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