Oslo: sync strutils

The strutils module has been improved with regards to Python 3
compatibility.  For instance, safe_{encode,decode} may now take bytes
as input, which is needed to completely port heatclient to Python 3.

This module is now in sync with commit
c1f1a6d87d3f8a5420f5e749ae5ed85e15ff5fe4.

Change-Id: I658467dc85038da029e0ae8b40fc027cdc4d5eaf

3 files changed, 360 insertions, 234 deletions

diff --git a/heatclient/openstack/common/__init__.py b/heatclient/openstack/common/__init__.py
index e69de29..2a00f3b 100644
--- a/heatclient/openstack/common/__init__.py
+++ b/heatclient/openstack/common/__init__.py
@@ -0,0 +1,2 @@
+import six
+six.add_move(six.MovedModule('mox', 'mox', 'mox3.mox'))
diff --git a/heatclient/openstack/common/gettextutils.py b/heatclient/openstack/common/gettextutils.py
index 1b3ede9..1a49c9d 100644
--- a/heatclient/openstack/common/gettextutils.py
+++ b/heatclient/openstack/common/gettextutils.py
@@ -1,5 +1,3 @@
-# vim: tabstop=4 shiftwidth=4 softtabstop=4
-
 # Copyright 2012 Red Hat, Inc.
 # Copyright 2013 IBM Corp.
 # All Rights Reserved.
@@ -25,14 +23,12 @@ Usual usage in an openstack.common module:
 """
 
 import copy
+import functools
 import gettext
-import logging
+import locale
+from logging import handlers
 import os
 import re
-try:
-    import UserString as _userString
-except ImportError:
-    import collections as _userString
 
 from babel import localedata
 import six
@@ -40,6 +36,17 @@ import six
 _localedir = os.environ.get('heatclient'.upper() + '_LOCALEDIR')
 _t = gettext.translation('heatclient', localedir=_localedir, fallback=True)
 
+# We use separate translation catalogs for each log level, so set up a
+# mapping between the log level name and the translator. The domain
+# for the log level is project_name + "-log-" + log_level so messages
+# for each level end up in their own catalog.
+_t_log_levels = dict(
+    (level, gettext.translation('heatclient' + '-log-' + level,
+                                localedir=_localedir,
+                                fallback=True))
+    for level in ['info', 'warning', 'error', 'critical']
+)
+
 _AVAILABLE_LANGUAGES = {}
 USE_LAZY = False
 
@@ -58,13 +65,35 @@ def enable_lazy():
 
 def _(msg):
     if USE_LAZY:
-        return Message(msg, 'heatclient')
+        return Message(msg, domain='heatclient')
     else:
         if six.PY3:
             return _t.gettext(msg)
         return _t.ugettext(msg)
 
 
+def _log_translation(msg, level):
+    """Build a single translation of a log message
+    """
+    if USE_LAZY:
+        return Message(msg, domain='heatclient' + '-log-' + level)
+    else:
+        translator = _t_log_levels[level]
+        if six.PY3:
+            return translator.gettext(msg)
+        return translator.ugettext(msg)
+
+# Translators for log levels.
+#
+# The abbreviated names are meant to reflect the usual use of a short
+# name like '_'. The "L" is for "log" and the other letter comes from
+# the level.
+_LI = functools.partial(_log_translation, level='info')
+_LW = functools.partial(_log_translation, level='warning')
+_LE = functools.partial(_log_translation, level='error')
+_LC = functools.partial(_log_translation, level='critical')
+
+
 def install(domain, lazy=False):
     """Install a _() function using the given translation domain.
 
@@ -90,11 +119,6 @@ def install(domain, lazy=False):
         # messages in OpenStack. We override the standard _() function
         # and % (format string) operation to build Message objects that can
         # later be translated when we have more information.
-        #
-        # Also included below is an example LocaleHandler that translates
-        # Messages to an associated locale, effectively allowing many logs,
-        # each with their own locale.
-
         def _lazy_gettext(msg):
             """Create and return a Message object.
 
