Binary Read

gistfile1.rs

* Reads a ROM file and returns a vector containing
 * its bytes if successful. Otherwise an error string
 * if the file is too large or IoError is raised */
fn read_rom(file_path: String) -> Result<Vec<u8>,String> {
    
    match File::open(&Path::new(file_path)).read_to_end() {

        Ok(rom_contents) =>  {
            /* Programs start at address 0x200, in original implementation
             * 0x000 - 0x1FF reserved for VM, just pad start of mem with 
             * 0s in this case */
            let start_mem : Vec<u8>  = iter::repeat(0u8).take(START_RAM).collect();
            let mem = start_mem + rom_contents.as_slice();
            let size = mem.len();

            if size <= MAX_RAM { 
                    Ok(mem)                    
            } else { /* Memory read in from game ROM is too large */
                Err(format!("game image is too large 
                    ({} bytes), must be a maximum of {} bytes"
                    ,size , MAX_RAM - START_RAM).to_string())
            }
        },
        /* Error reading file */
        Err(e) => Err(e.detail.unwrap_or("".to_string()))       
    }
}