| 16 | _WHO = "ugoa"
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| 17 | _OP = "+-="
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| 18 | _PERM_U_PERMCOPY = "rwxXstugo"
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| 19 |
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| 20 | # NOTE: bitsets are a great way to store fixed width sets & add / remove
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| 21 | # items easily. Thus, we use different bitsets for $wholist, $permlist,
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| 22 | # $perm, and $mask.
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| 23 |
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| 24 |
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| 25 | def _WhoCharToBitset(who_ch):
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| 26 | # type: (str) -> int
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| 27 | if who_ch == "u":
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| 28 | return 0o4
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| 29 | if who_ch == "g":
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| 30 | return 0o2
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| 31 | if who_ch == "o":
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| 32 | return 0o1
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| 33 |
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| 34 | # equivalent to 'ugo' bits
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| 35 | if who_ch == "a":
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| 36 | return 0o7
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| 37 |
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| 38 | raise AssertionError()
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| 39 |
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| 40 |
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| 41 | def _PermlistCharToBitset(permlist_ch):
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| 42 | # type: (str) -> int
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| 43 | if permlist_ch == "r":
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| 44 | return 0o400
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| 45 | if permlist_ch == "w":
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| 46 | return 0o200
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| 47 | if permlist_ch == "x":
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| 48 | return 0o100
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| 49 | if permlist_ch == "X":
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| 50 | return 0o040
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| 51 |
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| 52 | if permlist_ch == "s":
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| 53 | return 0o020
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| 54 | if permlist_ch == "t":
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| 55 | return 0o010
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| 56 |
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| 57 | if permlist_ch == "u":
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| 58 | return 0o004
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| 59 | if permlist_ch == "g":
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| 60 | return 0o002
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| 61 | if permlist_ch == "o":
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| 62 | return 0o001
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| 63 |
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| 64 | raise AssertionError()
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| 65 |
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| 66 |
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| 67 | # perm = [rwx][Xst][ugo]
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| 68 | def _PermlistToBits(permlist, initial_mask):
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| 69 | # type: (int, int) -> int
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| 70 | perm = 0o0
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| 71 | if (permlist & 0o400) != 0:
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| 72 | perm |= 0o4 # r
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| 73 | if (permlist & 0o200) != 0:
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| 74 | perm |= 0o2 # w
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| 75 | if (permlist & 0o100) != 0:
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| 76 | perm |= 0o1 # x
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| 77 | if (permlist & 0o040) != 0 and (initial_mask & 0o111) != 0:
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| 78 | # X == x iff one of the execute bits are set on the mask
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| 79 | perm |= 0o1 # X
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| 80 |
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| 81 | if (permlist & 0o020) != 0:
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| 82 | # does nothing b/c umask ignores the set-on-execution bits
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| 83 | perm |= 0o0 # s
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| 84 | if (permlist & 0o010) != 0:
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| 85 | # also does nothing
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| 86 | perm |= 0o0 # t
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| 87 |
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| 88 | if (permlist & 0o4) != 0:
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| 89 | perm |= (~initial_mask & 0o700) >> 6 # u
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| 90 | if (permlist & 0o2) != 0:
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| 91 | perm |= (~initial_mask & 0o070) >> 3 # g
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| 92 | if (permlist & 0o1) != 0:
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| 93 | perm |= (~initial_mask & 0o007) >> 0 # o
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| 94 |
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| 95 | return perm
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| 96 |
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| 97 |
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| 98 | def _SetMask(wholist, perm, mask):
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| 99 | # type: (int, int, int) -> int
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| 100 | """ For operator - """
