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io.vlingo.xoom.actors.testkit.AccessSafely Maven / Gradle / Ivy
// Copyright © 2012-2021 VLINGO LABS. All rights reserved.
//
// This Source Code Form is subject to the terms of the
// Mozilla Public License, v. 2.0. If a copy of the MPL
// was not distributed with this file, You can obtain
// one at https://mozilla.org/MPL/2.0/.
package io.vlingo.xoom.actors.testkit;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Supplier;
/**
* Facilitate thread-safe accessing of shared data, both for writing and reading. The
* Factory Method {@code afterCompleting()} is used to determine how many times the
* {@code writeUsing()} behavior is employed before the {@code readUsing()} can complete.
*/
public class AccessSafely {
private final AtomicInteger totalWrites = new AtomicInteger(0);
private final Object lock;
private final Map> biConsumers;
private final Map> consumers;
private final Map> functions;
private final Map> suppliers;
private final TestUntil until;
@SuppressWarnings("unchecked")
private Function getRequiredFunction(String name) {
final Function function = (Function) functions.get(name);
if (function == null) {
throw new IllegalArgumentException("Unknown function: " + name);
}
return function;
}
@SuppressWarnings("unchecked")
private Supplier getRequiredSupplier(String name) {
final Supplier supplier = (Supplier) suppliers.get(name);
if (supplier == null) {
throw new IllegalArgumentException("Unknown supplier: " + name);
}
return supplier;
}
/**
* Answer a new {@code AccessSafely} with a completion count of {@code happenings}. This construct
* provides a reliable barrier/fence around data access between two or more threads, given that the
* number of {@code happenings} is accurately predicted.
* @param happenings the int number of times that writeUsing() is employed prior to readFrom() answering
* @return AccessSafely
*/
public static AccessSafely afterCompleting(final int happenings) {
return new AccessSafely(happenings);
}
/**
* Answer a new {@code AccessSafely} with immediate {@code readFrom()} results. Note
* that this is not recommended due to highly probably inconsistencies in the data
* seen by the reader as opposed to that written by the writer. See the Java memory
* model literature for details.
* @return AccessSafely
*/
public static AccessSafely immediately() {
return new AccessSafely();
}
/**
* Answer a new AccessSafely with my existing reads and writes functionality.
* @param happenings the int number of times that writeUsing() is employed prior to readFrom() answering
* @return AccessSafely
*/
public AccessSafely resetAfterCompletingTo(final int happenings) {
return new AccessSafely(this, happenings);
}
/**
* Answer me with {@code function} registered for reading.
* @param name the String name of the {@code Function} to register
* @param function the {@code Function} to register
* @param the type of the Function parameter
* @param the type of the Function return value
* @return TestAccessSafely
*/
public AccessSafely readingWith(final String name, final Function function) {
functions.put(name, function);
return this;
}
/**
* Answer me with {@code supplier} registered for reading.
* @param name the String name of the {@code Supplier} to register
* @param supplier the {@code Supplier} to register
* @param the type of the Supplier to register
* @return TestAccessSafely
*/
public AccessSafely readingWith(final String name, final Supplier supplier) {
suppliers.put(name, supplier);
return this;
}
/**
* Answer me with {@code consumer} registered for writing.
* @param name the String name of the {@code Consumer} to register
* @param consumer the {@code Consumer} to register
* @param the type of the Consumer to register
* @return TestAccessSafely
*/
public AccessSafely writingWith(final String name, final Consumer consumer) {
consumers.put(name, consumer);
return this;
}
/**
* Answer me with {@code consumer} registered for writing.
* @param name the String name of the {@code Consumer} to register
* @param consumer the {@code Consumer} to register
* @param the type of the first BiConsumer parameter to register
* @param the type of the second BiConsumer parameter to register
* @return TestAccessSafely
*/
public AccessSafely writingWith(final String name, final BiConsumer consumer) {
biConsumers.put(name, consumer);
return this;
}
/**
* Answer the value associated with {@code name}.
* @param name the String name of the value to answer
* @param the type of the value associated with name
* @return T
*/
public T readFrom(final String name) {
final Supplier supplier = getRequiredSupplier(name);
until.completes();
synchronized (lock) {
return supplier.get();
}
}
/**
* Answer the value associated with {@code name}.
* @param name the String name of the value to answer
* @param parameter the T typed function parameter
* @param the type of the parameter to the {@code Function}
* @param the type of the return value associated with name
* @return R
*/
public R readFrom(final String name, final T parameter) {
final Function function = getRequiredFunction(name);
until.completes();
synchronized (lock) {
return function.apply(parameter);
}
}
/**
* Answer the value associated with {@code name} but not until
* it reaches the {@code expected} value.
