Class: RDF::NTriples::Writer

Inherits:
Writer
  • Object
show all
Includes:
Util::Logger
Defined in:
lib/rdf/ntriples/writer.rb

Overview

N-Triples serializer.

Output is serialized for UTF-8, to serialize as ASCII (with) unicode escapes, set encoding: Encoding::ASCII as an option to #initialize.

Examples:

Obtaining an NTriples writer class

RDF::Writer.for(:ntriples)     #=> RDF::NTriples::Writer
RDF::Writer.for("etc/test.nt")
RDF::Writer.for(file_name:      "etc/test.nt")
RDF::Writer.for(file_extension: "nt")
RDF::Writer.for(content_type:   "application/n-triples")

Serializing RDF statements into an NTriples file

RDF::NTriples::Writer.open("etc/test.nt") do |writer|
  graph.each_statement do |statement|
    writer << statement
  end
end

Serializing RDF statements into an NTriples string

RDF::NTriples::Writer.buffer do |writer|
  graph.each_statement do |statement|
    writer << statement
  end
end

Serializing RDF statements into an NTriples string with escaped UTF-8

RDF::NTriples::Writer.buffer(encoding: Encoding::ASCII) do |writer|
  graph.each_statement do |statement|
    writer << statement
  end
end

See Also:

Direct Known Subclasses

RDF::NQuads::Writer

Constant Summary collapse

ESCAPE_PLAIN =

See Also:

/\A[\x20-\x21\x23-\x26\x28#{Regexp.escape '['}#{Regexp.escape ']'}-\x7E]*\z/m.freeze
ESCAPE_PLAIN_U = 
/\A(?:#{Reader::IRI_RANGE}|#{Reader::UCHAR})*\z/.freeze

Constants included from Util::Logger

Util::Logger::IOWrapper

Instance Attribute Summary

Attributes inherited from Writer

#options

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Util::Logger

#log_debug, #log_depth, #log_error, #log_fatal, #log_info, #log_recover, #log_recovering?, #log_statistics, #log_warn, #logger

Methods inherited from Writer

accept?, #base_uri, buffer, #canonicalize?, dump, each, #encoding, #flush, for, format, #format_list, #format_term, open, options, #prefix, #prefixes, #prefixes=, #to_sym, to_sym, #validate?, #write_epilogue, #write_prologue, #write_statement, #write_triples

Methods included from Util::Aliasing::LateBound

#alias_method

Methods included from Writable

#<<, #insert, #writable?

Constructor Details

#initialize(output = $stdout, validate: true, **options) {|writer| ... } ⇒ Writer

Initializes the writer.

Parameters:

  • output (IO, File) (defaults to: $stdout) —

    the output stream

  • validate (Boolean) (defaults to: true) —

    (true) whether to validate terms when serializing

  • options (Hash{Symbol => Object}) —

    ({}) any additional options. See Writer#initialize

Yields:

  • (writer) —

    ‘self`

Yield Parameters:

Yield Returns:

  • (void) 


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# File 'lib/rdf/ntriples/writer.rb', line 192

def initialize(output = $stdout, validate: true, **options, &block)
  super
end

Class Method Details

.escape(string, encoding = nil) ⇒ String

Escape Literal and URI content. If encoding is ASCII, all unicode is escaped, otherwise only ASCII characters that must be escaped are escaped.

Parameters:

  • string (String)
  • encoding (Encoding) (defaults to: nil)

Returns:

  • (String)

See Also:



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# File 'lib/rdf/ntriples/writer.rb', line 57

def self.escape(string, encoding = nil)
  ret = case
    when string.match?(ESCAPE_PLAIN) # a shortcut for the simple case
      string
    when string.ascii_only?
      StringIO.open do |buffer|
        buffer.set_encoding(Encoding::ASCII)
        string.each_byte { |u| buffer << escape_ascii(u, encoding) }
        buffer.string
      end
    when encoding && encoding != Encoding::ASCII
      # Not encoding UTF-8 characters
      StringIO.open do |buffer|
        buffer.set_encoding(encoding)
        string.each_char do |u|
          buffer << case u.ord
          when (0x00..0x7F)
            escape_ascii(u, encoding)
          else
            u
          end
        end
        buffer.string
      end
    else
      # Encode ASCII && UTF-8 characters
      StringIO.open do |buffer|
        buffer.set_encoding(Encoding::ASCII)
        string.each_codepoint { |u| buffer << escape_unicode(u, encoding) }
        buffer.string
      end
  end
  encoding ? ret.encode(encoding) : ret
end

.escape_ascii(u, encoding) ⇒ String

Standard ASCII escape sequences. If encoding is ASCII, use Test-Cases sequences, otherwise, assume the test-cases escape sequences. Otherwise, the N-Triples recommendation includes ‘b` and `f` escape sequences.

