--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/planemo/lib/python3.7/site-packages/networkx/readwrite/graph6.py	Fri Jul 31 00:32:28 2020 -0400
@@ -0,0 +1,410 @@
+# Original author: D. Eppstein, UC Irvine, August 12, 2003.
+# The original code at http://www.ics.uci.edu/~eppstein/PADS/ is public domain.
+#    Copyright (C) 2004-2019 by
+#    Aric Hagberg <hagberg@lanl.gov>
+#    Dan Schult <dschult@colgate.edu>
+#    Pieter Swart <swart@lanl.gov>
+#    Tomas Gavenciak <gavento@ucw.cz>
+#    All rights reserved.
+#    BSD license.
+#
+# Authors: Tomas Gavenciak <gavento@ucw.cz>
+#          Aric Hagberg <aric.hagberg@lanl.gov>
+"""Functions for reading and writing graphs in the *graph6* format.
+
+The *graph6* file format is suitable for small graphs or large dense
+graphs. For large sparse graphs, use the *sparse6* format.
+
+For more information, see the `graph6`_ homepage.
+
+.. _graph6: http://users.cecs.anu.edu.au/~bdm/data/formats.html
+
+"""
+from itertools import islice
+import sys
+
+import networkx as nx
+from networkx.exception import NetworkXError
+from networkx.utils import open_file, not_implemented_for
+
+__all__ = ['from_graph6_bytes', 'read_graph6', 'to_graph6_bytes',
+           'write_graph6']
+
+
+def _generate_graph6_bytes(G, nodes, header):
+    """Yield bytes in the graph6 encoding of a graph.
+
+    `G` is an undirected simple graph. `nodes` is the list of nodes for
+    which the node-induced subgraph will be encoded; if `nodes` is the
+    list of all nodes in the graph, the entire graph will be
+    encoded. `header` is a Boolean that specifies whether to generate
+    the header ``b'>>graph6<<'`` before the remaining data.
+
+    This function generates `bytes` objects in the following order:
+
+    1. the header (if requested),
+    2. the encoding of the number of nodes,
+    3. each character, one-at-a-time, in the encoding of the requested
+       node-induced subgraph,
+    4. a newline character.
+
+    This function raises :exc:`ValueError` if the graph is too large for
+    the graph6 format (that is, greater than ``2 ** 36`` nodes).
+
+    """
+    n = len(G)
+    if n >= 2 ** 36:
+        raise ValueError('graph6 is only defined if number of nodes is less '
+                         'than 2 ** 36')
+    if header:
+        yield b'>>graph6<<'
+    for d in n_to_data(n):
+        yield str.encode(chr(d + 63))
+    # This generates the same as `(v in G[u] for u, v in combinations(G, 2))`,
+    # but in "column-major" order instead of "row-major" order.
+    bits = (nodes[j] in G[nodes[i]] for j in range(1, n) for i in range(j))
+    chunk = list(islice(bits, 6))
+    while chunk:
+        d = sum(b << 5 - i for i, b in enumerate(chunk))
+        yield str.encode(chr(d + 63))
+        chunk = list(islice(bits, 6))
+    yield b'\n'
+
+
+def from_graph6_bytes(string):
+    """Read a simple undirected graph in graph6 format from string.
+
+    Parameters
+    ----------
+    string : string
+       Data in graph6 format, without a trailing newline.
+
+    Returns
+    -------
+    G : Graph
+
+    Raises
+    ------
+    NetworkXError
+        If the string is unable to be parsed in graph6 format
+
+    ValueError
+        If any character ``c`` in the input string does not satisfy
+        ``63 <= ord(c) < 127``.
+
+    Examples
+    --------
+    >>> G = nx.from_graph6_bytes(b'A_')
+    >>> sorted(G.edges())
+    [(0, 1)]
+
+    See Also
+    --------
+    read_graph6, write_graph6
+
+    References
+    ----------
+    .. [1] Graph6 specification
+           <http://users.cecs.anu.edu.au/~bdm/data/formats.html>
+
+    """
+    def bits():
+        """Returns sequence of individual bits from 6-bit-per-value
+        list of data values."""
