instiki/vendor/plugins/HTML5lib/lib/html5/inputstream.rb
2007-08-30 12:19:10 -05:00

655 lines
18 KiB
Ruby
Executable file

require 'stringio'
require 'html5/constants'
module HTML5
# Provides a unicode stream of characters to the HTMLTokenizer.
# This class takes care of character encoding and removing or replacing
# incorrect byte-sequences and also provides column and line tracking.
class HTMLInputStream
attr_accessor :queue, :char_encoding, :errors
# Initialises the HTMLInputStream.
#
# HTMLInputStream(source, [encoding]) -> Normalized stream from source
# for use by the HTML5Lib.
#
# source can be either a file-object, local filename or a string.
#
# The optional encoding parameter must be a string that indicates
# the encoding. If specified, that encoding will be used,
# regardless of any BOM or later declaration (such as in a meta
# element)
#
# parseMeta - Look for a <meta> element containing encoding information
def initialize(source, options = {})
@encoding = nil
@parse_meta = true
@chardet = true
options.each {|name, value| instance_variable_set("@#{name}", value) }
# Raw Stream
@raw_stream = open_stream(source)
# Encoding Information
#Number of bytes to use when looking for a meta element with
#encoding information
@NUM_BYTES_META = 512
#Number of bytes to use when using detecting encoding using chardet
@NUM_BYTES_CHARDET = 256
#Number of bytes to use when reading content
@NUM_BYTES_BUFFER = 1024
#Encoding to use if no other information can be found
@DEFAULT_ENCODING = 'windows-1252'
#Detect encoding iff no explicit "transport level" encoding is supplied
if @encoding.nil? or not HTML5.is_valid_encoding(@encoding)
@char_encoding = detect_encoding
else
@char_encoding = @encoding
end
# Read bytes from stream decoding them into Unicode
@buffer = @raw_stream.read(@NUM_BYTES_BUFFER) || ''
if @char_encoding == 'windows-1252'
@win1252 = true
elsif @char_encoding != 'utf-8'
begin
require 'iconv'
begin
@buffer << @raw_stream.read unless @raw_stream.eof?
@buffer = Iconv.iconv('utf-8', @char_encoding, @buffer).first
rescue
@win1252 = true
end
rescue LoadError
@win1252 = true
end
end
@queue = []
@errors = []
# Reset position in the list to read from
@tell = 0
@line = @col = 0
@line_lengths = []
end
# Produces a file object from source.
#
# source can be either a file object, local filename or a string.
def open_stream(source)
# Already an IO like object
if source.respond_to?(:read)
@stream = source
else
# Treat source as a string and wrap in StringIO
@stream = StringIO.new(source)
end
return @stream
end
def detect_encoding
#First look for a BOM
#This will also read past the BOM if present
encoding = detect_bom
#If there is no BOM need to look for meta elements with encoding
#information
if encoding.nil? and @parse_meta
encoding = detect_encoding_meta
end
#Guess with chardet, if avaliable
if encoding.nil? and @chardet
begin
require 'rubygems'
require 'UniversalDetector' # gem install chardet
buffers = []
detector = UniversalDetector::Detector.instance
detector.reset
until @raw_stream.eof?
buffer = @raw_stream.read(@NUM_BYTES_CHARDET)
break if !buffer or buffer.empty?
buffers << buffer
detector.feed(buffer)
break if detector.instance_eval {@done}
detector.instance_eval {
@_mLastChar = @_mLastChar.chr if Fixnum === @_mLastChar
}
end
detector.close
encoding = detector.result['encoding']
seek(buffers*'', 0)
rescue LoadError
end
end
# If all else fails use the default encoding
if encoding.nil?
