From: "Ara.T.Howard" <ahoward@...>
Date: 2003-12-05T12:32:06+09:00
Subject: Re: how to navigate in a file ?

On Fri, 5 Dec 2003, Boris "BXS" Schulz wrote:

> Date: Fri, 05 Dec 2003 01:58:22 +0100
> From: Boris "BXS" Schulz <bxs@hadiko.de>
> Newsgroups: comp.lang.ruby
> Subject: how to navigate in a file ?
> 
> Hi,
> 
> I would like to open a binary file and read its contents.
> The opening is no problem, but if I wanted to jump to a specific byte, 
> how would I do that ? Also, how would I read this specific byte ? I have 
> some code reading the byte, but it quite ugly. Is there something like 
> DATA.readbyte(position) ?
> 
> greetings, BXS

~/eg/ruby > cat byte.rb

require 'mmap' # guy's package from the RAA - get it!

binary = 'bin.dat'

# create a binary file
open(binary, 'wb') do |f|
  bytes = [1 << 2, 1 << 1].pack 'cc'
  f.write bytes
end

# memory map it (man mmap)
mmap = Mmap.new binary, 'r'
byte_a, byte_b = mmap[0], mmap[1]

print byte_a
print byte_b
puts

~/eg/ruby > ruby byte.rb
42


in addition to being really easy to use, this package is _really_ fast.

-a
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