Add a ZipUtils class for unpacking zip files

app/src/main/java/emu/skyline/utils/ZipUtils.kt

@@ -0,0 +1,111 @@
+/*
+ * SPDX-License-Identifier: MPL-2.0
+ * Copyright © 2022 Skyline Team and Contributors (https://github.com/skyline-emu/)
+ */
+
+package emu.skyline.utils
+
+import java.io.*
+import java.lang.reflect.Field
+import java.util.zip.ZipEntry
+import java.util.zip.ZipFile
+import java.util.zip.ZipInputStream
+
+interface ZipUtils {
+    companion object {
+        /**
+         * Extracts a zip file to the given target directory.
+         * @exception IOException if unzipping fails for any reason
+         */
+        @Throws(IOException::class)
+        fun unzip(file : File, targetDirectory : File) {
+            ZipFile(file).use { zipFile ->
+                for (zipEntry in zipFile.entries()) {
+                    val destFile = createNewFile(targetDirectory, zipEntry)
+                    // If the zip entry is a file, we need to create its parent directories
+                    val destDirectory : File? = if (zipEntry.isDirectory) destFile else destFile.parentFile
+
+                    // Create the destination directory
+                    if (destDirectory == null || (!destDirectory.isDirectory && !destDirectory.mkdirs()))
+                        throw FileNotFoundException("Failed to create destination directory: $destDirectory")
+
+                    // If the entry is a directory we don't need to copy anything
+                    if (zipEntry.isDirectory)
+                        continue
+
+                    // Copy bytes to destination
+                    try {
+                        zipFile.getInputStream(zipEntry).use { inputStream ->
+                            destFile.outputStream().use { outputStream ->
+                                inputStream.copyTo(outputStream)
+                            }
+                        }
+                    } catch (e : IOException) {
+                        if (destFile.exists())
+                            destFile.delete()
+                        throw e
+                    }
+                }
+            }
+        }
+
+        /**
+         * Extracts a zip file from the given stream to the given target directory.
+         *
+         * This method is ~5x slower than [unzip], as [ZipInputStream] uses a fixed `512` bytes buffer for inflation,
+         * instead of `8192` bytes or more used by input streams returned by [ZipFile].
+         * This results in ~8x the amount of JNI calls, producing an increased number of array bounds checking, which kills performance.
+         * Usage of this method is discouraged when possible, [unzip] should be used instead.
+         * Nevertheless, it's the only option when extracting zips obtained from content URIs, as a [File] object cannot be obtained from them.
+         * @exception IOException if unzipping fails for any reason
+         */
+        @Throws(IOException::class)
+        fun unzip(stream : InputStream, targetDirectory : File) {
+            ZipInputStream(BufferedInputStream(stream)).use { zis ->
+                do {
+                    // Get the next entry, break if we've reached the end
+                    val zipEntry = zis.nextEntry ?: break
+
+                    val destFile = createNewFile(targetDirectory, zipEntry)
+                    // If the zip entry is a file, we need to create its parent directories
+                    val destDirectory : File? = if (zipEntry.isDirectory) destFile else destFile.parentFile
+
+                    // Create the destination directory
+                    if (destDirectory == null || (!destDirectory.isDirectory && !destDirectory.mkdirs()))
+                        throw FileNotFoundException("Failed to create destination directory: $destDirectory")
+
+                    // If the entry is a directory we don't need to copy anything
+                    if (zipEntry.isDirectory)
+                        continue
+
+                    // Copy bytes to destination
+                    try {
+                        BufferedOutputStream(destFile.outputStream()).use { zis.copyTo(it) }
+                    } catch (e : IOException) {
+                        if (destFile.exists())
+                            destFile.delete()
+                        throw e
+                    }
+                } while (true)
+            }
+        }
+
+        /**
+         * Safely creates a new destination file where the given zip entry will be extracted to.
+         *
+         * @exception IOException if the file was being created outside of the target directory
+         * **see:** [Zip Slip](https://github.com/snyk/zip-slip-vulnerability)
+         */
+        @Throws(IOException::class)
+        private fun createNewFile(destinationDir : File, zipEntry : ZipEntry) : File {
+            val destFile = File(destinationDir, zipEntry.name)
+            val destDirPath = destinationDir.canonicalPath
+            val destFilePath = destFile.canonicalPath
+
+            if (!destFilePath.startsWith(destDirPath + File.separator))
+                throw IOException("Entry is outside of the target dir: " + zipEntry.name)
+
+            return destFile
+        }
+    }
+}