1 files changed, 273 insertions, 0 deletions
diff --git a/netaddr/strategy/__init__.py b/netaddr/strategy/__init__.py
new file mode 100644
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--- /dev/null
+++ b/netaddr/strategy/__init__.py
@@ -0,0 +1,273 @@
+#-----------------------------------------------------------------------------
+#   Copyright (c) 2008 by David P. D. Moss. All rights reserved.
+#
+#   Released under the BSD license. See the LICENSE file for details.
+#-----------------------------------------------------------------------------
+"""
+Shared logic for various address types.
+"""
+import re as _re
+
+from netaddr.compat import _range, _is_str
+
+
+def bytes_to_bits():
+    """
+    :return: A 256 element list containing 8-bit binary digit strings. The
+        list index value is equivalent to its bit string value.
+    """
+    lookup = []
+    bits_per_byte = _range(7, -1, -1)
+    for num in range(256):
+        bits = 8 * [None]
+        for i in bits_per_byte:
+            bits[i] = '01'[num & 1]
+            num >>= 1
+        lookup.append(''.join(bits))
+    return lookup
+
+#: A lookup table of 8-bit integer values to their binary digit bit strings.
+BYTES_TO_BITS = bytes_to_bits()
+
+
+def valid_words(words, word_size, num_words):
+    """
+    :param words: A sequence of unsigned integer word values.
+
+    :param word_size: Width (in bits) of each unsigned integer word value.
+
+    :param num_words: Number of unsigned integer words expected.
+
+    :return: ``True`` if word sequence is valid for this address type,
+        ``False`` otherwise.
+    """
+    if not hasattr(words, '__iter__'):
+        return False
+
+    if len(words) != num_words:
+        return False
+
+    max_word = 2 ** word_size - 1
+
+    for i in words:
+        if not 0 <= i <= max_word:
+            return False
+
+    return True
+
+
+def int_to_words(int_val, word_size, num_words):
+    """
+    :param int_val: Unsigned integer to be divided into words of equal size.
+
+    :param word_size: Width (in bits) of each unsigned integer word value.
+
+    :param num_words: Number of unsigned integer words expected.
+
+    :return: A tuple contain unsigned integer word values split according
+        to provided arguments.
+    """
+    max_int = 2 ** (num_words * word_size) - 1
+
+    if not 0 <= int_val <= max_int:
+        raise IndexError('integer out of bounds: %r!' % hex(int_val))
+
+    max_word = 2 ** word_size - 1
+
+    words = []
+    for _ in range(num_words):
+        word = int_val & max_word
+        words.append(int(word))
+        int_val >>= word_size
+
+    return tuple(reversed(words))
+
+
+def words_to_int(words, word_size, num_words):
+    """
+    :param words: A sequence of unsigned integer word values.
+
+    :param word_size: Width (in bits) of each unsigned integer word value.
+
+    :param num_words: Number of unsigned integer words expected.
+
+    :return: An unsigned integer that is equivalent to value represented
+        by word sequence.
+    """
+    if not valid_words(words, word_size, num_words):
+        raise ValueError('invalid integer word sequence: %r!' % (words,))
+
+    int_val = 0
+    for i, num in enumerate(reversed(words)):
+        word = num
+        word = word << word_size * i
+        int_val = int_val | word
+
+    return int_val
+
+
+def valid_bits(bits, width, word_sep=''):
+    """
+    :param bits: A network address in a delimited binary string format.
+
+    :param width: Maximum width (in bits) of a network address (excluding
+        delimiters).
+
+    :param word_sep: (optional) character or string used to delimit word
+        groups (default: '', no separator).
+
+    :return: ``True`` if network address is valid, ``False`` otherwise.
+    """
+    if not _is_str(bits):
+        return False
+
+    if word_sep != '':
+        bits = bits.replace(word_sep, '')
+
+    if len(bits) != width:
+        return False
+
+    max_int = 2 ** width - 1
+
+    try:
+        if 0 <= int(bits, 2) <= max_int:
+            return True
+    except ValueError:
+        pass
+
+    return False
+
+
+def bits_to_int(bits, width, word_sep=''):
+    """
+    :param bits: A network address in a delimited binary string format.
