[vsipl++] Matlab IO

[Assem Salama]

Stefan Seefeld wrote:
> Assem,
>
> I just checked in my png bits, so your patch may already get a bit smaller.
>
> Assem Salama wrote:
>
>   
>> +  // generic reader that allows us to read a generic type and cast to another
>> +  
>> +  // the read function for real or complex depending of the view that was
>> +  // passed in
>> +  template <typename T1,
>> +            typename T2,
>> +	    typename ViewT>
>> +  void read(std::istream& is,ViewT v)
>> +  {
>> +    vsip::dimension_type const View_dim = ViewT::dim;
>> +    vsip::Index<View_dim> my_index;
>> +    vsip::impl::Length<View_dim> v_extent = extent(v);
>> +    T1 data;
>> +
>> +    // get num_points
>> +    vsip::length_type num_points = v.size();
>> +
>> +    // read all the points
>> +    for(vsip::index_type i=0;i<num_points;i++) {
>> +      is.read(reinterpret_cast<char*>(&data),sizeof(data));
>> +      put(v,my_index,T2(data));
>> +
>> +      // increment index
>> +      my_index = vsip::impl::next(v_extent,my_index);
>> +    }
>> +
>> +  }
>>     
>
> What's the reason for you using the 'put' function here, instead of
> some v method ? And, why are you casting to T2 in that call, instead
> of casting to ViewT::value_type ? As it stands, the above read function
> takes three distinct type parameters: T1, T2, and ViewT::value_type.
> I think only two are required (and the first may default to ViewT::value_type,
> actually).
>
> How portable is the above code ? It doesn't appear to care for endianness,
> i.e. you cast between 'char *' and T2 without any endianness check. If you
> write on a big-endian machine, and read it back on a little-endian
> machine, you will thus get different values.
>
>   
>> +  // a write function to output a view to a matlab file.
>> +  template <typename T,
>> +	    typename ViewT>
>> +  void write(std::ostream& os,ViewT v)
>> +  {
>> +    vsip::dimension_type const View_dim = ViewT::dim;
>> +    vsip::Index<View_dim> my_index;
>> +    vsip::impl::Length<View_dim> v_extent = extent(v);
>> +    T data;
>> +
>> +    // get num_points
>> +    vsip::length_type num_points = v.size();
>> +
>> +    // write all the points
>> +    for(vsip::index_type i=0;i<num_points;i++) {
>> +      data = get(v,my_index);
>> +      os.write(reinterpret_cast<char*>(&data),sizeof(data));
>>     
>
> The same point about endianness applies here.
>   

I disagree. We can write in either endian format and we chose to write 
in the native format of the machine.
>
>   
>> +
>> +      // increment index
>> +      my_index = vsip::impl::next(v_extent,my_index);
>> +    }
>> +
>> +  }
>>     
>
> Thanks,
> 		Stefan
>
>