feat: wrap GZIPInputStream for connection reuse

google-http-client/src/main/java/com/google/api/client/http/ConsumingInputStream.java

@@ -0,0 +1,47 @@
+/*
+ * 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
+ *
+ *     https://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.api.client.http;
+
+import com.google.common.io.ByteStreams;
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * This class in meant to wrap an {@link InputStream} so that all bytes in the steam are read and
+ * discarded on {@link InputStream#close()}. This ensures that the underlying connection has the
+ * option to be reused.
+ */
+final class ConsumingInputStream extends FilterInputStream {
+  private boolean closed = false;
+
+  ConsumingInputStream(InputStream inputStream) {
+    super(inputStream);
+  }
+
+  @Override
+  public void close() throws IOException {
+    if (!closed && in != null) {
+      try {
+        ByteStreams.exhaust(this);
+        super.in.close();
+      } finally {
+        this.closed = true;
+      }
+    }
+  }
+}

google-http-client/src/main/java/com/google/api/client/http/HttpResponse.java

@@ -331,7 +331,8 @@ public InputStream getContent() throws IOException {
           if (!returnRawInputStream
               && contentEncoding != null
               && contentEncoding.contains("gzip")) {
-            lowLevelResponseContent = new GZIPInputStream(lowLevelResponseContent);
+            lowLevelResponseContent =
+                new ConsumingInputStream(new GZIPInputStream(lowLevelResponseContent));
           }
           // logging (wrap content with LoggingInputStream)
           Logger logger = HttpTransport.LOGGER;

google-http-client/src/test/java/com/google/api/client/http/ConsumingInputStreamTest.java

@@ -0,0 +1,65 @@
+/*
+ * 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
+ *
+ *     https://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.api.client.http;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import org.junit.Test;
+
+public class ConsumingInputStreamTest {
+
+  @Test
+  public void testClose_drainsBytesOnClose() throws IOException {
+    MockInputStream mockInputStream = new MockInputStream("abc123".getBytes(StandardCharsets.UTF_8));
+    InputStream consumingInputStream = new ConsumingInputStream(mockInputStream);
+
+    assertEquals(6, mockInputStream.getBytesToRead());
+
+    // read one byte
+    consumingInputStream.read();
+    assertEquals(5, mockInputStream.getBytesToRead());
+
+    // closing the stream should read the remaining bytes
+    consumingInputStream.close();
+    assertEquals(0, mockInputStream.getBytesToRead());
+  }
+
+  private class MockInputStream extends InputStream {
+    private int bytesToRead;
+
+    MockInputStream(byte[] data) {
+      this.bytesToRead = data.length;
+    }
+
+    @Override
+    public int read() throws IOException {
+      if (bytesToRead == 0) {
+        return -1;
+      }
+      bytesToRead--;
+      return 1;
+    }
+
+    int getBytesToRead() {
+      return bytesToRead;
+    }
+  }
+}

google-http-client/src/test/java/com/google/api/client/http/HttpResponseTest.java

@@ -26,10 +26,12 @@
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.lang.reflect.Type;
+import java.nio.charset.StandardCharsets;
 import java.text.NumberFormat;
 import java.util.Arrays;
 import java.util.logging.Level;
 import java.util.zip.GZIPInputStream;
+import java.util.zip.GZIPOutputStream;
 import junit.framework.TestCase;
 
 /**
@@ -457,4 +459,40 @@ public LowLevelHttpResponse execute() throws IOException {
         "it should not decompress stream",
         request.execute().getContent() instanceof GZIPInputStream);
   }
+
+  public void testGetContent_gzipEncoding_finishReading() throws IOException {
+    byte[] dataToCompress = "abcd".getBytes(StandardCharsets.UTF_8);
+    byte[] mockBytes;
+    try (ByteArrayOutputStream byteStream = new ByteArrayOutputStream(dataToCompress.length)) {
+      GZIPOutputStream zipStream = new GZIPOutputStream((byteStream));
+      zipStream.write(dataToCompress);
+      zipStream.close();
+      mockBytes = byteStream.toByteArray();
+    }
+    final MockLowLevelHttpResponse mockResponse = new MockLowLevelHttpResponse();
+    mockResponse.setContent(mockBytes);
+    mockResponse.setContentEncoding("gzip");
+    mockResponse.setContentType("text/plain");
+
+    HttpTransport transport =
+        new MockHttpTransport() {
+          @Override
+          public LowLevelHttpRequest buildRequest(String method, final String url)
+              throws IOException {
+            return new MockLowLevelHttpRequest() {
+              @Override
+              public LowLevelHttpResponse execute() throws IOException {
+                return mockResponse;
+              }
+            };
+          }
+        };
+    HttpRequest request =
+        transport.createRequestFactory().buildHeadRequest(HttpTesting.SIMPLE_GENERIC_URL);
+    HttpResponse response = request.execute();
+    TestableByteArrayInputStream output = (TestableByteArrayInputStream) mockResponse.getContent();
+    assertFalse(output.isClosed());
+    assertEquals("abcd", response.parseAsString());
+    assertTrue(output.isClosed());
+  }
 }