source: asp3_tinet_ecnl_rx/trunk/musl-1.1.18/src/stdio/vswprintf.c@ 337

#include "stdio_impl.h"
#include <limits.h>
#include <string.h>
#include <errno.h>
#include <stdint.h>
#include <wchar.h>

struct cookie {
        wchar_t *ws;
        size_t l;
};

static size_t sw_write(FILE *f, const unsigned char *s, size_t l)
{
        size_t l0 = l;
        int i = 0;
        struct cookie *c = f->cookie;
        if (s!=f->wbase && sw_write(f, f->wbase, f->wpos-f->wbase)==-1)
                return -1;
        while (c->l && l && (i=mbtowc(c->ws, (void *)s, l))>=0) {
                s+=i;
                l-=i;
                c->l--;
                c->ws++;
        }
        *c->ws = 0;
        if (i < 0) {
                f->wpos = f->wbase = f->wend = 0;
                f->flags |= F_ERR;
                return i;
        }
        f->wend = f->buf + f->buf_size;
        f->wpos = f->wbase = f->buf;
        return l0;
}

int vswprintf(wchar_t *restrict s, size_t n, const wchar_t *restrict fmt, va_list ap)
{
        int r;
        FILE f;
        unsigned char buf[256];
        struct cookie c = { s, n-1 };

        memset(&f, 0, sizeof(FILE));
        f.lbf = EOF;
        f.write = sw_write;
        f.buf_size = sizeof buf;
        f.buf = buf;
        f.lock = -1;
        f.cookie = &c;
        if (!n) {
                return -1;
        } else if (n > INT_MAX) {
                errno = EOVERFLOW;
                return -1;
        }
        r = vfwprintf(&f, fmt, ap);
        sw_write(&f, 0, 0);
        return r>=n ? -1 : r;
}