From: Mark Hubbart <discord@...>
Date: 2004-07-15T03:34:39+09:00
Subject: Re: How to encode binary for http.post()


On Jul 5, 2004, at 2:43 PM, Randy Lawrence wrote:

> I'm having problems posting a binary string (around 256 characters) 
> using http.post().
>
> When I encode the binary string using Base64.encode64() and then 
> http.post() the data, the "+" characters are replaced by " " so the 
> data is no longer valid.
>
> I've tried URI.escape(Base64(encode64(data))) to post and 
> URI.unescape(data) to receive but the same problem appears.
>
> Any suggestions?

The rfc that describes the base64 encoding has a slightly different 
version of the encoding that is url/filename-safe. It is rather simple 
to tr the characters around to get the right results:

   http://www.faqs.org/rfcs/rfc3548.html

something like this:

   require 'base64'
     => nil
   def Base64.encode64url(str)
     Base64.encode64(str).tr("+/","-_")
   end
     => nil
   def Base64.decode64url(str)
     Base64.decode64(str.tr("-_","+/"))
   end
     => nil
   (data = (0..255).inject(""){|a,v|a<<v}).size # all bytes from 0 to 255
     => 256
   (encoded = Base64.encode64url(data)).count "+/" # any prohibited 
characters?
     => 0
   # raise error if encoded data is incorrect
   x=0; Base64.decode(encoded).each_byte{|b| raise if x!=b; x=b+1}; 0
     => 0

I wonder if this should be added to the module? In the rfc, it seems to 
be a standard extension, for use in filenames, urls, etc.

Additionally, it might be nice to have a base32 implementation shipped. 
I've coded it myself twice, I recall, and I think it takes all of 20 
loc at most.

cheers,
Mark