# -*- coding: utf-8 -*-
"""FAT date time implementation."""
import decimal
from dfdatetime import definitions
from dfdatetime import factory
from dfdatetime import interface
[docs]
class FATDateTimeEpoch(interface.DateTimeEpoch):
"""FAT date time time epoch."""
[docs]
def __init__(self):
"""Initializes a FAT date time epoch."""
super(FATDateTimeEpoch, self).__init__(1980, 1, 1)
[docs]
class FATDateTime(interface.DateTimeValues):
"""FAT date time.
The FAT date time is mainly used in DOS/Windows file formats and FAT.
The FAT date and time is a 32-bit value containing two 16-bit values:
* The date (lower 16-bit).
* bits 0 - 4: day of month, where 1 represents the first day
* bits 5 - 8: month of year, where 1 represent January
* bits 9 - 15: year since 1980
* The time of day (upper 16-bit).
* bits 0 - 4: seconds (in 2 second intervals)
* bits 5 - 10: minutes
* bits 11 - 15: hours
The FAT date time has no time zone information and is typically stored
in the local time of the computer.
Attributes:
is_local_time (bool): True if the date and time value is in local time.
"""
_EPOCH = FATDateTimeEpoch()
# The difference between January 1, 1980 and January 1, 1970 in seconds.
_FAT_DATE_TO_POSIX_BASE = 315532800
[docs]
def __init__(self, fat_date_time=None, precision=None, time_zone_offset=None):
"""Initializes a FAT date time.
Args:
fat_date_time (Optional[int]): FAT date time.
precision (Optional[str]): precision of the date and time value, which
should be one of the PRECISION_VALUES in definitions.
time_zone_offset (Optional[int]): time zone offset in number of minutes
from UTC or None if not set.
"""
super(FATDateTime, self).__init__(
precision=precision or definitions.PRECISION_2_SECONDS,
time_zone_offset=time_zone_offset)
self._fat_date_time = fat_date_time
self._number_of_seconds = None
if fat_date_time is not None:
self._number_of_seconds = self._GetNumberOfSeconds(fat_date_time)
@property
def fat_date_time(self):
"""int: FAT date time or None if not set."""
return self._fat_date_time
def _GetNormalizedTimestamp(self):
"""Retrieves the normalized timestamp.
Returns:
decimal.Decimal: normalized timestamp, which contains the number of
seconds since January 1, 1970 00:00:00 and a fraction of second used
for increased precision, or None if the normalized timestamp cannot be
determined.
"""
if self._normalized_timestamp is None:
if self._number_of_seconds is not None and self._number_of_seconds >= 0:
self._normalized_timestamp = (
decimal.Decimal(self._number_of_seconds) +
self._FAT_DATE_TO_POSIX_BASE)
if self._time_zone_offset:
self._normalized_timestamp -= self._time_zone_offset * 60
return self._normalized_timestamp
def _GetNumberOfSeconds(self, fat_date_time):
"""Retrieves the number of seconds from a FAT date time.
Args:
fat_date_time (int): FAT date time.
Returns:
int: number of seconds since January 1, 1980 00:00:00.
Raises:
ValueError: if the month, day of month, hours, minutes or seconds
value is out of bounds.
"""
day_of_month = fat_date_time & 0x1f
month = (fat_date_time >> 5) & 0x0f
year = (fat_date_time >> 9) & 0x7f
days_per_month = self._GetDaysPerMonth(year, month)
if day_of_month < 1 or day_of_month > days_per_month:
raise ValueError('Day of month value out of bounds.')
number_of_days = self._GetDayOfYear(1980 + year, month, day_of_month)
number_of_days -= 1
for past_year in range(0, year):
number_of_days += self._GetNumberOfDaysInYear(past_year)
fat_date_time >>= 16
seconds = (fat_date_time & 0x1f) * 2
minutes = (fat_date_time >> 5) & 0x3f
hours = (fat_date_time >> 11) & 0x1f
if hours not in range(0, 24):
raise ValueError('Hours value out of bounds.')
if minutes not in range(0, 60):
raise ValueError('Minutes value out of bounds.')
if seconds not in range(0, 60):
raise ValueError('Seconds value out of bounds.')
number_of_seconds = (((hours * 60) + minutes) * 60) + seconds
number_of_seconds += number_of_days * definitions.SECONDS_PER_DAY
return number_of_seconds
[docs]
def CopyFromDateTimeString(self, time_string):
"""Copies a FAT date time from a date and time string.
Args:
time_string (str): date and time value formatted as:
YYYY-MM-DD hh:mm:ss.######[+-]##:##
Where # are numeric digits ranging from 0 to 9 and the seconds
fraction can be either 3, 6 or 9 digits. The time of day, seconds
fraction and time zone offset are optional. The default time zone
is UTC.
Raises:
ValueError: if the time string is invalid or not supported.
