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Kotlin Standard Library

There is a newer version: 2.1.0-RC

/*
 * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
 * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
 */

@file:JvmName("CloseableKt")
package kotlin.io

import java.io.Closeable
import kotlin.contracts.*
import kotlin.internal.*

/**
 * Executes the given [block] function on this resource and then closes it down correctly whether an exception
 * is thrown or not.
 *
 * @param block a function to process this [Closeable] resource.
 * @return the result of [block] function invoked on this resource.
 */
@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 {
        when {
            apiVersionIsAtLeast(1, 1, 0) -> this.closeFinally(exception)
            this == null -> {}
            exception == null -> close()
            else ->
                try {
                    close()
                } catch (closeException: Throwable) {
                    // cause.addSuppressed(closeException) // ignored here
                }
        }
    }
}

/**
 * Closes this [Closeable], suppressing possible exception or error thrown by [Closeable.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, when it's supported.
 */
@SinceKotlin("1.1")
@PublishedApi
internal fun Closeable?.closeFinally(cause: Throwable?): Unit = when {
    this == null -> {}
    cause == null -> close()
    else ->
        try {
            close()
        } catch (closeException: Throwable) {
            cause.addSuppressed(closeException)
        }
}