Class: Antlr4::Runtime::PredictionContextUtils

Inherits:
Object
  • Object
show all
Defined in:
lib/antlr4/runtime/prediction_context_utils.rb

Constant Summary collapse

INITIAL_HASH = 
1
EMPTY_RETURN_STATE = 
Integer::MAX
@@_hash = 
nil

Class Method Summary collapse

Class Method Details

.all_context_nodes(context) ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 373

def self.all_context_nodes(context)
  nodes = []
  visited = {}
  all_context_nodes_(context, nodes, visited)
  nodes
end

.all_context_nodes_(context, nodes, visited) ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 380

def self.all_context_nodes_(context, nodes, visited)
  return if context.nil? || visited.key?(context)

  visited[context] = context
  nodes.add(context)
  i = 0
  while i < context.size
    all_context_nodes_(context.get_parent(i), nodes, visited)
    i += 1
  end
end

.cached_context(context, context_cache, visited) ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 319

def self.cached_context(context, context_cache, visited)
  return context if context.empty?

  existing = visited[context]
  return existing unless existing.nil?

  existing = context_cache.get(context)
  unless existing.nil?
    visited[context] = existing
    return existing
  end

  changed = false
  parents = []
  i = 0
  while i < context.size
    parent = cached_context(context.get_parent(i), context_cache, visited)
    if changed || parent != context.get_parent(i)
      unless changed
        parents = []
        j = 0
        while j < context.size
          parents[j] = context.get_parent(j)
          j += 1
        end
        changed = true
      end
      parents[i] = parent
    end
    i += 1
  end

  unless changed
    context_cache.add(context)
    visited[context] = context
    return context
  end

  if parents.empty?
    updated = EMPTY
  elsif parents.length == 1
    updated = SingletonPredictionContext.create(parents[0], context.get_return_state(0))
  else
    array_pred_ctx = context
    updated = ArrayPredictionContext.new(parents, array_pred_ctx.return_states)
  end

  context_cache.add(updated)
  visited[updated] = updated
  visited[context] = updated

  updated
end

.calculate_empty_hash_code ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 392

def self.calculate_empty_hash_code
  return @@_hash unless @@_hash.nil?

  @@_hash = RumourHash.calculate([INITIAL_HASH])
end

.calculate_hash_code1(parent, return_state) ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 398

def self.calculate_hash_code1(parent, return_state)
  RumourHash.calculate([return_state, parent])
end

.calculate_hash_code2(parents, return_states) ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 402

def self.calculate_hash_code2(parents, return_states)
  RumourHash.calculate(return_states + parents)
end

.combine_common_parents(parents) ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 238

def self.combine_common_parents(parents)
  unique_parents = {}

  p = 0
  while p < parents.length
    parent = parents[p]
    unique_parents[parent] = parent unless unique_parents.key?(parent) # don't replace
    p += 1
  end

  p = 0
  while p < parents.length
    parents[p] = unique_parents[parents[p]]
    p += 1
  end
end

.from_rule_context(atn, outer_ctx) ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 9

def self.from_rule_context(atn, outer_ctx)
  outer_ctx = ParserRuleContext::EMPTY if outer_ctx.nil?

  # if we are in RuleContext of start rule, s, then PredictionContext
  # is EMPTY. Nobody called us. (if we are empty, return empty)
  if outer_ctx.parent.nil? || outer_ctx == ParserRuleContext::EMPTY
    return EmptyPredictionContext::EMPTY
  end

  # If we have a parent, convert it to a PredictionContext graph
  parent = PredictionContextUtils.from_rule_context(atn, outer_ctx.parent)

  state = atn.states[outer_ctx.invoking_state]
  transition = state.transition(0)
  SingletonPredictionContext.new(parent, transition.follow_state.state_number)
end

.merge(a, b, root_is_wildcard, merge_cache) ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 26

def self.merge(a, b, root_is_wildcard, merge_cache)
  # share same graph if both same
  return a if a == b || a.eql?(b)

  if a.is_a?(SingletonPredictionContext) && b.is_a?(SingletonPredictionContext)
    return merge_singletons(a, b, root_is_wildcard, merge_cache)
  end

  # At least one of a or b is array
  # If one is $ and root_is_wildcard, return $ as * wildcard
  if root_is_wildcard
    return a if a.is_a? EmptyPredictionContext
    return b if b.is_a? EmptyPredictionContext
  end