"""
date_time_values = self._CopyDateTimeFromString(time_string)
year = date_time_values.get('year', 0)
month = date_time_values.get('month', 0)
day_of_month = date_time_values.get('day_of_month', 0)
hours = date_time_values.get('hours', 0)
minutes = date_time_values.get('minutes', 0)
seconds = date_time_values.get('seconds', 0)
time_zone_offset = date_time_values.get('time_zone_offset', None)
if year < 1980 or year > (1980 + 0x7f):
raise ValueError(f'Year value not supported: {year!s}.')
self._normalized_timestamp = None
self._number_of_seconds = self._GetNumberOfSecondsFromElements(
year, month, day_of_month, hours, minutes, seconds)
self._number_of_seconds -= self._FAT_DATE_TO_POSIX_BASE
self._time_zone_offset = time_zone_offset
[docs]
def CopyToDateTimeString(self):
"""Copies the FAT date time to a date and time string.
Returns:
str: date and time value formatted as: "YYYY-MM-DD hh:mm:ss" or None
if number of seconds is missing.
"""
if self._number_of_seconds is None:
return None
number_of_days, hours, minutes, seconds = self._GetTimeValues(
self._number_of_seconds)
year, month, day_of_month = self._GetDateValuesWithEpoch(
number_of_days, self._EPOCH)
return (f'{year:04d}-{month:02d}-{day_of_month:02d} '
f'{hours:02d}:{minutes:02d}:{seconds:02d}')
[docs]
class FATTimestamp(interface.DateTimeValues):
"""FAT timestamp.
The FAT timestamp is an unsigned integer that contains the number of
10 milli seconds intervals since 1980-01-01 00:00:00 (also known as
the FAT date time epoch).
Attributes:
is_local_time (bool): True if the date and time value is in local time.
"""
_EPOCH = FATDateTimeEpoch()
# The difference between January 1, 1980 and January 1, 1970 in seconds.
_FAT_DATE_TO_POSIX_BASE = 315532800
[docs]
def __init__(self, precision=None, time_zone_offset=None, timestamp=None):
"""Initializes a FAT timestamp.
Args:
precision (Optional[str]): precision of the date and time value, which
should be one of the PRECISION_VALUES in definitions.
time_zone_offset (Optional[int]): time zone offset in number of minutes
from UTC or None if not set.
timestamp (Optional[int]): FAT timestamp.
"""
super(FATTimestamp, self).__init__(
precision=precision or definitions.PRECISION_10_MILLISECONDS,
time_zone_offset=time_zone_offset)
self._timestamp = timestamp
@property
def timestamp(self):
"""int: FAT timestamp or None if not set."""
return self._timestamp
def _GetNormalizedTimestamp(self):
"""Retrieves the normalized timestamp.
Returns:
decimal.Decimal: normalized timestamp, which contains the number of
seconds since January 1, 1970 00:00:00 and a fraction of second used
for increased precision, or None if the normalized timestamp cannot be
determined.
"""
if self._normalized_timestamp is None:
if self._timestamp is not None:
self._normalized_timestamp = (
(decimal.Decimal(self._timestamp) / 100) +
self._FAT_DATE_TO_POSIX_BASE)
if self._time_zone_offset:
self._normalized_timestamp -= self._time_zone_offset * 60
return self._normalized_timestamp
[docs]
def CopyFromDateTimeString(self, time_string):
"""Copies a FAT timestamp from a date and time string.
Args:
time_string (str): date and time value formatted as:
YYYY-MM-DD hh:mm:ss.######[+-]##:##
Where # are numeric digits ranging from 0 to 9 and the seconds
fraction can be either 3, 6 or 9 digits. The time of day, seconds
fraction and time zone offset are optional. The default time zone
is UTC.
Raises:
ValueError: if the time string is invalid or not supported.
"""
date_time_values = self._CopyDateTimeFromString(time_string)
year = date_time_values.get('year', 0)
month = date_time_values.get('month', 0)
day_of_month = date_time_values.get('day_of_month', 0)
hours = date_time_values.get('hours', 0)
minutes = date_time_values.get('minutes', 0)
seconds = date_time_values.get('seconds', 0)
nanoseconds = date_time_values.get('nanoseconds', 0)
time_zone_offset = date_time_values.get('time_zone_offset', None)
if year < 1980 or year > (1980 + 0x7f):
raise ValueError(f'Year value not supported: {year!s}.')
milliseconds, _ = divmod(nanoseconds, 10000000)
timestamp = self._GetNumberOfSecondsFromElements(
year, month, day_of_month, hours, minutes, seconds)
timestamp -= self._FAT_DATE_TO_POSIX_BASE
timestamp *= 100
timestamp += milliseconds
self._timestamp = timestamp
self._time_zone_offset = time_zone_offset
[docs]
def CopyToDateTimeString(self):
"""Copies the FAT timestamp to a date and time string.
Returns:
str: date and time value formatted as: "YYYY-MM-DD hh:mm:ss.######" or
None if the timestamp is missing.
"""
if self._timestamp is None:
return None
timestamp, milliseconds = divmod(self._timestamp, 100)
number_of_days, hours, minutes, seconds = self._GetTimeValues(timestamp)
year, month, day_of_month = self._GetDateValuesWithEpoch(
number_of_days, self._EPOCH)
return (f'{year:04d}-{month:02d}-{day_of_month:02d} '
f'{hours:02d}:{minutes:02d}:{seconds:02d}.{milliseconds:02d}')
factory.Factory.RegisterDateTimeValues(FATDateTime)
factory.Factory.RegisterDateTimeValues(FATTimestamp)