From: Aaron Patterson <aaron@...>
Date: 2009-10-03T02:22:42+09:00
Subject: Re: Rolling String Buffer needed

On Oct 2, 2009, at 9:55 AM, Matt Brooks wrote:

> I have constant ascii data streaming in, each message terminated with
> \n, currently I look for something specific and throw away the other
> stuff and then look for something specific and throw away the other
> stuff...etc
>
> What I need now is a way to keep everything received exactly as is,  
> in a
> rolling string buffer.  So say the last 100 messages (a message to  
> me is
> a whole string terminated with \n) which could be available at any  
> time
> in a string variable, maybe called: last_100_messages
>
> And when I append another variable length message/line to this string
> buffer that ends with a \n, I want the oldest message to go
> away(specifically go into a text file), so ALL messages are  
> available in
> a text file for later.
>
>
>
>
> Problem is the append << method, puts the new lines on the end of the
> string, I want the end of the string to always be the oldest message
> that is about to be placed into a txt file that has all messages at  
> some
> point.
>
> So in short, a rolling buffer that holds a specific amount of \n
> terminated messages(100 strings terminated with \n's), not a specific
> amount of data/bytes.  Where the front of the string holds the most
> recent addition to the rolling buffer, and where the end of the string
> holds the message that is about to be added to a file.
>
>
>
>
> Also if easier, an array where each element is one message would  
> work as
> well, where array[0] is the most recent message.
>
> I have been looking at strio, but not sure how to use it in this  
> manner.

I think you could just write a class that wraps up a list.  Something  
like this:

class MyBuff
   def initialize max_size, filename
     @max_size = max_size
     @list = []
     @file = File.open(filename, 'wb')
   end

   def push string
     @list.push string
     while @list.length > @max_size
       @file.write @list.pop
     end
   end

   def [] i
     @list[i]
   end
end

---
Aaron Patterson
http://tenderlovemaking.com