41 lines
847 B
C
41 lines
847 B
C
#include <stdio.h>
|
|
#include <limits.h>
|
|
#include <string.h>
|
|
#include <errno.h>
|
|
#include <stdint.h>
|
|
|
|
static size_t sn_write(FILE *f, const char *s, size_t l)
|
|
{
|
|
size_t k = f->wend - f->wpos;
|
|
if (k > l) k = l;
|
|
memcpy(f->wpos, s, k);
|
|
f->wpos += k;
|
|
/* pretend to succeed, but discard extra data */
|
|
return l;
|
|
}
|
|
|
|
int vsnprintf(char *restrict s, size_t n, const char *restrict fmt, va_list ap)
|
|
{
|
|
int r;
|
|
char b;
|
|
FILE f = { .write = sn_write };
|
|
|
|
if (n-1 > INT_MAX-1) {
|
|
if (n) {
|
|
errno = EOVERFLOW;
|
|
return -1;
|
|
}
|
|
s = &b;
|
|
n = 1;
|
|
}
|
|
|
|
/* Ensure pointers don't wrap if "infinite" n is passed in */
|
|
if (n > (char *)0+SIZE_MAX-s-1) n = (char *)0+SIZE_MAX-s-1;
|
|
f.wpos = s;
|
|
f.wend = (s+n);
|
|
r = vfprintf(&f, fmt, ap);
|
|
|
|
/* Null-terminate, overwriting last char if dest buffer is full */
|
|
if (n) f.wpos[-(f.wpos == f.wend)] = 0;
|
|
return r;
|
|
}
|