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"""Compare files."""
import os, stat, statcache
_cache = {}
BUFSIZE=8*1024
def cmp(f1, f2, shallow=1,use_statcache=0):
"""Compare two files.
Arguments:
f1 -- First file name
f2 -- Second file name
shallow -- Just check stat signature (do not read the files).
defaults to 1.
use_statcache -- Do not stat() each file directly: go through
the statcache module for more efficiency.
Return value:
integer -- 1 if the files are the same, 0 otherwise.
This function uses a cache for past comparisons and the results,
with a cache invalidation mechanism relying on stale signatures.
Of course, if 'use_statcache' is true, this mechanism is defeated,
and the cache will never grow stale.
"""
if use_statcache:
stat_function = statcache.stat
else:
stat_function = os.stat
s1 = _sig(stat_function(f1))
s2 = _sig(stat_function(f2))
if s1[0] != stat.S_IFREG or s2[0] != stat.S_IFREG:
return 0
if shallow and s1 == s2:
return 1
if s1[1] != s2[1]:
return 0
result = _cache.get((f1, f2))
if result and (s1, s2) == result[:2]:
return result[2]
outcome = _do_cmp(f1, f2)
_cache[f1, f2] = s1, s2, outcome
return outcome
def _sig(st):
return (stat.S_IFMT(st[stat.ST_MODE]),
st[stat.ST_SIZE],
st[stat.ST_MTIME])
def _do_cmp(f1, f2):
bufsize = BUFSIZE
fp1 = open(f1, 'rb')
fp2 = open(f2, 'rb')
while 1:
b1 = fp1.read(bufsize)
b2 = fp2.read(bufsize)
if b1 != b2:
return 0
if not b1:
return 1
|
