timecode.py

# encoding: utf-8
from datetime import timedelta, datetime

from grain import Grain

__copyright__ = "Copyright (C) 2015 University of Wisconsin SSEC. All rights reserved."

UNIX_EPOCH = datetime(1970, 1, 1)
CDS_EPOCH = datetime(1958, 1, 1)

_grain = Grain()


def unixtime(dt):
    """
    Datetime to Unix timestamp.
    """
    return (dt - datetime(1970, 1, 1)).total_seconds()


def timecode_parts_to_dt(days, ms, us, epoch):
    """
    Convert components to a UTC datetime based on arbitrary epoch.
    """
    return epoch + timedelta(days=days, microseconds=1e3 * ms + us)


def timecode_parts_to_iet(days, ms, us, epoch):
    """
    Convert components to a IET based on arbitrary epoch.
    """
    return _grain.utc2tai(
        epoch + timedelta(days=days, milliseconds=ms, microseconds=us),
        epoch)


def cds_to_iet(days, ms, us):
    """
    CCSDS Day Segmented timecode (UTC) parts to IET (microseconds)
    """
    return timecode_parts_to_iet(days, ms, us, CDS_EPOCH)


def cds_to_dt(days, ms, us):
    """
    CCSDS Day Segmented timecode to UTC datetime.
    """
    return timecode_parts_to_dt(days, ms, us, CDS_EPOCH)


def dt_to_cds(dt):
    """
    UTC datetime to (day, millis, micros)
    """
    d = (dt - CDS_EPOCH)
    return (d.days, int(d.seconds * 1e3), d.microseconds)


iet_to_dt = _grain.iet2utc