encoding = @DEFAULT_ENCODING
end
#Substitute for equivalent encodings
encoding_sub = {'iso-8859-1' => 'windows-1252'}
if encoding_sub.has_key?(encoding.downcase)
encoding = encoding_sub[encoding.downcase]
end
return encoding
end
# Attempts to detect at BOM at the start of the stream. If
# an encoding can be determined from the BOM return the name of the
# encoding otherwise return nil
def detect_bom
bom_dict = {
"\xef\xbb\xbf" => 'utf-8',
"\xff\xfe" => 'utf-16le',
"\xfe\xff" => 'utf-16be',
"\xff\xfe\x00\x00" => 'utf-32le',
"\x00\x00\xfe\xff" => 'utf-32be'
}
# Go to beginning of file and read in 4 bytes
string = @raw_stream.read(4)
return nil unless string
# Try detecting the BOM using bytes from the string
encoding = bom_dict[string[0...3]] # UTF-8
seek = 3
unless encoding
# Need to detect UTF-32 before UTF-16
encoding = bom_dict[string] # UTF-32
seek = 4
unless encoding
encoding = bom_dict[string[0...2]] # UTF-16
seek = 2
end
end
# Set the read position past the BOM if one was found, otherwise
# set it to the start of the stream
seek(string, encoding ? seek : 0)
return encoding
end
def seek(buffer, n)
if @raw_stream.respond_to?(:unget)
@raw_stream.unget(buffer[n..-1])
return
end
if @raw_stream.respond_to?(:seek)
begin
@raw_stream.seek(n)
return
rescue Errno::ESPIPE
end
end
require 'delegate'
@raw_stream = SimpleDelegator.new(@raw_stream)
class << @raw_stream
def read(chars=-1)
if chars == -1 or chars > @data.length
result = @data
@data = ''
return result if __getobj__.eof?
return result + __getobj__.read if chars == -1
return result + __getobj__.read(chars-result.length)
elsif @data.empty?
return __getobj__.read(chars)
else
result = @data[1...chars]
@data = @data[chars..-1]
return result
end
end
def unget(data)
if !@data or @data.empty?
@data = data
else
@data += data
end
end
end
@raw_stream.unget(buffer[n .. -1])
end
# Report the encoding declared by the meta element
def detect_encoding_meta
buffer = @raw_stream.read(@NUM_BYTES_META)
parser = EncodingParser.new(buffer)
seek(buffer, 0)
return parser.get_encoding
end
# Returns (line, col) of the current position in the stream.
def position
line, col = @line, @col
@queue.reverse.each do |c|
if c == "\n"
line -= 1
raise RuntimeError.new("col=#{col}") unless col == 0
col = @line_lengths[line]
else
col -= 1
end
end
return [line+1, col]
end
# Read one character from the stream or queue if available. Return
# EOF when EOF is reached.
def char
unless @queue.empty?
return @queue.shift
else
if @tell + 3 > @buffer.length and !@raw_stream.eof?
# read next block
@buffer = @buffer[@tell .. -1] + @raw_stream.read(@NUM_BYTES_BUFFER)
@tell = 0
end
c = @buffer[@tell]
@tell += 1
case c
when 0x01 .. 0x7F
if c == 0x0D
# normalize newlines
@tell += 1 if @buffer[@tell] == 0x0A
c = 0x0A
end
# update position in stream
if c == 0x0a
@line_lengths << @col
@line += 1
@col = 0
else
@col += 1
end
c.chr
when 0x80 .. 0xBF
if !@win1252
[0xFFFD].pack('U') # invalid utf-8
elsif c <= 0x9f
[ENTITIES_WINDOWS1252[c-0x80]].pack('U')
else
"\xC2" + c.chr # convert to utf-8
end
when 0xC0 .. 0xFF
if instance_variables.include?("@win1252") && @win1252
"\xC3" + (c-64).chr # convert to utf-8
elsif @buffer[@tell-1 .. @tell+3] =~ /^
( [\xC2-\xDF][\x80-\xBF] # non-overlong 2-byte
| \xE0[\xA0-\xBF][\x80-\xBF] # excluding overlongs
| [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2} # straight 3-byte
| \xED[\x80-\x9F][\x80-\xBF] # excluding surrogates
| \xF0[\x90-\xBF][\x80-\xBF]{2} # planes 1-3
| [\xF1-\xF3][\x80-\xBF]{3} # planes 4-15
| \xF4[\x80-\x8F][\x80-\xBF]{2} # plane 16
)/x
@tell += $1.length - 1
$1
else
[0xFFFD].pack('U') # invalid utf-8
end
when 0x00
@errors.push('null character found in input stream, ' +
'replaced with U+FFFD')
