Class Automaton

  • All Implemented Interfaces:
    Accountable

    public class Automaton
    extends Object
    implements Accountable
    Represents an automaton and all its states and transitions. States are integers and must be created using createState(). Mark a state as an accept state using setAccept(int, boolean). Add transitions using addTransition(int, int, int). Each state must have all of its transitions added at once; if this is too restrictive then use Automaton.Builder instead. State 0 is always the initial state. Once a state is finished, either because you've starting adding transitions to another state or you call finishState(), then that states transitions are sorted (first by min, then max, then dest) and reduced (transitions with adjacent labels going to the same dest are combined).
    WARNING: This API is experimental and might change in incompatible ways in the next release.
    • Constructor Summary

      Constructors 
      Constructor Description
      Automaton()
      Sole constructor; creates an automaton with no states.
      Automaton​(int numStates, int numTransitions)
      Constructor which creates an automaton with enough space for the given number of states and transitions.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void addEpsilon​(int source, int dest)
      Add a [virtual] epsilon transition between source and dest.
      void addTransition​(int source, int dest, int label)
      Add a new transition with min = max = label.
      void addTransition​(int source, int dest, int min, int max)
      Add a new transition with the specified source, dest, min, max.
      void copy​(Automaton other)
      Copies over all states/transitions from other.
      int createState()
      Create a new state.
      void finishState()
      Finishes the current state; call this once you are done adding transitions for a state.
      void getNextTransition​(Transition t)
      Iterate to the next transition after the provided one
      int getNumStates()
      How many states this automaton has.
      int getNumTransitions()
      How many transitions this automaton has.
      int getNumTransitions​(int state)
      How many transitions this state has.
      Transition[][] getSortedTransitions()
      Sugar to get all transitions for all states.
      void getTransition​(int state, int index, Transition t)
      Fill the provided Transition with the index'th transition leaving the specified state.
      int initTransition​(int state, Transition t)
      Initialize the provided Transition to iterate through all transitions leaving the specified state.
      boolean isAccept​(int state)
      Returns true if this state is an accept state.
      boolean isDeterministic()
      Returns true if this automaton is deterministic (for ever state there is only one transition for each label).
      int next​(Transition transition, int label)
      Looks for the next transition that matches the provided label, assuming determinism.
      long ramBytesUsed()
      Return the memory usage of this object in bytes.
      void setAccept​(int state, boolean accept)
      Set or clear this state as an accept state.
      int step​(int state, int label)
      Performs lookup in transitions, assuming determinism.
      String toDot()
      Returns the dot (graphviz) representation of this automaton.
    • Constructor Detail

      • Automaton

        public Automaton()
        Sole constructor; creates an automaton with no states.
      • Automaton

        public Automaton​(int numStates,
                         int numTransitions)
        Constructor which creates an automaton with enough space for the given number of states and transitions.
        Parameters:
        numStates - Number of states.
        numTransitions - Number of transitions.
    • Method Detail

      • createState

        public int createState()
        Create a new state.
      • setAccept

        public void setAccept​(int state,
                              boolean accept)
        Set or clear this state as an accept state.
      • getSortedTransitions

        public Transition[][] getSortedTransitions()
        Sugar to get all transitions for all states. This is object-heavy; it's better to iterate state by state instead.
      • isAccept

        public boolean isAccept​(int state)
        Returns true if this state is an accept state.
      • addTransition

        public void addTransition​(int source,
                                  int dest,
                                  int label)
        Add a new transition with min = max = label.
      • addTransition

        public void addTransition​(int source,
                                  int dest,
                                  int min,
                                  int max)
        Add a new transition with the specified source, dest, min, max.
      • addEpsilon

        public void addEpsilon​(int source,
                               int dest)
        Add a [virtual] epsilon transition between source and dest. Dest state must already have all transitions added because this method simply copies those same transitions over to source.
      • copy

        public void copy​(Automaton other)
        Copies over all states/transitions from other. The states numbers are sequentially assigned (appended).
      • isDeterministic

        public boolean isDeterministic()
        Returns true if this automaton is deterministic (for ever state there is only one transition for each label).
      • finishState

        public void finishState()
        Finishes the current state; call this once you are done adding transitions for a state. This is automatically called if you start adding transitions to a new source state, but for the last state you add you need to this method yourself.
      • getNumStates

        public int getNumStates()
        How many states this automaton has.
      • getNumTransitions

        public int getNumTransitions()
        How many transitions this automaton has.
      • getNumTransitions

        public int getNumTransitions​(int state)
        How many transitions this state has.
      • getNextTransition

        public void getNextTransition​(Transition t)
        Iterate to the next transition after the provided one
      • getTransition

        public void getTransition​(int state,
                                  int index,
                                  Transition t)
        Fill the provided Transition with the index'th transition leaving the specified state.
      • toDot

        public String toDot()
        Returns the dot (graphviz) representation of this automaton. This is extremely useful for visualizing the automaton.
      • step

        public int step​(int state,
                        int label)
        Performs lookup in transitions, assuming determinism.
        Parameters:
        state - starting state
        label - codepoint to look up
        Returns:
        destination state, -1 if no matching outgoing transition
      • next

        public int next​(Transition transition,
                        int label)
        Looks for the next transition that matches the provided label, assuming determinism.

        This method is similar to step(int, int) but is used more efficiently when iterating over multiple transitions from the same source state. It keeps the latest reached transition index in transition.transitionUpto so the next call to this method can continue from there instead of restarting from the first transition.

        Parameters:
        transition - The transition to start the lookup from (inclusive, using its Transition.source and Transition.transitionUpto). It is updated with the matched transition; or with Transition.dest = -1 if no match.
        label - The codepoint to look up.
        Returns:
        The destination state; or -1 if no matching outgoing transition.
      • ramBytesUsed

        public long ramBytesUsed()
        Description copied from interface: Accountable
        Return the memory usage of this object in bytes. Negative values are illegal.
        Specified by:
        ramBytesUsed in interface Accountable