com.hazelcast.org.apache.calcite.runtime.Automaton Maven / Gradle / Ivy
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* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hazelcast.org.apache.calcite.runtime;
import com.hazelcast.org.apache.calcite.rel.core.Match;
import com.hazelcast.org.apache.calcite.util.ImmutableBitSet;
import com.hazelcast.com.google.common.collect.ImmutableList;
import com.hazelcast.org.checkerframework.checker.nullness.qual.Nullable;
import java.util.Objects;
/** A nondeterministic finite-state automaton (NFA).
*
* It is used to implement the {@link Match}
* relational expression (for the {@code MATCH_RECOGNIZE} clause in SQL).
*
* @see Pattern
* @see AutomatonBuilder
* @see DeterministicAutomaton
*/
public class Automaton {
final State startState;
final State endState;
private final ImmutableList transitions;
private final ImmutableList epsilonTransitions;
final ImmutableList symbolNames;
/** Use an {@link AutomatonBuilder}. */
Automaton(State startState, State endState,
ImmutableList transitions,
ImmutableList epsilonTransitions,
ImmutableList symbolNames) {
this.startState = Objects.requireNonNull(startState, "startState");
this.endState = Objects.requireNonNull(endState, "endState");
this.transitions = Objects.requireNonNull(transitions, "transitions");
this.epsilonTransitions = epsilonTransitions;
this.symbolNames = Objects.requireNonNull(symbolNames, "symbolNames");
}
/** Returns the set of states, represented as a bit set, that the graph is
* in when starting from {@code state} and receiving {@code symbol}.
*
* @param fromState Initial state
* @param symbol Symbol received
* @param bitSet Set of successor states (output)
*/
void successors(int fromState, int symbol,
ImmutableBitSet.Builder bitSet) {
for (SymbolTransition transition : transitions) {
if (transition.fromState.id == fromState
&& transition.symbol == symbol) {
epsilonSuccessors(transition.toState.id, bitSet);
}
}
}
void epsilonSuccessors(int state, ImmutableBitSet.Builder bitSet) {
bitSet.set(state);
for (EpsilonTransition transition : epsilonTransitions) {
if (transition.fromState.id == state) {
if (!bitSet.get(transition.toState.id)) {
epsilonSuccessors(transition.toState.id, bitSet);
}
}
}
}
public ImmutableList getTransitions() {
return this.transitions;
}
public ImmutableList getEpsilonTransitions() {
return this.epsilonTransitions;
}
/** Node in the finite-state automaton. A state has a number of
* transitions to other states, each labeled with the symbol that
* causes that transition. */
static class State {
final int id;
State(int id) {
this.id = id;
}
@Override public boolean equals(@Nullable Object o) {
return o == this
|| o instanceof State
&& ((State) o).id == id;
}
@Override public int hashCode() {
return Objects.hash(id);
}
@Override public String toString() {
return "State{"
+ "id=" + id
+ '}';
}
}
/** Transition from one state to another in the finite-state automaton. */
abstract static class Transition {
final State fromState;
final State toState;
Transition(State fromState, State toState) {
this.fromState = Objects.requireNonNull(fromState, "fromState");
this.toState = Objects.requireNonNull(toState, "toState");
}
}
/** A transition caused by reading a symbol. */
static class SymbolTransition extends Transition {
final int symbol;
SymbolTransition(State fromState, State toState, int symbol) {
super(fromState, toState);
this.symbol = symbol;
}
@Override public String toString() {
return symbol + ":" + fromState.id + "->" + toState.id;
}
}
/** A transition that may happen without reading a symbol. */
static class EpsilonTransition extends Transition {
EpsilonTransition(State fromState, State toState) {
super(fromState, toState);
}
@Override public String toString() {
return "epsilon:" + fromState.id + "->" + toState.id;
}
}
}