    /*====================================================================*
     *
     *   Copyright (c) 2015 Qualcomm Atheros, Inc.
     *
     *   All rights reserved.
     *
     *   Redistribution and use in source and binary forms, with or
     *   without modification, are permitted (subject to the limitations
     *   in the disclaimer below) 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 Qualcomm Atheros nor the names of
     *     its contributors may be used to endorse or promote products
     *     derived from this software without specific prior written
     *     permission.
     *
     *   NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE
     *   GRANTED BY THIS LICENSE. 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 THE COPYRIGHT OWNER
     *   OR CONTRIBUTORS 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.
     *
     *--------------------------------------------------------------------*/
    /*====================================================================*
     *
     *   char * strnpwd (char buffer [], unsigned length, unsigned count, unsigned group, char space);
     *
     *   keys.h
     *
     *   encode a buffer with a password containing the specified number
     *   of random letters and digits; optionally, group the letters and
     *   digits and separate groups with a space character; return the
     *   address of the byte following the encoded password;
     *
     *   alphabet is an array of 32 printable password characters;
     *   count is the number of characters to be selected from alphabet;
     *   group is the grouping factor;
     *   space is the group separator;
     *
     *   grouping is suppressed when group is zero or greater than or
     *   equal to count;
     *
     *   Contributors:
     *	Charles Maier <cmaier@qca.qualcomm.com>
     *
     *--------------------------------------------------------------------*/

    #ifndef STRNPWD_SOURCE
    #define STRNPWD_SOURCE

    #include <unistd.h>
    #include <fcntl.h>
    #include <errno.h>

    #include "../tools/types.h"
    #include "../tools/error.h"
    #include "../key/keys.h"

    char * strnpwd (char buffer [], unsigned length, unsigned count, unsigned group, char space)

    {
    	signed fd;
    	if ((fd = open ("/dev/urandom", O_RDONLY)) == -1)
    	{
    		error (1, errno, "can't open /dev/urandom");
    	}
    	while (count--)
    	{
    		static const char alphabet [] =
    		{
    			'2',
    			'3',
    			'4',
    			'5',
    			'6',
    			'7',
    			'8',
    			'9',
    			'A',
    			'B',
    			'C',
    			'D',
    			'E',
    			'F',
    			'G',
    			'H',
    			'J',
    			'K',
    			'L',
    			'M',
    			'N',
    			'P',
    			'Q',
    			'R',
    			'S',
    			'T',
    			'U',
    			'V',
    			'W',
    			'X',
    			'Y',
    			'Z'
    		};
    		unsigned member;
    		if (read (fd, & member, sizeof (member)) != sizeof (member))
    		{
    			error (1, errno, "can't read /dev/urandom");
    		}
    		if (length)
    		{
    			*buffer = alphabet [member % sizeof (alphabet)];
    			buffer++;
    			length--;
    		}
    		if ((count) && (group) && ! (count % group))
    		{
    			if (length)
    			{
    				*buffer = space;
    				buffer++;
    				length--;
    			}
    		}
    	}
    	close (fd);
    	return (buffer);
    }

    #endif

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