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Swirlds is a software platform designed to build fully-distributed applications that harness the power of the cloud without servers. Now you can develop applications with fairness in decision making, speed, trust and reliability, at a fraction of the cost of traditional server-based platforms.
/*
* Copyright (C) 2022-2024 Hedera Hashgraph, LLC
*
* 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.swirlds.common.io;
import com.swirlds.common.AutoCloseableNonThrowing;
import java.io.IOException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.function.Consumer;
import java.util.function.Function;
/**
* Similar to an {@link Iterator} but throws IO exceptions.
*
* @param
* the type that is being iterated over
*/
public interface IOIterator extends AutoCloseableNonThrowing {
/**
* Check if there is another object available. If this method returns true then {@link #next()} will
* return a valid object without throwing. If this method returns false then {@link #next()} will throw
* a {@link NoSuchElementException}.
*
* @return true if there is another object available
* @throws IOException
* if there is a problem reading the next object
*/
boolean hasNext() throws IOException;
/**
* Get the next object if there is one available.
*
* @return the next object
* @throws IOException
* if there is a problem reading the next object
* @throws NoSuchElementException
* if {@link #hasNext()} returns false and this method is called
*/
T next() throws IOException;
/**
* Get the next item without advancing the iterator. Optional method.
*
* @return the object that will be returned when {@link #next()} is called
* @throws IOException
* if there is a problem reading the next object
* @throws NoSuchElementException
* if {@link #hasNext()} returns false and this method is called
*/
default T peek() throws IOException {
throw new UnsupportedOperationException();
}
/**
* For each remaining object in the iterator, pass that object to a lambda method.
*
* @param action
* the action that will operate on each object still in the iterator
* @throws IOException
* if there is a problem reading an object
*/
default void forEachRemaining(Consumer action) throws IOException {
while (hasNext()) {
action.accept(next());
}
}
/**
* {@inheritDoc}
*/
@Override
default void close() {
// Override if needed
}
/**
* Transform this iterator into an iterator that returns a different type. Iterating
* over the returned iterator causes the parent iterator to also advance.
*
* @param converter
* a function that converts from the old type into the new type.
* @param
* the type returned by the new iterator
* @return an iterator that walks the same data but returns a differnet type
*/
default IOIterator transform(final Function converter) {
final IOIterator parentIterator = this;
return new IOIterator<>() {
private U next;
@Override
public boolean hasNext() throws IOException {
if (next != null) {
return true;
}
if (!parentIterator.hasNext()) {
return false;
}
next = converter.apply(parentIterator.next());
return true;
}
@Override
public U peek() throws IOException {
if (!hasNext()) {
throw new NoSuchElementException();
}
return next;
}
@Override
public U next() throws IOException {
if (!hasNext()) {
throw new NoSuchElementException();
}
try {
return next;
} finally {
next = null;
}
}
};
}
}