@@ -105,7 +129,7 @@ def install(domain, lazy=False):
             Message encapsulates a string so that we can translate
             it later when needed.
             """
-            return Message(msg, domain)
+            return Message(msg, domain=domain)
 
         from six import moves
         moves.builtins.__dict__['_'] = _lazy_gettext
@@ -120,182 +144,169 @@ def install(domain, lazy=False):
                             unicode=True)
 
 
-class Message(_userString.UserString, object):
-    """Class used to encapsulate translatable messages."""
-    def __init__(self, msg, domain):
-        # _msg is the gettext msgid and should never change
-        self._msg = msg
-        self._left_extra_msg = ''
-        self._right_extra_msg = ''
-        self._locale = None
-        self.params = None
-        self.domain = domain
-
-    @property
-    def data(self):
-        # NOTE(mrodden): this should always resolve to a unicode string
-        # that best represents the state of the message currently
-
-        localedir = os.environ.get(self.domain.upper() + '_LOCALEDIR')
-        if self.locale:
-            lang = gettext.translation(self.domain,
-                                       localedir=localedir,
-                                       languages=[self.locale],
-                                       fallback=True)
-        else:
-            # use system locale for translations
-            lang = gettext.translation(self.domain,
-                                       localedir=localedir,
-                                       fallback=True)
+class Message(six.text_type):
+    """A Message object is a unicode object that can be translated.
 
+    Translation of Message is done explicitly using the translate() method.
+    For all non-translation intents and purposes, a Message is simply unicode,
+    and can be treated as such.
+    """
+
+    def __new__(cls, msgid, msgtext=None, params=None,
+                domain='heatclient', *args):
+        """Create a new Message object.
+
+        In order for translation to work gettext requires a message ID, this
+        msgid will be used as the base unicode text. It is also possible
+        for the msgid and the base unicode text to be different by passing
+        the msgtext parameter.
+        """
+        # If the base msgtext is not given, we use the default translation
+        # of the msgid (which is in English) just in case the system locale is
+        # not English, so that the base text will be in that locale by default.
+        if not msgtext:
+            msgtext = Message._translate_msgid(msgid, domain)
+        # We want to initialize the parent unicode with the actual object that
+        # would have been plain unicode if 'Message' was not enabled.
+        msg = super(Message, cls).__new__(cls, msgtext)
+        msg.msgid = msgid
+        msg.domain = domain
+        msg.params = params
+        return msg
+
+    def translate(self, desired_locale=None):
+        """Translate this message to the desired locale.
+
+        :param desired_locale: The desired locale to translate the message to,
+                               if no locale is provided the message will be
+                               translated to the system's default locale.
+
+        :returns: the translated message in unicode
+        """
+
+        translated_message = Message._translate_msgid(self.msgid,
+                                                      self.domain,
+                                                      desired_locale)
+        if self.params is None:
+            # No need for more translation
+            return translated_message
+
+        # This Message object may have been formatted with one or more
+        # Message objects as substitution arguments, given either as a single
+        # argument, part of a tuple, or as one or more values in a dictionary.
+        # When translating this Message we need to translate those Messages too
+        translated_params = _translate_args(self.params, desired_locale)
+
+        translated_message = translated_message % translated_params
+
+        return translated_message
+
+    @staticmethod
+    def _translate_msgid(msgid, domain, desired_locale=None):
+        if not desired_locale:
+            system_locale = locale.getdefaultlocale()
+            # If the system locale is not available to the runtime use English
+            if not system_locale[0]:
+                desired_locale = 'en_US'
+            else:
+                desired_locale = system_locale[0]
+
+        locale_dir = os.environ.get(domain.upper() + '_LOCALEDIR')
+        lang = gettext.translation(domain,
+                                   localedir=locale_dir,
+                                   languages=[desired_locale],
+                                   fallback=True)
         if six.PY3:
-            ugettext = lang.gettext
-        else:
-            ugettext = lang.ugettext
-
-        full_msg = (self._left_extra_msg +
-                    ugettext(self._msg) +
-                    self._right_extra_msg)
-
-        if self.params is not None:
-            full_msg = full_msg % self.params
-
-        return six.text_type(full_msg)
-
-    @property
-    def locale(self):
-        return self._locale
-
-    @locale.setter
-    def locale(self, value):
-        self._locale = value
-        if not self.params:
-            return
-
-        # This Message object may have been constructed with one or more
-        # Message objects as substitution parameters, given as a single
-        # Message, or a tuple or Map containing some, so when setting the
-        # locale for this Message we need to set it for those Messages too.
-        if isinstance(self.params, Message):
-            self.params.locale = value
-            return
-        if isinstance(self.params, tuple):
-            for param in self.params:
-                if isinstance(param, Message):
-                    param.locale = value
-            return
-        if isinstance(self.params, dict):
-            for param in self.params.values():
-                if isinstance(param, Message):
-                    param.locale = value
-
-    def _save_dictionary_parameter(self, dict_param):
-        full_msg = self.data
-        # look for %(blah) fields in string;
-        # ignore %% and deal with the
-        # case where % is first character on the line
-        keys = re.findall('(?:[^%]|^)?%\((\w*)\)[a-z]', full_msg)
-
-        # if we don't find any %(blah) blocks but have a %s
-        if not keys and re.findall('(?:[^%]|^)%[a-z]', full_msg):
-            # apparently the full dictionary is the parameter
-            params = copy.deepcopy(dict_param)
+            translator = lang.gettext
         else:
-            params = {}
-            for key in keys:
-                try:
-                    params[key] = copy.deepcopy(dict_param[key])
-                except TypeError:
-                    # cast uncopyable thing to unicode string
-                    params[key] = six.text_type(dict_param[key])
+            translator = lang.ugettext
 
