580 lines
16 KiB
Ruby
Executable file
580 lines
16 KiB
Ruby
Executable file
require 'stringio'
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require 'html5lib/constants'
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module HTML5lib
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# Provides a unicode stream of characters to the HTMLTokenizer.
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# This class takes care of character encoding and removing or replacing
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# incorrect byte-sequences and also provides column and line tracking.
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class HTMLInputStream
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attr_accessor :queue, :char_encoding
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# Initialises the HTMLInputStream.
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#
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# HTMLInputStream(source, [encoding]) -> Normalized stream from source
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# for use by the HTML5Lib.
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#
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# source can be either a file-object, local filename or a string.
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#
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# The optional encoding parameter must be a string that indicates
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# the encoding. If specified, that encoding will be used,
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# regardless of any BOM or later declaration (such as in a meta
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# element)
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#
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# parseMeta - Look for a <meta> element containing encoding information
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def initialize(source, options = {})
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@encoding = nil
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@parse_meta = true
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@chardet = true
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options.each { |name, value| instance_variable_set("@#{name}", value) }
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# List of where new lines occur
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@new_lines = []
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# Raw Stream
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@raw_stream = open_stream(source)
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# Encoding Information
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#Number of bytes to use when looking for a meta element with
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#encoding information
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@NUM_BYTES_META = 512
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#Encoding to use if no other information can be found
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@DEFAULT_ENCODING = 'windows-1252'
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#Detect encoding iff no explicit "transport level" encoding is supplied
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if @encoding.nil? or not HTML5lib.is_valid_encoding(@encoding)
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@char_encoding = detect_encoding
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else
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@char_encoding = @encoding
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end
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# Read bytes from stream decoding them into Unicode
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uString = @raw_stream.read
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unless @char_encoding == 'utf-8'
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begin
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require 'iconv'
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uString = Iconv.iconv('utf-8', @char_encoding, uString)[0]
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rescue LoadError
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rescue Exception
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end
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end
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# Normalize newlines and null characters
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uString.gsub!(/\r\n?/, "\n")
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uString.gsub!("\x00", [0xFFFD].pack('U'))
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# Convert the unicode string into a list to be used as the data stream
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@data_stream = uString
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@queue = []
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# Reset position in the list to read from
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reset
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end
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# Produces a file object from source.
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#
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# source can be either a file object, local filename or a string.
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def open_stream(source)
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# Already an IO like object
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if source.respond_to?(:read)
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@stream = source
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else
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# Treat source as a string and wrap in StringIO
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@stream = StringIO.new(source)
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end
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return @stream
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end
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def detect_encoding
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#First look for a BOM
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#This will also read past the BOM if present
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encoding = detect_bom
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#If there is no BOM need to look for meta elements with encoding
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#information
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if encoding.nil? and @parse_meta
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encoding = detect_encoding_meta
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end
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#Guess with chardet, if avaliable
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if encoding.nil? and @chardet
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begin
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require 'rubygems'
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require 'UniversalDetector' # gem install chardet
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buffer = @raw_stream.read
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encoding = UniversalDetector::chardet(buffer)['encoding']
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@raw_stream = open_stream(buffer)
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rescue LoadError
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end
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end
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# If all else fails use the default encoding
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if encoding.nil?
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encoding = @DEFAULT_ENCODING
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end
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#Substitute for equivalent encodings:
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encoding_sub = {'iso-8859-1' => 'windows-1252'}
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if encoding_sub.has_key?(encoding.downcase)
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encoding = encoding_sub[encoding.downcase]
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end
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return encoding
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end
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# Attempts to detect at BOM at the start of the stream. If
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# an encoding can be determined from the BOM return the name of the
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# encoding otherwise return nil
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def detect_bom
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bom_dict = {
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"\xef\xbb\xbf" => 'utf-8',
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"\xff\xfe" => 'utf16le',
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"\xfe\xff" => 'utf16be',
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"\xff\xfe\x00\x00" => 'utf32le',
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"\x00\x00\xfe\xff" => 'utf32be'
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}
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# Go to beginning of file and read in 4 bytes
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@raw_stream.seek(0)
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string = @raw_stream.read(4)
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return nil unless string
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# Try detecting the BOM using bytes from the string
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encoding = bom_dict[string[0...3]] # UTF-8
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seek = 3
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unless encoding
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# Need to detect UTF-32 before UTF-16
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encoding = bom_dict[string] # UTF-32
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seek = 4
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unless encoding
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encoding = bom_dict[string[0...2]] # UTF-16
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seek = 2
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end
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end
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#AT - move this to the caller?
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# Set the read position past the BOM if one was found, otherwise
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# set it to the start of the stream
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@raw_stream.seek(encoding ? seek : 0)
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return encoding
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end
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# Report the encoding declared by the meta element
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def detect_encoding_meta
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parser = EncodingParser.new(@raw_stream.read(@NUM_BYTES_META))
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@raw_stream.seek(0)
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return parser.get_encoding
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end
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def determine_new_lines
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# Looks through the stream to find where new lines occur so
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# the position method can tell where it is.