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| 101 | if (wholist & 0o4) != 0:
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| 102 | mask |= perm << 6
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| 103 | if (wholist & 0o2) != 0:
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| 104 | mask |= perm << 3
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| 105 | if (wholist & 0o1) != 0:
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| 106 | mask |= perm << 0
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| 107 | return mask
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| 108 |
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| 109 |
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| 110 | def _ClearMask(wholist, perm, mask):
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| 111 | # type: (int, int, int) -> int
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| 112 | """ For operators + = """
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| 113 | if (wholist & 0o4) != 0:
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| 114 | mask &= 0o777 - (perm << 6)
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| 115 | if (wholist & 0o2) != 0:
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| 116 | mask &= 0o777 - (perm << 3)
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| 117 | if (wholist & 0o1) != 0:
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| 118 | mask &= 0o777 - (perm << 0)
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| 119 | return mask
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| 120 |
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| 121 |
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| 122 | class SymbolicClauseParser:
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| 123 |
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| 124 | def __init__(self, clause):
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| 125 | # type: (str) -> None
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| 126 | self.clause = clause
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| 127 | self.i = 0
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| 128 |
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| 129 | def AtEnd(self):
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| 130 | # type: () -> bool
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| 131 | return self.i >= len(self.clause)
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| 132 |
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| 133 | def Ch(self):
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| 134 | # type: () -> str
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| 135 | return self.clause[self.i]
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| 136 |
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| 137 | def ParseWholist(self):
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| 138 | # type: () -> int
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| 139 | if self.Ch() not in _WHO:
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| 140 | return 0o7
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| 141 |
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| 142 | wholist = 0o0
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| 143 | while not self.AtEnd():
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| 144 | if self.Ch() not in _WHO:
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| 145 | break
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| 146 |
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| 147 | wholist |= _WhoCharToBitset(self.Ch())
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| 148 | self.i += 1
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| 149 |
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| 150 | return wholist
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| 151 |
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| 152 | # An actionlist is a sequence of actions. An action always starts with an op.
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| 153 | # returns success
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| 154 | def ParseNextAction(self, wholist, mask, initial_mask):
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| 155 | # type: (int, int, int) -> Tuple[bool, int]
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| 156 |
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| 157 | op = self.Ch()
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| 158 | if op not in _OP:
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| 159 | print_stderr(
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| 160 | "oils warning: expected one of `%s` at start of action instead of `%s`"
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| 161 | % (_OP, op))
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| 162 | return False, 0
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| 163 |
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| 164 | self.i += 1
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| 165 |
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| 166 | if op == "=":
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| 167 | mask = _SetMask(wholist, 0o7, mask)
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| 168 |
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| 169 | if self.AtEnd() or self.Ch() not in _PERM_U_PERMCOPY:
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| 170 | if op == "+" or op == "=":
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| 171 | return True, mask
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| 172 | elif op == "-":
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| 173 | return True, mask
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| 174 |
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| 175 | # perm represents the bits [rwx] for a single permission
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| 176 | perm = 0o0
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| 177 |
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| 178 | # permlist = [rwx][Xst][ugo]
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| 179 | permlist = 0o000
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| 180 | while not (self.AtEnd() or self.Ch() in _OP):
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| 181 | # While a list of permcopy chars mixed with permlist is not posix, both dash and mksh
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| 182 | # support it.
