(this post is pure geek - you can move along to the next blog in your RSA feed : )


                                                                


I have always liked the Java programming language; still do, but today I found a weird one.

I was writing code to send stream of bytes to an LDAP (Lightweight Directory Access Protocol) server, doing address resolutions - nothing fancy. Standard BSD socket stuff. I was reading the bytes to read as hex integers out of a text file - 04 5a 4b 40 etc etc etc - and converting each pair of characters to a byte value.

I'd come up with a way that seemed towork when I ran into a weird one. I was reading these two-digit strings in and using parseByte to turn them into byte values:

            s = byteFile.readLine();                            
                         //this reads in a line of text full of those two-char bytes - "04 64 4c 6b 6f..."
            String[] byteStrings = s.split(" ");              
                         //this creates an array of short strings, each two bytes long."04", "64", "4c", "6b", "6f"....
            for (int i=0; i<byteStrings.length;i++)
                 byte b = Byte.parseByte(byteStrings[i],16);
                               //this goes through and turns each of those short strings into a byte value

to get the bytes to stream out through the socket. Suddenly I get an error -

            Exception in thread "main" java.lang.NumberFormatException: Value out of range. Value:"a5" Radix:16

Yep, that's right. a1 in hex - 161 to you and me, in decimal - is outside of the byte range, which is (I thought) 0-255.

Okay, sure - it's "signed byte", right? And that's using up one of the bits, making the range -128 to 127?

Doesn't seem like that's the problem.

I messed with this for quite a while, and couldn't figure it out; finally a friend suggested this route of investigation:

                    byte b = (byte) Integer.parseInt(byteStrings[i],16);

...and that WORKS.

Java is saying "Hey, I can't turn that string into a byte for you, but I can turn it into an INTEGER, and I can turn THAT Integer into a byte".

It reminds me of when my eldest brother, Chuck, was very sick as a small child - maybe age 4 or 5. He had some sort of respiratory illness that wouldn't go away - it just kept hanging on and on.

Eventually the doctor told my father to take Chuck and douse him in icewater.

Dad said "But...but that'll give him pneumonia!"

The doctor said "Yes, it will - and pneumonia we can cure!"

If you can't solve one problem, turn that problem into a problem you can solve.