paul@147 | 1 | #!/usr/bin/env python |
paul@147 | 2 | |
paul@147 | 3 | """ |
paul@147 | 4 | Filesystem utilities. |
paul@147 | 5 | |
paul@147 | 6 | Copyright (C) 2014, 2015 Paul Boddie <paul@boddie.org.uk> |
paul@147 | 7 | |
paul@147 | 8 | This program is free software; you can redistribute it and/or modify it under |
paul@147 | 9 | the terms of the GNU General Public License as published by the Free Software |
paul@147 | 10 | Foundation; either version 3 of the License, or (at your option) any later |
paul@147 | 11 | version. |
paul@147 | 12 | |
paul@147 | 13 | This program is distributed in the hope that it will be useful, but WITHOUT |
paul@147 | 14 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS |
paul@147 | 15 | FOR A PARTICULAR PURPOSE. See the GNU General Public License for more |
paul@147 | 16 | details. |
paul@147 | 17 | |
paul@147 | 18 | You should have received a copy of the GNU General Public License along with |
paul@147 | 19 | this program. If not, see <http://www.gnu.org/licenses/>. |
paul@147 | 20 | """ |
paul@147 | 21 | |
paul@303 | 22 | import errno |
paul@330 | 23 | from imiptools.config import DEFAULT_PERMISSIONS, DEFAULT_DIR_PERMISSIONS |
paul@694 | 24 | from os.path import abspath, commonprefix, exists, join, split |
paul@702 | 25 | from os import chmod, getpid, makedirs, mkdir, rename, rmdir |
paul@303 | 26 | from time import sleep, time |
paul@147 | 27 | |
paul@694 | 28 | def check_dir(base, filename): |
paul@694 | 29 | |
paul@694 | 30 | "Return whether 'base' contains 'filename'." |
paul@694 | 31 | |
paul@694 | 32 | return commonprefix([base, abspath(filename)]) == base |
paul@694 | 33 | |
paul@694 | 34 | def remaining_parts(base, filename): |
paul@694 | 35 | |
paul@694 | 36 | "Return the remaining parts from 'base' provided by 'filename'." |
paul@694 | 37 | |
paul@694 | 38 | if not check_dir(base, filename): |
paul@694 | 39 | return None |
paul@694 | 40 | |
paul@694 | 41 | filename = abspath(filename) |
paul@694 | 42 | |
paul@694 | 43 | parts = [] |
paul@694 | 44 | while True: |
paul@694 | 45 | filename, part = split(filename) |
paul@694 | 46 | if check_dir(base, filename): |
paul@694 | 47 | parts.insert(0, part) |
paul@694 | 48 | else: |
paul@694 | 49 | break |
paul@694 | 50 | |
paul@694 | 51 | return parts |
paul@147 | 52 | |
paul@330 | 53 | def fix_permissions(filename, is_dir=False): |
paul@694 | 54 | |
paul@694 | 55 | """ |
paul@694 | 56 | Fix permissions for 'filename', with 'is_dir' indicating whether the object |
paul@694 | 57 | should be a directory or not. |
paul@694 | 58 | """ |
paul@694 | 59 | |
paul@147 | 60 | try: |
paul@330 | 61 | chmod(filename, is_dir and DEFAULT_DIR_PERMISSIONS or DEFAULT_PERMISSIONS) |
paul@147 | 62 | except OSError: |
paul@147 | 63 | pass |
paul@147 | 64 | |
paul@356 | 65 | def make_path(base, parts): |
paul@694 | 66 | |
paul@694 | 67 | """ |
paul@694 | 68 | Make the path within 'base' having components defined by the given 'parts'. |
paul@694 | 69 | Note that this function does not check the parts for suitability. To do so, |
paul@694 | 70 | use the FileBase methods instead. |
paul@694 | 71 | """ |
paul@694 | 72 | |
paul@356 | 73 | for part in parts: |