-        return params
+        translated_message = translator(msgid)
+        return translated_message
 
-    def _save_parameters(self, other):
-        # we check for None later to see if
-        # we actually have parameters to inject,
-        # so encapsulate if our parameter is actually None
+    def __mod__(self, other):
+        # When we mod a Message we want the actual operation to be performed
+        # by the parent class (i.e. unicode()), the only thing  we do here is
+        # save the original msgid and the parameters in case of a translation
+        params = self._sanitize_mod_params(other)
+        unicode_mod = super(Message, self).__mod__(params)
+        modded = Message(self.msgid,
+                         msgtext=unicode_mod,
+                         params=params,
+                         domain=self.domain)
+        return modded
+
+    def _sanitize_mod_params(self, other):
+        """Sanitize the object being modded with this Message.
+
+        - Add support for modding 'None' so translation supports it
+        - Trim the modded object, which can be a large dictionary, to only
+        those keys that would actually be used in a translation
+        - Snapshot the object being modded, in case the message is
+        translated, it will be used as it was when the Message was created
+        """
         if other is None:
-            self.params = (other, )
+            params = (other,)
         elif isinstance(other, dict):
-            self.params = self._save_dictionary_parameter(other)
+            params = self._trim_dictionary_parameters(other)
         else:
-            # fallback to casting to unicode,
-            # this will handle the problematic python code-like
-            # objects that cannot be deep-copied
-            try:
-                self.params = copy.deepcopy(other)
-            except TypeError:
-                self.params = six.text_type(other)
-
-        return self
-
-    # overrides to be more string-like
-    def __unicode__(self):
-        return self.data
-
-    def __str__(self):
-        if six.PY3:
-            return self.__unicode__()
-        return self.data.encode('utf-8')
+            params = self._copy_param(other)
+        return params
 
