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