Class: Weskit::WML::Parsers::KPEG

Inherits:
Object
  • Object
show all
Defined in:
lib/weskit/wml/parsers/kpeg.rb

Defined Under Namespace

Classes: MemoEntry, ParseError, RuleInfo

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(str, debug = false) ⇒ KPEG

This is distinct from setup_parser so that a standalone parser can redefine #initialize and still have access to the proper parser setup code.



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 8

def initialize(str, debug=false)
  setup_parser(str, debug)
end

Instance Attribute Details

#failed_rule ⇒ Object (readonly)

Returns the value of attribute failed_rule.



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 149

def failed_rule
  @failed_rule
end

#failing_rule_offset ⇒ Object (readonly)

Returns the value of attribute failing_rule_offset.



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 28

def failing_rule_offset
  @failing_rule_offset
end

#pos ⇒ Object

Returns the value of attribute pos.



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 29

def pos
  @pos
end

#result ⇒ Object

Returns the value of attribute result.



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 29

def result
  @result
end

#string ⇒ Object (readonly)

Returns the value of attribute string.



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 27

def string
  @string
end

Class Method Details

.rule_info(name, rendered) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 349

def self.rule_info(name, rendered)
  RuleInfo.new(name, rendered)
end

Instance Method Details

#apply(rule) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 284

def apply(rule)
  if m = @memoizations[rule][@pos]
    @pos = m.pos
    if !m.set
      m.left_rec = true
      return nil
    end

    @result = m.result

    return m.ans
  else
    m = MemoEntry.new(nil, @pos)
    @memoizations[rule][@pos] = m
    start_pos = @pos

    ans = __send__ rule

    lr = m.left_rec

    m.move! ans, @pos, @result

    # Don't bother trying to grow the left recursion
    # if it's failing straight away (thus there is no seed)
    if ans and lr
      return grow_lr(rule, nil, start_pos, m)
    else
      return ans
    end

    return ans
  end
end

#apply_with_args(rule, *args) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 249

def apply_with_args(rule, *args)
  memo_key = [rule, args]
  if m = @memoizations[memo_key][@pos]
    @pos = m.pos
    if !m.set
      m.left_rec = true
      return nil
    end

    @result = m.result

    return m.ans
  else
    m = MemoEntry.new(nil, @pos)
    @memoizations[memo_key][@pos] = m
    start_pos = @pos

    ans = __send__ rule, *args

    lr = m.left_rec

    m.move! ans, @pos, @result

    # Don't bother trying to grow the left recursion
    # if it's failing straight away (thus there is no seed)
    if ans and lr
      return grow_lr(rule, args, start_pos, m)
    else
      return ans
    end

    return ans
  end
end

#current_column(target = pos) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 32

def current_column(target=pos)
  if c = string.rindex("\n", target-1)
    return target - c - 1
  end

  target + 1
end

#current_line(target = pos) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 40

def current_line(target=pos)
  cur_offset = 0
  cur_line = 0

  string.each_line do |line|
    cur_line += 1
    cur_offset += line.size
    return cur_line if cur_offset >= target
  end

  -1
end

#external_invoke(other, rule, *args) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 228

def external_invoke(other, rule, *args)
  old_pos = @pos
  old_string = @string

  @pos = other.pos
  @string = other.string

  begin
    if val = __send__(rule, *args)
      other.pos = @pos
      other.result = @result
    else
      other.set_failed_rule "#{self.class}##{rule}"
    end
    val
  ensure
    @pos = old_pos
    @string = old_string
  end
end

#failure_caret ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 86

def failure_caret
  l = current_line @failing_rule_offset
  c = current_column @failing_rule_offset

  line = lines[l-1]
  "#{line}\n#{' ' * (c - 1)}^"
end

#failure_character ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 94

def failure_character
  l = current_line @failing_rule_offset
  c = current_column @failing_rule_offset
  lines[l-1][c-1, 1]
end

