From: Bill Kelly <billk@...>
Date: 2006-03-19T14:45:37+09:00
Subject: Re: safe way to calc md5 on very large files

From: "rtilley" <rtilley@vt.edu>
>
> I'm calculating md5 checksums on very large files (2 GB). This is a safe 
> way to do so, right? Also... is the file closed when the block exits? 
> I'm using 'rb' as this is used on Windows and Linux computers.
> 
> md5 = Digest::MD5.new()
> File.open(file, 'rb').each {|line| md5.update(line)}

Hi - does the file really contain text lines?  Or is it a file
full of binary data.  If it's a binary file, there may be no
guarantee the whole thing isn't one very long "line".  In that
case I'd recommend reading it in chunks.

Untested:

md5 = Digest::MD5.new()
File.open(file, 'rb') do |io|
  while (buf = io.read(4096)) && buf.length > 0
    md5.update(buf)
  end
end


Regards,

Bill