Synnefo

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from synnefo.lib.ordereddict import OrderedDict

import re

PRACTICALLY_INFINITE = 2**63 - 1

DEFAULT_PARSE_BASE = 1024

PARSE_EXPONENTS = {

    '':      0,

    'bytes': 0,

    'K':     1,

    'KB':    1,

    'KIB':   1,

    'M':     2,

    'MB':    2,

    'MIB':   2,

    'G':     3,

    'GB':    3,

    'GIB':   3,

    'T':     4,

    'TB':    4,

    'TIB':   4,

    'P':     5,

    'PB':    5,

    'PIB':   5,

}

_MATCHER = re.compile('^(\d+\.?\d*)(.*)$')

class ParseError(Exception):

    pass

def _parse_number_with_unit(s):

    match = _MATCHER.match(s)

    if not match:

        raise ParseError()

    number, unit = match.groups()

    try:

        number = long(number)

    except ValueError:

        number = float(number)

    return number, unit.strip().upper()

def parse_with_style(s):

    if s in ['inf', 'infinite']:

        return PRACTICALLY_INFINITE, 0

    n, unit = _parse_number_with_unit(s)

    try:

        exponent = PARSE_EXPONENTS[unit]

    except KeyError:

        raise ParseError()

    multiplier = DEFAULT_PARSE_BASE ** exponent

    return long(n * multiplier), exponent

def parse(s):

    n, _ = parse_with_style(s)

    return n

UNITS = {

    'bytes': {

        'DISPLAY': ['bytes', 'kB', 'MB', 'GB', 'TB', 'PB'],

        'BASE': 1024,

    }

}

STYLE_TO_EXP = OrderedDict(

    [('b',  0),

     ('kb', 1),

     ('mb', 2),

     ('gb', 3),

     ('tb', 4),

     ('pb', 5),

     ]

)

STYLES = STYLE_TO_EXP.keys() + ['auto', 'none']

class StyleError(Exception):

    pass

def show_float(n):

    if n < 1:

        return "%.3f" % n

    if n < 10:

        return "%.2f" % n

    return "%.1f" % n

def get_exponent(style):

    if isinstance(style, (int, long)):

        if style in STYLE_TO_EXP.values():

            return style

        else:

            raise StyleError()

    else:

        try:

            return STYLE_TO_EXP[style]

        except KeyError:

            raise StyleError()

def show(n, unit, style=None):

    if style == 'none':

        return str(n)

    if n == PRACTICALLY_INFINITE:

        return 'inf'

    try:

        unit_dict = UNITS[unit]

    except KeyError:

        return str(n)

    BASE = unit_dict['BASE']

    DISPLAY = unit_dict['DISPLAY']

    if style is None or style == 'auto':

        if n < BASE:

            return "%d %s" % (n, DISPLAY[0])

        n = float(n)

        for i in DISPLAY[1:]:

            n = n / BASE

            if n < BASE:

                break

        return "%s %s" % (show_float(n), i)

    exponent = get_exponent(style)

    unit_display = DISPLAY[exponent]

    if exponent == 0:

        return "%d %s" % (n, unit_display)

    divisor = BASE ** exponent

    n = float(n)

    n = n / divisor

    return "%s %s" % (show_float(n), unit_display)