kotlin.AutoCloseable.kt Maven / Gradle / Ivy

/*
 * Copyright 2010-2017 JetBrains s.r.o.
 *
 * 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.
 */

@file:Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
@file:JvmName("AutoCloseableKt")
@file:kotlin.jvm.JvmPackageName("kotlin.jdk7")
package kotlin

import kotlin.contracts.*

/**
 * Executes the given [block] function on this resource and then closes it down correctly whether an exception
 * is thrown or not.
 *
 * In case if the resource is being closed due to an exception occurred in [block], and the closing also fails with an exception,
 * the latter is added to the [suppressed][java.lang.Throwable.addSuppressed] exceptions of the former.
 *
 * @param block a function to process this [AutoCloseable] resource.
 * @return the result of [block] function invoked on this resource.
 */
@SinceKotlin("1.2")
@kotlin.internal.InlineOnly
public inline fun  T.use(block: (T) -> R): R {
    contract {
        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
    }
    var exception: Throwable? = null
    try {
        return block(this)
    } catch (e: Throwable) {
        exception = e
        throw e
    } finally {
        this.closeFinally(exception)
    }
}

/**
 * Closes this [AutoCloseable], suppressing possible exception or error thrown by [AutoCloseable.close] function when
 * it's being closed due to some other [cause] exception occurred.
 *
 * The suppressed exception is added to the list of suppressed exceptions of [cause] exception.
 */
@SinceKotlin("1.2")
@PublishedApi
internal fun AutoCloseable?.closeFinally(cause: Throwable?) = when {
    this == null -> {}
    cause == null -> close()
    else ->
        try {
            close()
        } catch (closeException: Throwable) {
            cause.addSuppressed(closeException)
        }
}