From 03e5dc61174e057723d20437b60869527af8f28b Mon Sep 17 00:00:00 2001
From: "Denis.Zharkov" <denis.zharkov@jetbrains.com>
Date: Mon, 7 Jun 2021 13:51:05 +0300
Subject: [PATCH] Force unmapping MappedByteBuffer

Otherwise, on Windows daemon might hold mapped regions for some time
(until those objects are collection) and during the time those file become
locked (it's impossible to modify or remove them)

Reflection/Unsafe of course is not a cool thing to use, but JDK still
(already for 18 years) doesn't have public API for this

See https://bugs.java.com/bugdatabase/view_bug.do?bug_id=4724038
And https://stackoverflow.com/questions/2972986/how-to-unmap-a-file-from-memory-mapped-using-filechannel-in-java
---
 .../cli/jvm/compiler/jarfs/FastJarHandler.kt  | 48 ++++++++++++++++++-
 1 file changed, 46 insertions(+), 2 deletions(-)

diff --git a/compiler/cli/src/org/jetbrains/kotlin/cli/jvm/compiler/jarfs/FastJarHandler.kt b/compiler/cli/src/org/jetbrains/kotlin/cli/jvm/compiler/jarfs/FastJarHandler.kt
index 766754defbc..df183eda624 100644
--- a/compiler/cli/src/org/jetbrains/kotlin/cli/jvm/compiler/jarfs/FastJarHandler.kt
+++ b/compiler/cli/src/org/jetbrains/kotlin/cli/jvm/compiler/jarfs/FastJarHandler.kt
@@ -14,6 +14,7 @@ import java.io.File
 import java.io.FileNotFoundException
 import java.io.IOException
 import java.io.RandomAccessFile
+import java.nio.ByteBuffer
 import java.nio.MappedByteBuffer
 import java.nio.channels.FileChannel
 
@@ -26,8 +27,12 @@ class FastJarHandler(val fileSystem: FastJarFileSystem, path: String) : ZipHandl
     init {
         RandomAccessFile(file, "r").use { randomAccessFile ->
             val mappedByteBuffer = randomAccessFile.channel.map(FileChannel.MapMode.READ_ONLY, 0, randomAccessFile.length())
-            ourEntryMap = mappedByteBuffer.parseCentralDirectory().associateBy { it.relativePath }
-            cachedManifest = ourEntryMap[MANIFEST_PATH]?.let(mappedByteBuffer::contentsToByteArray)
+            try {
+                ourEntryMap = mappedByteBuffer.parseCentralDirectory().associateBy { it.relativePath }
+                cachedManifest = ourEntryMap[MANIFEST_PATH]?.let(mappedByteBuffer::contentsToByteArray)
+            } finally {
+                mappedByteBuffer.unmapBuffer()
+            }
         }
 
         val entries: MutableMap<EntryInfo, FastJarVirtualFile> = HashMap()
@@ -167,9 +172,48 @@ private val cachedOpenFileHandles: FileAccessorCache<File, RandomAccessFileAndBu
         @Throws(IOException::class)
         override fun disposeAccessor(fileAccessor: RandomAccessFileAndBuffer) {
             fileAccessor.first.close()
+            fileAccessor.second.unmapBuffer()
         }
 
         override fun isEqual(val1: File, val2: File): Boolean {
             return val1 == val2 // reference equality to handle different jars for different ZipHandlers on the same path
         }
     }
+
+private val IS_PRIOR_9_JRE = System.getProperty("java.specification.version", "").startsWith("1.")
+
+private fun ByteBuffer.unmapBuffer() {
+    if (!isDirect) return
+
+    try {
+        if (IS_PRIOR_9_JRE) {
+            val cleaner = this::class.java.getMethod("cleaner")
+
+            cleaner.isAccessible = true
+
+            val clean = Class.forName("sun.misc.Cleaner").getMethod("clean")
+            clean.isAccessible = true
+
+            clean.invoke(cleaner.invoke(this))
+        } else {
+            val unsafeClass = try {
+                Class.forName("sun.misc.Unsafe")
+            } catch (ex: Exception) {
+                // jdk.internal.misc.Unsafe doesn't yet have an invokeCleaner() method,
+                // but that method should be added if sun.misc.Unsafe is removed.
+                Class.forName("jdk.internal.misc.Unsafe")
+            }
+
+            val clean = unsafeClass.getMethod("invokeCleaner", ByteBuffer::class.java)
+            clean.isAccessible = true
+
+            val theUnsafeField = unsafeClass.getDeclaredField("theUnsafe")
+            theUnsafeField.isAccessible = true
+
+            val theUnsafe = theUnsafeField.get(null)
+
+            clean.invoke(theUnsafe, this)
+        }
+    } catch (ex: Exception) {
+    }
+}