-    def __getstate__(self):
-        to_copy = ['_msg', '_right_extra_msg', '_left_extra_msg',
-                   'domain', 'params', '_locale']
-        new_dict = self.__dict__.fromkeys(to_copy)
-        for attr in to_copy:
-            new_dict[attr] = copy.deepcopy(self.__dict__[attr])
+    def _trim_dictionary_parameters(self, dict_param):
+        """Return a dict that only has matching entries in the msgid."""
+        # NOTE(luisg): Here we trim down the dictionary passed as parameters
+        # to avoid carrying a lot of unnecessary weight around in the message
+        # object, for example if someone passes in Message() % locals() but
+        # only some params are used, and additionally we prevent errors for
+        # non-deepcopyable objects by unicoding() them.
+
+        # Look for %(param) keys in msgid;
+        # Skip %% and deal with the case where % is first character on the line
+        keys = re.findall('(?:[^%]|^)?%\((\w*)\)[a-z]', self.msgid)
+
+        # If we don't find any %(param) keys but have a %s
+        if not keys and re.findall('(?:[^%]|^)%[a-z]', self.msgid):
+            # Apparently the full dictionary is the parameter
+            params = self._copy_param(dict_param)
+        else:
+            params = {}
+            # Save our existing parameters as defaults to protect
+            # ourselves from losing values if we are called through an
+            # (erroneous) chain that builds a valid Message with
+            # arguments, and then does something like "msg % kwds"
+            # where kwds is an empty dictionary.
+            src = {}
+            if isinstance(self.params, dict):
+                src.update(self.params)
+            src.update(dict_param)
+            for key in keys:
+                params[key] = self._copy_param(src[key])
 
-        return new_dict
+        return params
 
-    def __setstate__(self, state):
-        for (k, v) in state.items():
-            setattr(self, k, v)
+    def _copy_param(self, param):
+        try:
+            return copy.deepcopy(param)
+        except TypeError:
+            # Fallback to casting to unicode this will handle the
+            # python code-like objects that can't be deep-copied
+            return six.text_type(param)
 
-    # operator overloads
     def __add__(self, other):
-        copied = copy.deepcopy(self)
-        copied._right_extra_msg += other.__str__()
-        return copied
+        msg = _('Message objects do not support addition.')
+        raise TypeError(msg)
 
     def __radd__(self, other):
-        copied = copy.deepcopy(self)
-        copied._left_extra_msg += other.__str__()
-        return copied
+        return self.__add__(other)
 
-    def __mod__(self, other):
-        # do a format string to catch and raise
-        # any possible KeyErrors from missing parameters
-        self.data % other
-        copied = copy.deepcopy(self)
-        return copied._save_parameters(other)
-
-    def __mul__(self, other):
-        return self.data * other
-
-    def __rmul__(self, other):
-        return other * self.data
-
-    def __getitem__(self, key):
-        return self.data[key]
-
-    def __getslice__(self, start, end):
-        return self.data.__getslice__(start, end)
-
-    def __getattribute__(self, name):
-        # NOTE(mrodden): handle lossy operations that we can't deal with yet
-        # These override the UserString implementation, since UserString
-        # uses our __class__ attribute to try and build a new message
-        # after running the inner data string through the operation.
-        # At that point, we have lost the gettext message id and can just
-        # safely resolve to a string instead.
-        ops = ['capitalize', 'center', 'decode', 'encode',
-               'expandtabs', 'ljust', 'lstrip', 'replace', 'rjust', 'rstrip',
-               'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']
-        if name in ops:
-            return getattr(self.data, name)
-        else:
-            return _userString.UserString.__getattribute__(self, name)
+    def __str__(self):
+        # NOTE(luisg): Logging in python 2.6 tries to str() log records,
+        # and it expects specifically a UnicodeError in order to proceed.
+        msg = _('Message objects do not support str() because they may '
+                'contain non-ascii characters. '
+                'Please use unicode() or translate() instead.')
+        raise UnicodeError(msg)
 