[0xFFFD].pack('U') # null characters are invalid
else
:EOF
end
end
end
# Returns a string of characters from the stream up to but not
# including any character in characters or EOF. characters can be
# any container that supports the in method being called on it.
def chars_until(characters, opposite=false)
char_stack = [char]
while char_stack.last != :EOF
break unless (characters.include?(char_stack.last)) == opposite
char_stack.push(char)
end
# Put the character stopped on back to the front of the queue
# from where it came.
c = char_stack.pop
@queue.insert(0, c) unless c == :EOF
return char_stack.join('')
end
def unget(characters)
@queue.unshift(*characters.to_a) unless characters == :EOF
end
end
# String-like object with an assosiated position and various extra methods
# If the position is ever greater than the string length then an exception is raised
class EncodingBytes < String
attr_accessor :position
def initialize(value)
super(value)
@position = -1
end
def each
while @position < length
@position += 1
yield self[@position]
end
rescue EOF
end
def current_byte
raise EOF if @position >= length
return self[@position].chr
end
# Skip past a list of characters
def skip(chars=SPACE_CHARACTERS)
while chars.include?(current_byte)
@position += 1
end
end
# Look for a sequence of bytes at the start of a string. If the bytes
# are found return true and advance the position to the byte after the
# match. Otherwise return false and leave the position alone
def match_bytes(bytes, lower=false)
data = self[position ... position+bytes.length]
data.downcase! if lower
rv = (data == bytes)
@position += bytes.length if rv == true
return rv
end
# Look for the next sequence of bytes matching a given sequence. If
# a match is found advance the position to the last byte of the match
def jump_to(bytes)
new_position = self[position .. -1].index(bytes)
if new_position
@position += (new_position + bytes.length-1)
return true
else
raise EOF
end
end
# Move the pointer so it points to the next byte in a set of possible
# bytes
def find_next(byte_list)
until byte_list.include?(current_byte)
@position += 1
end
end
end
# Mini parser for detecting character encoding from meta elements
class EncodingParser
# string - the data to work on for encoding detection
def initialize(data)
@data = EncodingBytes.new(data.to_s)
@encoding = nil
end
@@method_dispatch = [
['<!--', :handle_comment],
['<meta', :handle_meta],
['</', :handle_possible_end_tag],
['<!', :handle_other],
['<?', :handle_other],
['<', :handle_possible_start_tag]
]
def get_encoding
@data.each do |byte|
keep_parsing = true
@@method_dispatch.each do |(key, method)|
if @data.match_bytes(key, lower = true)
keep_parsing = send(method)
break
end
end
break unless keep_parsing
end
@encoding = @encoding.strip unless @encoding.nil?
return @encoding
end
# Skip over comments
def handle_comment
return @data.jump_to('-->')
end
def handle_meta
# if we have <meta not followed by a space so just keep going
return true unless SPACE_CHARACTERS.include?(@data.current_byte)
#We have a valid meta element we want to search for attributes
while true
#Try to find the next attribute after the current position
attr = get_attribute
return true if attr.nil?