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@new_lines.push(0)
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(0...@data_stream.length).each { |i| @new_lines.push(i) if @data_stream[i] == ?\n }
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end
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# Returns (line, col) of the current position in the stream.
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def position
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# Generate list of new lines first time around
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determine_new_lines if @new_lines.empty?
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line = 0
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tell = @tell
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@new_lines.each do |pos|
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break unless pos < tell
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line += 1
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end
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col = tell - @new_lines[line-1] - 1
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return [line, col]
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end
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# Resets the position in the stream back to the start.
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def reset
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@tell = 0
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end
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# Read one character from the stream or queue if available. Return
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# EOF when EOF is reached.
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def char
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unless @queue.empty?
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return @queue.shift
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else
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@tell += 1
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c = @data_stream[@tell - 1]
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case c
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when 0xC2 .. 0xDF
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if @data_stream[@tell .. @tell] =~ /[\x80-\xBF]/
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@tell += 1
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@data_stream[@tell-2..@tell-1]
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else
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[0xFFFD].pack('U')
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end
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when 0xE0 .. 0xEF
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if @data_stream[@tell .. @tell+1] =~ /[\x80-\xBF]{2}/
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@tell += 2
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@data_stream[@tell-3..@tell-1]
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else
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[0xFFFD].pack('U')
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end
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when 0xF0 .. 0xF3
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if @data_stream[@tell .. @tell+2] =~ /[\x80-\xBF]{3}/
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@tell += 3
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@data_stream[@tell-4..@tell-1]
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else
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[0xFFFD].pack('U')
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end
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else
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begin
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c.chr
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rescue
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:EOF
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end
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end
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end
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end
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# Returns a string of characters from the stream up to but not
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# including any character in characters or EOF. characters can be
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# any container that supports the in method being called on it.
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def chars_until(characters, opposite=false)
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char_stack = [char]
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unless char_stack[0] == :EOF
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while (characters.include? char_stack[-1]) == opposite
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unless @queue.empty?
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# First from the queue
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char_stack.push(@queue.shift)
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break if char_stack[-1] == :EOF
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else
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# Then the rest
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begin
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@tell += 1
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char_stack.push(@data_stream[@tell-1].chr)
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rescue
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char_stack.push(:EOF)
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break
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end
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end
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end
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end
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# Put the character stopped on back to the front of the queue
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# from where it came.
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@queue.insert(0, char_stack.pop)
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return char_stack.join('')
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end
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end
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# String-like object with an assosiated position and various extra methods
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# If the position is ever greater than the string length then an exception is raised
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class EncodingBytes < String
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attr_accessor :position
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def initialize(value)
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super(value)
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@position = -1
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end
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def each
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while @position < length
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@position += 1
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yield self[@position]
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end
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rescue EOF
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end
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def current_byte
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raise EOF if @position >= length
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return self[@position].chr
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end
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# Skip past a list of characters
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def skip(chars=SPACE_CHARACTERS)
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while chars.include?(current_byte)
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@position += 1
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end
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end
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# Look for a sequence of bytes at the start of a string. If the bytes
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# are found return true and advance the position to the byte after the
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# match. Otherwise return false and leave the position alone
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def match_bytes(bytes, lower=false)
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data = self[position ... position+bytes.length]
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data.downcase! if lower
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rv = (data == bytes)
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@position += bytes.length if rv == true
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return rv
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end
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# Look for the next sequence of bytes matching a given sequence. If
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# a match is found advance the position to the last byte of the match
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def jump_to(bytes)
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new_position = self[position .. -1].index(bytes)
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if new_position
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@position += (new_position + bytes.length-1)
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return true
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else
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raise EOF
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end
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end
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# Move the pointer so it points to the next byte in a set of possible
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# bytes
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def find_next(byte_list)
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until byte_list.include?(current_byte)
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@position += 1
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end
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end
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end
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# Mini parser for detecting character encoding from meta elements
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class EncodingParser
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# string - the data to work on for encoding detection
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def initialize(data)
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@data = EncodingBytes.new(data.to_s)
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@encoding = nil
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end
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@@method_dispatch = [
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['<!--', :handle_comment],
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['<meta', :handle_meta],
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['</', :handle_possible_end_tag],
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['<!', :handle_other],
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['<?', :handle_other],
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['<', :handle_possible_start_tag]
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]
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def get_encoding
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@data.each do |byte|
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keep_parsing = true
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@@method_dispatch.each do |(key, method)|
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if @data.match_bytes(key, lower = true)
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keep_parsing = send(method)
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break
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end
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end
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break unless keep_parsing
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end
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@encoding = @encoding.strip unless @encoding.nil?
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return @encoding
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end
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# Skip over comments
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def handle_comment
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return @data.jump_to('-->')
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end
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def handle_meta
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# if we have <meta not followed by a space so just keep going
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return true unless SPACE_CHARACTERS.include?(@data.current_byte)
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#We have a valid meta element we want to search for attributes
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while true
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#Try to find the next attribute after the current position
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attr = get_attribute
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return true if attr.nil?
