updater_sample: add FileDownloader
Test: unit tests
Change-Id: I10933e7172d7ebc34c7cf5e4274625d7b8399246
Signed-off-by: Zhomart Mukhamejanov <zhomart@google.com>
diff --git a/updater_sample/src/com/example/android/systemupdatersample/util/FileDownloader.java b/updater_sample/src/com/example/android/systemupdatersample/util/FileDownloader.java
new file mode 100644
index 0000000..806f173
--- /dev/null
+++ b/updater_sample/src/com/example/android/systemupdatersample/util/FileDownloader.java
@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * 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.example.android.systemupdatersample.util;
+
+import android.util.Log;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.URL;
+import java.net.URLConnection;
+
+/**
+ * Downloads chunk of a file from given url using {@code offset} and {@code size},
+ * and saves to a given location.
+ *
+ * In real-life application this helper class should download from HTTP Server,
+ * but in this sample app it will only download from a local file.
+ */
+public final class FileDownloader {
+
+ private String mUrl;
+ private long mOffset;
+ private long mSize;
+ private File mOut;
+
+ public FileDownloader(String url, long offset, long size, File out) {
+ this.mUrl = url;
+ this.mOffset = offset;
+ this.mSize = size;
+ this.mOut = out;
+ }
+
+ /**
+ * Downloads the file with given offset and size.
+ */
+ public void download() throws IOException {
+ Log.d("FileDownloader", "downloading " + mOut.getName()
+ + " from " + mUrl
+ + " to " + mOut.getAbsolutePath());
+
+ URL url = new URL(mUrl);
+ URLConnection connection = url.openConnection();
+ connection.connect();
+
+ // download the file
+ try (InputStream input = connection.getInputStream()) {
+ try (OutputStream output = new FileOutputStream(mOut)) {
+ long skipped = input.skip(mOffset);
+ if (skipped != mOffset) {
+ throw new IOException("Can't download file "
+ + mUrl
+ + " with given offset "
+ + mOffset);
+ }
+ byte[] data = new byte[4096];
+ long total = 0;
+ while (total < mSize) {
+ int needToRead = (int) Math.min(4096, mSize - total);
+ int count = input.read(data, 0, needToRead);
+ if (count <= 0) {
+ break;
+ }
+ output.write(data, 0, count);
+ total += count;
+ }
+ if (total != mSize) {
+ throw new IOException("Can't download file "
+ + mUrl
+ + " with given size "
+ + mSize);
+ }
+ }
+ }
+ }
+
+}