# 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