diff options
Diffstat (limited to 'Lib/lib-old/cmp.py')
-rw-r--r-- | Lib/lib-old/cmp.py | 63 |
1 files changed, 0 insertions, 63 deletions
diff --git a/Lib/lib-old/cmp.py b/Lib/lib-old/cmp.py deleted file mode 100644 index 1146a25..0000000 --- a/Lib/lib-old/cmp.py +++ /dev/null @@ -1,63 +0,0 @@ -"""Efficiently compare files, boolean outcome only (equal / not equal). - -Tricks (used in this order): - - Files with identical type, size & mtime are assumed to be clones - - Files with different type or size cannot be identical - - We keep a cache of outcomes of earlier comparisons - - We don't fork a process to run 'cmp' but read the files ourselves -""" - -import os - -cache = {} - -def cmp(f1, f2, shallow=1): - """Compare two files, use the cache if possible. - Return 1 for identical files, 0 for different. - Raise exceptions if either file could not be statted, read, etc.""" - s1, s2 = sig(os.stat(f1)), sig(os.stat(f2)) - if s1[0] != 8 or s2[0] != 8: - # Either is a not a plain file -- always report as different - return 0 - if shallow and s1 == s2: - # type, size & mtime match -- report same - return 1 - if s1[:2] != s2[:2]: # Types or sizes differ, don't bother - # types or sizes differ -- report different - return 0 - # same type and size -- look in the cache - key = (f1, f2) - try: - cs1, cs2, outcome = cache[key] - # cache hit - if s1 == cs1 and s2 == cs2: - # cached signatures match - return outcome - # stale cached signature(s) - except KeyError: - # cache miss - pass - # really compare - outcome = do_cmp(f1, f2) - cache[key] = s1, s2, outcome - return outcome - -def sig(st): - """Return signature (i.e., type, size, mtime) from raw stat data - 0-5: st_mode, st_ino, st_dev, st_nlink, st_uid, st_gid - 6-9: st_size, st_atime, st_mtime, st_ctime""" - type = st[0] / 4096 - size = st[6] - mtime = st[8] - return type, size, mtime - -def do_cmp(f1, f2): - """Compare two files, really.""" - bufsize = 8*1024 # Could be tuned - 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 |