vstrconat

#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
 
/*
  vstrconcat() - return a newly allocated string that is the concatenation of
                all the string passed in the variable length argument list.
                
        The argument list *must* be terminated with a NULL pointer.
        
        All other arguments must be char* to ASCIIZ strings.
        
        Thre return value is a pointer to a dynamically allocated
        buffer that contains a null terminated string with 
        all the argument strings concatenated.
        
        The returned pointer must be freed with the standard free()
        function.
 
 */
 
char* vstrconcat( char const* s1, ...)
{
    size_t len = 0;
    char const* src = NULL;
    char* result = NULL;
    char* curpos = NULL;
 
    va_list argp;
 
    if (!s1) {
        return NULL;            // maybe should return strdup("")?
    }
 
    // determine the buffer size needed
 
    src = s1;
    va_start(argp, s1);
 
    while (src) {
        len += strlen(src);     //TODO: protect against overflow
 
        src = va_arg(argp, char const*);
    }
 
    va_end(argp);
 
    result = malloc(len + 1);
    if (!result) {
        return NULL;
    }
 
    // copy the data
 
    src = s1;
    va_start(argp, s1);
    curpos = result;
 
    while (src) {
        size_t tmp = strlen(src);
 
        memcpy(curpos, src, tmp);
        curpos += tmp;
 
        src = va_arg(argp, char const*);
    }
    va_end(argp);
 
    result[len] = '\0';
 
    return result;
}
 
/*
    strconcat() - simple wrapper for the common of concatenating exactly 
                  two strings into a dynamically allocated buffer
                  
 */
char* strconcat( char const* s1, char const* s2)
{
    return vstrconcat( s1, s2, NULL);
}