rust-index: simplification in find_gca_candidates()
`parent_seen` can be made a mutable ref, making this part more obvious,
not needing to be commented so much.
The micro-optimization of avoiding the union if `parent_seen` and
`current_seen` agree is pushed down in the `union()` method of the
fast, `u64` based bit set implementation (in case it matters).
# Copyright Mercurial Contributors
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
import functools
import os
import stat
from .. import error
rangemask = 0x7FFFFFFF
@functools.total_ordering
class timestamp(tuple):
"""
A Unix timestamp with optional nanoseconds precision,
modulo 2**31 seconds.
A 3-tuple containing:
`truncated_seconds`: seconds since the Unix epoch,
truncated to its lower 31 bits
`subsecond_nanoseconds`: number of nanoseconds since `truncated_seconds`.
When this is zero, the sub-second precision is considered unknown.
`second_ambiguous`: whether this timestamp is still "reliable"
(see `reliable_mtime_of`) if we drop its sub-second component.
"""
def __new__(cls, value):
truncated_seconds, subsec_nanos, second_ambiguous = value
value = (truncated_seconds & rangemask, subsec_nanos, second_ambiguous)
return super(timestamp, cls).__new__(cls, value)
def __eq__(self, other):
raise error.ProgrammingError(
'timestamp should never be compared directly'
)
def __gt__(self, other):
raise error.ProgrammingError(
'timestamp should never be compared directly'
)
def get_fs_now(vfs):
"""return a timestamp for "now" in the current vfs
This will raise an exception if no temporary files could be created.
"""
tmpfd, tmpname = vfs.mkstemp()
try:
return mtime_of(os.fstat(tmpfd))
finally:
os.close(tmpfd)
vfs.unlink(tmpname)
def zero():
"""
Returns the `timestamp` at the Unix epoch.
"""
return tuple.__new__(timestamp, (0, 0))
def mtime_of(stat_result):
"""
Takes an `os.stat_result`-like object and returns a `timestamp` object
for its modification time.
"""
try:
# TODO: add this attribute to `osutil.stat` objects,
# see `mercurial/cext/osutil.c`.
#
# This attribute is also not available on Python 2.
nanos = stat_result.st_mtime_ns
except AttributeError:
# https://docs.python.org/2/library/os.html#os.stat_float_times
# "For compatibility with older Python versions,
# accessing stat_result as a tuple always returns integers."
secs = stat_result[stat.ST_MTIME]
subsec_nanos = 0
else:
billion = int(1e9)
secs = nanos // billion
subsec_nanos = nanos % billion
return timestamp((secs, subsec_nanos, False))
def reliable_mtime_of(stat_result, present_mtime):
"""Same as `mtime_of`, but return `None` or a `Timestamp` with
`second_ambiguous` set if the date might be ambiguous.
A modification time is reliable if it is older than "present_time" (or
sufficiently in the future).
Otherwise a concurrent modification might happens with the same mtime.
"""
file_mtime = mtime_of(stat_result)
file_second = file_mtime[0]
file_ns = file_mtime[1]
boundary_second = present_mtime[0]
boundary_ns = present_mtime[1]
# If the mtime of the ambiguous file is younger (or equal) to the starting
# point of the `status` walk, we cannot garantee that another, racy, write
# will not happen right after with the same mtime and we cannot cache the
# information.
#
# However if the mtime is far away in the future, this is likely some
# mismatch between the current clock and previous file system operation. So
# mtime more than one days in the future are considered fine.
if boundary_second == file_second:
if file_ns and boundary_ns:
if file_ns < boundary_ns:
return timestamp((file_second, file_ns, True))
return None
elif boundary_second < file_second < (3600 * 24 + boundary_second):
return None
else:
return file_mtime