compat.py

# -*- coding: utf-8 -*-
# Copyright (c) 2012, Jonas Obrist
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#    * Redistributions of source code must retain the above copyright
#      notice, this list of conditions and the following disclaimer.
#    * Redistributions in binary form must reproduce the above copyright
#      notice, this list of conditions and the following disclaimer in the
#      documentation and/or other materials provided with the distribution.
#    * Neither the name of the Jonas Obrist nor the
#      names of its contributors may be used to endorse or promote products
#      derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL JONAS OBRIST BE LIABLE FOR ANY
# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
from array import array
import itertools
import struct

try:  # see :pyver:old
    array.tostring
except:
    def tostring(row):
        l = len(row)
        return struct.pack('%dB' % l, *row)
else:
    def tostring(row):
        """Convert row of bytes to string.  Expects `row` to be an
        ``array``.
        """
        return row.tostring()


# Conditionally convert to bytes.  Works on Python 2 and Python 3.
try:
    bytes('', 'ascii')
    def strtobytes(x): return bytes(x, 'iso8859-1')
    def bytestostr(x): return str(x, 'iso8859-1')
except:
    strtobytes = str
    bytestostr = str
    
try:
    itertools.count(1,2)
    icount = itertools.count
except TypeError:
    def icount(start, step):
        counter = itertools.count(start)
        while True:
            thing = counter.next()
            if (thing - start) % step == 0:
                yield thing

def irange(start, stop, step):
    """
    like range, but returns an iterator
    """
    return itertools.islice(icount(start, step), (stop-start+step-1)//step)