/*
 *  call-seq:
 *     file.truncate(integer)    => 0
 *  
 *  Truncates <i>file</i> to at most <i>integer</i> bytes. The file
 *  must be opened for writing. Not available on all platforms.
 *     
 *     f = File.new("out", "w")
 *     f.syswrite("1234567890")   #=> 10
 *     f.truncate(5)              #=> 0
 *     f.close()                  #=> nil
 *     File.size("out")           #=> 5
 */

static VALUE
rb_file_truncate(obj, len)
    VALUE obj, len;
{
    OpenFile *fptr;
    FILE *f;
    off_t pos;

    rb_secure(2);
    pos = NUM2OFFT(len);
    GetOpenFile(obj, fptr);
    if (!(fptr->mode & FMODE_WRITABLE)) {
        rb_raise(rb_eIOError, "not opened for writing");
    }
    f = GetWriteFile(fptr);
    fflush(f);
    fseeko(f, (off_t)0, SEEK_CUR);
#ifdef HAVE_TRUNCATE
    if (ftruncate(fileno(f), pos) < 0)
        rb_sys_fail(fptr->path);
#else
# ifdef HAVE_CHSIZE
    if (chsize(fileno(f), pos) < 0)
        rb_sys_fail(fptr->path);
# else
    rb_notimplement();
# endif
#endif
    return INT2FIX(0);
}