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| 183 | if self.Ch() not in _PERM_U_PERMCOPY:
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| 184 | print_stderr(
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| 185 | "oil warning: expected one of `%s` in permlist instead of `%s`"
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| 186 | % (_PERM_U_PERMCOPY, self.Ch()))
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| 187 | return False, 0
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| 188 |
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| 189 | permlist |= _PermlistCharToBitset(self.Ch())
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| 190 | self.i += 1
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| 191 |
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| 192 | perm = _PermlistToBits(permlist, initial_mask)
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| 193 |
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| 194 | if op == "+" or op == "=":
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| 195 | return True, _ClearMask(wholist, perm, mask)
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| 196 | elif op == "-":
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| 197 | return True, _SetMask(wholist, perm, mask)
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| 198 |
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| 199 | assert False, "unreachable"
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| 200 | return False, 0
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| 201 |
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| 202 |
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| 203 | def _ParseClause(mask, initial_mask, clause):
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| 204 | # type: (int, int, str) -> Tuple[bool, int]
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| 205 | if len(clause) == 0:
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| 206 | # TODO: location highlighting would be nice
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| 207 | print_stderr("oils warning: symbolic mode operator cannot be empty")
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| 208 | return False, 0
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| 209 |
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| 210 | parser = SymbolicClauseParser(clause)
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| 211 | wholist = parser.ParseWholist()
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| 212 | if parser.AtEnd():
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| 213 | print_stderr("oils warning: actionlist is required")
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| 214 | return False, 0
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| 215 |
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| 216 | while True:
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| 217 | ok, mask = parser.ParseNextAction(wholist, mask, initial_mask)
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| 218 | if not ok:
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| 219 | return False, 0
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| 220 | elif parser.AtEnd():
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| 221 | return True, mask
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| 222 |
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| 223 |
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| 224 | def _ParseClauseList(initial_mask, clause_list):
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| 225 | # type: (int, List[str]) -> Tuple[bool, int]
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| 226 | """
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| 227 | There is a grammar for symbolic masks at
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| 228 | https://pubs.opengroup.org/onlinepubs/009696899/utilities/chmod.html
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| 229 | """
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| 230 | mask = initial_mask
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| 231 | for clause in clause_list:
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| 232 | ok, mask = _ParseClause(mask, initial_mask, clause)
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| 233 | if not ok:
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| 234 | return False, 0
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| 235 |
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| 236 | return True, mask
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| 237 |
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| 238 |
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| 239 | class Umask(vm._Builtin):
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| 240 |
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| 241 | def __init__(self):
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| 242 | # type: () -> None
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| 243 | """Dummy constructor for mycpp."""
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| 244 | pass
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| 245 |
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| 246 | def Run(self, cmd_val):
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| 247 | # type: (cmd_value.Argv) -> int
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| 248 |
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| 249 | attrs, arg_r = flag_util.ParseCmdVal('umask', cmd_val)
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| 250 |
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| 251 | if arg_r.AtEnd(): # no args
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| 252 | # umask() has a dumb API: to get the umask, we must modify it
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| 253 | # see: https://man7.org/linux/man-pages/man2/umask.2.html
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| 254 | # NOTE: dash disables interrupts around the two umask() calls, but that
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| 255 | # shouldn't be a concern for us. Signal handlers won't call umask().
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| 256 | mask = posix.umask(0)
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| 257 | posix.umask(mask)
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| 258 | print('0%03o' % mask) # octal format
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| 259 | return 0
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| 260 |
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| 261 | first_arg, first_loc = arg_r.ReadRequired2('expected an argument')
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| 262 | arg_r.Done() # only one arg
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| 263 |
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| 264 | octal_mask = -1
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| 265 | try:
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| 266 | octal_mask = int(first_arg, 8)
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| 267 | except ValueError:
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| 268 | pass
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| 269 | if octal_mask != -1:
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| 270 | posix.umask(octal_mask)
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| 271 | return 0
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| 272 |
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| 273 | # NOTE: it's possible to avoid this extra syscall in cases where we don't care about
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| 274 | # the initial value (ex: umask ...,a=rwx) although it's non-trivial to determine
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| 275 | # when, so it's probably not worth it
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| 276 | initial_mask = posix.umask(0)
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| 277 | try:
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| 278 | ok, new_mask = _ParseClauseList(initial_mask, first_arg.split(","))
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| 279 | if not ok:
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| 280 | posix.umask(initial_mask)
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| 281 | return 1
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| 282 |
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| 283 | posix.umask(new_mask)
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| 284 | return 0
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| 285 |
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| 286 | except Exception as e:
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| 287 | # this guard protects the umask value against any accidental exceptions
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| 288 | posix.umask(initial_mask)
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| 289 | raise
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