From: Tim Hammerquist <penryu@...>
Date: 2006-01-01T07:32:56+09:00
Subject: Re: A few questions of function and style from a newbie

Sven Johansson <sven_u_johansson@spray.se> wrote:
[ snip ]
> Using:
> require 'Digest/mp5'
> Dir['*'].each {|f|print f, " "; puts
> Digest::MD5.hexdigest(File.read(f)) if File.file? f}
>
> gives
>
> 001.mp3 6ce4ad47bfa79b6c0e48636040c1dfb9
> 002.mp3 6ce4ad47bfa79b6c0e48636040c1dfb9
> 0022-042.ogg 4cac5ea5e666942920aff937aa9b3ee5
> 0022-043.ogg 5947035093bbfa22a9e7cf6e69b82a4e
> 0022-044.ogg 4cac5ea5e666942920aff937aa9b3ee5
> 0022-045.ogg 4cac5ea5e666942920aff937aa9b3ee5
> 0022-046.ogg 4cac5ea5e666942920aff937aa9b3ee5
> 0022-047.ogg 4cac5ea5e666942920aff937aa9b3ee5
> [snip]
>
> which clearly isn't good. However, both your suggestested
> alternatives above work just fine. It would seem that binary
> mode really is a must on Win32 - exhanging 'rb' for 'r' in
> those suggestions gives me the hash repeat problem again. Good
> to know.

Just for our edification, would you run this following code on
those same files?

require 'digest/md5'

files = Dir['*'].select { |f| File.file?(f) }

files.each { |filename|
    fs_size = File.size(filename) # get size of file from OS

    data = File.read(filename)    # read the file
    data_size = data.length       # get the size of the data read

    hash = Digest::MD5.hexdigest(data)  # calculate hash

    # compare amount of data on filesystem
    #  with amount of data read
    puts "#{hash} - #{filename}: #{data_size}/#{fs_size}"
}


If my guess is correct, you should get some strange results.
Please post these results, no matter the outcome, to the group
so we can preserve a real-world example.

Cheers!
Tim Hammerquist