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List:       jacorb-bugs
Subject:    [jacorb-bugs] [Bug 501] New: Bad use of '+' instead of '|' to
From:       bugzilla-daemon () inf ! fu-berlin ! de
Date:       2004-07-10 1:43:21
Message-ID: E1Bj6td-0003cQ-00 () berners ! inf ! fu-berlin ! de
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http://www.jacorb.org/cgi-bin/bugzilla/show_bug.cgi?id=501

           Summary: Bad use of '+' instead of '|' to convert byte[] to int
           Product: JacORB
           Version: 2.2
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ORB
        AssignedTo: gerald.brose@acm.org
        ReportedBy: jjowdy@levanta.com
         QAContact: jacorb-bugs@lists.spline.inf.fu-berlin.de


This affects at least these two files:

org/jacorb/orb/giop/Messages.java
org/jacorb/orb/CDRInputStream.java


E.g., Messages::readULong(...)
{
        if( little_endian )
        {
            return (( (buf[pos+3] & 0xff) << 24) +
                    ( (buf[pos+2] & 0xff) << 16) +
                    ( (buf[pos+1] & 0xff) <<  8) +
                    ( (buf[pos]   & 0xff) <<  0));
        }
        else //big endian
        {
            return (( (buf[pos]   & 0xff) << 24) +
                    ( (buf[pos+1] & 0xff) << 16) +
                    ( (buf[pos+2] & 0xff) <<  8) +
                    ( (buf[pos+3] & 0xff) <<  0));
        }
}

If little endian and the top bit of buf[pos+3] is set, or if big endian and top
bit of buf[pos] is set, you'll get incorrect results. 

Compare with this code to see why:

public class IntTest
{
        public static void main(String[] args)
        {
                byte[] bytes = { (byte)0xFF, (byte)0xFF, (byte)0xFF, (byte)0xFF };
                System.out.println(0xFFFFFFFF);
                System.out.println(
                        (bytes[0] << 24) |
                        (bytes[1] << 16) |
                        (bytes[2] << 8) |
                        (bytes[3] << 0)
                );
                System.out.println(
                        (bytes[0] << 24) +
                        (bytes[1] << 16) +
                        (bytes[2] << 8) +
                        (bytes[3] << 0)
                );
        }
}



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