+
+    :param width: Maximum width (in bits) of a network address (excluding
+        delimiters).
+
+    :param word_sep: (optional) character or string used to delimit word
+        groups (default: '', no separator).
+
+    :return: An unsigned integer that is equivalent to value represented
+        by network address in readable binary form.
+    """
+    if not valid_bits(bits, width, word_sep):
+        raise ValueError('invalid readable binary string: %r!' % (bits,))
+
+    if word_sep != '':
+        bits = bits.replace(word_sep, '')
+
+    return int(bits, 2)
+
+
+def int_to_bits(int_val, word_size, num_words, word_sep=''):
+    """
+    :param int_val: An unsigned integer.
+
+    :param word_size: Width (in bits) of each unsigned integer word value.
+
+    :param num_words: Number of unsigned integer words expected.
+
+    :param word_sep: (optional) character or string used to delimit word
+        groups (default: '', no separator).
+
+    :return: A network address in a delimited binary string format that is
+        equivalent in value to unsigned integer.
+    """
+    bit_words = []
+
+    for word in int_to_words(int_val, word_size, num_words):
+        bits = []
+        while word:
+            bits.append(BYTES_TO_BITS[word & 255])
+            word >>= 8
+        bits.reverse()
+        bit_str = ''.join(bits) or '0' * word_size
+        bits = ('0' * word_size + bit_str)[-word_size:]
+        bit_words.append(bits)
+
+    if word_sep != '':
+        #   Check custom separator.
+        if not _is_str(word_sep):
+            raise ValueError('word separator is not a string: %r!' % (word_sep,))
+
+    return word_sep.join(bit_words)
+
+
+def valid_bin(bin_val, width):
+    """
+    :param bin_val: A network address in Python's binary representation format
+        ('0bxxx').
+
+    :param width: Maximum width (in bits) of a network address (excluding
+        delimiters).
+
+    :return: ``True`` if network address is valid, ``False`` otherwise.
+    """
+    if not _is_str(bin_val):
+        return False
+
+    if not bin_val.startswith('0b'):
+        return False
+
+    bin_val = bin_val.replace('0b', '')
+
+    if len(bin_val) > width:
+        return False
+
+    max_int = 2 ** width - 1
+
+    try:
+        if 0 <= int(bin_val, 2) <= max_int:
+            return True
+    except ValueError:
+        pass
+
+    return False
+
+
+def int_to_bin(int_val, width):
+    """
+    :param int_val: An unsigned integer.
+
+    :param width: Maximum allowed width (in bits) of a unsigned integer.
+
+    :return: Equivalent string value in Python's binary representation format
+        ('0bxxx').
+    """
+    bin_tokens = []
+
+    try:
+        #   Python 2.6.x and upwards.
+        bin_val = bin(int_val)
+    except NameError:
+        #   Python 2.4.x and 2.5.x
+        i = int_val
+        while i > 0:
+            word = i & 0xff
+            bin_tokens.append(BYTES_TO_BITS[word])
+            i >>= 8
+
+        bin_tokens.reverse()
+        bin_val = '0b' + _re.sub(r'^[0]+([01]+)$', r'\1', ''.join(bin_tokens))
+
+    if len(bin_val[2:]) > width:
+        raise IndexError('binary string out of bounds: %s!' % (bin_val,))
+
+    return bin_val
+
+
+def bin_to_int(bin_val, width):
+    """
+    :param bin_val: A string containing an unsigned integer in Python's binary
+        representation format ('0bxxx').
+
+    :param width: Maximum allowed width (in bits) of a unsigned integer.
+
+    :return: An unsigned integer that is equivalent to value represented
+        by Python binary string format.
+    """
+    if not valid_bin(bin_val, width):
+        raise ValueError('not a valid Python binary string: %r!' % (bin_val,))
+
+    return int(bin_val.replace('0b', ''), 2)