Mercurial > hg
view mercurial/pure/mpatch.py @ 52053:af54626bf358
dirstate-map: add a missing debug wait point when accessing the v2 docket
fc8e37c380d3 added synchronization points to the dirstate to allow for race
condition testing without actually requiring a time-based race condition
to happen.
This changes adds the `pre-read-file` wait point before we read the docket,
since callers might ask for the parents before anything else is
read, leading to the first read being done before the wait point.
This removes some differences in test output which were presumed to be
speed related, but weren't.
author | Raphaël Gomès <rgomes@octobus.net> |
---|---|
date | Mon, 14 Oct 2024 14:14:21 +0200 |
parents | f4733654f144 |
children |
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# mpatch.py - Python implementation of mpatch.c # # Copyright 2009 Olivia Mackall <olivia@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 annotations import io import struct from typing import ( List, Tuple, ) stringio = io.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: List[Tuple[int, int]], src: List[Tuple[int, int]], l: int ) -> None: # 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: stringio, dest: int, src: int, count: int) -> None: """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: stringio, buf: int, list: List[Tuple[int, int]] ) -> Tuple[int, int]: start = buf for l, p in reversed(list): _move(m, buf, p, l) buf += l return (buf - start, start) def patches(a: bytes, bins: List[bytes]) -> bytes: 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(b">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: int, delta: bytes) -> int: outlen, last, bin = 0, 0, 0 binend = len(delta) data = 12 while data <= binend: decode = delta[bin : bin + 12] start, end, length = struct.unpack(b">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