From: Adam Shelly <adam.shelly@...>
Date: 2008-03-08T02:58:38+09:00
Subject: Re: IO#Foreach -- Max line length

On 3/6/08, Peņa, Botp <botp@delmonte-phil.com> wrote:
> On Behalf Of Tristin Davis:
> # But by the time you actually get count, isn't the line
> # already read in
> # memory.  So if the line is 7 gigabytes, it'll probably crash
> # the system.
>
> read will accept arg on how many bytes to read.
>
> so how about,
>
...
> irb(main):043:0> File.open "test.rb" do |f| while x=f.read(2); p x; end; end

That solution essentially ignores linebreaks.
If you want to read up to a linebreak or N characters, whichever comes
first, you could one of these:

------
class IO
  #read by characters
  def for_eachA(linelen)
    c=0
    while (c)
      buf=''
      linelen.times {
        break unless c=getc
        buf<<c
        break if c.chr== $/
      }
      yield buf
    end
  end

  #read by lines
  def for_eachB(linelen)
    re = Regexp.new(".*?#{Regexp.escape($/)}")
    buf=''
    while (line = read(linelen-buf.length))
      buf = (buf+line).gsub(re){|l| yield l;''}
      if buf.length == linelen
        yield buf
        buf=''
      end
    end
    yield buf
  end
end

File.open("foreach.rb") do |f|
f.for_eachA(10){|l| p l}
end

File.open("foreach.rb") do |f|
f.for_eachB(10){|l| p l}
end
------

I'd guess the second version would be faster, but I didn't time it.

-Adam