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?
55
71
The iter method here will generally read through the whole index file
56
72
in one go. With readahead in the kernel and python/libc (typically
57
73
128kB) this means that there should be no seeks and often only one
73
89
# if there are gaps and that can happen if we're interrupted while
74
90
# writing to the datafile. Overlapping would be very bad though.
78
import sys, zlib, struct, mdiff, stat, os, sha
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.
79
102
from binascii import hexlify, unhexlify
104
import bzrlib.mdiff as mdiff
227
250
return self._add_compressed(text_sha, text, _NO_RECORD, compress)
254
def _choose_base(self, seed, base):
256
if base == _NO_RECORD:
259
if idxrec[I_BASE] == _NO_RECORD:
262
base = idxrec[I_BASE]
265
return base # relative to this full text
230
269
def _add_delta(self, text, text_sha, base, compress):
231
270
"""Add a text stored relative to a previous text."""
232
271
self._check_index(base)
235
base_text = self.get(base, recursion_limit=CHAIN_LIMIT)
274
base_text = self.get(base, CHAIN_LIMIT)
236
275
except LimitHitException:
237
276
return self._add_full_text(text, text_sha, compress)
239
278
data = mdiff.bdiff(base_text, text)
281
if True: # paranoid early check for bad diff
282
result = mdiff.bpatch(base_text, data)
283
assert result == text
241
286
# If the delta is larger than the text, we might as well just
242
287
# store the text. (OK, the delta might be more compressible,
248
293
return self._add_compressed(text_sha, data, base, compress)
251
def add(self, text, base=_NO_RECORD, compress=True):
296
def add(self, text, base=None, compress=True):
252
297
"""Add a new text to the revfile.
254
299
If the text is already present them its existing id is
272
320
# it's the same, in case someone ever breaks SHA-1.
273
321
return idx # already present
323
# base = self._choose_base(ord(text_sha[0]), base)
275
325
if base == _NO_RECORD:
276
326
return self._add_full_text(text, text_sha, compress)
296
346
text = self._get_patched(idx, idxrec, recursion_limit)
298
348
if sha.new(text).digest() != idxrec[I_SHA]:
299
raise RevfileError("corrupt SHA-1 digest on record %d"
349
raise RevfileError("corrupt SHA-1 digest on record %d in %s"
350
% (idx, self.basename))
388
438
"""Read back all index records.
390
440
Do not seek the index file while this is underway!"""
391
sys.stderr.write(" ** iter called ** \n")
441
## sys.stderr.write(" ** iter called ** \n")
392
442
self._seek_index(0)
394
444
idxrec = self._read_next_index()
436
486
for idx in range(len(self)):
437
487
t += len(self.get(idx))
491
def check(self, pb=None):
492
"""Extract every version and check its hash."""
494
for i in range(total):
496
pb.update("check revision", i, total)
497
# the get method implicitly checks the SHA-1
445
508
except IndexError:
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"
509
sys.stderr.write("usage: revfile dump REVFILE\n"
510
" revfile add REVFILE < INPUT\n"
511
" revfile add-delta REVFILE BASE < INPUT\n"
512
" revfile add-series REVFILE BASE FILE...\n"
513
" revfile get REVFILE IDX\n"
514
" revfile find-sha REVFILE HEX\n"
515
" revfile total-text-size REVFILE\n"
516
" revfile last REVFILE\n")
519
if filename.endswith('.drev') or filename.endswith('.irev'):
520
filename = filename[:-5]
456
return Revfile('testrev', 'w')
523
return Revfile(filename, 'w')
459
return Revfile('testrev', 'r')
526
return Revfile(filename, 'r')
462
529
print rw().add(sys.stdin.read())
463
530
elif cmd == 'add-delta':
464
print rw().add(sys.stdin.read(), int(argv[2]))
531
print rw().add(sys.stdin.read(), int(argv[3]))
532
elif cmd == 'add-series':
537
rev = r.add(file(fn).read(), rev)
465
538
elif cmd == 'dump':
467
540
elif cmd == 'get':
470
543
except IndexError:
471
sys.stderr.write("usage: revfile get IDX\n")
544
sys.stderr.write("usage: revfile get FILE IDX\n")
474
549
if idx < 0 or idx >= len(r):
475
550
sys.stderr.write("invalid index %r\n" % idx)
478
sys.stdout.write(ro().get(idx))
553
sys.stdout.write(r.get(idx))
479
554
elif cmd == 'find-sha':
481
s = unhexlify(argv[2])
556
s = unhexlify(argv[3])
482
557
except IndexError:
483
sys.stderr.write("usage: revfile find-sha HEX\n")
558
sys.stderr.write("usage: revfile find-sha FILE HEX\n")
486
561
idx = ro().find_sha(s)
added
removed
bzrlib/revfile.py
