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authorFred Drake <fdrake@acm.org>2000-02-03 15:26:16 (GMT)
committerFred Drake <fdrake@acm.org>2000-02-03 15:26:16 (GMT)
commitd89ffebd85e782f584e7d815b7567eb834c79450 (patch)
tree93108efe1fa2293dde56fc521899c18837fadfd7 /Lib/cmp.py
parentff484183de25b477db56e7fe04f9b60f6558787a (diff)
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These modules are now declared obsolete.
Diffstat (limited to 'Lib/cmp.py')
-rw-r--r--Lib/cmp.py63
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diff --git a/Lib/cmp.py b/Lib/cmp.py
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-"""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