nilmdb/nilmdb/fileinterval.py

"""FileInterval

An Interval that is backed with file data storage"""

from nilmdb.interval import Interval, IntervalSet, IntervalError
from datetime import datetime
import bisect

class FileInterval(Interval):
    """Represents an interval of time and its corresponding data"""

    def __init__(self, start, end, 
                 filename, 
                 start_offset = None, end_offset = None):
        self.start = start
        self.end = end
        self.filename = filename
        if start_offset is None:
            start_offset = 0
        self.start_offset = start_offset
        if end_offset is None:
            f = open(filename, 'rb')
            f.seek(0, os.SEEK_END)
            end_offset = f.tell()
        self.end_offset = end_offset

    def __setattr__(self, name, value):
        pass

    def subset(self, start, end):
        """Return a new Interval that is a subset of this one"""
        # TODO: Any magic regarding file/offset/length mapping for subsets
        if (start < self.start or end > self.end):
            raise IntervalError("not a subset")
        return FileInterval(start, end)