From: Eleanor McHugh <eleanor@...>
Date: 2011-07-31T02:34:32+09:00
Subject: Re: How to read contents of a Memory Mapped File created in ruby through some other app. like .Net?

On 30 Jul 2011, at 11:51, Premjeet Singh H. wrote:
> We are creating a Memory Mapped file in ruby using win32-mmap gem.
> 
> The code used for creating the file is given below:
> 
> require 'win32/mmap'
> include Win32
> 
> mmap = MMap.new(:name => 'myFile', :size => 2000)
> 
> mmap.foo = 'hello'
> mmap.bar = 27
> 
> sleep 100
> 
> mmap.close
> 
> Now, when we try to read this file in our other application which is in
> .Net we get this string {"foo"hello"bari
> 
> There were some special symbols also in this string which can't be
> posted here so the sample file is attached as an attachment.
> 
> So how can we read its contents without the special symbols and without
> these foo and bar variables in the other application?
> 
> Also is there any way we can write the string directly into the Memory
> Mapped file without other variables like here we have used .foo and
> .bar?

I can't speak with authority on win32-mmap as I don't develop for Windows systems. However I can offer some general observations regarding memory-mapped files:

1. ensure you have the file open in binary mode in all programs reading it;
2. keep specific data items at fixed locations in the file;
3. pay attention to concurrency issues - i.e. use file locks defensively;
4. serialise data into an intermediate format that can be decoded in all languages used;
5. use pipes instead - for most real-world use cases they're much less pain to work with.


Ellie

Eleanor McHugh
Games With Brains
http://feyeleanor.tel
----
raise ArgumentError unless @reality.responds_to? :reason