  # convert singleton so both are arrays to normalize
  a = ArrayPredictionContext.new(a) if a.is_a? SingletonPredictionContext
  b = ArrayPredictionContext.new(b) if b.is_a? SingletonPredictionContext
  merge_arrays(a, b, root_is_wildcard, merge_cache)
end

.merge_arrays(a, b, root_is_wildcard, merge_cache) ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 142

def self.merge_arrays(a, b, root_is_wildcard, merge_cache)
  unless merge_cache.nil?
    previous = merge_cache.get2(a, b)
    return previous unless previous.nil?

    previous = merge_cache.get2(b, a)
    return previous unless previous.nil?
  end

  # merge sorted payloads a + b => M
  i = 0 # walks a
  j = 0 # walks b
  k = 0 # walks target M array

  merged_return_states = []
  merged_parents = []
  # walk and merge to yield merged_parents, merged_return_states
  while i < a.return_states.length && j < b.return_states.length
    a_parent = a.parents[i]
    b_parent = b.parents[j]
    if a.return_states[i] == b.return_states[j]
      # same payload (stack tops are equal), must yield merged singleton
      payload = a.return_states[i]
      # $+$ = $
      both = payload == EMPTY_RETURN_STATE && a_parent.nil? && b_parent.nil?
      ax_ax = (!a_parent.nil? && !b_parent.nil?) && a_parent.eql?(b_parent) # ax+ax -> ax
      if both || ax_ax
        merged_parents[k] = a_parent # choose left
        merged_return_states[k] = payload
      else # ax+ay -> a'[x,y]
        merged_parent = merge(a_parent, b_parent, root_is_wildcard, merge_cache)
        merged_parents[k] = merged_parent
        merged_return_states[k] = payload
      end
      i += 1 # hop over left one as usual
      j += 1 # but also skip one in right side since we merge
    elsif a.return_states[i] < b.return_states[j] # copy a[i] to M
      merged_parents[k] = a_parent
      merged_return_states[k] = a.return_states[i]
      i += 1
    else # b > a, copy b[j] to M
      merged_parents[k] = b_parent
      merged_return_states[k] = b.return_states[j]
      j += 1
    end

    k += 1
  end

  # copy over any payloads remaining in either array
  if i < a.return_states.length
    p = i
    while p < a.return_states.length
      merged_parents[k] = a.parents[p]
      merged_return_states[k] = a.return_states[p]
      k += 1
      p += 1
    end
  else
    p = j
    while p < b.return_states.length
      merged_parents[k] = b.parents[p]
      merged_return_states[k] = b.return_states[p]
      k += 1
      p += 1
    end
  end

  # trim merged if we combined a few that had same stack tops
  if k < merged_parents.length # write index < last position trim
    if k == 1 # for just one merged element, return singleton top
      a_ = SingletonPredictionContext.create(merged_parents[0], merged_return_states[0])
      merge_cache.put(a, b, a_) unless merge_cache.nil?
      return a_
    end
  end

  m = ArrayPredictionContext.new(merged_parents, merged_return_states)

  # if we created same array as a or b, return that instead
  # TODO: track whether this is possible above during merge sort for speed
  if m.equals(a)
    merge_cache.put(a, b, a) unless merge_cache.nil?
    return a
  end
  if m.equals(b)
    merge_cache.put(a, b, b) unless merge_cache.nil?
    return b
  end

  combine_common_parents(merged_parents)

  merge_cache.put(a, b, m) unless merge_cache.nil?
  m
end

.merge_root(a, b, root_is_wildcard) ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 113

def self.merge_root(a, b, root_is_wildcard)
  if root_is_wildcard
    if a.return_state == EMPTY_RETURN_STATE
      return EmptyPredictionContext::EMPTY # * + b = *
    end
    if b.return_state == EMPTY_RETURN_STATE
      return EmptyPredictionContext::EMPTY # a + * = *
    end
  else
    if a.return_state == EMPTY_RETURN_STATE && b.return_state == EMPTY_RETURN_STATE
      return EmptyPredictionContext::EMPTY # $ + $ = $
    end

    if a.return_state == EMPTY_RETURN_STATE # $ + x = [x,$]
      payloads = [b.return_state, EMPTY_RETURN_STATE]
      parents = [b.parent, nil]
      joined = ArrayPredictionContext.new(parents, payloads)
      return joined
    end
    if b.return_state == EMPTY_RETURN_STATE # x + $ = [x,$] ($ is always last if present)
      payloads = [a.return_state, EMPTY_RETURN_STATE]
      parents = [a.parent, nil]
      joined = ArrayPredictionContext.new(parents, payloads)
      return joined
    end
  end
  nil
end

