FormattedRead hex string

[monarch_dodra]

On Monday, 24 September 2012 at 15:05:54 UTC, Jason Spencer wrote:
> I imagine there's a slick way to do this, but I'm not seeing it.
>
> I have a string of hex digits which I'd like to convert to an 
> array of 8 ubytes:
>
> 0123456789abcdef --> [0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 
> 0xEF]
>
> I'm looking at std.format.formattedRead, but the documentation 
> is...lightish.  First of all, it seems there's no format 
> specifier except %s on reads and type information is gleaned 
> from the args' types.  I was able to experiment and show that 
> %x works, but no documentation on exactly how.
>
> Second, array syntax seems to work only if there's some 
> delimiter.  With:
>
> void main(string[] args)
> {
>    ubyte[8] b;
>
>    formattedRead(args[1], "%(%s%)", &b);
> }
>
> I get
>
> std.conv.ConvOverflowException at C:\Tools\D\dmd2\windows\bin\..\..\src\phobos\std\
> conv.d(2006): Overflow in integral conversion
>
> at least once. :)  But that makes sense--hard to tell how many 
> input chars to assign to one byte versus another (although it 
> seems to me a hungry algorithm would work--saturate one type's 
> max and move to the next.)
>
> There doesn't seem to be any support for field sizes or counts 
> in formatted read, similar to old C "%16x".  This barks at me 
> right away--"%1 not supported."
>
> I know I could read (in this case) as two longs or a uint16, 
> but I don't want to deal with endianess--just data.
>
> Is there some trick to use the fact that b is fixed size 8 
> bytes and know that requires 16 hex digits and converts 
> automatically?  Is there some other suggestion for how to do 
> this eloquently?  I can play around with split and join, but it 
> seemed like there is probably some way to do this directly that 
> I'm  not seeing.
>
> Thanks!
> Jason

I think that you are not supposed to use a static array: If there 
are not EXACTLY as many array elements as there are parse-able 
elements, then the formatted read will consider the parse to have 
failed.

Try this, it's what you want, right?

--------
void main()
{
     string s = "ffff fff ff f";
     ushort[] vals;
     formattedRead(s, "%(%x %)", &vals);
     writefln("%(%s - %)", vals);
}
--------
65535 - 4095 - 255 - 15
--------

Regarding the %1x, well, I guess it just isn't supported (yet?)