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repository: formalize interfaces for revision deltas and requests...
repository: formalize interfaces for revision deltas and requests Now that we've sufficiently abstracted how revision deltas are produced in changegroup code, we can now start the process of formalizing that as part of the interfaces defined in the repository module. This commit essentially converts the revisiondelta and revisiondeltarequest classes into well-defined interfaces. This is not strictly necessary. But I want all types formalized by the storage interface to have interfaces. This makes it much easier to test for interface conformance and for implementing new storage backends. Because the interface is documented, comments and docstrings from changegroup.py have been dropped. Differential Revision: https://phab.mercurial-scm.org/D4225

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mpatch.py
128 lines | 3.3 KiB | text/x-python | PythonLexer
# mpatch.py - Python implementation of mpatch.c
#
# Copyright 2009 Matt Mackall <mpm@selenic.com> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
import struct
from .. import pycompat
stringio = pycompat.bytesio
class mpatchError(Exception):
"""error raised when a delta cannot be decoded
"""
# This attempts to apply a series of patches in time proportional to
# the total size of the patches, rather than patches * len(text). This
# means rather than shuffling strings around, we shuffle around
# pointers to fragments with fragment lists.
#
# When the fragment lists get too long, we collapse them. To do this
# efficiently, we do all our operations inside a buffer created by
# mmap and simply use memmove. This avoids creating a bunch of large
# temporary string buffers.
def _pull(dst, src, l): # pull l bytes from src
while l:
f = src.pop()
if f[0] > l: # do we need to split?
src.append((f[0] - l, f[1] + l))
dst.append((l, f[1]))
return
dst.append(f)
l -= f[0]
def _move(m, dest, src, count):
"""move count bytes from src to dest
The file pointer is left at the end of dest.
"""
m.seek(src)
buf = m.read(count)
m.seek(dest)
m.write(buf)
def _collect(m, buf, list):
start = buf
for l, p in reversed(list):
_move(m, buf, p, l)
buf += l
return (buf - start, start)
def patches(a, bins):
if not bins:
return a
plens = [len(x) for x in bins]
pl = sum(plens)
bl = len(a) + pl
tl = bl + bl + pl # enough for the patches and two working texts
b1, b2 = 0, bl
if not tl:
return a
m = stringio()
# load our original text
m.write(a)
frags = [(len(a), b1)]
# copy all the patches into our segment so we can memmove from them
pos = b2 + bl
m.seek(pos)
for p in bins:
m.write(p)
for plen in plens:
# if our list gets too long, execute it
if len(frags) > 128:
b2, b1 = b1, b2
frags = [_collect(m, b1, frags)]
new = []
end = pos + plen
last = 0
while pos < end:
m.seek(pos)
try:
p1, p2, l = struct.unpack(">lll", m.read(12))
except struct.error:
raise mpatchError("patch cannot be decoded")
_pull(new, frags, p1 - last) # what didn't change
_pull([], frags, p2 - p1) # what got deleted
new.append((l, pos + 12)) # what got added
pos += l + 12
last = p2
frags.extend(reversed(new)) # what was left at the end
t = _collect(m, b2, frags)
m.seek(t[1])
return m.read(t[0])
def patchedsize(orig, delta):
outlen, last, bin = 0, 0, 0
binend = len(delta)
data = 12
while data <= binend:
decode = delta[bin:bin + 12]
start, end, length = struct.unpack(">lll", decode)
if start > end:
break
bin = data + length
data = bin + 12
outlen += start - last
last = end
outlen += length
if bin != binend:
raise mpatchError("patch cannot be decoded")
outlen += orig - last
return outlen