cpython/Lib/filecmp.py
Pablo Galindo 293dd23477
Remove binding of captured exceptions when not used to reduce the chances of creating cycles (GH-17246)
Capturing exceptions into names can lead to reference cycles though the __traceback__ attribute of the exceptions in some obscure cases that have been reported previously and fixed individually. As these variables are not used anyway, we can remove the binding to reduce the chances of creating reference cycles.

See for example GH-13135
2019-11-19 21:34:03 +00:00

306 lines
9.6 KiB
Python

"""Utilities for comparing files and directories.
Classes:
dircmp
Functions:
cmp(f1, f2, shallow=True) -> int
cmpfiles(a, b, common) -> ([], [], [])
clear_cache()
"""
import os
import stat
from itertools import filterfalse
__all__ = ['clear_cache', 'cmp', 'dircmp', 'cmpfiles', 'DEFAULT_IGNORES']
_cache = {}
BUFSIZE = 8*1024
DEFAULT_IGNORES = [
'RCS', 'CVS', 'tags', '.git', '.hg', '.bzr', '_darcs', '__pycache__']
def clear_cache():
"""Clear the filecmp cache."""
_cache.clear()
def cmp(f1, f2, shallow=True):
"""Compare two files.
Arguments:
f1 -- First file name
f2 -- Second file name
shallow -- Just check stat signature (do not read the files).
defaults to True.
Return value:
True if the files are the same, False otherwise.
This function uses a cache for past comparisons and the results,
with cache entries invalidated if their stat information
changes. The cache may be cleared by calling clear_cache().
"""
s1 = _sig(os.stat(f1))
s2 = _sig(os.stat(f2))
if s1[0] != stat.S_IFREG or s2[0] != stat.S_IFREG:
return False
if shallow and s1 == s2:
return True
if s1[1] != s2[1]:
return False
outcome = _cache.get((f1, f2, s1, s2))
if outcome is None:
outcome = _do_cmp(f1, f2)
if len(_cache) > 100: # limit the maximum size of the cache
clear_cache()
_cache[f1, f2, s1, s2] = outcome
return outcome
def _sig(st):
return (stat.S_IFMT(st.st_mode),
st.st_size,
st.st_mtime)
def _do_cmp(f1, f2):
bufsize = BUFSIZE
with open(f1, 'rb') as fp1, open(f2, 'rb') as fp2:
while True:
b1 = fp1.read(bufsize)
b2 = fp2.read(bufsize)
if b1 != b2:
return False
if not b1:
return True
# Directory comparison class.
#
class dircmp:
"""A class that manages the comparison of 2 directories.
dircmp(a, b, ignore=None, hide=None)
A and B are directories.
IGNORE is a list of names to ignore,
defaults to DEFAULT_IGNORES.
HIDE is a list of names to hide,
defaults to [os.curdir, os.pardir].
High level usage:
x = dircmp(dir1, dir2)
x.report() -> prints a report on the differences between dir1 and dir2
or
x.report_partial_closure() -> prints report on differences between dir1
and dir2, and reports on common immediate subdirectories.
x.report_full_closure() -> like report_partial_closure,
but fully recursive.
Attributes:
left_list, right_list: The files in dir1 and dir2,
filtered by hide and ignore.
common: a list of names in both dir1 and dir2.
left_only, right_only: names only in dir1, dir2.
common_dirs: subdirectories in both dir1 and dir2.
common_files: files in both dir1 and dir2.
common_funny: names in both dir1 and dir2 where the type differs between
dir1 and dir2, or the name is not stat-able.
same_files: list of identical files.
diff_files: list of filenames which differ.
funny_files: list of files which could not be compared.
subdirs: a dictionary of dircmp objects, keyed by names in common_dirs.
"""
def __init__(self, a, b, ignore=None, hide=None): # Initialize
self.left = a
self.right = b
if hide is None:
self.hide = [os.curdir, os.pardir] # Names never to be shown
else:
self.hide = hide
if ignore is None:
self.ignore = DEFAULT_IGNORES
else:
self.ignore = ignore
def phase0(self): # Compare everything except common subdirectories
self.left_list = _filter(os.listdir(self.left),
self.hide+self.ignore)
self.right_list = _filter(os.listdir(self.right),
self.hide+self.ignore)
self.left_list.sort()
self.right_list.sort()
def phase1(self): # Compute common names
a = dict(zip(map(os.path.normcase, self.left_list), self.left_list))
b = dict(zip(map(os.path.normcase, self.right_list), self.right_list))
self.common = list(map(a.__getitem__, filter(b.__contains__, a)))
self.left_only = list(map(a.__getitem__, filterfalse(b.__contains__, a)))
