Returns the modification timestamp resolution for the given path supported by the used Python interpreter/OS/filesystem combination. Will not check for resolutions less than the given minimum value. Will change the path's modification timestamp in the process.
(self, path, minimum_resolution)
| 979 | pass |
| 980 | |
| 981 | def __python_timestamp_resolution(self, path, minimum_resolution): |
| 982 | """ |
| 983 | Returns the modification timestamp resolution for the given path |
| 984 | supported by the used Python interpreter/OS/filesystem combination. |
| 985 | Will not check for resolutions less than the given minimum value. Will |
| 986 | change the path's modification timestamp in the process. |
| 987 | |
| 988 | Return values: |
| 989 | 0 - nanosecond resolution supported |
| 990 | positive decimal - timestamp resolution in seconds |
| 991 | |
| 992 | """ |
| 993 | # Note on Python's floating point timestamp support: |
| 994 | # Python interpreter versions prior to Python 2.3 did not support |
| 995 | # floating point timestamps. Versions 2.3 through 3.3 may or may not |
| 996 | # support it depending on the configuration (may be toggled by calling |
| 997 | # os.stat_float_times(True/False) at program startup, disabled by |
| 998 | # default prior to Python 2.5 and enabled by default since). Python 3.3 |
| 999 | # deprecated this configuration and 3.4 removed support for it after |
| 1000 | # which floating point timestamps are always supported. |
| 1001 | ver = sys.version_info[0:2] |
| 1002 | python_nanosecond_support = ver >= (3, 4) or (ver >= (2, 3) and |
| 1003 | os.stat_float_times()) |
| 1004 | |
| 1005 | # Minimal expected floating point difference used to account for |
| 1006 | # possible imprecise floating point number representations. We want |
| 1007 | # this number to be small (at least smaller than 0.0001) but still |
| 1008 | # large enough that we can be sure that increasing a floating point |
| 1009 | # value by 2 * eta guarantees the value read back will be increased by |
| 1010 | # at least eta. |
| 1011 | eta = 0.00005 |
| 1012 | |
| 1013 | stats_orig = os.stat(path) |
| 1014 | def test_time(diff): |
| 1015 | """Returns whether a timestamp difference is detectable.""" |
| 1016 | os.utime(path, (stats_orig.st_atime, stats_orig.st_mtime + diff)) |
| 1017 | return os.stat(path).st_mtime > stats_orig.st_mtime + eta |
| 1018 | |
| 1019 | # Test for nanosecond timestamp resolution support. |
| 1020 | if not minimum_resolution and python_nanosecond_support: |
| 1021 | if test_time(2 * eta): |
| 1022 | return 0 |
| 1023 | |
| 1024 | # Detect the filesystem timestamp resolution. Note that there is no |
| 1025 | # need to make this code 'as fast as possible' as, this function gets |
| 1026 | # called before having to sleep until the next detectable modification |
| 1027 | # timestamp value and that, since we already know nanosecond resolution |
| 1028 | # is not supported, will surely take longer than whatever we do here to |
| 1029 | # detect this minimal detectable modification timestamp resolution. |
| 1030 | step = 0.1 |
| 1031 | if not python_nanosecond_support: |
| 1032 | # If Python does not support nanosecond timestamp resolution we |
| 1033 | # know the minimum possible supported timestamp resolution is 1 |
| 1034 | # second. |
| 1035 | minimum_resolution = max(1, minimum_resolution) |
| 1036 | index = max(1, int(minimum_resolution / step)) |
| 1037 | while step * index < minimum_resolution: |
| 1038 | # Floating point number representation errors may cause our |
no test coverage detected