if attr[0] == 'charset'
tentative_encoding = attr[1]
if HTML5.is_valid_encoding(tentative_encoding)
@encoding = tentative_encoding
return false
end
elsif attr[0] == 'content'
content_parser = ContentAttrParser.new(EncodingBytes.new(attr[1]))
tentative_encoding = content_parser.parse
if HTML5.is_valid_encoding(tentative_encoding)
@encoding = tentative_encoding
return false
end
end
end
end
def handle_possible_start_tag
return handle_possible_tag(false)
end
def handle_possible_end_tag
@data.position += 1
return handle_possible_tag(true)
end
def handle_possible_tag(end_tag)
unless ASCII_LETTERS.include?(@data.current_byte)
#If the next byte is not an ascii letter either ignore this
#fragment (possible start tag case) or treat it according to
#handleOther
if end_tag
@data.position -= 1
handle_other
end
return true
end
@data.find_next(SPACE_CHARACTERS + ['<', '>'])
if @data.current_byte == '<'
#return to the first step in the overall "two step" algorithm
#reprocessing the < byte
@data.position -= 1
else
#Read all attributes
{} until get_attribute.nil?
end
return true
end
def handle_other
return @data.jump_to('>')
end
# Return a name,value pair for the next attribute in the stream,
# if one is found, or nil
def get_attribute
@data.skip(SPACE_CHARACTERS + ['/'])
if @data.current_byte == '<'
@data.position -= 1
return nil
elsif @data.current_byte == '>'
return nil
end
attr_name = []
attr_value = []
space_found = false
#Step 5 attribute name
while true
if @data.current_byte == '=' and attr_name
break
elsif SPACE_CHARACTERS.include?(@data.current_byte)
space_found = true
break
elsif ['/', '<', '>'].include?(@data.current_byte)
return [attr_name.join(''), '']
elsif ASCII_UPPERCASE.include?(@data.current_byte)
attr_name.push(@data.current_byte.downcase)
else
attr_name.push(@data.current_byte)
end
#Step 6
@data.position += 1
end
#Step 7
if space_found
@data.skip
#Step 8
unless @data.current_byte == '='
@data.position -= 1
return [attr_name.join(''), '']
end
end
#XXX need to advance position in both spaces and value case
#Step 9
@data.position += 1
#Step 10
@data.skip
#Step 11
if ["'", '"'].include?(@data.current_byte)
#11.1
quote_char = @data.current_byte
while true
@data.position+=1
#11.3
if @data.current_byte == quote_char
@data.position += 1
return [attr_name.join(''), attr_value.join('')]
#11.4
elsif ASCII_UPPERCASE.include?(@data.current_byte)
attr_value.push(@data.current_byte.downcase)
#11.5
else
attr_value.push(@data.current_byte)
end
end
elsif ['>', '<'].include?(@data.current_byte)
return [attr_name.join(''), '']
elsif ASCII_UPPERCASE.include?(@data.current_byte)
attr_value.push(@data.current_byte.downcase)
else
attr_value.push(@data.current_byte)
end
while true
@data.position += 1
if (SPACE_CHARACTERS + ['>', '<']).include?(@data.current_byte)
return [attr_name.join(''), attr_value.join('')]
elsif ASCII_UPPERCASE.include?(@data.current_byte)
attr_value.push(@data.current_byte.downcase)
else
attr_value.push(@data.current_byte)
end
end
end
end
class ContentAttrParser
def initialize(data)
@data = data
end
def parse
begin
#Skip to the first ";"
@data.position = 0
@data.jump_to(';')
@data.position += 1
@data.skip
#Check if the attr name is charset
#otherwise return
@data.jump_to('charset')
@data.position += 1
@data.skip
unless @data.current_byte == '='
#If there is no = sign keep looking for attrs
return nil
end
@data.position += 1
@data.skip
#Look for an encoding between matching quote marks
if ['"', "'"].include?(@data.current_byte)
quote_mark = @data.current_byte
@data.position += 1
old_position = @data.position
@data.jump_to(quote_mark)
return @data[old_position ... @data.position]
else
#Unquoted value
old_position = @data.position
begin
@data.find_next(SPACE_CHARACTERS)
return @data[old_position ... @data.position]
rescue EOF
#Return the whole remaining value
return @data[old_position .. -1]
end
end
rescue EOF
return nil
end
end
end
# Determine if a string is a supported encoding
def self.is_valid_encoding(encoding)
(not encoding.nil? and encoding.kind_of?(String) and ENCODINGS.include?(encoding.downcase.strip))
end
end