From: Mathieu Bouchard <matju@...>
Date: 2001-07-10T08:19:34+09:00
Subject: [ruby-talk:17565] Re: writing arbitrary data to a socket


On Tue, 10 Jul 2001, Al Chou wrote:

> typedef struct all_thing {
> 	uint32_t	a;		
> 	uint8_t		b;	
> 	uint8_t		c;	
> 	int8_t		d;	
> 	uint8_t		e;	
> 	uint32_t	f;	
> 	uint64_t	g;	
> 	char_t		data[0];	
> } thing;
> where the final member is an arbitrarily long sequence of characters.
> Do I need to convert my data to a string of ASCII characters in order to
> write this struct to a socket? 



Into a String, yes, but Strings contain arbitrary data first and foremost,
and then only you have methods that support ASCII.

You can use Array#pack like this, to write an array of those values onto a
stream:

# 64bit hack assuming little-endian
foo.write([a,b,c,d,e,f,g&(1<<32-1),g>>32,data].pack("LCCcCLLLa*"))



Or you can use RubyX11's Type.rb to describe a struct like this:

class AllThing<Tuple; fields_are \
  [:a, Uint32],		
  [:b, Uint8],	
  [:c, Uint8],
  [:d, Int8],	
  [:e, Uint8],
  [:f, Uint32],
  [:g, Uint64],
  [:data, String8]
end	

and then:

bar = AllThing.new(a,b,c,d,e,f,g,data)
bar[0] # returns a
bar.a  # returns a
bar.class.xwrite(bar)

except you'll have to define Uint64 once beforehand (should take 3 lines)



matju