| // Copyright 2016 The Bazel Authors. All rights reserved. |
| // |
| // Licensed 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.google.devtools.build.lib.query2.engine; |
| |
| import com.google.common.collect.ImmutableMap; |
| import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable; |
| import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe; |
| import java.util.Map; |
| import java.util.Set; |
| import javax.annotation.Nullable; |
| |
| /** |
| * An immutable context, including variable bindings for variables introduced by {@link |
| * LetExpression}s. |
| */ |
| @Immutable |
| @ThreadSafe |
| public class QueryExpressionContext<T> { |
| protected final ImmutableMap<String, Set<T>> context; |
| |
| protected QueryExpressionContext(ImmutableMap<String, Set<T>> context) { |
| this.context = context; |
| } |
| |
| /** |
| * Returns the value bound to the specified variable given by {@code name}, or {@code null} if |
| * there is no such binding. |
| */ |
| @Nullable |
| Set<T> get(String name) { |
| return context.get(name); |
| } |
| |
| /** Returns a {@link QueryExpressionContext} with no variables defined. */ |
| public static <T> QueryExpressionContext<T> empty() { |
| return new QueryExpressionContext<>(ImmutableMap.<String, Set<T>>of()); |
| } |
| /** |
| * Returns a {@link QueryExpressionContext} that has all the same bindings as the given {@code |
| * variableContext} and also the binding of {@code name} to {@code value}. |
| */ |
| protected QueryExpressionContext<T> with(String name, Set<T> value) { |
| return new QueryExpressionContext<>(withNewVariable(name, value)); |
| } |
| |
| protected final ImmutableMap<String, Set<T>> withNewVariable(String name, Set<T> value) { |
| ImmutableMap.Builder<String, Set<T>> newContextBuilder = ImmutableMap.builder(); |
| for (Map.Entry<String, Set<T>> entry : context.entrySet()) { |
| if (!entry.getKey().equals(name)) { |
| // The binding of 'name' to 'value' should override any existing binding of name in |
| // 'variableContext'. These are the semantics we want in order for nested let-expressions |
| // to have the semantics we want. |
| newContextBuilder.put(entry); |
| } |
| } |
| newContextBuilder.put(name, value); |
| return newContextBuilder.build(); |
| } |
| |
| @Override |
| public String toString() { |
| return "QueryExpressionContext: " + context; |
| } |
| } |
| |