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.
# -*- coding: UTF-8 -*-
# beautifygraph.py - improve graph output by using Unicode characters
#
# Copyright 2018 John Stiles <johnstiles@gmail.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
'''beautify log -G output by using Unicode characters (EXPERIMENTAL)
A terminal with UTF-8 support and monospace narrow text are required.
'''
from __future__ import absolute_import
from mercurial.i18n import _
from mercurial import (
encoding,
extensions,
graphmod,
pycompat,
templatekw,
)
# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = 'ships-with-hg-core'
def prettyedge(before, edge, after):
if edge == '~':
return '\xE2\x95\xA7' # U+2567 ╧
if edge == '/':
return '\xE2\x95\xB1' # U+2571 ╱
if edge == '-':
return '\xE2\x94\x80' # U+2500 ─
if edge == '|':
return '\xE2\x94\x82' # U+2502 │
if edge == ':':
return '\xE2\x94\x86' # U+2506 ┆
if edge == '\\':
return '\xE2\x95\xB2' # U+2572 ╲
if edge == '+':
if before == ' ' and not after == ' ':
return '\xE2\x94\x9C' # U+251C ├
if after == ' ' and not before == ' ':
return '\xE2\x94\xA4' # U+2524 ┤
return '\xE2\x94\xBC' # U+253C ┼
return edge
def convertedges(line):
line = ' %s ' % line
pretty = []
for idx in pycompat.xrange(len(line) - 2):
pretty.append(prettyedge(line[idx:idx + 1],
line[idx + 1:idx + 2],
line[idx + 2:idx + 3]))
return ''.join(pretty)
def getprettygraphnode(orig, *args, **kwargs):
node = orig(*args, **kwargs)
if node == 'o':
return '\xE2\x97\x8B' # U+25CB ○
if node == '@':
return '\xE2\x97\x8D' # U+25CD ◍
if node == '*':
return '\xE2\x88\x97' # U+2217 ∗
if node == 'x':
return '\xE2\x97\x8C' # U+25CC ◌
if node == '_':
return '\xE2\x95\xA4' # U+2564 ╤
return node
def outputprettygraph(orig, ui, graph, *args, **kwargs):
(edges, text) = zip(*graph)
graph = zip([convertedges(e) for e in edges], text)
return orig(ui, graph, *args, **kwargs)
def extsetup(ui):
if ui.plain('graph'):
return
if encoding.encoding != 'UTF-8':
ui.warn(_('beautifygraph: unsupported encoding, UTF-8 required\n'))
return
if r'A' in encoding._wide:
ui.warn(_('beautifygraph: unsupported terminal settings, '
'monospace narrow text required\n'))
return
extensions.wrapfunction(graphmod, 'outputgraph', outputprettygraph)
extensions.wrapfunction(templatekw, 'getgraphnode', getprettygraphnode)