##// END OF EJS Templates
posix: always seek to EOF when opening a file in append mode...
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.

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r41458:fad627d2 default
r43163:97ada9b8 5.0.2 stable
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flagprocessorext.py
136 lines | 3.7 KiB | text/x-python | PythonLexer
# coding=UTF-8
from __future__ import absolute_import
import base64
import zlib
from mercurial import (
changegroup,
exchange,
extensions,
revlog,
util,
)
# Test only: These flags are defined here only in the context of testing the
# behavior of the flag processor. The canonical way to add flags is to get in
# touch with the community and make them known in revlog.
REVIDX_NOOP = (1 << 3)
REVIDX_BASE64 = (1 << 2)
REVIDX_GZIP = (1 << 1)
REVIDX_FAIL = 1
def validatehash(self, text):
return True
def bypass(self, text):
return False
def noopdonothing(self, text):
return (text, True)
def b64encode(self, text):
return (base64.b64encode(text), False)
def b64decode(self, text):
return (base64.b64decode(text), True)
def gzipcompress(self, text):
return (zlib.compress(text), False)
def gzipdecompress(self, text):
return (zlib.decompress(text), True)
def supportedoutgoingversions(orig, repo):
versions = orig(repo)
versions.discard(b'01')
versions.discard(b'02')
versions.add(b'03')
return versions
def allsupportedversions(orig, ui):
versions = orig(ui)
versions.add(b'03')
return versions
def makewrappedfile(obj):
class wrappedfile(obj.__class__):
def addrevision(self, text, transaction, link, p1, p2,
cachedelta=None, node=None,
flags=revlog.REVIDX_DEFAULT_FLAGS):
if b'[NOOP]' in text:
flags |= REVIDX_NOOP
if b'[BASE64]' in text:
flags |= REVIDX_BASE64
if b'[GZIP]' in text:
flags |= REVIDX_GZIP
# This addrevision wrapper is meant to add a flag we will not have
# transforms registered for, ensuring we handle this error case.
if b'[FAIL]' in text:
flags |= REVIDX_FAIL
return super(wrappedfile, self).addrevision(text, transaction, link,
p1, p2,
cachedelta=cachedelta,
node=node,
flags=flags)
obj.__class__ = wrappedfile
def reposetup(ui, repo):
class wrappingflagprocessorrepo(repo.__class__):
def file(self, f):
orig = super(wrappingflagprocessorrepo, self).file(f)
makewrappedfile(orig)
return orig
repo.__class__ = wrappingflagprocessorrepo
def extsetup(ui):
# Enable changegroup3 for flags to be sent over the wire
wrapfunction = extensions.wrapfunction
wrapfunction(changegroup,
'supportedoutgoingversions',
supportedoutgoingversions)
wrapfunction(changegroup,
'allsupportedversions',
allsupportedversions)
# Teach revlog about our test flags
flags = [REVIDX_NOOP, REVIDX_BASE64, REVIDX_GZIP, REVIDX_FAIL]
revlog.REVIDX_KNOWN_FLAGS |= util.bitsfrom(flags)
revlog.REVIDX_FLAGS_ORDER.extend(flags)
# Teach exchange to use changegroup 3
for k in exchange._bundlespeccontentopts.keys():
exchange._bundlespeccontentopts[k][b"cg.version"] = b"03"
# Register flag processors for each extension
revlog.addflagprocessor(
REVIDX_NOOP,
(
noopdonothing,
noopdonothing,
validatehash,
)
)
revlog.addflagprocessor(
REVIDX_BASE64,
(
b64decode,
b64encode,
bypass,
),
)
revlog.addflagprocessor(
REVIDX_GZIP,
(
gzipdecompress,
gzipcompress,
bypass
)
)