source: azure_iot_hub/trunk/musl-1.1.18/src/stdio/ftell.c@ 389

#include "stdio_impl.h"
#include <limits.h>
#include <errno.h>

off_t __ftello_unlocked(FILE *f)
{
        off_t pos = f->seek(f, 0,
                (f->flags & F_APP) && f->wpos > f->wbase
                ? SEEK_END : SEEK_CUR);
        if (pos < 0) return pos;

        /* Adjust for data in buffer. */
        return pos - (f->rend - f->rpos) + (f->wpos - f->wbase);
}

off_t __ftello(FILE *f)
{
        off_t pos;
        FLOCK(f);
        pos = __ftello_unlocked(f);
        FUNLOCK(f);
        return pos;
}

long ftell(FILE *f)
{
        off_t pos = __ftello(f);
        if (pos > LONG_MAX) {
                errno = EOVERFLOW;
                return -1;
        }
        return pos;
}

weak_alias(__ftello, ftello);

LFS64(ftello);