/*
* snprintf() quicky using temporary files.
* Not stress tested, but it seems to work.
*
* Returns the number of bytes that would have been output by printf.
* Does not check whether a negative value if passed in for n (as it's unsigned);
* some implementations cast n to int and than compare with 0.
*
* Casper Dik (Casper.Dik@Holland.Sun.COM)
*/

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

int snprintf(char * buf, size_t n, const char *fmt, ...)
{
va_list ap;
int ret;

va_start(ap, fmt);
ret = vsnprintf(buf, n, fmt, ap);
va_end(ap);
return ret;
}

static char template[] = "/tmp/snprintfXXXXXX";

int vsnprintf(char *buf, size_t n, const char *fmt, va_list ap)
{
char templ[sizeof(template)];
int s;
int ret, cnt = 0, nread;
FILE *fp;

strcpy(templ,template);

s = mkstemp(templ);

if (s < 0)
return -1;

(void) unlink(templ);

fp = fdopen(s, "w+");

if (fp == NULL) {
close(s);
return -1;
}

ret = vfprintf(fp, fmt, ap);

if (ret < 0 || fseek(fp, 0, SEEK_SET) < 0) {
fclose(fp);
return -1;
}

while (cnt < n && (nread = fread(buf + cnt, 1, n - cnt, fp)) > 0)
cnt += nread;

buf[cnt-1] = '\0'; /* cnt is atmost n */

fclose(fp);
return ret;
}