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if attr[0] == 'charset'
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tentative_encoding = attr[1]
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if HTML5lib.is_valid_encoding(tentative_encoding)
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@encoding = tentative_encoding
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return false
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end
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elsif attr[0] == 'content'
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content_parser = ContentAttrParser.new(EncodingBytes.new(attr[1]))
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tentative_encoding = content_parser.parse
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if HTML5lib.is_valid_encoding(tentative_encoding)
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@encoding = tentative_encoding
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return false
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end
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end
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end
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end
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def handle_possible_start_tag
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return handle_possible_tag(false)
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end
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def handle_possible_end_tag
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@data.position += 1
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return handle_possible_tag(true)
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end
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def handle_possible_tag(end_tag)
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unless ASCII_LETTERS.include?(@data.current_byte)
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#If the next byte is not an ascii letter either ignore this
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#fragment (possible start tag case) or treat it according to
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#handleOther
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if end_tag
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@data.position -= 1
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handle_other
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end
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return true
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end
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@data.find_next(SPACE_CHARACTERS + ['<', '>'])
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if @data.current_byte == '<'
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#return to the first step in the overall "two step" algorithm
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#reprocessing the < byte
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@data.position -= 1
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else
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#Read all attributes
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{} until get_attribute.nil?
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end
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return true
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end
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def handle_other
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return @data.jump_to('>')
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end
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# Return a name,value pair for the next attribute in the stream,
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# if one is found, or nil
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def get_attribute
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@data.skip(SPACE_CHARACTERS + ['/'])
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if @data.current_byte == '<'
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@data.position -= 1
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return nil
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elsif @data.current_byte == '>'
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return nil
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end
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attr_name = []
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attr_value = []
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space_found = false
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#Step 5 attribute name
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while true
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if @data.current_byte == '=' and attr_name:
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break
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elsif SPACE_CHARACTERS.include?(@data.current_byte)
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space_found = true
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break
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elsif ['/', '<', '>'].include?(@data.current_byte)
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return [attr_name.join(''), '']
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elsif ASCII_UPPERCASE.include?(@data.current_byte)
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attr_name.push(@data.current_byte.downcase)
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else
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attr_name.push(@data.current_byte)
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end
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#Step 6
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@data.position += 1
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end
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#Step 7
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if space_found
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@data.skip
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#Step 8
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unless @data.current_byte == '='
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@data.position -= 1
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return [attr_name.join(''), '']
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end
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end
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#XXX need to advance position in both spaces and value case
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#Step 9
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@data.position += 1
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#Step 10
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@data.skip
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#Step 11
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if ["'", '"'].include?(@data.current_byte)
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#11.1
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quote_char = @data.current_byte
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while true
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@data.position+=1
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#11.3
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if @data.current_byte == quote_char
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@data.position += 1
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return [attr_name.join(''), attr_value.join('')]
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#11.4
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elsif ASCII_UPPERCASE.include?(@data.current_byte)
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attr_value.push(@data.current_byte.downcase)
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#11.5
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else
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attr_value.push(@data.current_byte)
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end
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end
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elsif ['>', '<'].include?(@data.current_byte)
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return [attr_name.join(''), '']
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elsif ASCII_UPPERCASE.include?(@data.current_byte)
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attr_value.push(@data.current_byte.downcase)
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else
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attr_value.push(@data.current_byte)
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end
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while true
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@data.position += 1
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if (SPACE_CHARACTERS + ['>', '<']).include?(@data.current_byte)
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return [attr_name.join(''), attr_value.join('')]
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elsif ASCII_UPPERCASE.include?(@data.current_byte)
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attr_value.push(@data.current_byte.downcase)
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else
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attr_value.push(@data.current_byte)
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end
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end
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end
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end
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class ContentAttrParser
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def initialize(data)
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@data = data
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end
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def parse
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begin
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#Skip to the first ";"
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@data.position = 0
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@data.jump_to(';')
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@data.position += 1
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@data.skip
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#Check if the attr name is charset
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#otherwise return
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@data.jump_to('charset')
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@data.position += 1
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@data.skip
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unless @data.current_byte == '='
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#If there is no = sign keep looking for attrs
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return nil
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end
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@data.position += 1
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@data.skip
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#Look for an encoding between matching quote marks
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if ['"', "'"].include?(@data.current_byte)
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quote_mark = @data.current_byte
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@data.position += 1
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old_position = @data.position
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@data.jump_to(quote_mark)
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return @data[old_position ... @data.position]
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else
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#Unquoted value
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old_position = @data.position
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begin
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@data.find_next(SPACE_CHARACTERS)
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return @data[old_position ... @data.position]
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rescue EOF
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#Return the whole remaining value
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return @data[old_position .. -1]
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end
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end
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rescue EOF
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return nil
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end
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end
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end
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# Determine if a string is a supported encoding
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def self.is_valid_encoding(encoding)
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(not encoding.nil? and encoding.kind_of?(String) and ENCODINGS.include?(encoding.downcase.strip))
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end
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end
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