paul@356 | 74 | pathname = join(base, part) |
paul@356 | 75 | if not exists(pathname): |
paul@356 | 76 | mkdir(pathname) |
paul@356 | 77 | fix_permissions(pathname, True) |
paul@356 | 78 | base = pathname |
paul@356 | 79 | |
paul@147 | 80 | class FileBase: |
paul@147 | 81 | |
paul@147 | 82 | "Basic filesystem operations." |
paul@147 | 83 | |
paul@303 | 84 | lock_name = "__lock__" |
paul@715 | 85 | old_lock_name = "__unlock__" |
paul@303 | 86 | |
paul@147 | 87 | def __init__(self, store_dir): |
paul@147 | 88 | self.store_dir = store_dir |
paul@147 | 89 | if not exists(self.store_dir): |
paul@356 | 90 | makedirs(self.store_dir) |
paul@356 | 91 | fix_permissions(self.store_dir, True) |
paul@703 | 92 | self.lock_depth = 0 |
paul@147 | 93 | |
paul@147 | 94 | def get_file_object(self, base, *parts): |
paul@694 | 95 | |
paul@694 | 96 | """ |
paul@694 | 97 | Within the given 'base' location, return a path corresponding to the |
paul@694 | 98 | given 'parts'. |
paul@694 | 99 | """ |
paul@694 | 100 | |
paul@694 | 101 | # Handle "empty" components. |
paul@694 | 102 | |
paul@147 | 103 | pathname = join(base, *parts) |
paul@147 | 104 | return check_dir(base, pathname) and pathname or None |
paul@147 | 105 | |
paul@147 | 106 | def get_object_in_store(self, *parts): |
paul@147 | 107 | |
paul@147 | 108 | """ |
paul@147 | 109 | Return the name of any valid object stored within a hierarchy specified |
paul@147 | 110 | by the given 'parts'. |
paul@147 | 111 | """ |
paul@147 | 112 | |
paul@147 | 113 | parent = expected = self.store_dir |
paul@147 | 114 | |
paul@694 | 115 | # Handle "empty" components. |
paul@694 | 116 | |
paul@694 | 117 | parts = [p for p in parts if p] |
paul@694 | 118 | |
paul@147 | 119 | for part in parts: |
paul@147 | 120 | filename = self.get_file_object(expected, part) |
paul@147 | 121 | if not filename: |
paul@147 | 122 | return False |
paul@147 | 123 | parent = expected |
paul@147 | 124 | expected = filename |
paul@147 | 125 | |
paul@147 | 126 | if not exists(parent): |
paul@356 | 127 | make_path(self.store_dir, parts[:-1]) |
paul@147 | 128 | |
paul@147 | 129 | return filename |
paul@147 | 130 | |
paul@694 | 131 | def move_object(self, source, target): |
paul@694 | 132 | |
paul@694 | 133 | "Move 'source' to 'target'." |
paul@694 | 134 | |
paul@694 | 135 | if not self.ensure_parent(target): |
paul@694 | 136 | return False |
paul@694 | 137 | rename(source, target) |
paul@694 | 138 | |
paul@694 | 139 | def ensure_parent(self, target): |
paul@694 | 140 | |
paul@694 | 141 | "Ensure that the parent of 'target' exists." |
paul@694 | 142 | |
paul@694 | 143 | parts = remaining_parts(self.store_dir, target) |
paul@694 | 144 | if not parts or not self.get_file_object(self.store_dir, *parts[:-1]): |
paul@694 | 145 | return False |
paul@694 | 146 | |
paul@694 | 147 | make_path(self.store_dir, parts[:-1]) |
paul@694 | 148 | return True |
paul@694 | 149 | |
paul@303 | 150 | # Locking methods. |
paul@303 | 151 | # This uses the directory creation method exploited by MoinMoin.util.lock. |
paul@303 | 152 | # However, a simple single lock type mechanism is employed here. |
paul@303 | 153 | |
