>From
>http://www.openbsd.org/cgi-bin/cvsweb.cgi/src/lib/libc/stdio/vsnprintf.c?rev=1.5&content-type=text/x-cvsweb-markup,
> ...
[..]
#if defined(LIBC_SCCS) && !defined(lint)
static char rcsid[] = "$OpenBSD: vsnprintf.c,v 1.5 1998/07/27 02:28:28 millert Exp $";
#endif /* LIBC_SCCS and not lint */
#include <limits.h>
#include <stdio.h>
int
vsnprintf(str, n, fmt, ap)
char *str;
size_t n;
const char *fmt;
_BSD_VA_LIST_ ap;
{
int ret;
char dummy;
FILE f;
/* While snprintf(3) specifies size_t stdio uses an int internally */
if (n > INT_MAX)
n = INT_MAX;
/* Stdio internals do not deal correctly with zero length buffer */
if (n == 0) {
str = &dummy;
n = 1;
}
f._file = -1;
f._flags = __SWR | __SSTR;
f._bf._base = f._p = (unsigned char *)str;
f._bf._size = f._w = n - 1;
ret = vfprintf(&f, fmt, ap);
*f._p = 0;
return (ret);
}
Look here if you want vfprintf:
http://www.openbsd.org/cgi-bin/cvsweb.cgi/src/lib/libc/stdio/vfprintf.c?rev=1.17&content-type=text/x-cvsweb-markup
Penned by Christoph Egger on Sun, Jan 27, 2002 at 02:00:59PM +0100, we have:
| On Sun, 27 Jan 2002, Andreas Beck wrote:
|
| > Christoph Egger <[EMAIL PROTECTED]> wrote:
| >
| > > > Will it write a trailing \0 ? If not, that should be generated, to avoid
| > > snip from the manual page:
| > >
| > > Return value
| > > These functions return the number of characters printed
| > > (not including the trailing `\0' used to end output to
| > > strings). snprintf and vsnprintf do not write more than
| > > size bytes (including the trailing '\0'), and return -1 if
| > > the output was truncated due to this limit. (Thus until
| > > glibc 2.0.6. Since glibc 2.1 these functions follow the
| > > C99 standard and return the number of characters (exclud
| > > ing the trailing '\0') which would have been written to
| > > the final string if enough space had been available.)
| >
| > That's the point. I cannot derive from that, if snprintf will
| > terminate the string, if an overflow occurs, without leaving a little
| > doubt. Does anyone have the C99 standard ready and can confirm, that
| > snprintf is supposed to terminate the string in _any_ case?
| >
| > If that is not the case or unsure, I would suggest to explicitly
| > terminate the string after every usage of snprintf using something
| > like
| >
| > #define TERMINATE_ARRAY(x) x[sizeof(x)-1]='\0'
| > #define TERMINATE_POINTER(x,len) x[len-1]='\0'
|
|
| AFAIK sprintf() and snprintf() are nothing other than this:
|
| int sprintf(char *str, const char *format, ...)
| {
| int rc;
| va_list ap;
|
| va_start(ap, format);
|
| rc = vsnprintf(str, 0xFFFFFFFF, format, ap);
|
| va_end(ap);
|
| return rc;
| }
|
| int snprintf(char *str, size_t size, const char *format, ...)
| {
| int rc;
| va_list ap;
|
| va_start(ap, format);
|
| rc = vsnprintf(str, size, format, ap);
|
| va_end(ap);
|
| return rc;
| }
|
|
|
| So, the question is, what does vsnprintf() ?
|
|
|
| CU,
|
| Christoph Egger
| E-Mail: [EMAIL PROTECTED]
--
Todd Fries .. [EMAIL PROTECTED]
