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#include "stdio_impl.h"
static size_t sn_write(FILE *f, const unsigned 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 = { .lbf = EOF, .write = sn_write, .lock = -1 };
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.buf_size = n;
f.buf = f.wpos = (void *)s;
f.wbase = f.wend = (void *)(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;
}
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