CodeRay

h1. Scanner Requests

Scanners are the heart of CodeRay. They split input code into tokens and classify them.

Each language has its own scanner: You can see what languages are currently supported in the "repository":http://code.licenser.net/repositories/browse/coderay/trunk/lib/coderay/scanners.

h2. Why is the CodeRay language support list so short?

CodeRay developing is a slow process, because the total number of active developers is 1 and he insists on high software quality.

Special attention is paid to the scanners: every CodeRay scanner is being tested carefully against lots of example source code, and also randomized and junk code to make it safe. A CodeRay scanner is not officially released unless it highlights very, very well.

h2. I need a new Scanner - What can I do?

Here's what you can do to speed up the development of a new scanner:

# Request it! File a "new ticket":http://code.licenser.net/projects/coderay/issues/new unless it already "exists":http://code.licenser.net/projects/coderay/issues?query_id=3; add a +1 or something to existing tickets to show your interest.

# Upload or link to *example code* in the ticket discussion.

#* Typical code in large quantities is very helpful, also for benchmarking.

#* But we also need the most *weird and strange code* you can find to make the scanner.

# Provide links to useful *information about the language lexic*, such as:

#* a list of reserved words (Did you know that "void" is a JavaScript keyword?)

#* rules for string and number literals (Can a double quoted string contain a newline?)

#* rules for comments and other token types (Does XYZ have a special syntax for multiline comments?)

#* a description of any unusual syntactic features (There's this weird %w() thing in Ruby...)

#* If there are different versions / implementations / dialects of this language: How do they differ?

# Give examples for *good and bad highlighters / syntax definitions* for the language (usually from editors or other libraries)

# Find *more example code*!

Also, read the next paragraph.

h2. I want to write a Scanner myself

Wow, you're brave! Writing CodeRay scanners is not an easy task because:

* You need excellent knowledge about the language you want to scan. Every language has a dark side!

* You need good knowledge of (Ruby) regular expressions.

* There's no documentation to speak of.

** But this is a wiki ^hint hint^ ;o)

But it has been done before, so go and try it!

# You should still request the scanner (as described above) and announce that you are working on a patch yourself.

# Check out the "repository":http://code.licenser.net/wiki/coderay/Repository and try the test suite (@rake test:scanners[:lang]@).

# Copy a scanner of your choice as a base. You would know what language comes closest.

# Create a test case directory in @test/scanners@.

# --- Advertisement --- (No, just kidding.)

# Write your scanner!

# Also, look into @lib/coderay/scanners/_map.rb@ and @lib/coderay/helpers/file_type.rb@.

# Make a patch (scanner, test cases and other changes) and upload it to the ticket.

# Follow the following discussion.

# Prepare to be added to the THX list.

Contact me (murphy rubychan de) if you have any questions.

h2. How does a Scanner look?

For example, the JSON scanner:

<pre><code class="ruby">

# Namespace; use this form instead of CodeRay::Scanners to avoid messages like

# "uninitialized constant CodeRay" when testing it.

module CodeRay

module Scanners

  # Always inherit from CodeRay::Scanners::Scanner.

  # 

  # Scanner inherits directly from StringScanner, the Ruby class for fast

  # string scanning. Read the documentation to understand what's going on here:

  # 

  #   http://www.ruby-doc.org/stdlib/libdoc/strscan/rdoc/index.html

  class JSON < Scanner

    # This means your scanner is providing a token stream, that is, it doesn't

    # touch a token after it has been added to tokens. Streamable scanners

    # can be used in streaming mode to minimize memory usage.

    include Streamable

    # Scanners are plugins and must be registered like this.

    register_for :json

    # See the WordList documentation.

    CONSTANTS = %w( true false null )

    IDENT_KIND = WordList.new(:key).add(CONSTANTS, :reserved)

    ESCAPE = / [bfnrt\\"\/] /x

    UNICODE_ESCAPE =  / u[a-fA-F0-9]{4} /x

    # This is the only method you need to define. It scans code.

    # 

    # tokens is a Tokens or TokenStream object. Use tokens << [token, kind] to

    # add tokens to it.

    # 

    # options is reserved for later use.

    # 

    # scan_tokens must return the tokens variable it was given.

    # 

    # You are completely free to use any style you want, just make sure tokens

    # gets what it needs. But typically, a Scanner follows the following scheme.

    # 

    # See http://json.org/ for a definition of the JSON lexic/grammar.

    def scan_tokens tokens, options

      # The scanner is always in a certain state, which is :initial by default.

      # We use local variables and symbols to maximize speed.

      state = :initial

      # Sometimes, you need a stack. Ruby arrays are perfect for this.

      stack = []

      # Define more flags and variables as you need them.

      string_delimiter = nil

      key_expected = false

      # The main loop. eos? is true when the end of the code is reached.

      until eos?