* @param name the String name of the value to answer
* @param expected the T typed expected value
* @param the type of the value associated with name
* @return T
*/
public T readFromExpecting(final String name, final T expected) {
return readFromExpecting(name, expected, Long.MAX_VALUE);
}
/**
* Answer the value associated with {@code name} but not until
* it reaches the {@code expected} value or the total number
* of {@code retries} is reached.
* @param name the String name of the value to answer
* @param expected the T typed expected value
* @param retries the long number of retries
* @param the type of the value associated with name
* @return T
*/
public T readFromExpecting(final String name, final T expected, final long retries) {
final Supplier supplier = getRequiredSupplier(name);
for (long count = 0; count < retries; ++count) {
synchronized (lock) {
final T value = supplier.get();
if (expected == value || expected.equals(value)) {
return value;
}
}
try { Thread.sleep(1L); } catch (Exception e) { }
}
throw new IllegalStateException("Did not reach expected value: " + expected);
}
/**
* Answer the value associated with {@code name} immediately.
* @param name the String name of the value to answer
* @param the type of the value associated with name
* @return T
*/
public T readFromNow(final String name) {
final Supplier supplier = getRequiredSupplier(name);
synchronized (lock) {
return supplier.get();
}
}
/**
* Answer the value associated with {@code name} immediately.
* @param name the String name of the value to answer
* @param parameter the T typed function parameter
* @param the type of the parameter to the {@code Function}
* @param the type of the return value associated with name
* @return R
*/
public R readFromNow(final String name, final T parameter) {
final Function function = getRequiredFunction(name);
synchronized (lock) {
return function.apply(parameter);
}
}
/**
* Set the value associated with {@code name} to the parameter {@code value}.
* @param name the String name of the value to answer
* @param value the T typed value to write
* @param the type of the value associated with name that is to be written
*/
@SuppressWarnings("unchecked")
public void writeUsing(final String name, final T value) {
final Consumer consumer = (Consumer) consumers.get(name);
if (consumer == null) {
throw new IllegalArgumentException("Unknown function: " + name);
}
synchronized (lock) {
totalWrites.incrementAndGet();
consumer.accept(value);
until.happened();
}
}
/**
* Set the values associated with {@code name} using the parameters {@code value1} and {@code value2}.
* @param name the String name of the value to answer
* @param value1 the T1 typed value to write
* @param value2 the T2 typed value to write
* @param the type of the first value associated with name that is to be written
* @param the type of the second value associated with name that is to be written
*/
@SuppressWarnings("unchecked")
public void writeUsing(final String name, final T1 value1, final T2 value2) {
final BiConsumer biConsumer = (BiConsumer) biConsumers.get(name);
if (biConsumer == null) {
throw new IllegalArgumentException("Unknown function: " + name);
}
synchronized (lock) {
totalWrites.incrementAndGet();
biConsumer.accept(value1, value2);
until.happened();
}
}
/**
* Answer the total of writes completed.
* @return int
*/
public int totalWrites() {
synchronized (lock) {
return totalWrites.get();
}
}
/**
* Answer the total of writes completed after ensuring that it surpasses {@code lesser},
* or if {@code retries} is reached first throw {@code IllegalStateException}.
* @param lesser the int value that must be surpassed
* @param retries the int number of retries before failing
* @return int
* @throws IllegalStateException when the total is not surpassed before the maximum retries
*/
public int totalWritesGreaterThan(final int lesser, final long retries) {
for (long count = 0; count < retries; ++count) {
synchronized (lock) {
final int total = totalWrites.get();
if (total > lesser) {
return total;
}
}
try { Thread.sleep(1L); } catch (Exception e) { }
}
throw new IllegalStateException("Did not reach expected value: " + (lesser + 1));
}
/**
* Construct my default state.
* @param happenings the int number of times that {@code TestUntil} will count down before readUsing() completes
*/
private AccessSafely(final int happenings) {
this.until = TestUntil.happenings(happenings);
this.biConsumers = new HashMap<>();
this.consumers = new HashMap<>();
this.functions = new HashMap<>();
this.suppliers = new HashMap<>();
this.lock = new Object();
}
private AccessSafely(final AccessSafely existing, final int happenings) {
this.until = TestUntil.happenings(happenings);
this.biConsumers = existing.biConsumers;
this.consumers = existing.consumers;
this.functions = existing.functions;
this.suppliers = existing.suppliers;
this.lock = new Object();
}
/**
* Construct my default state.
*/
private AccessSafely() {
this(0);
}
}