.merge_singletons(a, b, root_is_wildcard, merge_cache) ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 47

def self.merge_singletons(a, b, root_is_wildcard, merge_cache)
  unless merge_cache.nil?
    previous = merge_cache.get2(a, b)
    return previous unless previous.nil?

    previous = merge_cache.get2(b, a)
    return previous unless previous.nil?
  end

  root_merge = merge_root(a, b, root_is_wildcard)
  unless root_merge.nil?
    merge_cache.put(a, b, root_merge) unless merge_cache.nil?
    return root_merge
  end

  if a.return_state == b.return_state # a == b
    parent = merge(a.parent, b.parent, root_is_wildcard, merge_cache)
    # if parent is same as existing a or b parent or reduced to a parent, return it
    if parent == a.parent
      return a # ax + bx = ax, if a=b
    end
    if parent == b.parent
      return b # ax + bx = bx, if a=b
    end

    # else: ax + ay = a'[x,y]
    # merge parents x and y, giving array node with x,y then remainders
    # of those graphs.  dup a, a' points at merged array
    # new joined parent so create new singleton pointing to it, a'
    a_ = SingletonPredictionContext.new(parent, a.return_state)
    merge_cache.put(a, b, a_) unless merge_cache.nil?
    return a_
  else # a != b payloads differ
    # see if we can collapse parents due to $+x parents if local ctx
    single_parent = nil
    if a == b || (!a.parent.nil? && a.parent.eql?(b.parent)) # ax + bx = [a,b]x
      single_parent = a.parent
    end
    unless single_parent.nil? # parents are same
      # sort payloads and use same parent
      payloads = [a.return_state, b.return_state]
      if a.return_state > b.return_state
        payloads[0] = b.return_state
        payloads[1] = a.return_state
      end
      parents = [single_parent, single_parent]
      a_ = ArrayPredictionContext.new(parents, payloads)
      merge_cache.put(a, b, a_) unless merge_cache.nil?
      return a_
    end
    # parents differ and can't merge them. Just pack together
    # into array can't merge.
    # ax + by = [ax,by]
    payloads = [a.return_state, b.return_state]
    parents = [a.parent, b.parent]
    if a.return_state > b.return_state # sort by payload
      payloads[0] = b.return_state
      payloads[1] = a.return_state
      parents = [b.parent, a.parent]
    end
    a_ = ArrayPredictionContext.new(parents, payloads)
    merge_cache.put(a, b, a_) unless merge_cache.nil?
    return a_
  end
end

.to_dot_string(context) ⇒ Object 



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# File 'lib/antlr4/runtime/prediction_context_utils.rb', line 255

def self.to_dot_string(context)
  return '' if context.nil?

  buf = ''
  buf << "digraph G \n"
  buf << "rankdir=LR\n"

  nodes = all_context_nodes(context)
  nodes.sort {|a, b| a.id - b.id}

  nodes.each do |current|
    if current.is_a? SingletonPredictionContext
      s = current.id.to_s
      buf << '  s' << s
      return_state = current.get_return_state(0).to_s
      return_state = '$' if current.is_a? EmptyPredictionContext
      buf << ' [label="' << return_state << "\"]\n"
      next
    end
    arr = current
    buf << '  s' << arr.id
    buf << ' [shape=box, label="'
    buf << '['
    first = true
    arr.return_states.each do |inv|
      buf << ', ' unless first
      buf << if inv == EMPTY_RETURN_STATE
               '$'
             else
               inv
             end
      first = false
    end
    buf << ']'
    buf << "\"]\n"
  end

  nodes.each do |current|
    next if current == EMPTY

    i = 0
    while i < current.size
      if current.get_parent(i).nil?
        i += 1
        next
      end
      String s = String.valueOf(current.id)
      buf << '  s' << s
      buf << '->'
      buf << 's'
      buf << current.get_parent(i).id
      buf << if current.size > 1
               ' [label="parent[' + i + "]\"]\n"
             else
               "\n"
             end
      i += 1
    end
  end

  buf << "end\n"
  buf
end