        # You can either add directly to tokens or set these variables. See

        # the end of this method to understand how they are used.

        kind = nil

        match = nil

        # Depending on the state, we want to do different things.

        case state

        # Normally, we use this case.

        when :initial

          # I like the / ... /x style regexps because white space makes them more

          # readable. x means white space is ignored.

          if match = scan(/ \s+ | \\\n /x)

            # White space and masked line ends are :space. We're using the tokens <<

            # style here instead of setting kind and match, because it is faster.

            # Just make sure you never send an empty token! /\s*/ for example would be

            # very bad (actually creating infinite loops).

            tokens << [match, :space]

            next

          elsif match = scan(/ [:,\[{\]}] /x)

            # Operators of JSON. stack is used to determine where we are. stack and

            # key_expected are set depending on which operator was found.

            # key_expected is used to decide whether a "quoted" thing should be

            # classified as key or string.

            kind = :operator

            case match

            when '{' then stack << :object; key_expected = true

            when '[' then stack << :array

            when ':' then key_expected = false

            when ',' then key_expected = true if stack.last == :object

            when '}', ']' then stack.pop  # no error recovery, but works for valid JSON

            end

          elsif match = scan(/ true | false | null /x)

            # These are the only idents that are allowed in JSON. Normally, IDENT_KIND

            # would be used to tell keywords and idents apart.

            kind = IDENT_KIND[match]

          elsif match = scan(/-?(?:0|[1-9]\d*)/)

            # Pay attention to the details: JSON doesn't allow numbers like 00.

            kind = :integer

            if scan(/\.\d+(?:[eE][-+]?\d+)?|[eE][-+]?\d+/)

              match << matched

              kind = :float

            end

          elsif match = scan(/"/)

            # A "quoted" token was found, and we know whether it is a key or a string.

            state = key_expected ? :key : :string

            # This opens a token group.

            tokens << [:open, state]

            kind = :delimiter

          else

            # Don't forget to add this case: If we reach invalid code, we try to discard

            # chars one by one and mark them as :error.

            getch

            kind = :error

          end

        # String scanning is a bit more complicated, so we use another state for it.

        # The scanner stays in :string state until the string ends or an error occurs.

        # 

        # JSON uses the same notation for strings and keys. We want keys to be in a

        # different color, but the lexical rules are the same. This is why we use this

        # case also for the :key state.

        when :string, :key

          # Another if-elsif-else-switch, for strings this time.

          if scan(/[^\\"]+/)

            # Everything that is not \ or " is just string content.

            kind = :content

          elsif scan(/"/)

            # A " is found, which means this string or key is ending here.

            # A special token class, :delimiter, is used for tokens like this one.

            tokens << ['"', :delimiter]

            # Always close your token groups!

            tokens << [:close, state]

            # We're going back to normal scanning here.

            state = :initial

            # Skip the rest of the loop, since we used tokens <<.

            next

          elsif scan(/ \\ (?: #{ESCAPE} | #{UNICODE_ESCAPE} ) /mox)

            # A valid special character should be classified as :char.

            kind = :char

          elsif scan(/\\./m)

            # Anything else that is escaped (including \n, we use the m modifier) is

            # just content.

            kind = :content

          elsif scan(/ \\ | $ /x)

            # A string that suddenly ends in the middle, or reaches the end of the

            # line. This is an error; we go back to :initial now.

            tokens << [:close, :delimiter]

            kind = :error

            state = :initial

          else

            # Nice for debugging. Should never happen.

            raise_inspect "else case \" reached; %p not handled." % peek(1), tokens

          end

        else

          # Nice for debugging. Should never happen.

          raise_inspect 'Unknown state: %p' % [state], tokens

        end

        # Unless the match local variable was set, use matched.

        match ||= matched

        # Debugging. Empty tokens and undefined kind are bad.

        if $CODERAY_DEBUG and not kind

          raise_inspect 'Error token %p in line %d' %

            [[match, kind], line], tokens

        end

        raise_inspect 'Empty token', tokens unless match

        # Finally, add the token and loop.

        tokens << [match, kind]

      end

      # If we still have a string or key token group open, close it.

      if [:string, :key].include? state

        tokens << [:close, state]

      end

      # Return tokens. This is the only rule to follow.

      tokens

    end

  end

end

end

</code></pre>

Highlighted with CodeRay, yeah :D