Within STRING_LITERAL_QUOTE, only the characters ‘U+0022`, `U+005C`, `U+000A`, `U+000D` are encoded using `ECHAR`. `ECHAR` must not be used for characters that are allowed directly in STRING_LITERAL_QUOTE.

Parameters:

  • u (Integer, #ord)

Returns:

  • (String)

Raises:

  • (ArgumentError) —

    if ‘u` is not a valid Unicode codepoint

See Also:



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# File 'lib/rdf/ntriples/writer.rb', line 126

def self.escape_ascii(u, encoding)
  case (u = u.ord)
  when (0x08)       then "\\b"
  when (0x09)       then "\\t"
  when (0x0A)       then "\\n"
  when (0x0C)       then "\\f"
  when (0x0D)       then "\\r"
  when (0x22)       then "\\\""
  when (0x5C)       then "\\\\"
  when (0x00..0x1F) then escape_utf16(u)
  when (0x7F)       then escape_utf16(u)
  when (0x20..0x7E) then u.chr
  else
    raise ArgumentError.new("expected an ASCII character in (0x00..0x7F), but got 0x#{u.to_s(16)}")
  end
end

.escape_unicode(u, encoding) ⇒ String

Escape ascii and unicode characters. If encoding is UTF_8, only ascii characters are escaped.

Parameters:

  • u (Integer, #ord)
  • encoding (Encoding)

Returns:

  • (String)

Raises:

  • (ArgumentError) —

    if ‘u` is not a valid Unicode codepoint

See Also:



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# File 'lib/rdf/ntriples/writer.rb', line 101

def self.escape_unicode(u, encoding)
  case (u = u.ord)
    when (0x00..0x7F)        # ASCII 7-bit
      escape_ascii(u, encoding)
    when (0x80..0xFFFF)      # Unicode BMP
      escape_utf16(u)
    when (0x10000..0x10FFFF) # Unicode
      escape_utf32(u)
    else
      raise ArgumentError.new("expected a Unicode codepoint in (0x00..0x10FFFF), but got 0x#{u.to_s(16)}")
  end
end

.escape_utf16(u) ⇒ String

Parameters:

  • u (Integer, #ord)

Returns:

  • (String)

See Also:



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# File 'lib/rdf/ntriples/writer.rb', line 147

def self.escape_utf16(u)
  sprintf("\\u%04X", u.ord)
end

.escape_utf32(u) ⇒ String

Parameters:

  • u (Integer, #ord)

Returns:

  • (String)

See Also:



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# File 'lib/rdf/ntriples/writer.rb', line 155

def self.escape_utf32(u)
  sprintf("\\U%08X", u.ord)
end

.serialize(value) ⇒ String

Returns the serialized N-Triples representation of the given RDF value.

Parameters:

Returns:

  • (String)

Raises:

  • (ArgumentError) —

    if ‘value` is not an `RDF::Statement` or `RDF::Term`



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# File 'lib/rdf/ntriples/writer.rb', line 166

def self.serialize(value)
  writer = (@serialize_writer_memo ||= self.new)
  case value
    when nil then nil
    when FalseClass then value.to_s
    when RDF::Statement
      writer.format_statement(value) + "\n"
    when RDF::Term
      writer.format_term(value)
    else
      raise ArgumentError, "expected an RDF::Statement or RDF::Term, but got #{value.inspect}"
  end
end

Instance Method Details

#escaped(string) ⇒ Object 



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# File 'lib/rdf/ntriples/writer.rb', line 338

def escaped(string)
  self.class.escape(string, encoding)
end

#format_literal(literal, **options) ⇒ String

Returns the N-Triples representation of a literal.

Parameters:

  • literal (RDF::Literal, String, #to_s)
  • options (Hash{Symbol => Object}) —

    ({})

Returns:

  • (String) 


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# File 'lib/rdf/ntriples/writer.rb', line 322

def format_literal(literal, **options)
  case literal
    when RDF::Literal
      # Note, escaping here is more robust than in Term
      text = quoted(escaped(literal.value))
      text << "@#{literal.language}" if literal.language?
      text << "--#{literal.direction}" if literal.direction?
      text << "^^<#{uri_for(literal.datatype)}>" if literal.datatype?
      text
    else
      quoted(escaped(literal.to_s))
  end
end

#format_node(node, unique_bnodes: false, **options) ⇒ String

Returns the N-Triples representation of a blank node.

