#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>

static void	vsnprintf_test(char **str, size_t *alloc_len, size_t *offset, const char *fmt, ...)
{
#if defined(__hpux)
//#define INITIAL_ALLOC_LEN      128
//#define INITIAL_ALLOC_LEN       1
#define INITIAL_ALLOC_LEN      20
	int	avail_len, written_len = 0;
	va_list	args;

	if (NULL == *str)
	{
		*alloc_len = INITIAL_ALLOC_LEN;
		printf("Allocating initial %d bytes\n", (int)*alloc_len);
		*str = (char *)malloc(*alloc_len);
		*offset = 0;
        }

	while (1)
	{
		avail_len = *alloc_len - *offset;
		va_start(args, fmt);
		written_len = vsnprintf(*str + *offset, avail_len, fmt, args);
		printf("written_len = %d\n", written_len);
		va_end(args);

                if (0 <= written_len)
			break;

                if (-1 == written_len)
                {
			*alloc_len *= 2;
			printf("Reallocating to %d bytes\n", (int)*alloc_len);
			*str = (char *)realloc(*str, *alloc_len);
			continue;
                }

		printf("written_len = %d exiting...\n", written_len);
		exit(1);
	}

        *offset += written_len;
#undef INITIAL_ALLOC_LEN
#endif
}

int main(void)
{
	char	*msg = NULL;
	size_t	msg_alloc = 0, msg_offset = 0;

	vsnprintf_test(&msg, &msg_alloc, &msg_offset, "%s", "ABCDEFGHIJ0123456789");
	printf("%s\n", msg);
	free(msg);
}