#include <stdio.h>

#include <stdlib.h>

#include <stdarg.h>

#include "portability.h"

/*

 * vasprintf() and asprintf() for platforms with a C99-compliant

 * snprintf() - so that, if you format into a 1-byte buffer, it

 * will return how many characters it would have produced had

 * it been given an infinite-sized buffer.

 */

int

pcap_vasprintf(char **strp, const char *format, va_list args)

{

	char buf;

	int len;

	size_t str_size;

	char *str;

	int ret;

	/*

	 * XXX - the C99 standard says, in section 7.19.6.5 "Thes

	 * nprintf function":

	 *

	 *    The snprintf function is equivalent to fprintf, except that

	 *    the output is written into an array (specified by argument s)

	 *    rather than to a stream.  If n is zero, nothing is written,

	 *    and s may be a null pointer.  Otherwise, output characters

	 *    beyond the n-1st are discarded rather than being written

	 *    to the array, and a null character is written at the end

	 *    of the characters actually written into the array.

	 *

	 *        ...

	 *

	 *    The snprintf function returns the number of characters that

	 *    would have been written had n been sufficiently large, not

	 *    counting the terminating null character, or a negative value

	 *    if an encoding error occurred. Thus, the null-terminated

	 *    output has been completely written if and only if the returned

	 *    value is nonnegative and less than n.

	 *

	 * That doesn't make it entirely clear whether, if a null buffer

	 * pointer and a zero count are passed, it will return the number

	 * of characters that would have been written had a buffer been

	 * passed.

	 *

	 * And, even if C99 *does*, in fact, say it has to work, it

	 * doesn't work in Solaris 8, for example - it returns -1 for

	 * NULL/0, but returns the correct character count for a 1-byte

	 * buffer.

	 *

	 * So we pass a one-character pointer in order to find out how

	 * many characters this format and those arguments will need

	 * without actually generating any more of those characters

	 * than we need.

	 *

	 * (The fact that it might happen to work with GNU libc or with

	 * various BSD libcs is completely uninteresting, as those tend

	 * to have asprintf() already and thus don't even *need* this

	 * code; this is for use in those UN*Xes that *don't* have

	 * asprintf().)

	 */

	len = vsnprintf(&buf, sizeof buf, format, args);

	if (len == -1) {

		*strp = NULL;

		return (-1);

	}

	str_size = len + 1;

	str = malloc(str_size);

	if (str == NULL) {

		*strp = NULL;

		return (-1);

	}

	ret = vsnprintf(str, str_size, format, args);

	if (ret == -1) {

		free(str);

		*strp = NULL;

		return (-1);

	}

	*strp = str;

	/*

	 * vsnprintf() shouldn't truncate the string, as we have

	 * allocated a buffer large enough to hold the string, so its

	 * return value should be the number of characters written.

	 */

	return (ret);

}

int

pcap_asprintf(char **strp, const char *format, ...)

{

	va_list args;

	int ret;

	va_start(args, format);

	ret = pcap_vasprintf(strp, format, args);

	va_end(args);

	return (ret);

}