instiki/vendor/plugins/HTML5lib/lib/html5lib/inputstream.rb
Jacques Distler bd8ba1f4b1 REXML Trees
Synced with latest HTML5lib.
Added preliminary support (currently disabled) for sanitizing REXML trees.
2007-06-05 16:34:49 -05:00

564 lines
16 KiB
Ruby
Executable file

require 'stringio'
require 'html5lib/constants'
module HTML5lib
# 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
# 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) }
# List of where new lines occur
@new_lines = []
# 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
#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 HTML5lib.is_valid_encoding(@encoding)
@char_encoding = detect_encoding
else
@char_encoding = @encoding
end
# Read bytes from stream decoding them into Unicode
uString = @raw_stream.read
unless @char_encoding == 'utf-8'
begin
require 'iconv'
uString = Iconv.iconv('utf-8', @char_encoding, uString)[0]
rescue
end
end
# Normalize newlines and null characters
uString.gsub!(/\r\n?/, "\n")
uString.gsub!("\x00", [0xFFFD].pack('U'))
# Convert the unicode string into a list to be used as the data stream
@data_stream = uString
@queue = []
# Reset position in the list to read from
reset
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
buffer = @raw_stream.read
encoding = UniversalDetector::chardet(buffer)['encoding']
@raw_stream = open_stream(buffer)
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" => 'utf16le',
"\xfe\xff" => 'utf16be',
"\xff\xfe\x00\x00" => 'utf32le',
"\x00\x00\xfe\xff" => 'utf32be'
}
# Go to beginning of file and read in 4 bytes
@raw_stream.seek(0)
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
#AT - move this to the caller?
# Set the read position past the BOM if one was found, otherwise
# set it to the start of the stream
@raw_stream.seek(encoding ? seek : 0)
return encoding
end
# Report the encoding declared by the meta element
def detect_encoding_meta
parser = EncodingParser.new(@raw_stream.read(@NUM_BYTES_META))
@raw_stream.seek(0)
return parser.get_encoding
end
def determine_new_lines
# Looks through the stream to find where new lines occur so
# the position method can tell where it is.
@new_lines.push(0)
(0...@data_stream.length).each { |i| @new_lines.push(i) if @data_stream[i] == ?\n }
end
# Returns (line, col) of the current position in the stream.
def position
# Generate list of new lines first time around
determine_new_lines if @new_lines.empty?
line = 0
tell = @tell
@new_lines.each do |pos|
break unless pos < tell
line += 1
end
col = tell - @new_lines[line-1] - 1
return [line, col]
end
# Resets the position in the stream back to the start.
def reset
@tell = 0
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
begin
@tell += 1
c = @data_stream[@tell - 1]
case c
when 0xC2 .. 0xDF
@tell += 1
c.chr + @data_stream[@tell-1].chr
when 0xE0 .. 0xF0
@tell += 2
c.chr + @data_stream[@tell-2].chr + @data_stream[@tell-1].chr
else
c.chr
end
rescue
return :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]
unless char_stack[0] == :EOF
while (characters.include? char_stack[-1]) == opposite
unless @queue.empty?
# First from the queue
char_stack.push(@queue.shift)
break if char_stack[-1] == :EOF
else
# Then the rest
begin
@tell += 1
char_stack.push(@data_stream[@tell-1].chr)
rescue
char_stack.push(:EOF)
break
end
end
end
end
# Put the character stopped on back to the front of the queue
# from where it came.
@queue.insert(0, char_stack.pop)
return char_stack.join('')
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 HTML5lib.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 HTML5lib.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