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"""unwrap_timestamp

The unwrap_timestamp module contains tools to unwrap timestamp values.
"""


# IMPORT

from blue_st_sdk.python_utils import synchronized


# CLASSES

class UnwrapTimestamp(object):
    """Class that unwraps a timestamp."""

    _NEAR_TO_END_TH = (1 << 16) - 100
    """Threshold."""

    def __init__(self):
        """Constructor."""
        # Number of times the timestamp has reset.
        # The timestamp is reset whenever the received timestamp has a value
        # greater than "2^16 - 100" and it is followed by a package with a
        # smaller value.
        self._reset_times = 0

        # Last raw timestamp received from the board.
        # It is a number between "0" and "2^16-1".
        self._last_timestamp = 0

    @synchronized
    def unwrap(self, timestamp):
        """Add a multiple of (1 << 16) to the timestamp to reset it, if needed.

        Args:
            timestamp (int): Timestamp.

        Returns:
            int: The unwrapped timestamp.
        """
        if self._last_timestamp > self._NEAR_TO_END_TH \
            and self._last_timestamp > timestamp:
            self._reset_times += 1
        self._last_timestamp = timestamp
        return long(self._reset_times) * (1 << 16) + long(timestamp)
