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*                                                                       *    
*  Copyright Digital Equipment Corporation 1998. All rights reserved.   *
*                                                                       *    
*  Restricted Rights: Use, duplication, or disclosure by the U.S.       *    
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*  (c) (1) (ii) of DFARS 252.227-7013, or in FAR 52.227-19, or in FAR   *    
*  52.227-14 Alt. III, as applicable.                                   *    
*                                                                       *    
*  This software is proprietary to and embodies the confidential        *    
*  technology of Digital Equipment Corporation. Possession, use, or     *    
*  copying of this software and media is authorized only pursuant to a  *    
*  valid written license from Digital or an authorized sublicensor.     *    
*                                                                       *    
************************************************************************/

/*      chap_3_stdarg.c         */

/* This routine accepts a variable number of string arguments,  */
/* preceded by a count of the number of such strings. It        */
/* allocates enough space in which to concatenate all of the    */
/* strings, concatenates them together, and returns the address */
/* of the new string. It returns NULL if there are no string    */
/* arguments, or if they are all null strings.                  */

#include <stdarg.h>     /* Include appropriate header files.    */
#include <stdlib.h>
#include <string.h>
#include <stdio.h>      /* For the "example" call in main       */

/* NSTRINGS is the maximum number of string arguments accepted  */
/* (arbitrary).                                                 */

#define NSTRINGS 10

char *concatenate(int n,...)
{
    va_list ap;         /* Declare the argument pointer. */

    char *list[NSTRINGS],
        *string;
    int index = 0,
        size = 0;

    /* Check that the number of arguments is within range.   */

    if (n <= 0)
        return NULL;
    if (n > NSTRINGS)
        n = NSTRINGS;

    va_start(ap, n);    /* Initialize the argument pointer.  */

    do {
        /* Extract the next argument and save it. */

        list[index] = va_arg(ap, char *);

        size += strlen(list[index]);
    } while (++index < n);

    va_end(ap); /* Terminate use of ap. */

    if (size == 0)
        return NULL;

    string = malloc(size + 1);
    string[0] = '\0';

    /* Append each argument to the end of the growing result    */
    /*  string.                                                 */

    for (index = 0; index < n; ++index)
        strcat(string, list[index]);

    return string;
}

/* An example of calling this routine is */

main() {
    char *ret_string ;

    ret_string = concatenate(7, "This ", "message ", "is ",
                                "built with ", "a", " variable arg",
                                " list.") ;

    puts(ret_string) ;
}