jinja_filter_bits.py

def bits(measurement, unit):
    '''Jinja filter to convert measurement from one unit to another.

    Example:
    
        {{ '1GiB' | bits('MiB') }}
            -> 1024
    '''
    return first(convertTo(unit)(decode(measurement)))


conv = {
    'b': 1,
    'B': 8,
    'Kib': 1024,
    'KiB': 8 * 1024,
    'Mib': 1024 ** 2,
    'MiB': 8 * 1024 ** 2,
    'Gib': 1024 ** 3,
    'GiB': 8 * 1024 ** 3,
    'Kb': 1000,
    'KB': 8 * 1000,
    'Mb': 1000 ** 2,
    'MB': 8 * 1000 ** 2,
    'Gb': 1000 ** 3,
    'GB': 8 * 1000 ** 3,
}

# splitAt: int -> str -> (str, str)
# split string into two at given index
splitAt = lambda i: lambda s: (s[:i], s[i:])

# firstNonNumericIndex: str -> int
# find index of first non-numeric character in a string
firstNonNumericIndex = lambda s: map(str.isdigit, s).index(False)

# decode: str -> (int, str)
# split a measurement (e.g. "1MiB") into magnitude and unit
# ! FIXME: `int("")` is an error
decode = lambda s: (lambda m, u: (int(m), u))(*splitAt(firstNonNumericIndex(s))(s))

# convertTo: str -> (int, str) -> (int, str)
# convert measurement from one unit to another
# ! FIXME: invalid units throws an exception
convertTo = lambda u_f: lambda x: (lambda m, u_0: (int(m * conv[u_0] / conv[u_f]), u_f))(*x)

# encode: (int, str) -> str
# encode measurement (e.g. "1MiB") from magnitude and unit
encode = lambda x: (lambda m, u: str(m) + u)(*x)

# first: (x, _) -> x
# return first element of a tuple
first = lambda x: (lambda x, _: x)(*x)