Initial Revision

[ohcount] / lib / ohcount / detector.rb

# Determines the language family (Monoglot or Polyglot) used by a source file.
class Ohcount::Detector

        module ContainsM
                # A performance hack -- once we've checked for the presence of *.m files, the result
                # is stored here to avoid checking twice.
                attr_accessor :contains_m
        end

        # The primary entry point for the detector.
        # Given a file context containing the file name, content, and an array of
        # other filenames in the source tree, attempts to detect which
        # language family (Monoglot or Polyglot) is in use for this file.
        #
        # Returns nil if the language is not recognized or if the file does not
        # contain any code.
        def self.detect(file_context)
                # start with extension
                polyglot = EXTENSION_MAP[File.extname(file_context.filename).downcase]
    case polyglot
    when String
      # simplest case
                  return polyglot if polyglot.is_a?(String)
    when Symbol
                  # extension is ambiguous - requires custom disambiguation
                        self.send(polyglot, file_context)
    when NilClass
      return disambiguate_nil(file_context)
    else
      raise RuntimeError.new("Unknown file detection type")
          end
  end

        # Based solely on the filename, makes a judgment whether a file is a binary format.
        def self.binary_filename?(filename)
                ignore = [
                        ".svn",
                        ".jar",
                        ".tar",
                        ".gz",
                        ".tgz",
                        ".zip",
                        ".gif",
                        ".jpg",
                        ".jpeg",
                        ".bmp",
                        ".png",
                        ".tif",
                        ".tiff",
                        ".ogg",
                        ".aiff",
                        ".wav",
                        ".mp3",
                        ".au",
                        ".ra",
                        ".m4a",
                        ".pdf",
                        ".mpg",
                        ".mov",
                        ".qt",
                        ".avi"
                        ]
                ignore.include?(File.extname(filename))
        end

        EXTENSION_MAP = {
                '.ada'  => "ada",
                '.adb'  => "ada",
                '.asm'  => "assembler",
                '.awk'  => "awk",
                '.bas'  => "visualbasic",
                '.bat'  => "bat",
                '.boo'  => "boo",
                '.c'    => "cncpp",
                '.cc'   => "cncpp",
                '.cpp'  => "cncpp",
                '.css'  => "css",
                '.c++'  => "cncpp",
                '.cxx'  => "cncpp",
                '.el'   => "emacslisp",
                #               '.cbl'  => "cobol",
                #               '.cob'  => "cobol",
                '.cs'   => :disambiguate_cs,
                '.dylan'=> "dylan",
                '.erl'  => "erlang",
                '.frx'  => "visualbasic",
                '.groovy'=> "groovy",
                '.h'    => :disambiguate_h_header,
                '.hpp'  => "cncpp",
                '.hh'   => "cncpp",
                '.hrl'  => "erlang",
                '.htm'  => "html",
                '.html' => "html",
                '.inc'  => :disambiguate_inc,
                '.java' => "java",
                '.js'   => "javascript",
                '.jsp'  => "jsp",
                '.lua'  => "lua",
                '.lsp'  => "lisp",
                '.lisp' => "lisp",
                '.m'    => :matlab_or_objective_c,
                '.mm'   => "objective_c",
                '.pas'  => "pascal",
                '.pp'   => "pascal",
                '.php'  => "php",
                '.php3' => "php",
                '.php4' => "php",
                '.php5' => "php",
                '.pl'   => "perl",
                '.pm'   => "perl",
                '.perl' => "perl",
                '.ph'   => "perl",
                '.py'   => "python",
                '.rhtml'=> "rhtml",
                '.rb'   => "ruby",
                '.rex'  => "rexx",
                '.rexx' => "rexx",
                '.s'    => "assembler",
                '.S'    => "assembler",
                '.sc'   => "scheme",
                '.scm'  => "scheme",
                '.sh'   => "shell",
                '.sql'  => "sql",
                '.tcl'  => "tcl",
                '.tpl'  => "html",
                '.vb'   => "visualbasic",
                '.vba'  => "visualbasic",
                '.vbs'  => "visualbasic",
                '.xml'  => "xml",
                '.d'            => 'dmd',
                '.di'           => 'dmd'
        }

        protected

        # Returns a count of lines in the buffer matching the given regular expression.
        def self.lines_matching(buffer, re)
                buffer.inject(0) { |total, line| line =~ re ? total+1 : total }
        end

        # For *.m files, differentiates Matlab from Objective-C.
        #
        # This is done with a weighted heuristic that
        # scans the *.m file contents for keywords,
        # and also checks for the presence of matching *.h files.
  def self.matlab_or_objective_c(file_context)
    buffer = file_context.contents

    # if there are .h files in same directory, this probably isn't matlab
    h_headers = 0.0
    h_headers = -0.5 if file_context.filenames.select { |a| a =~ /\.h$/ }.any?

