52
52
is that sequence numbers are stable references. But not every
53
53
repository in the world will assign the same sequence numbers,
54
54
therefore the SHA-1 is the only universally unique reference.
56
This is meant to scale to hold 100,000 revisions of a single file, by
57
which time the index file will be ~4.8MB and a bit big to read
60
Some of the reserved fields could be used to implement a (semi?)
61
balanced tree indexed by SHA1 so we can much more efficiently find the
62
index associated with a particular hash. For 100,000 revs we would be
63
able to find it in about 17 random reads, which is not too bad.
65
This performs pretty well except when trying to calculate deltas of
66
really large files. For that the main thing would be to plug in
67
something faster than difflib, which is after all pure Python.
68
Another approach is to just store the gzipped full text of big files,
69
though perhaps that's too perverse?
71
55
The iter method here will generally read through the whole index file
72
56
in one go. With readahead in the kernel and python/libc (typically
73
57
128kB) this means that there should be no seeks and often only one
89
73
# if there are gaps and that can happen if we're interrupted while
90
74
# writing to the datafile. Overlapping would be very bad though.
92
# TODO: Shouldn't need to lock if we always write in append mode and
93
# then ftell after writing to see where it went. In any case we
94
# assume the whole branch is protected by a lock.
96
78
import sys, zlib, struct, mdiff, stat, os, sha
97
79
from binascii import hexlify, unhexlify
101
85
_HEADER = "bzr revfile v1\n"
242
227
return self._add_compressed(text_sha, text, _NO_RECORD, compress)
246
def _choose_base(self, seed, base):
248
if base == _NO_RECORD:
251
if idxrec[I_BASE] == _NO_RECORD:
254
base = idxrec[I_BASE]
257
return base # relative to this full text
261
230
def _add_delta(self, text, text_sha, base, compress):
262
231
"""Add a text stored relative to a previous text."""
263
232
self._check_index(base)
266
base_text = self.get(base, CHAIN_LIMIT)
235
base_text = self.get(base, recursion_limit=CHAIN_LIMIT)
267
236
except LimitHitException:
268
237
return self._add_full_text(text, text_sha, compress)
270
239
data = mdiff.bdiff(base_text, text)
273
if True: # paranoid early check for bad diff
274
result = mdiff.bpatch(base_text, data)
275
assert result == text
278
241
# If the delta is larger than the text, we might as well just
279
242
# store the text. (OK, the delta might be more compressible,
285
248
return self._add_compressed(text_sha, data, base, compress)
288
def add(self, text, base=None, compress=True):
251
def add(self, text, base=_NO_RECORD, compress=True):
289
252
"""Add a new text to the revfile.
291
254
If the text is already present them its existing id is
312
272
# it's the same, in case someone ever breaks SHA-1.
313
273
return idx # already present
315
# base = self._choose_base(ord(text_sha[0]), base)
317
275
if base == _NO_RECORD:
318
276
return self._add_full_text(text, text_sha, compress)
338
296
text = self._get_patched(idx, idxrec, recursion_limit)
340
298
if sha.new(text).digest() != idxrec[I_SHA]:
341
raise RevfileError("corrupt SHA-1 digest on record %d in %s"
342
% (idx, self.basename))
299
raise RevfileError("corrupt SHA-1 digest on record %d"
430
388
"""Read back all index records.
432
390
Do not seek the index file while this is underway!"""
433
## sys.stderr.write(" ** iter called ** \n")
391
sys.stderr.write(" ** iter called ** \n")
434
392
self._seek_index(0)
436
394
idxrec = self._read_next_index()
478
436
for idx in range(len(self)):
479
437
t += len(self.get(idx))
483
def check(self, pb=None):
484
"""Extract every version and check its hash."""
486
for i in range(total):
488
pb.update("check revision", i, total)
489
# the get method implicitly checks the SHA-1
500
445
except IndexError:
501
sys.stderr.write("usage: revfile dump REVFILE\n"
502
" revfile add REVFILE < INPUT\n"
503
" revfile add-delta REVFILE BASE < INPUT\n"
504
" revfile add-series REVFILE BASE FILE...\n"
505
" revfile get REVFILE IDX\n"
506
" revfile find-sha REVFILE HEX\n"
507
" revfile total-text-size REVFILE\n"
508
" revfile last REVFILE\n")
446
sys.stderr.write("usage: revfile dump\n"
448
" revfile add-delta BASE\n"
450
" revfile find-sha HEX\n"
451
" revfile total-text-size\n"
511
if filename.endswith('.drev') or filename.endswith('.irev'):
512
filename = filename[:-5]
515
return Revfile(filename, 'w')
456
return Revfile('testrev', 'w')
518
return Revfile(filename, 'r')
459
return Revfile('testrev', 'r')
521
462
print rw().add(sys.stdin.read())
522
463
elif cmd == 'add-delta':
523
print rw().add(sys.stdin.read(), int(argv[3]))
524
elif cmd == 'add-series':
529
rev = r.add(file(fn).read(), rev)
464
print rw().add(sys.stdin.read(), int(argv[2]))
530
465
elif cmd == 'dump':
532
467
elif cmd == 'get':
535
470
except IndexError:
536
sys.stderr.write("usage: revfile get FILE IDX\n")
471
sys.stderr.write("usage: revfile get IDX\n")
541
474
if idx < 0 or idx >= len(r):
542
475
sys.stderr.write("invalid index %r\n" % idx)
545
sys.stdout.write(r.get(idx))
478
sys.stdout.write(ro().get(idx))
546
479
elif cmd == 'find-sha':
548
s = unhexlify(argv[3])
481
s = unhexlify(argv[2])
549
482
except IndexError:
550
sys.stderr.write("usage: revfile find-sha FILE HEX\n")
483
sys.stderr.write("usage: revfile find-sha HEX\n")
553
486
idx = ro().find_sha(s)
added
removed
bzrlib/revfile.py
