posix: always seek to EOF when opening a file in append mode
Python 3 already does this, so skip it there.
Consider the program:
#include <stdio.h>
int main() {
FILE *f = fopen("narf", "w");
fprintf(f, "narf\n");
fclose(f);
f = fopen("narf", "a");
printf("%ld\n", ftell(f));
fprintf(f, "troz\n");
printf("%ld\n", ftell(f));
return 0;
}
on macOS, FreeBSD, and Linux with glibc, this program prints
5
10
but on musl libc (Alpine Linux and probably others) this prints
0
10
By my reading of
https://pubs.opengroup.org/onlinepubs/009695399/functions/fopen.html
this is technically correct, specifically:
> Opening a file with append mode (a as the first character in the
> mode argument) shall cause all subsequent writes to the file to be
> forced to the then current end-of-file, regardless of intervening
> calls to fseek().
in other words, the file position doesn't really matter in append-mode
files, and we can't depend on it being at all meaningful unless we
perform a seek() before tell() after open(..., 'a'). Experimentally
after a .write() we can do a .tell() and it'll always be reasonable,
but I'm unclear from reading the specification if that's a smart thing
to rely on. This matches what we do on Windows and what Python 3 does
for free, so let's just be consistent. Thanks to Yuya for the idea.
# narrowwirepeer.py - passes narrow spec with unbundle command
#
# Copyright 2017 Google, Inc.
#
# 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
from mercurial import (
bundle2,
error,
extensions,
hg,
narrowspec,
pycompat,
wireprototypes,
wireprotov1peer,
wireprotov1server,
)
def uisetup():
wireprotov1peer.wirepeer.narrow_widen = peernarrowwiden
def reposetup(repo):
def wirereposetup(ui, peer):
def wrapped(orig, cmd, *args, **kwargs):
if cmd == 'unbundle':
# TODO: don't blindly add include/exclude wireproto
# arguments to unbundle.
include, exclude = repo.narrowpats
kwargs[r"includepats"] = ','.join(include)
kwargs[r"excludepats"] = ','.join(exclude)
return orig(cmd, *args, **kwargs)
extensions.wrapfunction(peer, '_calltwowaystream', wrapped)
hg.wirepeersetupfuncs.append(wirereposetup)
@wireprotov1server.wireprotocommand('narrow_widen', 'oldincludes oldexcludes'
' newincludes newexcludes'
' commonheads cgversion'
' known ellipses',
permission='pull')
def narrow_widen(repo, proto, oldincludes, oldexcludes, newincludes,
newexcludes, commonheads, cgversion, known, ellipses):
"""wireprotocol command to send data when a narrow clone is widen. We will
be sending a changegroup here.
The current set of arguments which are required:
oldincludes: the old includes of the narrow copy
oldexcludes: the old excludes of the narrow copy
newincludes: the new includes of the narrow copy
newexcludes: the new excludes of the narrow copy
commonheads: list of heads which are common between the server and client
cgversion(maybe): the changegroup version to produce
known: list of nodes which are known on the client (used in ellipses cases)
ellipses: whether to send ellipses data or not
"""
preferuncompressed = False
try:
oldincludes = wireprototypes.decodelist(oldincludes)
newincludes = wireprototypes.decodelist(newincludes)
oldexcludes = wireprototypes.decodelist(oldexcludes)
newexcludes = wireprototypes.decodelist(newexcludes)
# validate the patterns
narrowspec.validatepatterns(set(oldincludes))
narrowspec.validatepatterns(set(newincludes))
narrowspec.validatepatterns(set(oldexcludes))
narrowspec.validatepatterns(set(newexcludes))
common = wireprototypes.decodelist(commonheads)
known = None
if known:
known = wireprototypes.decodelist(known)
if ellipses == '0':
ellipses = False
else:
ellipses = bool(ellipses)
cgversion = cgversion
newmatch = narrowspec.match(repo.root, include=newincludes,
exclude=newexcludes)
oldmatch = narrowspec.match(repo.root, include=oldincludes,
exclude=oldexcludes)
bundler = bundle2.widen_bundle(repo, oldmatch, newmatch, common, known,
cgversion, ellipses)
except error.Abort as exc:
bundler = bundle2.bundle20(repo.ui)
manargs = [('message', pycompat.bytestr(exc))]
advargs = []
if exc.hint is not None:
advargs.append(('hint', exc.hint))
bundler.addpart(bundle2.bundlepart('error:abort', manargs, advargs))
preferuncompressed = True
chunks = bundler.getchunks()
return wireprototypes.streamres(gen=chunks,
prefer_uncompressed=preferuncompressed)
def peernarrowwiden(remote, **kwargs):
for ch in (r'oldincludes', r'newincludes', r'oldexcludes', r'newexcludes',
r'commonheads', r'known'):
kwargs[ch] = wireprototypes.encodelist(kwargs[ch])
kwargs[r'ellipses'] = '%i' % bool(kwargs[r'ellipses'])
f = remote._callcompressable('narrow_widen', **kwargs)
return bundle2.getunbundler(remote.ui, f)