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# Copyright 2013-2014 GRNET S.A. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or
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# without modification, are permitted provided that the following
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# conditions are met:
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#
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#   1. Redistributions of source code must retain the above
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#      copyright notice, this list of conditions and the following
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#      disclaimer.
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#
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#   2. Redistributions in binary form must reproduce the above
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#      copyright notice, this list of conditions and the following
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#      disclaimer in the documentation and/or other materials
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#      provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and
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# documentation are those of the authors and should not be
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# interpreted as representing official policies, either expressed
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# or implied, of GRNET S.A.
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from synnefo.lib.ordereddict import OrderedDict
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import re
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PRACTICALLY_INFINITE = 2**63 - 1
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DEFAULT_PARSE_BASE = 1024
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PARSE_EXPONENTS = {
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    '':      0,
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    'bytes': 0,
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    'K':     1,
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    'KB':    1,
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    'KIB':   1,
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    'M':     2,
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    'MB':    2,
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    'MIB':   2,
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    'G':     3,
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    'GB':    3,
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    'GIB':   3,
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    'T':     4,
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    'TB':    4,
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    'TIB':   4,
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    'P':     5,
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    'PB':    5,
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    'PIB':   5,
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}
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_MATCHER = re.compile('^(\d+\.?\d*)(.*)$')
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class ParseError(Exception):
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    pass
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def _parse_number_with_unit(s):
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    match = _MATCHER.match(s)
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    if not match:
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        raise ParseError()
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    number, unit = match.groups()
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    try:
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        number = long(number)
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    except ValueError:
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        number = float(number)
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    return number, unit.strip().upper()
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def parse_with_style(s):
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    if isinstance(s, (int, long)):
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        return s, 0
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    if s in ['inf', 'infinite']:
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        return PRACTICALLY_INFINITE, 0
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    n, unit = _parse_number_with_unit(s)
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    try:
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        exponent = PARSE_EXPONENTS[unit]
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    except KeyError:
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        raise ParseError()
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    multiplier = DEFAULT_PARSE_BASE ** exponent
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    return long(n * multiplier), exponent
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def parse(s):
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    n, _ = parse_with_style(s)
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    return n
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UNITS = {
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    'bytes': {
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        'DISPLAY': ['bytes', 'kB', 'MB', 'GB', 'TB', 'PB'],
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        'BASE': 1024,
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    }
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}
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STYLE_TO_EXP = OrderedDict(
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    [('b',  0),
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     ('kb', 1),
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     ('mb', 2),
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     ('gb', 3),
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     ('tb', 4),
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     ('pb', 5),
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     ]
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)
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STYLES = STYLE_TO_EXP.keys() + ['auto', 'none']
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class StyleError(Exception):
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    pass
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def show_float(n):
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    if n < 1:
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        return "%.3f" % n
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    if n < 10:
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        return "%.2f" % n
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    return "%.1f" % n
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def get_exponent(style):
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    if isinstance(style, (int, long)):
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        if style in STYLE_TO_EXP.values():
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            return style
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        else:
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            raise StyleError()
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    else:
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        try:
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            return STYLE_TO_EXP[style]
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        except KeyError:
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            raise StyleError()
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def show(n, unit, style=None):
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    if style == 'none':
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        return str(n)
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    if n == PRACTICALLY_INFINITE:
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        return 'inf'
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    try:
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        unit_dict = UNITS[unit]
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    except KeyError:
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        return str(n)
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    BASE = unit_dict['BASE']
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    DISPLAY = unit_dict['DISPLAY']
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    if style is None or style == 'auto':
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        if n < BASE:
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            return "%d %s" % (n, DISPLAY[0])
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        n = float(n)
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        for i in DISPLAY[1:]:
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            n = n / BASE
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            if n < BASE:
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                break
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        return "%s %s" % (show_float(n), i)
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    exponent = get_exponent(style)
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    unit_display = DISPLAY[exponent]
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    if exponent == 0:
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        return "%d %s" % (n, unit_display)
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    divisor = BASE ** exponent
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    n = float(n)
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    n = n / divisor
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    return "%s %s" % (show_float(n), unit_display)