Class: Ferret::Scanner

Inherits:
Object
  • Object
show all
Defined in:
lib/sql-ferret.rb

Instance Method Summary collapse

Constructor Details

#initialize(expr) ⇒ Scanner

Returns a new instance of Scanner.



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# File 'lib/sql-ferret.rb', line 772

def initialize expr
  raise 'type mismatch' unless expr.is_a? String
  super()
  @expr = expr
  @lex = Ferret::LEXICAL_RULESET

  @offset_ahead = 0
  @token_ahead = nil
  @offset_atail = nil
  @offset_behind = nil
  return
end

Instance Method Details

#expected!(expectation, **extra) ⇒ Object 



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# File 'lib/sql-ferret.rb', line 844

def expected! expectation, **extra
  # We'll call [[peek_token]] in advance so that
  # [[@offset_ahead]] would point exactly at the next token.
  tok = peek_token
  ugh('ferret-parse-error',
      expected: expectation,
      got: (tok || '*eof*').to_s,
      input: @expr,
      offset: @offset_ahead,
      **extra)
end

#expected_eof! ⇒ Object 



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# File 'lib/sql-ferret.rb', line 916

def expected_eof!
  expected! '*eof*' unless next_token_offset >= @expr.length
  return
end

#get_id(expectation) ⇒ Object 



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# File 'lib/sql-ferret.rb', line 887

def get_id expectation
  return (get_optional_id or expected! expectation)
end

#get_optional_escaped_id(expectation) ⇒ Object 



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# File 'lib/sql-ferret.rb', line 876

def get_optional_escaped_id expectation
  escaped_p = pass? :'\\'
  if escaped_p then
    return true, get_id(expectation)
  elsif id = get_optional_id then
    return false, id
  else
    return nil
  end
end

#get_optional_id ⇒ Object 



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# File 'lib/sql-ferret.rb', line 866

def get_optional_id
  tok = peek_token
  if tok.is_a? String then
    _consume_token_ahead
    return block_given? ? yield(tok) : tok
  else
    return nil
  end
end

#last_token_offset ⇒ Object 



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# File 'lib/sql-ferret.rb', line 906

def last_token_offset
  return @offset_behind
end

#next_token_offset ⇒ Object 



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# File 'lib/sql-ferret.rb', line 910

def next_token_offset
  _skip_intertoken_space \
      unless @token_ahead
  return @offset_ahead
end

#pass(etalon) ⇒ Object 



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# File 'lib/sql-ferret.rb', line 901

def pass etalon
  pass? etalon or expected! etalon
  return
end

#pass?(etalon) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/sql-ferret.rb', line 891

def pass? etalon
  tok = peek_token
  if tok == etalon then
    _consume_token_ahead
    return true
  else
    return false
  end
end

#peek_token ⇒ Object 



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# File 'lib/sql-ferret.rb', line 795

def peek_token
  return @token_ahead if @token_ahead

  # Note that [[peek_token]] advances [[@offset_ahead]] to
  # skip over preceding intertoken space but no further.
  # Instead, it'll store the end offset of the peeked token
  # in [[@offset_atail]].
  _skip_intertoken_space

  # check for eof
  if @offset_ahead >= @expr.length then
    @offset_atail = @offset_ahead
    return @token_ahead = nil
  end

  # check for an identifier
  if @lex.id_starter? @expr[@offset_ahead] then
    @offset_atail = @offset_ahead
    loop do
      @offset_atail += 1
      break unless @lex.id_continuer? @expr[@offset_atail]
    end
    return @token_ahead =
        @expr[@offset_ahead ... @offset_atail]
  end

  # check for multi-char particles
  @lex.multichar.each do |etalon|
    if @expr[@offset_ahead, etalon.length] == etalon then
      @offset_atail = @offset_ahead + etalon.length
      return @token_ahead = etalon.to_sym
    end
  end

  # check for single-char particles
  if @lex.simple_particle? @expr[@offset_ahead] then
    @offset_atail = @offset_ahead + 1
    return @token_ahead = @expr[@offset_ahead].chr.to_sym
  end

  # give up
  ugh 'ferret-lexical-error',
      input: @expr,
      offset: @offset_ahead,
      lookahead: @expr[@offset_ahead, 10],
      lookbehind: @expr[
          [@offset_ahead - 10, 0].max ... @offset_ahead]
end