 
 def get_available_languages(domain):
@@ -321,53 +332,143 @@ def get_available_languages(domain):
     list_identifiers = (getattr(localedata, 'list', None) or
                         getattr(localedata, 'locale_identifiers'))
     locale_identifiers = list_identifiers()
+
     for i in locale_identifiers:
         if find(i) is not None:
             language_list.append(i)
+
+    # NOTE(luisg): Babel>=1.0,<1.3 has a bug where some OpenStack supported
+    # locales (e.g. 'zh_CN', and 'zh_TW') aren't supported even though they
+    # are perfectly legitimate locales:
+    #     https://github.com/mitsuhiko/babel/issues/37
+    # In Babel 1.3 they fixed the bug and they support these locales, but
+    # they are still not explicitly "listed" by locale_identifiers().
+    # That is  why we add the locales here explicitly if necessary so that
+    # they are listed as supported.
+    aliases = {'zh': 'zh_CN',
+               'zh_Hant_HK': 'zh_HK',
+               'zh_Hant': 'zh_TW',
+               'fil': 'tl_PH'}
+    for (locale, alias) in six.iteritems(aliases):
+        if locale in language_list and alias not in language_list:
+            language_list.append(alias)
+
     _AVAILABLE_LANGUAGES[domain] = language_list
     return copy.copy(language_list)
 
 
-def get_localized_message(message, user_locale):
-    """Gets a localized version of the given message in the given locale.
+def translate(obj, desired_locale=None):
+    """Gets the translated unicode representation of the given object.
 
-    If the message is not a Message object the message is returned as-is.
-    If the locale is None the message is translated to the default locale.
+    If the object is not translatable it is returned as-is.
+    If the locale is None the object is translated to the system locale.
 
-    :returns: the translated message in unicode, or the original message if
+    :param obj: the object to translate
+    :param desired_locale: the locale to translate the message to, if None the
+                           default system locale will be used
+    :returns: the translated object in unicode, or the original object if
               it could not be translated
     """
-    translated = message
+    message = obj
+    if not isinstance(message, Message):
+        # If the object to translate is not already translatable,
+        # let's first get its unicode representation
+        message = six.text_type(obj)
     if isinstance(message, Message):
-        original_locale = message.locale
-        message.locale = user_locale
-        translated = six.text_type(message)
-        message.locale = original_locale
-    return translated
+        # Even after unicoding() we still need to check if we are
+        # running with translatable unicode before translating
+        return message.translate(desired_locale)
+    return obj
+
 
+def _translate_args(args, desired_locale=None):
+    """Translates all the translatable elements of the given arguments object.
 
-class LocaleHandler(logging.Handler):
-    """Handler that can have a locale associated to translate Messages.
+    This method is used for translating the translatable values in method
+    arguments which include values of tuples or dictionaries.
+    If the object is not a tuple or a dictionary the object itself is
+    translated if it is translatable.
 
-    A quick example of how to utilize the Message class above.
-    LocaleHandler takes a locale and a target logging.Handler object
-    to forward LogRecord objects to after translating the internal Message.
+    If the locale is None the object is translated to the system locale.
+
+    :param args: the args to translate
+    :param desired_locale: the locale to translate the args to, if None the
+                           default system locale will be used
+    :returns: a new args object with the translated contents of the original
     """
+    if isinstance(args, tuple):
+        return tuple(translate(v, desired_locale) for v in args)
+    if isinstance(args, dict):
+        translated_dict = {}
+        for (k, v) in six.iteritems(args):
+            translated_v = translate(v, desired_locale)
+            translated_dict[k] = translated_v
+        return translated_dict
+    return translate(args, desired_locale)
+
+
+class TranslationHandler(handlers.MemoryHandler):
+    """Handler that translates records before logging them.
+
+    The TranslationHandler takes a locale and a target logging.Handler object
+    to forward LogRecord objects to after translating them. This handler
+    depends on Message objects being logged, instead of regular strings.
+
+    The handler can be configured declaratively in the logging.conf as follows:
 
-    def __init__(self, locale, target):
-        """Initialize a LocaleHandler
+        [handlers]
+        keys = translatedlog, translator
+
+        [handler_translatedlog]
+        class = handlers.WatchedFileHandler
+        args = ('/var/log/api-localized.log',)
+        formatter = context
+
+        [handler_translator]
+        class = openstack.common.log.TranslationHandler
+        target = translatedlog
+        args = ('zh_CN',)
+
+    If the specified locale is not available in the system, the handler will
+    log in the default locale.
+    """
+
+    def __init__(self, locale=None, target=None):
+        """Initialize a TranslationHandler
 
