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/* Copyright (C) 2018 Curtis McEnroe <june@causal.agency>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <wchar.h>
// From <https://en.cppreference.com/w/c/io/fwprintf#Notes>:
//
// While narrow strings provide snprintf, which makes it possible to determine
// the required output buffer size, there is no equivalent for wide strings
// (until C11's snwprintf_s), and in order to determine the buffer size, the
// program may need to call swprintf, check the result value, and reallocate a
// larger buffer, trying again until successful.
//
// snwprintf_s, unlike swprintf_s, will truncate the result to fit within the
// array pointed to by buffer, even though truncation is treated as an error by
// most bounds-checked functions.
int vaswprintf(wchar_t **ret, const wchar_t *format, va_list ap) {
*ret = NULL;
for (size_t cap = 2 * wcslen(format);; cap *= 2) {
wchar_t *buf = realloc(*ret, sizeof(*buf) * (1 + cap));
if (!buf) goto fail;
*ret = buf;
va_list _ap;
va_copy(_ap, ap);
int len = vswprintf(*ret, 1 + cap, format, _ap);
va_end(_ap);
if (len >= 0) return len;
if (errno != EOVERFLOW) goto fail;
}
fail:
free(*ret);
*ret = NULL;
return -1;
}
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