tests/svnurlof.py
author Augie Fackler <augie@google.com>
Mon, 08 Jul 2019 13:12:20 -0400
branchstable
changeset 42562 97ada9b8d51b
parent 41480 eb6700e6c5ea
child 43076 2372284d9457
permissions -rw-r--r--
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.

from __future__ import absolute_import, print_function
import sys

from mercurial import (
    pycompat,
    util,
)

def main(argv):
    enc = util.urlreq.quote(pycompat.sysbytes(argv[1]))
    if pycompat.iswindows:
        fmt = 'file:///%s'
    else:
        fmt = 'file://%s'
    print(fmt % pycompat.sysstr(enc))

if __name__ == '__main__':
    main(sys.argv)