         :param locale: locale to use for translating messages
         :param target: logging.Handler object to forward
                        LogRecord objects to after translation
         """
-        logging.Handler.__init__(self)
+        # NOTE(luisg): In order to allow this handler to be a wrapper for
+        # other handlers, such as a FileHandler, and still be able to
+        # configure it using logging.conf, this handler has to extend
+        # MemoryHandler because only the MemoryHandlers' logging.conf
+        # parsing is implemented such that it accepts a target handler.
+        handlers.MemoryHandler.__init__(self, capacity=0, target=target)
         self.locale = locale
-        self.target = target
+
+    def setFormatter(self, fmt):
+        self.target.setFormatter(fmt)
 
     def emit(self, record):
-        if isinstance(record.msg, Message):
-            # set the locale and resolve to a string
-            record.msg.locale = self.locale
+        # We save the message from the original record to restore it
+        # after translation, so other handlers are not affected by this
+        original_msg = record.msg
+        original_args = record.args
+
+        try:
+            self._translate_and_log_record(record)
+        finally:
+            record.msg = original_msg
+            record.args = original_args
+
+    def _translate_and_log_record(self, record):
+        record.msg = translate(record.msg, self.locale)
+
+        # In addition to translating the message, we also need to translate
+        # arguments that were passed to the log method that were not part
+        # of the main message e.g., log.info(_('Some message %s'), this_one))
+        record.args = _translate_args(record.args, self.locale)
 
         self.target.emit(record)
diff --git a/heatclient/openstack/common/strutils.py b/heatclient/openstack/common/strutils.py
index dd152b3..d6aef26 100644
--- a/heatclient/openstack/common/strutils.py
+++ b/heatclient/openstack/common/strutils.py
@@ -17,25 +17,31 @@
 System-level utilities and helper functions.
 """
 
+import math
 import re
 import sys
 import unicodedata
 
 import six
 
-from heatclient.openstack.common.gettextutils import _  # noqa
+from heatclient.openstack.common.gettextutils import _
 
 
-# Used for looking up extensions of text
-# to their 'multiplied' byte amount
-BYTE_MULTIPLIERS = {
-    '': 1,
-    't': 1024 ** 4,
-    'g': 1024 ** 3,
-    'm': 1024 ** 2,
-    'k': 1024,
+UNIT_PREFIX_EXPONENT = {
+    'k': 1,
+    'K': 1,
+    'Ki': 1,
+    'M': 2,
+    'Mi': 2,
+    'G': 3,
+    'Gi': 3,
+    'T': 4,
+    'Ti': 4,
+}
+UNIT_SYSTEM_INFO = {
+    'IEC': (1024, re.compile(r'(^[-+]?\d*\.?\d+)([KMGT]i?)?(b|bit|B)$')),
+    'SI': (1000, re.compile(r'(^[-+]?\d*\.?\d+)([kMGT])?(b|bit|B)$')),
 }
-BYTE_REGEX = re.compile(r'(^-?\d+)(\D*)')
 
 TRUE_STRINGS = ('1', 't', 'true', 'on', 'y', 'yes')
 FALSE_STRINGS = ('0', 'f', 'false', 'off', 'n', 'no')
@@ -58,12 +64,12 @@ def int_from_bool_as_string(subject):
     return bool_from_string(subject) and 1 or 0
 
 
-def bool_from_string(subject, strict=False):
+def bool_from_string(subject, strict=False, default=False):
     """Interpret a string as a boolean.
 
     A case-insensitive match is performed such that strings matching 't',
     'true', 'on', 'y', 'yes', or '1' are considered True and, when
-    `strict=False`, anything else is considered False.
+    `strict=False`, anything else returns the value specified by 'default'.
 
     Useful for JSON-decoded stuff and config file parsing.
 
@@ -88,11 +94,12 @@ def bool_from_string(subject, strict=False):
                                       'acceptable': acceptable}
         raise ValueError(msg)
     else:
-        return False
+        return default
 
 
 def safe_decode(text, incoming=None, errors='strict'):
-    """Decodes incoming str using `incoming` if they're not already unicode.
+    """Decodes incoming text/bytes string using `incoming` if they're not
+       already unicode.
 
