getc

/*
 *  call-seq:
 *     ios.getc   => fixnum or nil
 *  
 *  Gets the next 8-bit byte (0..255) from <em>ios</em>. Returns
 *  <code>nil</code> if called at end of file.
 *     
 *     f = File.new("testfile")
 *     f.getc   #=> 84
 *     f.getc   #=> 104
 */

VALUE
rb_io_getc(io)
    VALUE io;
{
    OpenFile *fptr;
    FILE *f;
    int c;

    GetOpenFile(io, fptr);
    rb_io_check_readable(fptr);
    f = fptr->f;

  retry:
    READ_CHECK(f);
    clearerr(f);
    TRAP_BEG;
    c = getc(f);
    TRAP_END;

    if (c == EOF) {
        if (ferror(f)) {
            clearerr(f);
            if (!rb_io_wait_readable(fileno(f)))
                rb_sys_fail(fptr->path);
            goto retry;
        }
        return Qnil;
    }
    return INT2FIX(c & 0xff);
}