self.right_only = list(map(b.__getitem__, filterfalse(a.__contains__, b)))
def phase2(self): # Distinguish files, directories, funnies
self.common_dirs = []
self.common_files = []
self.common_funny = []
for x in self.common:
a_path = os.path.join(self.left, x)
b_path = os.path.join(self.right, x)
ok = 1
try:
a_stat = os.stat(a_path)
except OSError:
# print('Can\'t stat', a_path, ':', why.args[1])
ok = 0
try:
b_stat = os.stat(b_path)
except OSError:
# print('Can\'t stat', b_path, ':', why.args[1])
ok = 0
if ok:
a_type = stat.S_IFMT(a_stat.st_mode)
b_type = stat.S_IFMT(b_stat.st_mode)
if a_type != b_type:
self.common_funny.append(x)
elif stat.S_ISDIR(a_type):
self.common_dirs.append(x)
elif stat.S_ISREG(a_type):
self.common_files.append(x)
else:
self.common_funny.append(x)
else:
self.common_funny.append(x)
def phase3(self): # Find out differences between common files
xx = cmpfiles(self.left, self.right, self.common_files)
self.same_files, self.diff_files, self.funny_files = xx
def phase4(self): # Find out differences between common subdirectories
# A new dircmp object is created for each common subdirectory,
# these are stored in a dictionary indexed by filename.
# The hide and ignore properties are inherited from the parent
self.subdirs = {}
for x in self.common_dirs:
a_x = os.path.join(self.left, x)
b_x = os.path.join(self.right, x)
self.subdirs[x] = dircmp(a_x, b_x, self.ignore, self.hide)
def phase4_closure(self): # Recursively call phase4() on subdirectories
self.phase4()
for sd in self.subdirs.values():
sd.phase4_closure()
def report(self): # Print a report on the differences between a and b
# Output format is purposely lousy
print('diff', self.left, self.right)
if self.left_only:
self.left_only.sort()
print('Only in', self.left, ':', self.left_only)
if self.right_only:
self.right_only.sort()
print('Only in', self.right, ':', self.right_only)
if self.same_files:
self.same_files.sort()
print('Identical files :', self.same_files)
if self.diff_files:
self.diff_files.sort()
print('Differing files :', self.diff_files)
if self.funny_files:
self.funny_files.sort()
print('Trouble with common files :', self.funny_files)
if self.common_dirs:
self.common_dirs.sort()
print('Common subdirectories :', self.common_dirs)
if self.common_funny:
self.common_funny.sort()
print('Common funny cases :', self.common_funny)
def report_partial_closure(self): # Print reports on self and on subdirs
self.report()
for sd in self.subdirs.values():
print()
sd.report()
def report_full_closure(self): # Report on self and subdirs recursively
self.report()
for sd in self.subdirs.values():
print()
sd.report_full_closure()
methodmap = dict(subdirs=phase4,
same_files=phase3, diff_files=phase3, funny_files=phase3,
common_dirs = phase2, common_files=phase2, common_funny=phase2,
common=phase1, left_only=phase1, right_only=phase1,
left_list=phase0, right_list=phase0)
def __getattr__(self, attr):
if attr not in self.methodmap:
raise AttributeError(attr)
self.methodmap[attr](self)
return getattr(self, attr)
def cmpfiles(a, b, common, shallow=True):
"""Compare common files in two directories.
a, b -- directory names
common -- list of file names found in both directories
shallow -- if true, do comparison based solely on stat() information
Returns a tuple of three lists:
files that compare equal
files that are different
filenames that aren't regular files.
"""
res = ([], [], [])
for x in common:
ax = os.path.join(a, x)
bx = os.path.join(b, x)
res[_cmp(ax, bx, shallow)].append(x)
return res
# Compare two files.
# Return:
# 0 for equal
# 1 for different
# 2 for funny cases (can't stat, etc.)
#
def _cmp(a, b, sh, abs=abs, cmp=cmp):
try:
return not abs(cmp(a, b, sh))
except OSError:
return 2
# Return a copy with items that occur in skip removed.
#
def _filter(flist, skip):
return list(filterfalse(skip.__contains__, flist))
# Demonstration and testing.
#
def demo():
import sys
import getopt
options, args = getopt.getopt(sys.argv[1:], 'r')
if len(args) != 2:
raise getopt.GetoptError('need exactly two args', None)
dd = dircmp(args[0], args[1])
if ('-r', '') in options:
dd.report_full_closure()
else:
dd.report()
if __name__ == '__main__':
demo()