branchcache: skip entries that are topological heads in the on disk file
In the majority of cases, topological heads are also branch heads. We have
efficient way to get the topological heads and efficient way to retrieve
their branch information. So there is little value in putting them in the branch
cache file explicitly. On the contrary, writing them explicitly tend to create
very large cache file that are inefficient to read and update.
So the branch cache v3 format is no longer including them. This changeset focus
on the format aspect and have no focus on the performance aspect. We will cover
that later.
import glob
import os
import shutil
import stat
import tempfile
import unittest
from mercurial import (
util,
)
atomictempfile = util.atomictempfile
class testatomictempfile(unittest.TestCase):
def setUp(self):
self._testdir = tempfile.mkdtemp(b'atomictempfiletest')
self._filename = os.path.join(self._testdir, b'testfilename')
def tearDown(self):
shutil.rmtree(self._testdir, True)
def testsimple(self):
file = atomictempfile(self._filename)
self.assertFalse(os.path.isfile(self._filename))
tempfilename = file._tempname
self.assertTrue(
tempfilename
in glob.glob(os.path.join(self._testdir, b'.testfilename-*'))
)
file.write(b'argh\n')
file.close()
self.assertTrue(os.path.isfile(self._filename))
self.assertTrue(
tempfilename
not in glob.glob(os.path.join(self._testdir, b'.testfilename-*'))
)
# discard() removes the temp file without making the write permanent
def testdiscard(self):
file = atomictempfile(self._filename)
(dir, basename) = os.path.split(file._tempname)
file.write(b'yo\n')
file.discard()
self.assertFalse(os.path.isfile(self._filename))
self.assertTrue(basename not in os.listdir(b'.'))
# if a programmer screws up and passes bad args to atomictempfile, they
# get a plain ordinary TypeError, not infinite recursion
def testoops(self):
with self.assertRaises(TypeError):
atomictempfile()
# checkambig=True avoids ambiguity of timestamp
def testcheckambig(self):
def atomicwrite(checkambig):
f = atomictempfile(self._filename, checkambig=checkambig)
f.write(b'FOO')
f.close()
# try some times, because reproduction of ambiguity depends on
# "filesystem time"
for i in range(5):
atomicwrite(False)
oldstat = os.stat(self._filename)
if oldstat[stat.ST_CTIME] != oldstat[stat.ST_MTIME]:
# subsequent changing never causes ambiguity
continue
repetition = 3
# repeat atomic write with checkambig=True, to examine
# whether st_mtime is advanced multiple times as expected
for j in range(repetition):
atomicwrite(True)
newstat = os.stat(self._filename)
if oldstat[stat.ST_CTIME] != newstat[stat.ST_CTIME]:
# timestamp ambiguity was naturally avoided while repetition
continue
# st_mtime should be advanced "repetition" times, because
# all atomicwrite() occurred at same time (in sec)
oldtime = (oldstat[stat.ST_MTIME] + repetition) & 0x7FFFFFFF
self.assertTrue(newstat[stat.ST_MTIME] == oldtime)
# no more examination is needed, if assumption above is true
break
else:
# This platform seems too slow to examine anti-ambiguity
# of file timestamp (or test happened to be executed at
# bad timing). Exit silently in this case, because running
# on other faster platforms can detect problems
pass
def testread(self):
with open(self._filename, 'wb') as f:
f.write(b'foobar\n')
file = atomictempfile(self._filename, mode=b'rb')
self.assertTrue(file.read(), b'foobar\n')
file.discard()
def testcontextmanagersuccess(self):
"""When the context closes, the file is closed"""
with atomictempfile(b'foo') as f:
self.assertFalse(os.path.isfile(b'foo'))
f.write(b'argh\n')
self.assertTrue(os.path.isfile(b'foo'))
def testcontextmanagerfailure(self):
"""On exception, the file is discarded"""
try:
with atomictempfile(b'foo') as f:
self.assertFalse(os.path.isfile(b'foo'))
f.write(b'argh\n')
raise ValueError
except ValueError:
pass
self.assertFalse(os.path.isfile(b'foo'))
if __name__ == '__main__':
import silenttestrunner
silenttestrunner.main(__name__)