    # if the contents contain 'function (' on a single line - very likely to be matlab
    # if the contents contain lines starting with '%', its probably matlab comments
    matlab_signatures = /(^\s*function\s*)|(^\s*%)/
    matlab_sig_score = 0.1 * lines_matching(buffer, matlab_signatures)

    # if the contents contains '//' or '/*', likely objective_c
    objective_c_signatures = /(^\s*\/\/\s*)|(^\s*\/\*)|(^[+-])/
    obj_c_sig_score = -0.1 * lines_matching(buffer, objective_c_signatures)

    matlab = h_headers + matlab_sig_score + obj_c_sig_score

    matlab > 0 ? 'matlab' : 'objective_c'
  end

        # For *.h files, differentiates C/C++ from Objective-C.
        #
        # This is done with a weighted heuristic that
        # scans the *.h file contents for Objective-C keywords,
        # and also checks for the presence of matching *.m files.
        def self.disambiguate_h_header(file_context)
    buffer = file_context.contents

    objective_c = 0

    # could it be realistically be objective_c ? are there any .m files at all?
    # Speed hack - remember our findings in case we get the same filenames over and over
    unless defined?(file_context.filenames.contains_m)
      file_context.filenames.extend(ContainsM)
      file_context.filenames.contains_m = file_context.filenames.select { |a| a =~ /\.m$/ }.any?
    end
    return 'cncpp' unless file_context.filenames.contains_m

    # if the dir contains a matching *.m file, likely objective_c
    if file_context.filename =~ /\.h$/
      m_counterpart = file_context.filename.gsub(/\.h$/, ".m")
      return 'objective_c' if file_context.filenames.include?(m_counterpart)
    end

    # ok - it just might be objective_c, let's check contents for objective_c signatures
    objective_c_signatures = /(^\s*@interface)|(^\s*@end)/
    objective_c += lines_matching(buffer, objective_c_signatures)

    return objective_c > 1 ? 'objective_c' : 'cncpp'
        end

        # Tests whether the provided buffer contains binary or text content.
        # This is not fool-proof -- we basically just check for zero values
        # in the early bytes of the buffer. If we find a zero, we know it
        # is not (ascii) text.
  def self.binary_buffer?(buffer)
    100.times do |i|
      return true if buffer[i] == 0
    end
    false
  end

        # True if the provided buffer includes a '?php' directive
  def self.php_instruction?(buffer)
    buffer =~ /\?php/
  end

        # For *.inc files, checks for a PHP class.
  def self.disambiguate_inc(file_context)
    buffer = file_context.contents
    return nil if binary_buffer?(buffer)
    return 'php' if php_instruction?(buffer)
    nil
  end

        # For files with extention *.cs, differentiates C# from Clearsilver.
  def self.disambiguate_cs(file_context)
    buffer = file_context.contents
    return 'clearsilver_template' if lines_matching(file_context.contents, /\<\?cs/) > 0
    return 'csharp'
  end

        # Attempts to determine the Polyglot for files that do not have a
        # filename extension.
        #
        # Relies on the bash +file+ command line tool as its primary method.
        #
        # There must be a file at <tt>file_context.file_location</tt> for +file+
        # to operate on.
        #
  def self.disambiguate_nil(file_context)
    file_location = file_context.file_location
    output = `file -b #{ file_location }`
    case output
    when /([\w\/]+) script text/, /script text executable for ([\w\/]+)/
      script = $1
      if script =~ /\/(\w*)$/
        script = $1
      end
      known_languages = EXTENSION_MAP.values
      return script.downcase if known_languages.include?(script.downcase)
    when /([\w\-]*) shell script text/
      case $1
      when "Bourne-Again"
        return "shell"
      end
    end

    # dang... no dice
    nil
  end

end