     :param incoming: Text's current encoding
     :param errors: Errors handling policy. See here for valid
@@ -101,7 +108,7 @@ def safe_decode(text, incoming=None, errors='strict'):
                 representation of it.
     :raises TypeError: If text is not an instance of str
     """
-    if not isinstance(text, six.string_types):
+    if not isinstance(text, (six.string_types, six.binary_type)):
         raise TypeError("%s can't be decoded" % type(text))
 
     if isinstance(text, six.text_type):
@@ -131,7 +138,7 @@ def safe_decode(text, incoming=None, errors='strict'):
 
 def safe_encode(text, incoming=None,
                 encoding='utf-8', errors='strict'):
-    """Encodes incoming str/unicode using `encoding`.
+    """Encodes incoming text/bytes string using `encoding`.
 
     If incoming is not specified, text is expected to be encoded with
     current python's default encoding. (`sys.getdefaultencoding`)
@@ -144,7 +151,7 @@ def safe_encode(text, incoming=None,
                 representation of it.
     :raises TypeError: If text is not an instance of str
     """
-    if not isinstance(text, six.string_types):
+    if not isinstance(text, (six.string_types, six.binary_type)):
         raise TypeError("%s can't be encoded" % type(text))
 
     if not incoming:
@@ -167,34 +174,50 @@ def safe_encode(text, incoming=None,
     return text
 
 
-def to_bytes(text, default=0):
-    """Converts a string into an integer of bytes.
+def string_to_bytes(text, unit_system='IEC', return_int=False):
+    """Converts a string into an float representation of bytes.
+
+    The units supported for IEC ::
+
+        Kb(it), Kib(it), Mb(it), Mib(it), Gb(it), Gib(it), Tb(it), Tib(it)
+        KB, KiB, MB, MiB, GB, GiB, TB, TiB
+
+    The units supported for SI ::
 
-    Looks at the last characters of the text to determine
-    what conversion is needed to turn the input text into a byte number.
-    Supports "B, K(B), M(B), G(B), and T(B)". (case insensitive)
+        kb(it), Mb(it), Gb(it), Tb(it)
+        kB, MB, GB, TB
+
+    Note that the SI unit system does not support capital letter 'K'
 
     :param text: String input for bytes size conversion.
-    :param default: Default return value when text is blank.
+    :param unit_system: Unit system for byte size conversion.
+    :param return_int: If True, returns integer representation of text
+                       in bytes. (default: decimal)
+    :returns: Numerical representation of text in bytes.
+    :raises ValueError: If text has an invalid value.
 
     """
-    match = BYTE_REGEX.search(text)
+    try:
+        base, reg_ex = UNIT_SYSTEM_INFO[unit_system]
+    except KeyError:
+        msg = _('Invalid unit system: "%s"') % unit_system
+        raise ValueError(msg)
+    match = reg_ex.match(text)
     if match:
-        magnitude = int(match.group(1))
-        mult_key_org = match.group(2)
-        if not mult_key_org:
-            return magnitude
-    elif text:
+        magnitude = float(match.group(1))
+        unit_prefix = match.group(2)
+        if match.group(3) in ['b', 'bit']:
+            magnitude /= 8
+    else:
         msg = _('Invalid string format: %s') % text
-        raise TypeError(msg)
+        raise ValueError(msg)
+    if not unit_prefix:
+        res = magnitude
     else:
-        return default
-    mult_key = mult_key_org.lower().replace('b', '', 1)
-    multiplier = BYTE_MULTIPLIERS.get(mult_key)
-    if multiplier is None:
-        msg = _('Unknown byte multiplier: %s') % mult_key_org
-        raise TypeError(msg)
-    return magnitude * multiplier
+        res = magnitude * pow(base, UNIT_PREFIX_EXPONENT[unit_prefix])
+    if return_int:
+        return int(math.ceil(res))
+    return res
 
 
 def to_slug(value, incoming=None, errors="strict"):