strfbits.c
Author: cmaier@cmassoc.net

    /*====================================================================*
     *
     *   size_t strfbits (char  buffer [], size_t length, char const * operands [], char const * operator, unsigned flagword);
     *
     *   format.h
     *
     *   format buffer with an enumerated list of the bits in a flagword;
     *   each flagword bit position corresponds to a string in operands[]
     *   and operator is the string separating formatted operands;
     *
     *   enumeration continues until all bits are enumerated or operands
     *   are exhausted or the buffer fills;
     *
     *   for example, the following formats buffer with the literal string
     *   "one, three, five, six" since those bits are set;
     *
     *   char buffer[100];
     *   char const operator = ", ";
     *   char const *operands[] =
     *   {
     *      "zero",
     *      "one",
     *      "two",
     *      "three",
     *      "four",
     *      "five",
     *      "six",
     *      "seven",
     *      "eight",
     *      "nine",
     *      "ten",
     *      (char *)(0)
     *   };
     *   flag_t flags = 0x006C;
     *
     *   strfbits (buffer, sizeof(buffer), operands, operator, flags);
     *
     *   we decrement length before starting to reserve room for the NUL
     *   terminator; not room ... no write; we then add length to buffer
     *   before to compute the terminator address then subtract it after
     *   to compute the buffer start; this minimizes indexing and offset
     *   calculations within the loop;
     *
     *   Motley Tools by Charles Maier <cmaier@cmassoc.net>;
     *   Copyright (c) 2001-2006 by Charles Maier Associates;
     *   Licensed under the Internet Software Consortium License;
     *
     *--------------------------------------------------------------------*/

    #ifndef STRFBITS_SOURCE
    #define STRFBITS_SOURCE

    #include <unistd.h>

    #include "../tools/memory.h"
    #include "../tools/flags.h"

    size_t strfbits (char buffer [], size_t length, char const * operands [], char const * operator, unsigned flagword)

    {
    	char * string = (char *)(buffer);
    	char const *separator = "";
    	if (length--)
    	{
    		buffer += length;
    		while ((*operands) && (flagword))
    		{
    			if (flagword & 1)
    			{
    				char const *symbol;
    				for (symbol = separator; (*symbol) && (string < buffer); symbol++)
    				{
    					*string++ = *symbol;
    				}
    				for (symbol = *operands; (*symbol) && (string < buffer); symbol++)
    				{
    					*string++ = *symbol;
    				}
    				separator = operator;
    			}
    			flagword >>= 1;
    			operands++;
    		}
    		*string = (char) (0);
    		buffer -= length;
    	}
    	return (string - (char *)(buffer));
    }

    #endif

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