// 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.testing.junit.runner.util;
import static java.util.Collections.emptySet;
import static java.util.Collections.unmodifiableSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
* A {@link Factory} implementation used to implement {@link Set} bindings. This factory always
* returns a new {@link Set} instance for each call to {@link #get} (as required by {@link Factory})
* whose elements are populated by subsequent calls to their {@link Supplier#get} methods.
*/
public final class SetFactory<T> implements Factory<Set<T>> {
/**
* The maximum value for a signed 32-bit integer that is equal to a power of 2.
*/
private static final int MAX_POWER_OF_TWO = 1 << (Integer.SIZE - 2);
private static final Factory<Set<Object>> EMPTY_FACTORY =
new Factory<Set<Object>>() {
@Override
public Set<Object> get() {
return emptySet();
}
};
@SuppressWarnings({"unchecked", "rawtypes"}) // safe covariant cast
public static <T> Factory<Set<T>> empty() {
return (Factory) EMPTY_FACTORY;
}
/**
* Constructs a new {@link Builder} for a {@link SetFactory} with {@code individualSupplierSize}
* individual {@code Supplier<T>} and {@code collectionSupplierSize} {@code
* Supplier<Collection<T>>} instances.
*/
public static <T> Builder<T> builder(int individualSupplierSize, int collectionSupplierSize) {
return new Builder<T>(individualSupplierSize, collectionSupplierSize);
}
/**
* A builder to accumulate {@code Supplier<T>} and {@code Supplier<Collection<T>>} instances.
* These are only intended to be single-use and from within generated code. Do <em>NOT</em> add
* providers after calling {@link #build()}.
*/
public static final class Builder<T> {
private final List<Supplier<T>> individualSuppliers;
private final List<Supplier<Collection<T>>> collectionSuppliers;
private Builder(int individualSupplierSize, int collectionSupplierSize) {
individualSuppliers = presizedList(individualSupplierSize);
collectionSuppliers = presizedList(collectionSupplierSize);
}
@SuppressWarnings("unchecked")
public Builder<T> addSupplier(Supplier<? extends T> individualSupplier) {
assert individualSupplier != null : "Codegen error? Null provider";
// TODO(ronshapiro): Store a List<? extends Supplier<T>> and avoid the cast to Supplier<T>
individualSuppliers.add((Supplier<T>) individualSupplier);
return this;
}
@SuppressWarnings("unchecked")
public Builder<T> addCollectionSupplier(
Supplier<? extends Collection<? extends T>> collectionSupplier) {
assert collectionSupplier != null : "Codegen error? Null provider";
collectionSuppliers.add((Supplier<Collection<T>>) collectionSupplier);
return this;
}
public SetFactory<T> build() {
assert !hasDuplicates(individualSuppliers)
: "Codegen error? Duplicates in the provider list";
assert !hasDuplicates(collectionSuppliers)
: "Codegen error? Duplicates in the provider list";
return new SetFactory<T>(individualSuppliers, collectionSuppliers);
}
}
private final List<Supplier<T>> individualSuppliers;
private final List<Supplier<Collection<T>>> collectionSuppliers;
private SetFactory(
List<Supplier<T>> individualSuppliers, List<Supplier<Collection<T>>> collectionSuppliers) {
this.individualSuppliers = individualSuppliers;
this.collectionSuppliers = collectionSuppliers;
}
/**
* Returns a {@link Set} whose iteration order is that of the elements given by each of the
* providers, which are invoked in the order given at creation.
*
* @throws NullPointerException if any of the delegate {@link Set} instances or elements therein
* are {@code null}
*/
@Override
public Set<T> get() {
int size = individualSuppliers.size();
// Profiling revealed that this method was a CPU-consuming hotspot in some applications, so
// these loops were changed to use c-style for. Versus enhanced for-each loops, C-style for is
// faster for ArrayLists, at least through Java 8.
List<Collection<T>> providedCollections =
new ArrayList<Collection<T>>(collectionSuppliers.size());
for (int i = 0, c = collectionSuppliers.size(); i < c; i++) {
Collection<T> providedCollection = collectionSuppliers.get(i).get();
size += providedCollection.size();
providedCollections.add(providedCollection);
}
Set<T> providedValues = newHashSetWithExpectedSize(size);
for (int i = 0, c = individualSuppliers.size(); i < c; i++) {
providedValues.add(checkNotNull(individualSuppliers.get(i).get()));
}
for (int i = 0, c = providedCollections.size(); i < c; i++) {
for (T element : providedCollections.get(i)) {
providedValues.add(checkNotNull(element));
}
}
return unmodifiableSet(providedValues);
}
/**
* Returns true if at least one pair of items in {@code list} are equals.
*/
private static boolean hasDuplicates(List<?> list) {
if (list.size() < 2) {
return false;
}
Set<Object> asSet = new HashSet<Object>(list);
return list.size() != asSet.size();
}
/**
* Returns a new list that is pre-sized to {@code size}, or {@link Collections#emptyList()} if
* empty. The list returned is never intended to grow beyond {@code size}, so adding to a list
* when the size is 0 is an error.
*/
private static <T> List<T> presizedList(int size) {
if (size == 0) {
return Collections.emptyList();
}
return new ArrayList<T>(size);
}
/**
* Creates a {@link HashSet} instance, with a high enough "intial capcity" that it <em>should</em>
* hold {@code expectedSize} elements without growth.
*/
private static <T> HashSet<T> newHashSetWithExpectedSize(int expectedSize) {
return new HashSet<T>(calculateInitialCapacity(expectedSize));
}
private static int calculateInitialCapacity(int expectedSize) {
if (expectedSize < 3) {
return expectedSize + 1;
}
if (expectedSize < MAX_POWER_OF_TWO) {
// This is the calculation used in JDK8 to resize when a putAll
// happens; it seems to be the most conservative calculation we
// can make. 0.75 is the default load factor.
return (int) (expectedSize / 0.75F + 1.0F);
}
return Integer.MAX_VALUE; // any large value
}
private static <T> T checkNotNull(T reference) {
if (reference == null) {
throw new NullPointerException();
}
return reference;
}
}