From 9c30dd2c80e2f96640c7f67aade4420b20ef7375 Mon Sep 17 00:00:00 2001 From: Daira Hopwood Date: Fri, 29 May 2015 21:38:09 +0100 Subject: [PATCH] fileutil.py: add rename_no_overwrite and replace_file. Signed-off-by: Daira Hopwood --- src/allmydata/test/test_util.py | 68 +++++++++++++++++++++++++++++++++ src/allmydata/util/fileutil.py | 64 ++++++++++++++++++++++++++++++- 2 files changed, 130 insertions(+), 2 deletions(-) diff --git a/src/allmydata/test/test_util.py b/src/allmydata/test/test_util.py index db64bf19..8cca7b5e 100644 --- a/src/allmydata/test/test_util.py +++ b/src/allmydata/test/test_util.py @@ -441,6 +441,73 @@ class FileUtil(ReallyEqualMixin, unittest.TestCase): self.failIf(os.path.exists(fn)) self.failUnless(os.path.exists(fn2)) + def test_rename_no_overwrite(self): + workdir = fileutil.abspath_expanduser_unicode(u"test_rename_no_overwrite") + fileutil.make_dirs(workdir) + + source_path = os.path.join(workdir, "source") + dest_path = os.path.join(workdir, "dest") + + # when neither file exists + self.failUnlessRaises(OSError, fileutil.rename_no_overwrite, source_path, dest_path) + + # when only dest exists + fileutil.write(dest_path, "dest") + self.failUnlessRaises(OSError, fileutil.rename_no_overwrite, source_path, dest_path) + self.failUnlessEqual(fileutil.read(dest_path), "dest") + + # when both exist + fileutil.write(source_path, "source") + self.failUnlessRaises(OSError, fileutil.rename_no_overwrite, source_path, dest_path) + self.failUnlessEqual(fileutil.read(source_path), "source") + self.failUnlessEqual(fileutil.read(dest_path), "dest") + + # when only source exists + os.remove(dest_path) + fileutil.rename_no_overwrite(source_path, dest_path) + self.failUnlessEqual(fileutil.read(dest_path), "source") + self.failIf(os.path.exists(source_path)) + + def test_replace_file(self): + workdir = fileutil.abspath_expanduser_unicode(u"test_replace_file") + fileutil.make_dirs(workdir) + + backup_path = os.path.join(workdir, "backup") + replaced_path = os.path.join(workdir, "replaced") + replacement_path = os.path.join(workdir, "replacement") + + # when none of the files exist + self.failUnlessRaises(fileutil.ConflictError, fileutil.replace_file, replaced_path, replacement_path, backup_path) + + # when only replaced exists + fileutil.write(replaced_path, "foo") + self.failUnlessRaises(fileutil.ConflictError, fileutil.replace_file, replaced_path, replacement_path, backup_path) + self.failUnlessEqual(fileutil.read(replaced_path), "foo") + + # when both replaced and replacement exist, but not backup + fileutil.write(replacement_path, "bar") + fileutil.replace_file(replaced_path, replacement_path, backup_path) + self.failUnlessEqual(fileutil.read(backup_path), "foo") + self.failUnlessEqual(fileutil.read(replaced_path), "bar") + self.failIf(os.path.exists(replacement_path)) + + # when only replacement exists + os.remove(backup_path) + os.remove(replaced_path) + fileutil.write(replacement_path, "bar") + self.failUnlessRaises(fileutil.ConflictError, fileutil.replace_file, replaced_path, replacement_path, backup_path) + self.failUnlessEqual(fileutil.read(replacement_path), "bar") + self.failIf(os.path.exists(replaced_path)) + self.failIf(os.path.exists(backup_path)) + + # when replaced, replacement and backup all exist + fileutil.write(replaced_path, "foo") + fileutil.write(backup_path, "bak") + fileutil.replace_file(replaced_path, replacement_path, backup_path) + self.failUnlessEqual(fileutil.read(backup_path), "foo") + self.failUnlessEqual(fileutil.read(replaced_path), "bar") + self.failIf(os.path.exists(replacement_path)) + def test_du(self): basedir = "util/FileUtil/test_du" fileutil.make_dirs(basedir) @@ -567,6 +634,7 @@ class FileUtil(ReallyEqualMixin, unittest.TestCase): disk = fileutil.get_disk_stats('.', 2**128) self.failUnlessEqual(disk['avail'], 0) + class PollMixinTests(unittest.TestCase): def setUp(self): self.pm = pollmixin.PollMixin() diff --git a/src/allmydata/util/fileutil.py b/src/allmydata/util/fileutil.py index 54e34484..26943212 100644 --- a/src/allmydata/util/fileutil.py +++ b/src/allmydata/util/fileutil.py @@ -3,6 +3,7 @@ Futz with files like a pro. """ import sys, exceptions, os, stat, tempfile, time, binascii +from errno import EEXIST from twisted.python import log @@ -518,8 +519,7 @@ def get_available_space(whichdir, reserved_space): if sys.platform == "win32": - from ctypes import WINFUNCTYPE, windll, WinError - from ctypes.wintypes import BOOL, HANDLE, DWORD, LPCWSTR, LPVOID + from ctypes.wintypes import BOOL, HANDLE, DWORD, LPCWSTR, LPVOID, WinError, get_last_error # CreateFileW = WINFUNCTYPE(HANDLE, LPCWSTR, DWORD, DWORD, LPVOID, DWORD, DWORD, HANDLE) \ @@ -560,3 +560,63 @@ else: def flush_volume(path): # use sync()? pass + + +class ConflictError(Exception): + pass + +class UnableToUnlinkReplacementError(Exception): + pass + +def reraise(wrapper): + _, exc, tb = sys.exc_info() + wrapper_exc = wrapper("%s: %s" % (exc.__class__.__name__, exc)) + raise wrapper_exc.__class__, wrapper_exc, tb + +if sys.platform == "win32": + from ctypes import WINFUNCTYPE, windll, WinError, get_last_error + from ctypes.wintypes import BOOL, DWORD, LPCWSTR, LPVOID + + # + ReplaceFileW = WINFUNCTYPE( + BOOL, + LPCWSTR, LPCWSTR, LPCWSTR, DWORD, LPVOID, LPVOID, + use_last_error=True + )(("ReplaceFileW", windll.kernel32)) + + REPLACEFILE_IGNORE_MERGE_ERRORS = 0x00000002 + + def rename_no_overwrite(source_path, dest_path): + os.rename(source_path, dest_path) + + def replace_file(replaced_path, replacement_path, backup_path): + precondition_abspath(replaced_path) + precondition_abspath(replacement_path) + precondition_abspath(backup_path) + + r = ReplaceFileW(replaced_path, replacement_path, backup_path, + REPLACEFILE_IGNORE_MERGE_ERRORS, None, None) + if r == 0: + # The UnableToUnlinkReplacementError case does not happen on Windows; + # all errors should be treated as signalling a conflict. + err = get_last_error() + raise ConflictError("WinError: %s" % (WinError(err))) +else: + def rename_no_overwrite(source_path, dest_path): + # link will fail with EEXIST if there is already something at dest_path. + os.link(source_path, dest_path) + try: + os.unlink(source_path) + except EnvironmentError: + reraise(UnableToUnlinkReplacementError) + + def replace_file(replaced_path, replacement_path, backup_path): + precondition_abspath(replaced_path) + precondition_abspath(replacement_path) + precondition_abspath(backup_path) + + try: + os.rename(replaced_path, backup_path) + rename_no_overwrite(replacement_path, replaced_path) + except EnvironmentError: + reraise(ConflictError) -- 2.45.2