From: Tanaka Akira <akr@...>
Date: 2009-02-04T13:47:52+09:00
Subject: [ruby-core:21824] Re: [Feature #908] Should be an easy way of reading N characters from am I/O stream

In article <49884f719007d_84959c52d4271d@redmine.ruby-lang.org>,
  James Gray <redmine@ruby-lang.org> writes:

> My use case was that I peek ahead in the stream to determine what kind of line endings it has.  I just grab a block of characters and see if I find any standard line endings in there.  This was pretty challenging in Ruby 1.9, because just reading some bytes meant I had great chances to have picked up invalid data.  Then, when I hit it with a Regexp to find the line endings, an Exception is raised.

Ruby has similar situation.  Ruby peeks magic comments of a
script.

It reads some bytes and put back it to IO buffer.  It is
done on byte layer.  IO#read(n) and IO#ungetbyte is usable.

For line terminator detection, we need encoding conversion
because line terminator is defined in character layer, not
byte layer.

Since the data may be incomplete, String#encode may cause an
error.  Encoding::Converter can be used instead.
-- 
Tanaka Akira