[Haskell-cafe] Binary I/O

[Pepe Iborra]

On 02/04/2007, at 16:26, Daniel Brownridge wrote:

> Hello.
>
> I am a Computer Science student attempting to write an emulator  
> using Haskell.
> One of my main design choices is how to deal with machine code.
> Clearly it is possible to represent 0's and 1's as ASCII  
> characters, however it strikes me that it would be much nicer to  
> the I/O using raw binary. I don't seem to be able to find much  
> documentation on this.
> Does anybody know how it's done, or can point me in the direction  
> of some resources.
>
>

Imho, just read directly to an Array and work with that.
Probably you want to look at the OmegaGB Gameboy Emulator project for  
examples.

http://www.mutantlemon.com/omegagb

The code for loading ROM images to an Array of Words:

http://darcs.mutantlemon.com/omegagb/src/RomImage.hs

After that, opcodes are easily parsed by pattern matching on the  
hexadecimal values, e.g. see the mcti function in the Cpu module:

http://darcs.mutantlemon.com/omegagb/src/Cpu.hs

It would be nicer to write a Data.Binary instance for the Instruction  
datatype and use that to do the parsing, but I don't think that  
loading ROM files is a major speed concern here.

Another interesting resource you may want to look at for your  
emulator code can be ICFPC'06 Universal Machine implementations. Don  
Stewart has a page with a few highly performant implementations (and  
there are benchmarks too, yay!):

http://www.cse.unsw.edu.au/~dons/um.html

Cheers
pepe