+        for d in data:
+            for i in [5, 4, 3, 2, 1, 0]:
+                yield (d >> i) & 1
+
+    if string.startswith(b'>>graph6<<'):
+        string = string[10:]
+
+    if sys.version_info < (3, ):
+        data = [ord(c) - 63 for c in string]
+    else:
+        data = [c - 63 for c in string]
+    if any(c > 63 for c in data):
+        raise ValueError('each input character must be in range(63, 127)')
+
+    n, data = data_to_n(data)
+    nd = (n * (n - 1) // 2 + 5) // 6
+    if len(data) != nd:
+        raise NetworkXError(
+            'Expected %d bits but got %d in graph6' % (n * (n - 1) // 2, len(data) * 6))
+
+    G = nx.Graph()
+    G.add_nodes_from(range(n))
+    for (i, j), b in zip([(i, j) for j in range(1, n) for i in range(j)], bits()):
+        if b:
+            G.add_edge(i, j)
+
+    return G
+
+
+def to_graph6_bytes(G, nodes=None, header=True):
+    """Convert a simple undirected graph to bytes in graph6 format.
+
+    Parameters
+    ----------
+    G : Graph (undirected)
+
+    nodes: list or iterable
+       Nodes are labeled 0...n-1 in the order provided.  If None the ordering
+       given by ``G.nodes()`` is used.
+
+    header: bool
+       If True add '>>graph6<<' bytes to head of data.
+
+    Raises
+    ------
+    NetworkXNotImplemented
+        If the graph is directed or is a multigraph.
+
+    ValueError
+        If the graph has at least ``2 ** 36`` nodes; the graph6 format
+        is only defined for graphs of order less than ``2 ** 36``.
+
+    Examples
+    --------
+    >>> nx.to_graph6_bytes(nx.path_graph(2)) # doctest: +SKIP
+    b'>>graph6<<A_\\n'
+
+    See Also
+    --------
+    from_graph6_bytes, read_graph6, write_graph6_bytes
+
+    Notes
+    -----
+    The returned bytes end with a newline character.
+
+    The format does not support edge or node labels, parallel edges or
+    self loops. If self loops are present they are silently ignored.
+
+    References
+    ----------
+    .. [1] Graph6 specification
+           <http://users.cecs.anu.edu.au/~bdm/data/formats.html>
+
+    """
+    if nodes is not None:
+        G = G.subgraph(nodes)
+    H = nx.convert_node_labels_to_integers(G)
+    nodes = sorted(H.nodes())
+    return b''.join(_generate_graph6_bytes(H, nodes, header))
+
+
+@open_file(0, mode='rb')
+def read_graph6(path):
+    """Read simple undirected graphs in graph6 format from path.
+
+    Parameters
+    ----------
+    path : file or string
+       File or filename to write.
+
+    Returns
+    -------
+    G : Graph or list of Graphs
+       If the file contains multiple lines then a list of graphs is returned
+
+    Raises
+    ------
+    NetworkXError
+        If the string is unable to be parsed in graph6 format
+
+    Examples
+    --------
+    You can read a graph6 file by giving the path to the file::
+
+        >>> import tempfile
+        >>> with tempfile.NamedTemporaryFile() as f:
+        ...     _ = f.write(b'>>graph6<<A_\\n')
+        ...     _ = f.seek(0)
+        ...     G = nx.read_graph6(f.name)
+        >>> list(G.edges())
+        [(0, 1)]
+
+    You can also read a graph6 file by giving an open file-like object::
+
+        >>> import tempfile
+        >>> with tempfile.NamedTemporaryFile() as f:
+        ...     _ = f.write(b'>>graph6<<A_\\n')
+        ...     _ = f.seek(0)
+        ...     G = nx.read_graph6(f)
+        >>> list(G.edges())
+        [(0, 1)]
+
+    See Also
+    --------
+    from_graph6_bytes, write_graph6
+
+    References
+    ----------
+    .. [1] Graph6 specification
+           <http://users.cecs.anu.edu.au/~bdm/data/formats.html>
+
+    """
+    glist = []
+    for line in path:
+        line = line.strip()
+        if not len(line):
+            continue
+        glist.append(from_graph6_bytes(line))
+    if len(glist) == 1:
+        return glist[0]
+    else:
+        return glist
+
+
+@not_implemented_for('directed')
+@not_implemented_for('multigraph')
+@open_file(1, mode='wb')
+def write_graph6(G, path, nodes=None, header=True):
+    """Write a simple undirected graph to a path in graph6 format.
+
+    Parameters
+    ----------
+    G : Graph (undirected)
+
+    path : str
+       The path naming the file to which to write the graph.
+
+    nodes: list or iterable
+       Nodes are labeled 0...n-1 in the order provided.  If None the ordering
+       given by ``G.nodes()`` is used.
