Issue 4231 - Fix unstable FilterEngineTest.testSetRemoveFilterChangeCallback

libadblockplus-android/src/org/adblockplus/libadblockplus/FileSystemUtils.java

+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-2017 eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.adblockplus.libadblockplus;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.NoSuchElementException;
+import java.util.Scanner;
+import java.util.UUID;
+
+public class FileSystemUtils
+{
+  /**
+   * Read all the file data to string
+   *
+   * @param file path to read data
+   * @return file data
+   * @throws java.io.FileNotFoundException
+   */
+  public static String readFile(File file) throws FileNotFoundException
+  {
+    Scanner scanner = null;
+    try
+    {
+      scanner = new Scanner(file);
+      return scanner.useDelimiter("\\A").next();

[sergei, 2017/05/22 12:09:07]

I'm not sure that it's the best way to read files in java at least I don't see
any reason to parse it here and use any delimiter. What if \a will be a valid
byte in the file? I would recommend to rather not use strings but use just bytes
when we are writing and reading from a file. BTW, C++ interface is operating
bytes for reading and writing.

[anton, 2017/05/22 13:04:38]

there are lots of ways for "reading file as string" and lot's of research for
this topic.
as for me using scanner is pretty old-school so i'll change it to more
common-spread impl with streams.

+    }
+    catch (NoSuchElementException e)
+    {
+      return "";
+    }
+    finally
+    {
+      if (scanner != null)
+      {
+        scanner.close();
+      }
+    }
+  }
+
+  /**
+   * Write data to file (with rewriting)
+   *
+   * @param file file
+   * @param data file data
+   */
+  public static void writeFile(File file, String data) throws IOException
+  {
+    FileOutputStream fos = null;
+    try
+    {
+      fos = new FileOutputStream(file);
+      if (data != null)
+      {
+        fos.write(data.getBytes());

[sergei, 2017/05/22 12:09:07]

If we still use String then I think we should pass UTF-8 into getBytes method.

[anton, 2017/05/22 13:04:38]

Acknowledged.

+      }
+    }
+    finally
+    {
+      if (fos != null)
+      {
+        try
+        {
+          fos.close();
+        }
+        catch (IOException e)
+        {
+          // ignored
+        }
+      }
+    }
+  }
+
+  /**
+   * Generate unique filename
+   *
+   * @param prefix prefix
+   * @param suffix suffix
+   * @return generated unique filename
+   */
+  public static String generateUniqueFileName(String prefix, String suffix)
+  {
+    StringBuilder sb = new StringBuilder();
+    if (prefix != null)
+    {
+      sb.append(prefix);
+    }
+
+    sb.append(UUID.randomUUID().toString());
+
+    if (suffix != null)
+    {
+      sb.append(suffix);
+    }
+
+    return sb.toString();
+  }
+}