view tests/svn-safe-append.py @ 50400:95acba2c29f6

encoding: avoid quadratic time complexity when json-encoding non-UTF8 strings

Apparently the code uses "+=" with a bytes object, which is linear-time, so the
whole encoding is quadratic-time. This patch makes us use a bytearray object,
instead, which has a(n amortized-)constant-time append operation.

The encoding is still not particularly fast, but at least a 10MB file
takes tens of seconds, not many hours to encode.

#!/usr/bin/env python3


__doc__ = """Same as `echo a >> b`, but ensures a changed mtime of b.
Without this svn will not detect workspace changes."""

import os
import stat
import sys

if sys.version_info[0] >= 3:
    text = os.fsencode(sys.argv[1])
    fname = os.fsencode(sys.argv[2])
else:
    text = sys.argv[1]
    fname = sys.argv[2]

f = open(fname, "ab")
try:
    before = os.fstat(f.fileno())[stat.ST_MTIME]
    f.write(text)
    f.write(b"\n")
finally:
    f.close()
inc = 1
now = os.stat(fname)[stat.ST_MTIME]
while now == before:
    t = now + inc
    inc += 1
    os.utime(fname, (t, t))
    now = os.stat(fname)[stat.ST_MTIME]