#failure_info ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 74

def failure_info
  l = current_line @failing_rule_offset
  c = current_column @failing_rule_offset

  if @failed_rule.kind_of? Symbol
    info = self.class::Rules[@failed_rule]
    "line #{l}, column #{c}: failed rule '#{info.name}' = '#{info.rendered}'"
  else
    "line #{l}, column #{c}: failed rule '#{@failed_rule}'"
  end
end

#failure_oneline ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 100

def failure_oneline
  l = current_line @failing_rule_offset
  c = current_column @failing_rule_offset

  char = lines[l-1][c-1, 1]

  if @failed_rule.kind_of? Symbol
    info = self.class::Rules[@failed_rule]
    "@#{l}:#{c} failed rule '#{info.name}', got '#{char}'"
  else
    "@#{l}:#{c} failed rule '#{@failed_rule}', got '#{char}'"
  end
end

#get_byte ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 172

def get_byte
  if @pos >= @string.size
    return nil
  end

  s = @string.getbyte @pos
  @pos += 1
  s
end

#get_text(start) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 61

def get_text(start)
  @string[start..@pos-1]
end

#grow_lr(rule, args, start_pos, m) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 318

def grow_lr(rule, args, start_pos, m)
  while true
    @pos = start_pos
    @result = m.result

    if args
      ans = __send__ rule, *args
    else
      ans = __send__ rule
    end
    return nil unless ans

    break if @pos <= m.pos

    m.move! ans, @pos, @result
  end

  @result = m.result
  @pos = m.pos
  return m.ans
end

#lines ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 53

def lines
  lines = []
  string.each_line { |l| lines << l }
  lines
end

#match_string(str) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 151

def match_string(str)
  len = str.size
  if @string[pos,len] == str
    @pos += len
    return str
  end

  return nil
end

#parse(rule = nil) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 193

def parse(rule=nil)
  # We invoke the rules indirectly via apply
  # instead of by just calling them as methods because
  # if the rules use left recursion, apply needs to
  # manage that.

  if !rule
    apply(:_root)
  else
    method = rule.gsub("-","_hyphen_")
    apply :"_#{method}"
  end
end

#raise_error ⇒ Object

Raises:



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 117

def raise_error
  raise ParseError, failure_oneline
end

#scan(reg) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 161

def scan(reg)
  if m = reg.match(@string[@pos..-1])
    width = m.end(0)
    @pos += width
    return true
  end

  return nil
end

#set_failed_rule(name) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 142

def set_failed_rule(name)
  if @pos > @failing_rule_offset
    @failed_rule = name
    @failing_rule_offset = @pos
  end
end

#setup_parser(str, debug = false) ⇒ Object

Prepares for parsing str. If you define a custom initialize you must call this method before #parse



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 16

def setup_parser(str, debug=false)
  @string = str
  @pos = 0
  @memoizations = Hash.new { |h,k| h[k] = {} }
  @result = nil
  @failed_rule = nil
  @failing_rule_offset = -1

  setup_foreign_grammar
end

#show_error(io = STDOUT) ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 121

def show_error(io=STDOUT)
  error_pos = @failing_rule_offset
  line_no = current_line(error_pos)
  col_no = current_column(error_pos)

  io.puts "On line #{line_no}, column #{col_no}:"

  if @failed_rule.kind_of? Symbol
    info = self.class::Rules[@failed_rule]
    io.puts "Failed to match '#{info.rendered}' (rule '#{info.name}')"
  else
    io.puts "Failed to match rule '#{@failed_rule}'"
  end

  io.puts "Got: #{string[error_pos,1].inspect}"
  line = lines[line_no-1]
  io.puts "=> #{line}"
  io.print(" " * (col_no + 3))
  io.puts "^"
end

#show_pos ⇒ Object 



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# File 'lib/weskit/wml/parsers/kpeg.rb', line 65

def show_pos
  width = 10
  if @pos < width
    "#{@pos} (\"#{@string[0,@pos]}\" @ \"#{@string[@pos,width]}\")"
  else
    "#{@pos} (\"... #{@string[@pos - width, width]}\" @ \"#{@string[@pos,width]}\")"
  end
end