From: adam@address.invalid   
      
   Wolfgang Schelongowski wrote:   
   > Adam  writes:   
      
   >> I gather decompiling (as opposed to disassembling) still involves a   
   >> lot of guesswork.   
   >   
   > It did so last times I decompiled. A little bit of knowledge about   
   > code generation and the linkage editor is necessary.   
      
   I hadn't thought about library routines being linked in, but at   
   least I knew that it was compiled C and all parameters were passed   
   on the stack.  Also, I didn't need to decipher the entire thing or   
   recreate the C source, but just figure out certain parts of it and   
   what certain bits of the input represented.   
      
   >> For a while I was part of the team working on the JL2005B/C/D driver   
   >> for gphoto2.   
   >   
   > The current mailing list appears not to be very helpful to me.   
      
   I wouldn't know.  I haven't been involved with it in over a year.   
      
   > In my misspent youth^W^W^WWhile studying physics   
      
   Part of my misspent youth /was/ wasted in college "freshman   
   physics".  The course was so awful that it was one of the reasons I   
   left that university, and I wasn't even a physics major!  It was one   
   of the very few times that a course was so bad that it killed any   
   further interest I might have had in that field.   
      
   >>                  At one point I had to tell the "clean room" end   
   >> that only the bottom seven bits of a particular byte were   
   >> significant, but I couldn't suggest any code for that, even though   
   >> 99% of C programmers would have taken care of it the same way.   
   >   
   > Oh no, there is eternal dissent between the honorable members of   
   > the hex tribe and the heathen idol worshippers of the octal !!!11!   
      
   Well, besides "n & 127" (in any base) which is what I think almost   
   every C programmer would have used, there are numerous other   
   (although less efficient) ways that a programmer /could/ get only   
   the bottom seven bits of a byte:   
   	a) n modulo 128   
   	b) if n >= 128 then subtract 128; repeat   
   	c) shift byte left by 1 bit, then shift right by 1 bit   
   and I'm sure you can think of others.  As part of the "dirty room"   
   team, I couldn't suggest _any_ actual code, as I might   
   unintentionally disclose some of the copyrighted Windows driver code   
   I'd seen in the disassembly.   
      
   Adam   
   --   
   Registered Linux User #536473   
      
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