[ruby] ruby 1.9: invalid byte sequence in UTF-8

I'm writing a crawler in Ruby (1.9) that consumes lots of HTML from a lot of random sites.
When trying to extract links, I decided to just use .scan(/href="(.*?)"/i) instead of nokogiri/hpricot (major speedup). The problem is that I now receive a lot of "invalid byte sequence in UTF-8" errors.
From what I understood, the net/http library doesn't have any encoding specific options and the stuff that comes in is basically not properly tagged.
What would be the best way to actually work with that incoming data? I tried .encode with the replace and invalid options set, but no success so far...

If you don't "care" about the data you can just do something like:

search_params = params[:search].valid_encoding? ? params[:search].gsub(/\W+/, '') : "nothing"

I just used valid_encoding? to get passed it. Mine is a search field, and so i was finding the same weirdness over and over so I used something like: just to have the system not break. Since i don't control the user experience to autovalidate prior to sending this info (like auto feedback to say "dummy up!") I can just take it in, strip it out and return blank results.

attachment = file.read

begin
   # Try it as UTF-8 directly
   cleaned = attachment.dup.force_encoding('UTF-8')
   unless cleaned.valid_encoding?
     # Some of it might be old Windows code page
     cleaned = attachment.encode( 'UTF-8', 'Windows-1252' )
   end
   attachment = cleaned
 rescue EncodingError
   # Force it to UTF-8, throwing out invalid bits
   attachment = attachment.force_encoding("ISO-8859-1").encode("utf-8", replace: nil)
 end

I've encountered string, which had mixings of English, Russian and some other alphabets, which caused exception. I need only Russian and English, and this currently works for me:

ec1 = Encoding::Converter.new "UTF-8","Windows-1251",:invalid=>:replace,:undef=>:replace,:replace=>""
ec2 = Encoding::Converter.new "Windows-1251","UTF-8",:invalid=>:replace,:undef=>:replace,:replace=>""
t = ec2.convert ec1.convert t

This seems to work:

def sanitize_utf8(string)
  return nil if string.nil?
  return string if string.valid_encoding?
  string.chars.select { |c| c.valid_encoding? }.join
end

I recommend you to use a HTML parser. Just find the fastest one.

Parsing HTML is not as easy as it may seem.

Browsers parse invalid UTF-8 sequences, in UTF-8 HTML documents, just putting the "?" symbol. So once the invalid UTF-8 sequence in the HTML gets parsed the resulting text is a valid string.

Even inside attribute values you have to decode HTML entities like amp

Here is a great question that sums up why you can not reliably parse HTML with a regular expression: RegEx match open tags except XHTML self-contained tags

While Nakilon's solution works, at least as far as getting past the error, in my case, I had this weird f-ed up character originating from Microsoft Excel converted to CSV that was registering in ruby as a (get this) cyrillic K which in ruby was a bolded K. To fix this I used 'iso-8859-1' viz. CSV.parse(f, :encoding => "iso-8859-1"), which turned my freaky deaky cyrillic K's into a much more manageable /\xCA/, which I could then remove with string.gsub!(/\xCA/, '')

Before you use scan, make sure that the requested page's Content-Type header is text/html, since there can be links to things like images which are not encoded in UTF-8. The page could also be non-html if you picked up a href in something like a <link> element. How to check this varies on what HTTP library you are using. Then, make sure the result is only ascii with String#ascii_only? (not UTF-8 because HTML is only supposed to be using ascii, entities can be used otherwise). If both of those tests pass, it is safe to use scan.

My current solution is to run:

my_string.unpack("C*").pack("U*")

This will at least get rid of the exceptions which was my main problem

Try this:

def to_utf8(str)
  str = str.force_encoding('UTF-8')
  return str if str.valid_encoding?
  str.encode("UTF-8", 'binary', invalid: :replace, undef: :replace, replace: '')
end

The accepted answer nor the other answer work for me. I found this post which suggested

string.encode!('UTF-8', 'binary', invalid: :replace, undef: :replace, replace: '')

This fixed the problem for me.

In Ruby 1.9.3 it is possible to use String.encode to "ignore" the invalid UTF-8 sequences. Here is a snippet that will work both in 1.8 (iconv) and 1.9 (String#encode) :

require 'iconv' unless String.method_defined?(:encode)
if String.method_defined?(:encode)
  file_contents.encode!('UTF-8', 'UTF-8', :invalid => :replace)
else
  ic = Iconv.new('UTF-8', 'UTF-8//IGNORE')
  file_contents = ic.iconv(file_contents)
end

or if you have really troublesome input you can do a double conversion from UTF-8 to UTF-16 and back to UTF-8:

require 'iconv' unless String.method_defined?(:encode)
if String.method_defined?(:encode)
  file_contents.encode!('UTF-16', 'UTF-8', :invalid => :replace, :replace => '')
  file_contents.encode!('UTF-8', 'UTF-16')
else
  ic = Iconv.new('UTF-8', 'UTF-8//IGNORE')
  file_contents = ic.iconv(file_contents)
end