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Justine Tunney 2020-06-15 07:18:57 -07:00
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libc/fmt/vsnprintf.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ This program is free software; you can redistribute it and/or modify │
│ it under the terms of the GNU General Public License as published by │
│ the Free Software Foundation; version 2 of the License. │
│ │
│ This program is distributed in the hope that it will be useful, but │
│ WITHOUT ANY WARRANTY; without even the implied warranty of │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
│ General Public License for more details. │
│ │
│ You should have received a copy of the GNU General Public License │
│ along with this program; if not, write to the Free Software │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
│ 02110-1301 USA │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/bits/safemacros.h"
#include "libc/dce.h"
#include "libc/fmt/fmt.h"
#include "libc/limits.h"
#include "libc/runtime/runtime.h"
struct SprintfStr {
char *p;
size_t i, n;
};
static int vsnprintfputchar(unsigned char c, struct SprintfStr *str) {
if (str->i < str->n) {
if (str->p) str->p[str->i] = c;
str->i++;
} else {
if (!IsTrustworthy() && str->i >= INT_MAX) abort();
str->i++;
}
return 0;
}
/**
* Formats string to buffer.
*
* @param buf stores output and a NUL-terminator is always written,
* provided buf!=NULL && size!=0
* @param size is byte capacity buf
* @return number of bytes written, excluding the NUL terminator; or,
* if the output buffer wasn't passed, or was too short, then the
* number of characters that *would* have been written is returned
* @throw EOVERFLOW when a formatted field exceeds its limit, which can
* be checked by setting errno to 0 before calling
* @see libc/fmt/fmt.h for further documentation
*/
int(vsnprintf)(char *buf, size_t size, const char *fmt, va_list va) {
struct SprintfStr str = {buf, 0, size};
palandprintf(vsnprintfputchar, &str, fmt, va);
if (str.p && str.n) {
str.p[min(str.i, str.n - 1)] = '\0';
}
return str.i;
}