paul@702 | 154 | def make_lock_dir(self, *parts): |
paul@694 | 155 | |
paul@702 | 156 | "Make the lock directory defined by the given 'parts'." |
paul@694 | 157 | |
paul@303 | 158 | parts = parts and list(parts) or [] |
paul@303 | 159 | parts.append(self.lock_name) |
paul@715 | 160 | mkdir(self.get_object_in_store(*parts)) |
paul@702 | 161 | parts.append(str(getpid())) |
paul@715 | 162 | mkdir(self.get_object_in_store(*parts)) |
paul@702 | 163 | |
paul@702 | 164 | def remove_lock_dir(self, *parts): |
paul@702 | 165 | |
paul@702 | 166 | "Remove the lock directory defined by the given 'parts'." |
paul@702 | 167 | |
paul@702 | 168 | parts = parts and list(parts) or [] |
paul@715 | 169 | target = parts[:] |
paul@715 | 170 | |
paul@715 | 171 | # Move the directory. |
paul@715 | 172 | |
paul@702 | 173 | parts.append(self.lock_name) |
paul@715 | 174 | target.append(self.old_lock_name) |
paul@715 | 175 | rename(self.get_object_in_store(*parts), self.get_object_in_store(*target)) |
paul@715 | 176 | |
paul@715 | 177 | # Then remove the moved directory and its contents. |
paul@715 | 178 | |
paul@715 | 179 | target.append(str(getpid())) |
paul@715 | 180 | rmdir(self.get_object_in_store(*target)) |
paul@715 | 181 | target.pop() |
paul@715 | 182 | rmdir(self.get_object_in_store(*target)) |
paul@702 | 183 | |
paul@702 | 184 | def owning_lock_dir(self, *parts): |
paul@702 | 185 | |
paul@702 | 186 | "Return whether this process owns the lock directory." |
paul@702 | 187 | |
paul@702 | 188 | parts = parts and list(parts) or [] |
paul@702 | 189 | parts.append(self.lock_name) |
paul@702 | 190 | parts.append(str(getpid())) |
paul@702 | 191 | return exists(self.get_object_in_store(*parts)) |
paul@303 | 192 | |
paul@303 | 193 | def acquire_lock(self, timeout=None, *parts): |
paul@303 | 194 | |
paul@303 | 195 | """ |
paul@303 | 196 | Acquire an exclusive lock on the directory or a path within it described |
paul@303 | 197 | by 'parts'. |
paul@303 | 198 | """ |
paul@303 | 199 | |
paul@303 | 200 | start = now = time() |
paul@303 | 201 | |
paul@303 | 202 | while not timeout or now - start < timeout: |
paul@303 | 203 | try: |
paul@702 | 204 | self.make_lock_dir(*parts) |
paul@303 | 205 | break |
paul@303 | 206 | except OSError, exc: |
paul@303 | 207 | if exc.errno != errno.EEXIST: |
paul@303 | 208 | raise |
paul@702 | 209 | elif self.owning_lock_dir(*parts): |
paul@703 | 210 | self.lock_depth += 1 |
paul@702 | 211 | break |
paul@303 | 212 | sleep(1) |
paul@303 | 213 | now = time() |
paul@303 | 214 | |
paul@303 | 215 | def release_lock(self, *parts): |
paul@303 | 216 | |
paul@303 | 217 | """ |
paul@303 | 218 | Release an acquired lock on the directory or a path within it described |
paul@303 | 219 | by 'parts'. |
paul@303 | 220 | """ |
paul@303 | 221 | |
paul@303 | 222 | try: |
paul@703 | 223 | if self.lock_depth != 0: |
paul@703 | 224 | self.lock_depth -= 1 |
paul@703 | 225 | else: |
paul@703 | 226 | self.remove_lock_dir(*parts) |
paul@303 | 227 | except OSError, exc: |
paul@714 | 228 | if exc.errno not in (errno.ENOENT, errno.ENOTEMPTY): |
paul@303 | 229 | raise |
paul@303 | 230 | |
paul@147 | 231 | # vim: tabstop=4 expandtab shiftwidth=4 |