+
+    header: bool
+       If True add '>>graph6<<' string to head of data
+
+    Raises
+    ------
+    NetworkXNotImplemented
+        If the graph is directed or is a multigraph.
+
+    ValueError
+        If the graph has at least ``2 ** 36`` nodes; the graph6 format
+        is only defined for graphs of order less than ``2 ** 36``.
+
+    Examples
+    --------
+    You can write a graph6 file by giving the path to a file::
+
+        >>> import tempfile
+        >>> with tempfile.NamedTemporaryFile() as f:
+        ...     nx.write_graph6(nx.path_graph(2), f.name)
+        ...     _ = f.seek(0)
+        ...     print(f.read())  # doctest: +SKIP
+        b'>>graph6<<A_\\n'
+
+    See Also
+    --------
+    from_graph6_bytes, read_graph6
+
+    Notes
+    -----
+    The function writes a newline character after writing the encoding
+    of the graph.
+
+    The format does not support edge or node labels, parallel edges or
+    self loops.  If self loops are present they are silently ignored.
+
+    References
+    ----------
+    .. [1] Graph6 specification
+           <http://users.cecs.anu.edu.au/~bdm/data/formats.html>
+
+    """
+    return write_graph6_file(G, path, nodes=nodes, header=header)
+
+
+@not_implemented_for('directed')
+@not_implemented_for('multigraph')
+def write_graph6_file(G, f, nodes=None, header=True):
+    """Write a simple undirected graph to a file-like object in graph6 format.
+
+    Parameters
+    ----------
+    G : Graph (undirected)
+
+    f : file-like object
+       The file to write.
+
+    nodes: list or iterable
+       Nodes are labeled 0...n-1 in the order provided.  If None the ordering
+       given by ``G.nodes()`` is used.
+
+    header: bool
+       If True add '>>graph6<<' string to head of data
+
+    Raises
+    ------
+    NetworkXNotImplemented
+        If the graph is directed or is a multigraph.
+
+    ValueError
+        If the graph has at least ``2 ** 36`` nodes; the graph6 format
+        is only defined for graphs of order less than ``2 ** 36``.
+
+    Examples
+    --------
+    You can write a graph6 file by giving an open file-like object::
+
+        >>> import tempfile
+        >>> with tempfile.NamedTemporaryFile() as f:
+        ...     nx.write_graph6(nx.path_graph(2), f)
+        ...     _ = f.seek(0)
+        ...     print(f.read())  # doctest: +SKIP
+        b'>>graph6<<A_\\n'
+
+    See Also
+    --------
+    from_graph6_bytes, read_graph6
+
+    Notes
+    -----
+    The function writes a newline character after writing the encoding
+    of the graph.
+
+    The format does not support edge or node labels, parallel edges or
+    self loops.  If self loops are present they are silently ignored.
+
+    References
+    ----------
+    .. [1] Graph6 specification
+           <http://users.cecs.anu.edu.au/~bdm/data/formats.html>
+
+    """
+    if nodes is not None:
+        G = G.subgraph(nodes)
+    H = nx.convert_node_labels_to_integers(G)
+    nodes = sorted(H.nodes())
+    for b in _generate_graph6_bytes(H, nodes, header):
+        f.write(b)
+
+
+def data_to_n(data):
+    """Read initial one-, four- or eight-unit value from graph6
+    integer sequence.
+
+    Return (value, rest of seq.)"""
+    if data[0] <= 62:
+        return data[0], data[1:]
+    if data[1] <= 62:
+        return (data[1] << 12) + (data[2] << 6) + data[3], data[4:]
+    return ((data[2] << 30) + (data[3] << 24) + (data[4] << 18) +
+            (data[5] << 12) + (data[6] << 6) + data[7], data[8:])
+
+
+def n_to_data(n):
+    """Convert an integer to one-, four- or eight-unit graph6 sequence.
+
+    This function is undefined if `n` is not in ``range(2 ** 36)``.
+
+    """
+    if n <= 62:
+        return [n]
+    elif n <= 258047:
+        return [63, (n >> 12) & 0x3f, (n >> 6) & 0x3f, n & 0x3f]
+    else:  # if n <= 68719476735:
+        return [63, 63,
+                (n >> 30) & 0x3f, (n >> 24) & 0x3f, (n >> 18) & 0x3f,
+                (n >> 12) & 0x3f, (n >> 6) & 0x3f, n & 0x3f]