/*
 * asprintf.c -- basic port of asprintf / vsprintf functions
 *
 * Copyright (c) 2011, 2012 David Demelier <markand@malikania.fr>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

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

/*
 * The Microsoft implementation relies on the Win32 API function
 * _vscprintf which count the number of characters needed. Otherwise the C99
 * function vsnprintf returns the number of character that would be printed.
 *
 * Finally, if we don't have C99, we use an optimistic function.
 *
 * The asprintf function is common to every implementations.
 */

#if defined(_MSC_VER)

/*
 * Windows implementation.
 */
int
vasprintf(char **res, const char *fmt, va_list ap)
{
	int total = _vscprintf(fmt, ap);

	if (total < 0) {
		*res = NULL;
		return -1;
	}

	if ((*res = (char *)malloc(sizeof (total) + 1)) == NULL)
		return -1;

	return vsprintf_s(*res, total + 1, fmt, ap);
}

#elif __STDC_VERSION__ >= 199901L

/*
 * C99 implementation using vsnprintf's return value.
 */
int
vasprintf(char **res, const char *fmt, va_list ap)
{
	int total, nwritten;
	va_list copy;

	va_copy(copy, ap);
	total = vsnprintf(NULL, 0, fmt, copy);
	va_end(copy);

	if (total < 0) {
		*res = NULL;
		return total;
	}

	if ((*res = malloc(total + 1)) == NULL)
		return -1;

	if ((nwritten = vsnprintf(*res, total + 1, fmt, ap)) < 0) {
		free(*res);
		*res = NULL;

		return -1;
	}

	return nwritten;
}

#else

/*
 * Optimistic function fallback.
 */
int
vasprintf(char **res, const char *format, va_list ap)
{
	int rvalue, ok;
	size_t base = 80;

	if ((*res = malloc(base)) == NULL)
		return -1;

	ok = 0;
	do {
		rvalue = vsnprintf(*res, base, format, ap);

		if ((signed int)base <= rvalue || rvalue < 0) {
			*res = realloc(*res, base * 2);
			base *= 2;
		} else
			ok = 1;
	} while (!ok && *res != NULL);

	return rvalue;
}

#endif

int
asprintf(char **res, const char *fmt, ...)
{
	va_list ap;
	int rvalue;

	va_start(ap, fmt);
	rvalue = vasprintf(res, fmt, ap);
	va_end(ap);

	return rvalue;
}