Add tarball extractor

jib-core/src/main/java/com/google/cloud/tools/jib/tar/TarExtractor.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2019 Google LLC.
+ *
+ * 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.
+ */
+
+package com.google.cloud.tools.jib.tar;
+
+import java.io.BufferedInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import org.apache.commons.compress.archivers.tar.TarArchiveEntry;
+import org.apache.commons.compress.archivers.tar.TarArchiveInputStream;
+
+/** Extracts a tarball. */
+public class TarExtractor {
+
+  /**
+   * Extracts a tarball to the specified destination.
+   *
+   * @param source the tarball to extract
+   * @param destination the output directory
+   * @throws IOException if extraction fails
+   */
+  public static void extract(Path source, Path destination) throws IOException {
+    try (InputStream in = new BufferedInputStream(Files.newInputStream(source));
+        TarArchiveInputStream tarArchiveInputStream = new TarArchiveInputStream(in)) {
+      byte[] buffer = new byte[1024];
+      TarArchiveEntry entry = tarArchiveInputStream.getNextTarEntry();
+      while (entry != null) {
+        if (entry.isDirectory()) {
+          Files.createDirectories(destination.resolve(entry.getName()));
+        } else {
+          try (OutputStream out = Files.newOutputStream(destination.resolve(entry.getName()))) {
+            int read = tarArchiveInputStream.read(buffer);
+            while (read != -1) {
+              out.write(buffer, 0, read);
+              read = tarArchiveInputStream.read(buffer);
+            }
+          }
+        }
+        entry = tarArchiveInputStream.getNextTarEntry();
+      }
+    }
+  }
+}

jib-core/src/test/java/com/google/cloud/tools/jib/tar/TarExtractorTest.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2019 Google LLC.
+ *
+ * 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.
+ */
+
+package com.google.cloud.tools.jib.tar;
+
+import com.google.common.io.Resources;
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import org.junit.Assert;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+/** Tests for {@link TarExtractor}. */
+public class TarExtractorTest {
+
+  @ClassRule public static TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+  @Test
+  public void testExtract() throws URISyntaxException, IOException {
+    Path source = Paths.get(Resources.getResource("core/extract.tar").toURI());
+    Path destination = temporaryFolder.getRoot().toPath();
+    TarExtractor.extract(source, destination);
+
+    Assert.assertTrue(Files.exists(destination.resolve("file A")));
+    Assert.assertTrue(Files.exists(destination.resolve("file B")));
+    Assert.assertTrue(
+        Files.exists(destination.resolve("folder").resolve("nested folder").resolve("file C")));
+
+    try (Stream<String> lines = Files.lines(destination.resolve("file A"))) {
+      String contents = lines.collect(Collectors.joining());
+      Assert.assertEquals("Hello", contents);
+    }
+  }
+}