/*

* Copyright 2012-2020 the original author or authors.

*

* 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

*

* https://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.github.dockerjava.transport;

import java.io.Closeable;

import java.io.IOException;

import java.util.function.IntConsumer;

/**

* Provides access to the underlying file system representation of an open file.

*

* @author Phillip Webb

* @see #acquire()

*/

class FileDescriptor {

private final Handle openHandle;

private final Handle closedHandler;

private final IntConsumer closer;

private Status status = Status.OPEN;

private int referenceCount;

FileDescriptor(int handle, IntConsumer closer) {

this.openHandle = new Handle(handle);

this.closedHandler = new Handle(-1);

this.closer = closer;

}

@Override

protected void finalize() throws Throwable {

close();

}

/**

* Acquire an instance of the actual {@link Handle}. The caller must

* {@link Handle#close() close} the resulting handle when done.

* @return the handle

*/

synchronized Handle acquire() {

this.referenceCount++;

return (this.status != Status.OPEN) ? this.closedHandler : this.openHandle;

}

private synchronized void release() {

this.referenceCount--;

if (this.referenceCount == 0 && this.status == Status.CLOSE_PENDING) {

this.closer.accept(this.openHandle.value);

this.status = Status.CLOSED;

}

}

/**

* Close the underlying file when all handles have been released.

*/

synchronized void close() {

if (this.status == Status.OPEN) {

if (this.referenceCount == 0) {

this.closer.accept(this.openHandle.value);

this.status = Status.CLOSED;

} else {

this.status = Status.CLOSE_PENDING;

}

}

}

/**

* The status of the file descriptor.

*/

private enum Status {

OPEN, CLOSE_PENDING, CLOSED

}

/**

* Provides access to the actual file descriptor handle.

*/

final class Handle implements Closeable {

private final int value;

private Handle(int value) {

this.value = value;

}

boolean isClosed() {

return this.value == -1;

}

int intValue() {

return this.value;

}

@Override

public void close() throws IOException {

if (!isClosed()) {

release();

}

}

}

}