Parameters:

  • node (RDF::Node)
  • unique_bnodes (Boolean) (defaults to: false) —

    (false) Serialize node using unique identifier, rather than any used to create the node.

  • options (Hash{Symbol => Object}) —

    ({})

Returns:

  • (String) 


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# File 'lib/rdf/ntriples/writer.rb', line 268

def format_node(node, unique_bnodes: false, **options)
  unique_bnodes ? node.to_unique_base : node.to_s
end

#format_quotedTriple(statement, **options) ⇒ String

Deprecated.

Quoted triples are now deprecated

Returns the N-Triples representation of an RDF-star quoted triple.

Parameters:

  • statement (RDF::Statement)
  • options (Hash{Symbol => Object}) —

    ({})

Returns:

  • (String) 


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# File 'lib/rdf/ntriples/writer.rb', line 243

def format_quotedTriple(statement, **options)
  # FIXME: quoted triples are now deprecated
  "<<%s %s %s>>" % statement.to_a.map { |value| format_term(value, **options) }
end

#format_statement(statement, **options) ⇒ String

Returns the N-Triples representation of a statement.

Parameters:

  • statement (RDF::Statement)
  • options (Hash{Symbol => Object}) —

    ({})

Returns:

  • (String) 


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# File 'lib/rdf/ntriples/writer.rb', line 222

def format_statement(statement, **options)
  format_triple(*statement.to_triple, **options)
end

#format_triple(subject, predicate, object, **options) ⇒ String

Returns the N-Triples representation of a triple.

Parameters:

Returns:

  • (String) 


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# File 'lib/rdf/ntriples/writer.rb', line 256

def format_triple(subject, predicate, object, **options)
  "%s %s %s ." % [subject, predicate, object].map { |value| format_term(value, **options) }
end

#format_tripleTerm(statement, **options) ⇒ String

Returns the N-Triples representation of an RDF 1.2 triple term.

Parameters:

  • statement (RDF::Statement)
  • options (Hash{Symbol => Object}) —

    ({})

Returns:

  • (String) 


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# File 'lib/rdf/ntriples/writer.rb', line 232

def format_tripleTerm(statement, **options)
  "<<(%s %s %s)>>" % statement.to_a.map { |value| format_term(value, **options) }
end

#format_uri(uri, **options) ⇒ String

Returns the N-Triples representation of a URI reference using write encoding.

Parameters:

  • uri (RDF::URI)
  • options (Hash{Symbol => Object}) —

    ({})

Returns:

  • (String) 


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# File 'lib/rdf/ntriples/writer.rb', line 278

def format_uri(uri, **options)
  string = uri.to_s
  iriref = case
    when string.match?(ESCAPE_PLAIN_U) # a shortcut for the simple case
      string
    when string.ascii_only? || (encoding && encoding != Encoding::ASCII)
      StringIO.open do |buffer|
        buffer.set_encoding(encoding)
        string.each_char do |u|
          buffer << case u.ord
            when (0x00..0x20) then self.class.escape_utf16(u)
            when 0x22, 0x3c, 0x3e, 0x5c, 0x5e, 0x60, 0x7b, 0x7c, 0x7d # "<>\^`{|}
              self.class.escape_utf16(u)
            else u
          end
        end
        buffer.string
      end
    else
      # Encode ASCII && UTF-8/16 characters
      StringIO.open do |buffer|
        buffer.set_encoding(Encoding::ASCII)
        string.each_byte do |u|
          buffer << case u
            when (0x00..0x20) then self.class.escape_utf16(u)
            when 0x22, 0x3c, 0x3e, 0x5c, 0x5e, 0x60, 0x7b, 0x7c, 0x7d # "<>\^`{|}
              self.class.escape_utf16(u)
            when (0x80..0xFFFF)                then self.class.escape_utf16(u)
            when (0x10000..0x10FFFF)           then self.class.escape_utf32(u)
            else u
          end
        end
        buffer.string
      end
  end
  encoding ? "<#{iriref}>".encode(encoding) : "<#{iriref}>"
end

#write_comment(text) ⇒ void

This method returns an undefined value.

Outputs an N-Triples comment line.

Parameters:

  • text (String) 


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# File 'lib/rdf/ntriples/writer.rb', line 201

def write_comment(text)
  puts "# #{text.chomp}" # TODO: correctly output multi-line comments
end

#write_triple(subject, predicate, object) ⇒ void

This method returns an undefined value.

Outputs the N-Triples representation of a triple.

Parameters:



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# File 'lib/rdf/ntriples/writer.rb', line 212

def write_triple(subject, predicate, object)
  puts format_triple(subject, predicate, object, **@options)
end